LIBRARY 

UNIVERSITY   OF 
CAUFORN/A 

"EXRTH- 

fiC/ENCES 

LIBRARY 


4X         j          v 

ELEMENTS 


OF 


GEOLOGY; 


OR, 


THE   ANCIENT    CHANGES    OF    THE    EARTH  AND   ITS   INHABITANTS 
AS  ILLUSTRATED  BY  GEOLOGICAL  MONUMENTS. 


Jt     **o 
LYELL,  BABT.,  F.R.S., 

AUTHOR  OF  "PRINCIPLES  OF  GEOLOGY," 

GEOLOGICAL   EVIDENCES   OF  THE   ANTIQUITY  OF  MAN,"   ETC. 


N0MMULITB. 


AMMONITE. 


TERTIARY. 


SECONDARY. 


PRIMARY. 


SIXTH   EDITION, 

,  awl  Blu$tt!ato4  with  770 


NEW  YORK: 

D.  APPLETON  AND  COMPANY, 

443    &    445    BROADWAY. 

1866. 


EARTH 

SCIENCES 
LIBRARY 


PREFACE. 


THE  last,  or  fifth  edition  of  this  work,  was  published  in 
February,  1855,  so  that  nearly  ten  years  have  since  elapsed. 
I  have  allowed  it  to  remain  several  years  out  of  print,  having 
been  much  occupied  in  travelling  through  various  parts  of 
Europe,  and  latterly  in  writing  my  "  Geological  Evidences  of 
the  Antiquity  of  Man,"  as  well  as  the  appendices  to  the 
second  and  third  editions  of  that  treatise.  In  the  interval 
since  1855  I  have  published  several  supplements  to  the  "  Ele- 
ments," the  contents  of  which  are  now  incorporated  in  this 
work.  This  and  other  new  matter,  illustrated  by  more  than 
50  new  woodcuts,  has  added  130  pages  to  the  volume,  which 
has  thus  outgrown  the  dimensions  usually  assigned  to  a 
Manual.  I  have,  therefore,  restored  to  the  book  its  original 
title  of  u  The  Elements  of  Geology,"  under  which  name  it 
first  appeared  in  1838,  when  it  consisted  of  an  expansion  of 
the  fourth  book  of  my  "  Principles  of  Geology,"  which  had 
at  that  time  reached  a  fifth  edition. 

The  "  Elements "  were  successively  reedited,  and  in  each 
case  to  a  great  extent  recast,  in  the  years  1842,  1851,  1852, 
and  1855.  On  former  occasions  I  have  given  a  list  of  the 
principal  corrections  and  additions  in  which  each  new  edition 


vi  PREFACE. 

differed  from  its  predecessor ;  but  I  shall  not  attempt  to  offer 
the  reader  such  a  summary  in  the  present  case,  fearing  that 
that  would  prove  tediously  long.* 

A  fall  index  is  given  in  this  as  in  former  editions,  and 
the  student  will  observe  that  all  the  organic  remains  of  which 
there  are  woodcut  figures  in  the  text  are  printed  in  italics 
in  the  index. 

CHAELES  LYELL. 

63  HARLEY  STREET,  LONDON, 
December  20,  1864. 


*  As  it  is  impossible  to  enable  the  reader  to  recognize  rocks  and  minerals  at 
sight  by  aid  of  verbal  descriptions  or  figures,  he  will  do  well  to  obtain  a  well- 
arranged  collection  of  specimens,  such  as  may  be  procured  from  Mr.  Tennant 
(149  Strand),  teacher  of  Mineralogy  at  King's  College,  London. 


CONTENTS. 


i  CHAPTER  I. — On  the  Different  Classes  of  Rocks. 

Geology  defined — Successive  formation  of  the  earth's  crust — Classification  of  rocks 
according  to  their  origin  and  age — Aqueous  rocks — Their  stratification  and  im 
bedded  fossils-^- Volcanic  rocks,  with  and  without  cones  and  craters — Plutonic 
rocks,  afod  their  relation  to  the  volcanic — Metaraorphic  rocks,  and  their  probable 
origin — The  term  "Primitive,"  why  erroneously  applied  to  the  crystalline  forma- 
tions— Leading  division  of  the  work,  .  PAGE  1 

CHAPTER  II. — Aqueom  Rocks — Tlieir  Composition  and  Forms,  of  Stratification. 

V  ^ 

•4  Mineral, composition  of  strata — Arenaceous  rocks — Argillaceous — Calcareous — Gyp- 
sum-i-Forms  of  stratification — Original  horizontality-^-Thinning  out — Diagonal 
arrangement — Ripple  mark,  -  -  .  -  10 

i        CHAPTER  III. — Arrangement  of  Fossils/in  Strata— Freshwater  and  Marine. 

*  Successive  deposition  indicated  by  fossils — Limestones  formed  of  corals  and  shells 
* — Proofs  of  gradual  increase  of  strata  derived  from  fossils — Serpula  attached  to 
I  spatangus — Wood  bored  by  teredina — Tripoli  and  semi-opal  formed  of  infusoria 
*  — phalk  derived  principally  from  organic  bodies — Distinction  of  freshwate^fiW 
marine  formations— Genera  of  freshwater  and  land  shells — Rules  for  recognizing 
marine  testac«i — Gyrogonite  and  chara — Freshwater  fishes — Alternation  of  ma- 
rine and  freshwater  deposits — Lym-Fiord,     -  21 

CHAPTER  IV. — Consolidation,  of  Strata  and  Petrifaction  of  Fossils. 

J  V  v 

Chemical  and  mechanical  deposits — Cementing  together  of  particles — Hardening  by 
exposure  to  air — Concretionary  nodules — Consolidating  effects  of  pressure— Min- 
eralization of  organic  remains — Impressions  and  casts  how  fonned-^Fossil  wood 
— Goppert's  experiments — Precipitation  of  stony  matter  most  rapid  where  putre- 
faction is  going  On — Source  of  lime  in  solution — Silex  derived  from  decomposi- 
tion of  felspar-^-Proofs  of  the  lapidification  of  some  fossils  soon  after  burial,  of 
others  when  much  decayed,  -  -  -  -  33 


I 


CHAPTER  V. — Elevation  of  Strata  above  the  Sea — Horizontal  and  Inclined  Stratifi- 
cation. 

Why  the  position  of  marine  strata,  above  the  level  of  the  sea,  sliould  be  referred  to 
the  rising  up  of  the  land,  not  to  uie  going  down  of  the  sea-^-Upheaval  of  exten- 
sive masses  of  horizontal  strata — Inclined  and  vertical  stratification— Anticlinal 
and  synclinal  lines— Bent  strata  in  east  of  Scotland— Theory  of  folding  by 
lateral  movement — Creeps — Dip  and  strike — Structure  of  the  Jura — Various 


Viii  /  CONTENTS.      / 

V  1 

forms  of  outcrop— Rocks  broken  by  flexures-Inverted  position  of  d^fturbed 
strata— Unconfolrmable  stratification— Hutton  and  Playfair  on  the  same— Frac- 
tures of  strata-^-Polished  surfaces — Faults — Appearance  of  repeated  alternations 
produced  by  them — Origin  of  great  faults,  -  -  PAGE  44 

CHAPTER  VI. — Denudation. 

Denudation  defined— Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in 
the  earth's  crust— Horizontal  sandstone  denuded  in  Ross-shire — Levelled  surface 
of  countries  in  which  great  faults  occur— Coalbrook  Dale— Denuding  power  of 
the  ocean  during  the  emergence  of  land— Origin  of  valleys — Obliteration  of  sea- 
cliffs — Inland  sea-cliffs  and  terraces  in  the  Morea  and  Sicily — Limestone  pillars  at 
St.  Mihiel,  in  France — in  Canada — in  the  Bermudas,  -  66 

CHAPTER  VII. — Alluvium. 

Alluvium  described — Due  to  complicated  causes — Of  various  ages,  as  shown  in  Au- 
vergne — How  distinguished  from  rocks  in  situ — Sandpipes  in  Chalk — Alluvial 
terraces  caused  by  oscillation  in  the  level  of  land,  -  79 

CHAPTER  VIII. — Chronological  Classification  of  Rocks. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically — 
Lehman's  division  into  primitive  and  secondary — Werner's  addition  of  a  tran- 
sition class — Neptunian  theory — Hutton 'on  igneous  origin  of  granite — How  the 
name  of  primary  was  still  retained  for  granite — The  term  "  transition,"  why 
faulty — The  adherence  to  the  old  chronological  nomenclature  retarded  the 
progress  of  geology — New  hypothesis  intended  to  reconcile  the  igneous  origin 
of  granite  to  the  notion  of  its  high  antiquity — Explanation  of  the  chronological 
nomenclature  adopted  in  this  work,  so  far  as  regards  primary,  secondary,  and 
tertiary  periods,  -  -  85 

CHAPTER  IX. — On  the  Different  Ages  of  the  Aqueous  Rocks. 

On  the  three  principal  tests  of  relative  age — Superposition,  mineral  character,  and 
fossils — Change  of  mineral  character  and  fossils  in  the  same  continuous  forma- 
tion—Proofs that  distinct  species  of  animals  and  plants  have  lived  at  successive 
periods — Distinct  provinces  of  indigenous  species — Great  extent  of  single  prov- 
inces— Similar  laws  prevailed  at  successive  geological  periods — Relative  import- 
ance of  mineral  and  palgeontological  characters — Tests  of  age  by  included  frag- 
ments— Frequent  absence  of  strata  of  intervening  periods — Principal  groups  of 
strata  in  western  Europe — Tabular  views  of  fossiliferous  strata,  -  -  92 

CHAPTER  X. — Recent  and  Post-Pliocene  Periods. 

Recent  and  Post-pliocene  periods— Terms  defined — Formations  of  the  Recent 
period — Modern  littoral  deposits  containing  works  of  art  near  Naples — Danish 
peat  and  shell  mounds — Swiss  lake-dwellings — Periods  of  stone,  bronze,  and 
iron — Form  of  human  skulls  of  the  Recent  period — Post-pliocene  formations — 
Coexistence  of  man  with  extinct  mammalia — Higher  and  Lower-level  Valley- 
gravels — Loess  or  inundation  mud  of  the  Nile,  Rhine,  &c. — Antiquity  of  Post- 
pliocene  Lake-terraces  in  Switzerland — Upraised  marine  strata  in  Sardinia — 
Origin  of  caverns — Remains  of  man  and  extinct  quadrupeds  in  cavern  deposits 
• — Cave  of  Kirkdale — Reindeer  period  of  south  of  France — Australian  cave- 
breccias — Geographical  relationship  of  the  provinces  of  living  vertebrata  and 
those  of  extinct  Post-pliocene  species — Extinct  struthious  birds  of  New  Zealand 


CONTENTS.  • 

1A. 

— Fluctuations  of  climate  in  Post-glacial  period  —  Comparative  longevity  of 
species  in  the  mammalia  and  testacea — Teeth  of  recent  and  Post-pliocene  mam- 
malia, -  PAGE  107 

CHAPTER  XI. — Post-pliocene  Period,  continued — Glacial  Epoch. 

Geographical  distribution,  form,  and  characters  of  glacial  drift — Fundamental  rocks, 
polished,  grooved,  and  scratched — Abrading  and  striating  action  of  glaciers — 
Moraines,  erratic  blocks,  and  "  Roches  Moutonnees  " — Alpine  blocks  on  the  Jura 
— Colossal  size  of  ancient  Swiss  glaciers — Continental  ice  of  Greenland — Ancient 
centres  of  the  dispersion  of  erratics — Transportation  of  drift  by  floating  ice- 
bergs— Bed  of  the  sea  furrowed  and  polished  by  the  running  aground  of  floating 
ice-islands — How  to  distinguish  glacial  drift  of  submarine  from  that  of  terrestrial 
origin,  -  136 

CHAPTER  XII. — Post-pliocene  Period,  continued — Glacial  Epoch,  concluded. 

Glaciation  of  Scandinavia  and  Russia — Glaciation  of  Scotland — Marine  shells  in 
Scotch  glacial  drift — Their  Arctic  character — Rarity  of  organic  remains  in 
glacial  deposits — Contorted  strata  in  drift — Glaciation  of  Wales,  England,  and 
Ireland — Marine  shells  of  Moel  Tryfaen — Norfolk  drift — Glacial  formations  of 
North  America — How  far  of  submarine  origin — Many  species  of  testacea  and 
quadrupeds  survived  the  glacial  cold — Connection  of  the  predominance  of  lakes 
with  glacial  action — Morainic  lakes — Objections  to  the  hypothesis  of  the  erosion 
of  large  lake-basins  by  ice — Conversion  of  valleys  of  denudation  into  lakes  by 
upward  and  downward  movements — Action  of  ice  in  preventing  the  silting-up 
of  lake-basins— How  the  bed  of  a  sea  where  icebergs  have  abounded  may,  on 
emergence,  afford  lake-basins — General  causes  of  change  of  climate — Submer- 
gence of  the  Sahara  in  the  Post-pliocene  period  a  cause  of  Alpine  cold — Meteor- 
ites in  drift,  -  149 

CHAPTER  XIII. — Classification  of  Tertiary  Formations. — Pliocene  Period. 

Order  of  succession  of  sedimentary  formations — Imperfection  of  the  record — Defec- 
tiveness  and  obscurity  of  the  monuments  greater  in  proportion  to  their  antiquity 
— Reasons  for  studying  the  newer  groups  first — General  principles  of  classifica- 
tion of  tertiary  strata — Detached  formations  scattered  over  Europe — Strata  of 
Paris  and  London — More  modern  groups — Peculiar  difficulties  in  determining  the 
chronology  of  tertiary  formations — Increasing  proportion  of  living  species  of 
shells  in  strata  of  newer  origin — Eocene,  Miocene,  and  Pliocene  terms  explained 
— Formations  of  the  Newer  Pliocene  period — Island  of  Ischia — Eastern  base  of 
Mount  Etna — Newer  Pliocene  strata  of  great  height  and  extent  in  Sicily — For- 
mations of  same  age  in  the  Upper  Val  d'Arno — Norwich  Crag — Chillesford 
beds— Bridlington  beds— Older  Pliocene  strata— Red  Crag  of  Suffolk— White 
or  coralline  Crag — Successive  refrigeration  of  climate  proved  by  the  pliocene 
shells  of  Suffolk  and  Norfolk — Antwerp  Crag — Subapennine  strata — Aralo-Cas- 
pian  formations,  -  -  178 

CHAPTER  XIV.— Miocene  Period. 

Upper  Miocene  strata  of  France — Faluns  of  Touraine — Depth  of  sea  and  littoral 
character  of  fauna — Tropical  climate  implied  by  the  testacea — Proportion  of 
recent  species  of  shells — Faluns  more  ancient  than  the  Suffolk  Crag — Varieties 
of  Yoluta  Lamberti  peculiar  to  Faluns  and  to  Suffolk  Crag— The  same  spe- 
cies are  common  to  more  than  one  geological  Period — Lower  Miocene  strata 
of  France — Remarks  on  classification,  and  where  to  draw  the  line  of  separation 


x  CONTENTS. 

between  Miocene  and  Eocene  strata — Relations  of  the  Gres  de  Fontainebieau  to 
the  Faluns  and  to  the  Calcaire  Grossier — Lower  Miocene  strata  of  Central 
France— Lacustrine  strata  of  Auvergne— Indusial  limestone— Fossil  mammalia 
of  the  Limagne  d' Auvergne — Freshwater  strata  of  the  Cantal — Its  resemblance 
in  some  places  to  white  chalk  with  flints — Proofs  of  gradual  deposition — Miocene 
strata  of  Bordeaux  and  South  of  France — Upper  Miocene  strata  of  Gers— 
Dryopithecus — Belgian  and  British  Miocene  formations — Edeghem  beds  near 
Antwerp — Diest  sands  of  Belgium  and  contemporaneous  iron-sands  of  North 
Downs — Upper  Miocene  beds  of  Belgium— Bolderberg — Lower  Miocene  strata 
of  Kleyn  Spawen — Hempstead  beds,  Isle  of  Wight — Bovey  Tracey  Lignites 
in  Devonshire— Isle  of  Mull  Leaf-beds — Miocene  formations  of  Germany— 
Mayence  basin — Upper  Miocene  beds  of  Vienna  basin — Lower  Miocene  of 
Croatia — Fossil  Lepidoptera — Oligocene  strata  of  Professor  Beyrich — Miocene 
strata  of  Italy,  -  -  -  PAGE  212 

CHAPTER  XV. — Miocene  Formations,  continued. 

Miocene  Strata  of  Switzerland — Upper  Miocene  beds  of  (Eningen — Importance  of 
Fossil  Plants — Heer's  work  on  the  Swiss  Miocene  flora — Plants  and  insects  of 
(Eningen  imbedded  in  different  seasons — Fossil  fruits  and  flowers,  as  well  as 
leaves — Middle  or  Marine  Molasse  of  Switzerland — Lower  Molasse,  or  Lower 
Miocene — Dense  conglomerates  and  proofs  of  subsidence — Fossil  plants  of 
Lower  Miocene  period  more  tropical — Preponderance  of  arborescent  species — 
Supposed  discordance  in  relative  numbers  of  living  species  of  plants  and  shells 
in  Upper  Miocene  formations — Theory  of  a  Miocene  Atlantis — Whether  the 
American  plants  abounding  in  the  Miocene  of  Europe  migrated  by  a  westerly 
or  an  easterly  route — Objections  derived  from  depth  and  width  of  the  Atlantic — 
Arguments  in  favor  of  a  Trans-Asiatic  migration — Miocene  fossils  of  Oregon — 
Agreement  of  Miocene  corals  of  the  West  Indies  and  Europe  opposed  to  the 
theory  of  an  Atlantic  Continent — Upper  Miocene  formations  of  India — Sub- 
Himalayan  or  Siwalik  Hills — Older  Pliocene  and  Miocene  formations  in  the 
United  States  of  America,  -  -  248 

CHAPTER  XVI. — Eocene  Formations. 

Upper  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  mammalia — Boundary-line  between 
Lower  Miocene  and  Eocene — Fossils  of  Barton  Clay — British  Middle  Eocene — 
Shells,  nummulites,  fishes,  and  reptiles  of  the  Bagshot  and  Bracklesham  beds — 
Vegetation  of  Middle  Eocene  period — Lower  Eocene  strata  of  England — Fossil 
plants  and  shells  of  the  London  Clay  proper — Strata  of  Kyson  in  Suffolk — Plas- 
tic clays  and  sands — Thanet  sands — Eocene  formations  of  France — Gypseous 
series  of  Montmartre  and  extinct  quadrupeds — Fossil  footprints — Calcaire  gros- 
sier — Miliolites — Lower  Eocene  in  France — Nummulitic  formations  of  Europe, 
Africa,  and  Asia  —Their  wide  extent — Referable  to  the  Middle  Eocene  period — 
Eocene  strata  in  the  United  States — Section  at  Claiborne,  Alabama — Colossal 
cetacean — Orbitoidal  limestone— Burr  stone,  -  280 

CHAPTER  XVII. — Crelaceow  Group. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods — Whether  certain  forma- 
tions in  Belgium  and  France  are  of  intermediate  age — Pisolitic  limestone — Divis- 
ions of  the  Cretaceous  series  in  North- Western  Europe — Maestricht  beds — Chalk 
of  Faxoe — White  chalk — Its  geographical  extent  and  origin — Formed  in  an  open 
and  deep  sea — How  far  derived  from  shells  and  corals — A  similar  rock  now  in 
progress  in  the  depths  of  the  Atlantic  made  up  of  Globigerinae — Origin  of  Flint 


CONTENTS. 

Al 

in  Chalk — Siliceous  Diatomacese  of  the  Atlantic — By  what  intermittent  action 
the  alternate  layers  of  white  chalk  and  flint  may  have  been  caused — Pot- 
stones  of  Horstead — Isolated  pebbles  of  quartz  and  foreign  rocks  in  chalk 

Fossils  of  the  Upper  Cretaceous  rocks  —  Echinoderms,  Mollusca,  Bryozoa, 
Sponges — Upper  Greensand  and  Gault — Blackdown  beds — Flora  of  the  Upper 
Cretaceous  period — Fossil  plants  of  Aix-la-Chapelle — Large  proportion  of  Dico- 
tyledonous Angiosperms — Their  coexistence  with  large  extinct  genera  of  reptiles 
— Chalk  of  South  of  Europe — Hippurite  limestone — Cretaceous  rocks  of  the 
United  States,  -  -  PAGE  312 

CHAPTER  XVIII. — Lower  Cretaceous  and  Wealden  Formations. 

Lower  Greensand — Term  "Neocomian" — Atherfield  section,  Isle  of  Wight — Fos- 
sils of  Lower  Greensand — Palseontological  relations  of  the  Upper  and  Lower  Cre- 
taceous strata — Wealden  Formation — Freshwater  strata  intercalated  between  two 
marine  groups— Weald  Clay  and  Hastings  Sand— Tunbridge  rocks — Fossil  shells, 
fish,  and  plants  of  Wealden — Their  relation  to  the  Cretaceous  type — Geographi- 
cal extent  of  Wealden — Movements  in  the  earth's  crust  to  which  the  Wealden 
owed  its  origin  and  submergence,  -  -  341 

CHAPTER  XIX.— Denudation  of  the  Chalk  and  Wealden. 

Physical  geography  of  certain  districts  composed  of  Cretaceous  and  Wealden  strata 
— Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy — Outstanding  pillars  and 
needles  of  chalk — Denudation  of  the  chalk  and  Wealden  in  Surrey,  Kent,  and 
Sussex — Chalk  once  continuous  from  the  North  to  the  South  Downs — Anticlinal 
axis  and  parallel  ridges — Longitudinal  and  transverse  valleys — Chalk  escarp- 
ments— Rise  and  denudation  of  the  strata  gradual — Ridges  formed  by  harder, 
valleys  by  softer  beds — At  what  periods  the  Weald  Valley  was  denuded — Why  no 
alluvium,  or  wreck  of  the  chalk,  in  the  central  district  of  the  Weald — Successive 
periods  of  marine  denudation — The  latest  of  these  posterior  to  the  Upper  Mio- 
cene era — Elephant-bed,  Brighton— Sangatte  Cliff— The  great  escarpments  and 
transverse  valleys  of  the  chalk  mainly  due  to  the  waves  and  tides  of  the  sea — 
Paroxysmal  causes  unnecessary  for  explaining  the  external  configuration  of  the 
Wealden,  -  -  353 

CHAPTER  XX. — Jurassic  Group — Purbeck  Beds  and  Oolite. 

The  Purbeck  beds  a  member  of  the  Jurassic  group — Subdivisions  of  that  group — 
Physical  geography  of  the  Oolite  in  England  and  France — Upper  Oolite — Purbeck 
beds — New  genera  of  fossil  mammalia  in  the  Middle  Purbeck  of  Dorsetshire — 
Dirt-bed  or  ancient  soil — Fossils  of  the  Purbeck  beds — Portland  stone  and  fossils 
— Lithographic  stone  of  Solenhofen — Arehseopteryx — Middle  Oolite — Coral  rag — 
Zoophytes — Nerinjean  limestone — Diceras  limestone — Oxford  clay,  Ammonites, 
and  Belemnites — Kelloway  Rock — Lower  Oolite,  Crinoideans — Great  Oolite  and 
Bradford  clay — Stonesfield  slate — Fossil  mammalia — Resemblance  to  an  Austra- 
lian fauna — Northamptonshire  slates — Yorkshire  Oolitic  coal-field — Brora  coal — 
Fuller's  earth — Inferior  Oolite  and  fossils — Paloeontological  relations  of  the  sev- 
eral subdivisions  of  the  Oolitic  group,  -  -  -  377 

CHAPTER  XXI. — Jurassic  Group,  continued — Lias. 

Mineral  character  of  Lias — Numerous  successive  Zones  in  the  Lias,  marked  by  dis- 
tinct fossils,  without  unconformity  in  the  stratification,  or  change  in  the  mineral 
character  of  the  deposits — Name  of  Gryphite  limestone — Fossil  shells  and  fish — 
Radiata— Ichthyodorulites — Reptiles  of  the  Lias — Ichthyosaur  and  Plesiosaur — 


Xii  CONTENTS. 

Marine  Reptile  of  the  Galapagos  Islands — Sudden  destruction  and  burial  of  fos- 
sil animals  in  Lias — Fluvio-marine  beds  in  Gloucestershire,  and  insect  limestone 
— Fossil  plants — Origin  of  the  Oolite  and  Lias,  and  of  alternating  calcareous  and 
argillaceous  formations,  -  -  PAGE  415 

CHAPTER  XXII. — Trias  or  New  Red  Sandstone  Group. 

Distinction  between  New  and  Old  Red  Sandstone — Between  Upper  and  Lower  New 
Red — The  Trias  and  its  three  divisions — Most  largely  developed  in  Germany — 
Recognition  of  a  Marine  equivalent  of  the  Upper  Trias  in  the  Austrian  Alps — 
True  position  of  the  St.  Cassian  and  Hallstadt  Beds — 800  new  species  of  triassic 
Mollusca  and  Radiata — Links  thus  supplied  for  connecting  the  Palaeozoic  and 
Neozoic  faunas — Keuper  and  its  fossils— Muschelkalk  and  fossils — Fossil  plants 
of  the  Bunter — Triassic  group  in  England — Bone-bed  of  Axmouth  and  Aust — 
Red  Sandstone  of  Warwickshire  and  Cheshire — Footsteps  of  Cheirotherium  in 
England  and  Germany — Osteology  of  the  Labyrinthodon — Whether  this  Batra- 
chian  was  identical  with  Cheirotherium — Dolomitic  Conglomerate  of  Bristol — 
Origin  of  Red  Sandstone  and  Rock-salt — Hypothesis  of  saline  volcanic  exhala- 
tions— Theory  of  the  precipitation  of  salt  from  inland  lakes  or  lagoons — Saltness 
of  the  Red  Sea — Triassic  coal-field  of  Eastern  Virginia,  near  Richmond — New 
Red  Sandstone  in  the  United  States — Fossil  footprints  of  birds  and  reptiles  in  the 
valley  of  the  Connecticut — Antiquity  of  the  Red  Sandstone  containing  them — 
Triassic  mammifer  of  North  Carolina,  -  431 

CHAPTER  XXIII. — Permian  or  Magnesian  Limestone  Group. 

Fossils  of  Magnesian  Limestone  and  Lower  New  Red  distinct  from  the  Triassic — 
Term  "  Permian  " — English  and  German  equivalents — Marine  shells  and  corals 
of  English  Magnesian  Limestone — Palaeoniscus  and  other  fish  of  the  marl-slate — 
Zechstein  and  Rothh'egendes  of  Thuringia — Permian  Flora — Its  generic  affinity 
to  the  Carboniferous — Psaronites  or  tree-ferns,  -  -  458 

CHAPTER  XXIV. — The  Coal,  or  Carboniferous  Group. 

Carboniferous  strata  in  the  southwest  of  England — Superposition  of  Coal-measures 
to  Mountain  Limestone — Departure  from  this  type  in  North  of  England  and 
Scotland — Carboniferous  series  in  Ireland — Section  in  South  Wales — Under-clays 
with  Stigmaria — Carboniferous  Flora — Ferns,  Lepidodendra,  Equisetaccse,  Cala- 
mites,  Asterophyllites,  Sigillariae,  Stigmarise — Coniferse — Sternbergia — Trigono- 
carpon— Grade  of  Conifers  in  the  Vegetable  Kingdom — Absence  of  Angiospcrms 
— Coal,  how  formed — Erect  fossil  trees — Parkfield  Colliery — St.  Etienne  Coal- 
field— Oblique  trees  or  snags — Fossil  forests  in  Nova  Scotia — Rain-prints — Purity 
of  the  Coal  explained — Time  required  for  the  accumulation  of  the  Coal-measures 
— Brackish-water  and  marine  strata — Crustaceans  of  the  Coal — Origin  of  Clay 
iron-stone,  -  .....  465 

CHAPTER  XXV. —  Carboniferous  Group)  continued. 

Coal-fields  of -the  United  States— Section  of  the  country  between  the  Atlantic  and 
Mississippi — Position  of  land  in  the  carboniferous  period  eastward  of  the  Alle- 
ghanies — Mechanically  formed  rocks  thinning  out  westward,  and  limestones 
thickening — Uniting  of  many  coal-seams  into  one  thick  bed — Horizontal  coal 
at  Brownsville,  Pennsylvania — Vast  extent  and  continuity  of  single  seams  of 
coal— Ancient  river-channel  in  Forest  of  Dean  coal-field — Climate  of  car- 
boniferous period — Insects  in  coal — Rarity  of  air-breathing  animals — Great 
number  of  fossil  fish— First  discovery  of  the  skeletons  of  fossil  reptiles — Foot- 


CONTENTS.  x[ft 

prints  of  reptilians — First  land-shell  found — Rarity  of  air-breathers,  whether 
vertebrate  or  invertebrate,  in  Coal-measures — Mountain  limestone — Its  corals  and 
marine  shells,  -  PAGE  496 

CHAPTER  XXVI. —  Old  Red  Sandstone,  or  Devonian  Group. 

Old  Red  Sandstone  of  the  Borders  of  Wales — Of  Scotland  and  the  South  of  Ire- 
land— Fossil  Devonian  plants  at  Kilkenny — Holoptychius  of  the  Middle  and 
Cephalaspis  of  the  Lower  Old  Red  of  Forfarshire — Pterygotus  and  supposed 
eggs  of  Crustaceans — Northern  type  of  Old  Red  in  Scotland — Classification  of 
the  Ichthyolites  of  the  Old  Red,  and  their  relation  to  living  types — Distinct 
lithological  type  of  Old  Red  in  Devon  and  Cornwall — Term  "Devonian" — Or- 
ganic remains  of  intermediate  character  between  those  of  the  Carboniferous  and 
Silurian  systems — Devonian  series  of  England  and  the  Continent — Upper  Devo- 
nian rocks  and  fossils — Middle — Lower — Old  Red  Sandstone  of  Russia — Prepon- 
derance of  Brachiopoda — Devonian  strata  of  the  United  States  and  Canada — 
Coral  reefs  at  the  falls  of  the  Ohio — Gaspe  Sandstone — Vegetation  of  the  Devo- 
nian period,  -  -  -  523 

CHAPTER  XXVII. — Silurian  and  Cambrian  Groups. 

Silurian  strata  formerly  called  Transition — Term  u  Grauwacke  " — Subdivisions  of 
Upper,  Middle,  and  Lower  Silurians — Ludlow  formation  and  fossils — Oldest 
known  remains  of  fossil  fish — Wenlock  formation,  corals,  cystideans,  trilobites — 
Middle  Silurian  or  Llandovery  Beds — Lower  Silurian  rocks — Caradoc  and  Bala 
Beds — Upper  and  Lower  Llandeilo  formations — Cystidese — Trilobites— Grapto- 
lites — Vast  thickness  of  Lower  Silurian  strata,  sedimentary  and  volcanic,  hi 
Wales — Foreign  Silurian  equivalents  in  Europe — Silurian  strata  of  the  United 
States — Amount  of  specific  agreement  of  fossils  with  those  of  Europe — Canadian 
equivalents — Whether  Silurian  strata  of  deep-sea  origin — Cambrian  rocks — 
Classification  and  nomenclature — Barrande's  primordial  fauna — Upper  Cam- 
brian of  .Wales — Tremadoc  slates  —  Lingula  flags — Lower  Cambrian  —  Long- 
mynd  group — Oldest  organic  remains  known  in  Europe — Foreign  equivalents  of 
the  Cambrian  group — Primordial  zone  of  Bohemia — Characteristic  trilobites — 
Metamorphosis  of  trilobites — Alum  schists  of  Sweden  and  Norway — Potsdam 
sandstone  of  United  States  and  Canada — Footprints  near  Montreal — Quebec 
strata  and  Huronian  rocks— Minnesota  trilobites — Rocks  older  than  the  Cam- 
brian— Laurentian  group,  Upper  and  Lower — Oldest  known  fossil,  Eozoon  Cana- 
dense — No  remains  of  vertebrate  animals  known  in  strata  below  the  Upper 
Silurian — Progressive  discovery  of  vertebrata  in  older  rocks — Theoretical  infer- 
ences from  the  rarity  or  absence  of  vertebrata  in  the  most  ancient  fossiliferous 
formations,  -  ...  649 

.  CHAPTER  XXVEH.—  Volcanic  Rocks. 

Trap  Rocks — Name,  whence  derived — Their  igneous  origin  at  first  doubted — Their 
general  appearance  and  character — Volcanic  cones  and  craters,  how  formed — 
Mineral  composition  and  texture  of  volcanic  rocks — Varieties  of  felspar — 
Hornblende  and  augite — Isomorphism — Rocks,  how  to  be  studied — Basalt, 
trachyte,  greenstone,  porphyry,  scoria,  amygdaloid,  lava,  tuff—  Agglomerate-— 
Laterite — Alphabetical  list,  and  explanation  of  names  and  synonyms,  of  volcanic 
rocks — Table  of  the  analyses  of  minerals  most  abundant  in  the  volcanic  and 
hypogene  rocks, 

CHAPTER  XXIX. —  Volcanic  Rocks,  continued. 

Trap  dikes — sometimes  project — sometimes  leave  fissures  vacant  by  decomposi- 
tion— Branches  and  veins  of  trap— Dikes  more  crystalline  in  the  centre — 


xiv  CONTENTS. 

Strata  altered  at  or  near  the  contact — Obliteration  of  organic  remains — Con- 
version of  chalk  into  marble— Trap  interposed  between  strata— Columnar  and 
globular  structure — Relation  of  trappean  rocks  to  the  products  of  active  vol- 
canoes— Form,  external  structure,  and  origin  of  volcanic  mountains — Craters 
and  Calderas — Sandwich  Islands— Lava  flowing  underground — Truncation  of 
cones — Javanese  calderas — Canary  Islands — Structure  and  origin  of  the  Cal- 
dera  of  Palma — Older  and  newer  volcanic  rocks  in,  unconformable — Aqueous 
conglomerate  in  Palma — Hypothesis  of  upheaval  considered — Slope  on  which 
stony  lavas  may  form — Extent  and  nature  of  aqueous  erosion  in  Palma — Island 
of  St.  Paul  in  the  Indian  Ocean — Peak  of  Teneriffe,  and  ruins  of  older  cone — 
Madeira — Its  volcanic  rocks,  partly  of  marine,  and  partly  of  subaerial  origin — 
Central  axis  of  eruptions — Varying  dip  of  solid  lavas  near  the  axis,  and  further 
from  it — Leaf-bed,  and  fossil  land-plants — Central  valleys  of  Madeira  not  craters, 
or  calderas,  -  -  PAGE  609 

CHAPTER  XXX. —  On  the  different  Ages  of  the  Volcanic  Rocks. 

Tests  of  relative  age  of  volcanic  rocks — Tests  by  superposition  and  intrusion — 
Test  by  alteration  of  rocks  in  contact — Test  by  organic  remains — Test  of  age 
by  mineral  character — Test  by  included  fragments — Volcanic  rocks  of  the  Post- 
Pliocene  period — Basalt  of  the  Bay  of  Trezza  in  Sicily — Post-Pliocene  volcanic 
rocks  near  Naples — Dikes  of  Somma,  -  655 


CHAPTER  XXXI. — On  the  different  Ages  of  the  Volcanic  Rocks,  continued. 

Volcanic  rocks  of  the  Newer  Pliocene  period — Val  di  Noto — Sicilian  dikes — Region 
of  Olot  in  Catalonia — Volcanic  rocks  of  the  Older  Pliocene  period — Tuscany — 
Rome — Volcanic  region  of  Olot  in  Catalonia — Cones  and  lava-currents — Ravines 
and  ancient  gravel-beds — Jets  of  air  called  Bufadors — Age  of  the  Catalonian 
volcanoes — Upper  Miocene  period — Volcanic  archipelagoes  of  Madeira,  the  Ca- 
naries, and  the  Azores — Lower  Miocene  period — Brown-coal  of  the  Eifel  and 
contemporaneous  trachytic  breccias — Age  of  the  brown-coal — Peculiar  characters 
of  the  volcanoes  of  the  upper  and  lower  Eifel — Lake  Craters — Trass — Hungarian 
volcanoes,  ....  ....  665 

CHAPTER  XXXII. — On  the  different  Ages  of  the  Volcanic  Rocks,  continued. 

Volcanic  rocks  of  the  Tertiary  period,  continued — Extinct  volcanoes  of  Auvergne — 
Mont  Dor — Breccias  and  alluviums  of  Mont  Perrier,  with  bones  of  quadrupeds — 
River  dammed  up  by  lava-current — Range  of  minor  cones  from  Auvergne  to  the 
Vivarais — Monts  Dome — Puy  de  Come— Puy  de  Pariou — Cones  not  denuded  by 
general  flood — Lower  Miocene  volcanic  rocks  near  Clermont — Hill  of  Gergovia — 
Eocene  volcanic  rocks  of  Monte  Bolca — Trap  of  Cretaceous  period— Oolitic  pe- 
riod— New  Red  Sandstone  period — Carboniferous  period — "  Rock  and  Spindle  " 
near  St.  Andrew's — Old  Red  Sandstone  period — Silurian  period — Cambrian  pe- 
riod— Laurentian  volcanic  rocks,  ...  -  684 

CHAPTER  XXXIII.— Plutonic  RocTcs— Granite. 

General  aspect  of  granite — Decomposing  into  spherical  masses — Rude  columnar 
structure — Analogy  and  difference  of  volcanic  and  plutonic  formations — Minerals 
in  granite,  and  their  arrangement — Graphic  and  porphyritic  granite — Mutual 
penetration  of  crystals  of  quartz  and  felspar — Occasional  minerals — Syenite — 
Syenitic,  talcose,  and  schorly  granites — Eurite — Passage  of  granite  into  trap — 
Examples  near  Christiania  and  in  Aberdeenshire — Analogy  in  composition  of 


CONTENTS.  xv 

trachyte  and  granite — Granite  veins  in  Glen  Tilt,  Cornwall,  the  Valorsine,  and 

other  countries — Different  composition  of  veins  from  main  body  of  granite 

Metalliferous  veins  in  strata  near  their  junction  with  granite — Apparent  isolation 
of  nodules  of  granite — Quartz  veins — Whether  plutonic  rocks  are  ever  overlying 
— Their  exposure  at  the  surface  due  to  denudation,  -  -  PAGE  702 


CHAPTER  XXXIV.—  On  the  different  Ages  of  the  Plutonic  Rocks. 

Difficulty  in  ascertaining  the  precise  age  of  a  plutonic  rock — Test  of  age  by  relative 
position — Test  by  intrusion  and  alteration — Test  by  mineral  composition — Test 
by  included  fragments — Recent  and  Pliocene  plutonic  rocks,  why  invisible — Ter- 
tiary plutonic  rocks  in  the  Andes — Granite  altering  Cretaceous  rocks — Granite 
altering  Lias  in  the  Alps  and  in  Skye — Granite  of  Dartmoor  altering  Carbonifer- 
ous strata — Granite  of  the  Old  Red  Sandstone  period — Syenite  altering  Silurian 
strata  in  Norway — Blending  of  the  same  with  gneiss — Most  ancient  plutonic 
rocks — Granite  protruded  in  a  solid  form — On  the  probable  age  of  the  granites 
of  Arran,  in  Scotland,  -  _.  •  i  -  -  -  -717 


CHAPTER  XXXV.— Metamorphic  Rocks. 

General  character  of  metamorphic  rocks — Gneiss — Hornblende-schist — Mica-schist — 
Clay-slate — Quartzite — Chlorite-schist — Metamorphic  limestone — Alphabetical  list 
and  explanation  of  the  more  abundant  rocks  of  this  family — Origin  of  the  meta- 
morphic strata — Their  stratification — Fossiliferous  strata  near  intrusive  masses 
of  granite  converted  into  rocks  identical  with  different  members  of  the  metamor- 
phic series — Arguments  hence  derived  as  to  the  nature  of  plutonic  action — Time 
may  enable  this  action  to  pervade  denser  masses — From  what  kinds  of  sedi- 
mentary rock  each  variety  of  the  metamorphic  class  may  be  derived — Certain 
objections  to  the  metamorphic  theory  considered — Partial  conversion  of  Eocene 
slate  into  gneiss,  --------  732 


CHAPTER  XXXVI. — Metamorphic  Roclcs,  continued. 

Definition  of  joints,  slaty  cleavage,  and  foliation — Supposed  causes  of  these  struc- 
tures— Mechanical  theory  of  cleavage — Condensation  and  elongation  of  slate 
rocks  by  lateral  pressure — Supposed  combination  of  crystalline  and  mechanical 
forces — Lamination  of  some  volcanic  rocks  due  to  motion — Whether  the  folia- 
tion of  the  crystalline  schists  be  usually  parallel  with  the  original  planes  of  strati- 
fication— Examples  in  Norway  and  Scotland — Foliation  in  homogeneous  rocks 
may  coincide  with  planes  of  cleavage,  and  in  uncleaved  rocks  with  those  of 
stratification — Causes  of  irregularity  in  the  planes  of  foliation,  -  -  746 


CHAPTER  XXXVII.— On  the  different  Ages  of  the  Metamorphic  Rocks. 

Age  of  eacTi  set  of  metamorphic  strata  twofold — Test  of  age  by  fossils  and  mineral 
character  not  available — Test  by  superposition  ambiguous — Conversion  of  dense 
masses  of  fossiliferous  strata  into  metamorphic  rocks — Limestone  and  shale  of 
Carrara — Metamorphic  strata  of  older  date  than  the  Cambrian  rocks — Others  of 
Lower  Silurian  origin — Others  of  the  Jurassic  and  Eocene  periods  in  the  Alps 
of  Switzerland  and  Savoy — Why  scarcely  any  of  the  visible  crystalline  strata 
are  very  modern — Order  of  succession  in  metamorphic  rocks — Uniformity  of 
mineral  character — Why  the  metamorphic  strata  are  less  calcareous  than  the 
fossiliferous,  ...  -  758 


xvi  CONTENTS. 

CHAPTER  XXXVIII.— Mineral  Veins. 

Werner's  doctrine  that  mineral  veins  were  fissures  filled  from  above — Veins  of 
segregation — Ordinary  metalliferous  veins  or  lodes — Their  frequent  coincidence 
with  faults — Proofs  that  they  originated  in  fissures  in  solid  rock — Veins  shifting 
other  veins — Polishing  of  their  walls  or  "  slicken-sides  " — Shells  and  pebbles  in 
lodes — Evidence  of  the  successive  enlargement  and  reopening  of  veins — Four- 
net's  observations  in  Auvergne — Dimensions  of  veins — Why  some  alternately 
swell  out  and  contract — Filling  of  lodes  by  sublimation  from  below — Chemical 
and  electrical  action — Relative  age  of  the  precious  metals — Copper  and  lead 
veins  in  Ireland  older  than  Cornish  tin — Lead  vein  in  lias,  Glamorganshire — 
Gold  in  Russia,  California,  and  Australia — Connection  of  hot  springs  and  min- 
eral veins — Concluding  remarks,  -  -  PAGE  767 


ELEMENTS  OF  GEOLOGY. 


CHAPTER  I. 

ON    THE    DIFFERENT    CLASSES    OF    ROCKS. 

Geology  defined — Successive  formation  of  the  earth's  crust — Classification  of 
rocks  according  to  their  origin  and  age — Aqueous  rocks — Their  stratification 
and  imbedded  fossils — Volcanic  rocks,  with  and  without  cones  and  craters — 
Plutonic  rocks,  and  their  relation  to  the  volcanic — Metamorphic  rocks  and  their 
probable  origin — The  term  primitive,  why  erroneously  applied  to  the  crystal- 
line formations — Leading  division  of  the  work. 

OF  what  materials  is  the  earth  composed,  and  in  what  manner  are  these 
materials  arranged  ?  These  are  the  first  inquiries  with  which  Geology 
is  occupied,  a  science  which  derives  its  name  from  the  Greek  y5j,  ye,  the 
earth,  and  Xoyo£,  logos,  a  discourse.  Previously  to  experience,  we  might 
have  imagined  that  investigations  of  this  kind  would  relate  exclusively 
to  the  mineral  kingdom,  and  to  the  various  rocks,  soils,  and  metals, 
which  occur  upon  the  surface  of  the  earth,  or  at  various  depths  beneath 
it.  But,  in  pursuing  such  researches,  we  soon  find  ourselves  led  on  to 
consider  the  successive  changes  which  have  taken  place  in  the  former 
state  of  the  earth's  surface  and  interior,  and  the  causes  which  have  given 
rise  to  these  changes  ;  and,  what  is  still  more  singular  and  unexpected, 
we  soon  become  engaged  in  researches  into  the  history  of  the  animate 
creation,  or  of  the  various  tribes  of  animals  and  plants  which  have,  at 
different  periods  of  the  past,  inhabited  the  globe. 

All  are  aware  that  the  solid  parts  of  the  earth  consist  of  distinct  sub- 
stances, such  as  clay,  chalk,  sand,  limestone,  coal,  slate,  granite,  and  thf 
like;  but  previously  to  observation  it  is  commonly  imagined  that  all 
these  had  remained  from  the  first  in  the  state  in  which  we  now  see 
them, — that  they  were  created  in  their  present  form,  and  in  their  present 
position.  The  geologist  soon  comes  to  a  different  conclusion,  discovering 
proofs  that  the  external  parts  of  the  earth  were  not  all  produced  in  the 
beginning  of  things,  in  the  state  in  which  we  now  behold  them,  nor  in 
an  instant  of  time.  On  the  contrary,  he  can  show  that  they  have  acquired 
their  actual  configuration  and  condition  gradually,  under  a  great  variety 

1 


2  CLASSIFICATION  OF  EOCKS.  [Cn.  1. 

of  circumstances,  and  at  successive  periods,  during  each  of  which  distinct 
races  of  living  beings  have  flourished  on  the  land  and  in  the  waters,  the 
remains  of  these  creatures  still  lying  buried  in  the  crust  of  the  earth. 

By  the  "  earth's  crust,"  is  meant  that  small  portion  of  the  exterior  of 
our  planet  which  is  accessible  to  human  observation,  or  on  which  we  are 
enabled  to  reason  by  observations  made  at  or  near  the  surface.  These 
reasonings  may  extend  to  a  depth  of  several  miles,  perhaps  ten  miles  ; 
and  even  then  it  may  be  said,  that  such  a  thickness  is  no  more  than  ^^ 
part  of  the  distance  from  the  surface  to  the  centre.  The  remark  is  just ; 
but  although  the  dimensions  of  such  a  crust  are,  in  truth,  insignificant 
when  compared  to  the  entire  globe,  yet  they  are  vast,  and  of  magnificent 
extent  in  relation  to  man,  and  to  the  organic  beings  which  people  our 
globe.  Referring  to  this  standard  of  magnitude,  the  geologist  may 
admire  the  ample  limits  of  his  domain,  and  admit,  at  the  same  time, 
that  not  only  the  exterior  of  the  planet,  but  the  entire  earth,  is  but  an 
atom  in  the  midst  of  the  countless  worlds  surveyed  by  the  astronomer. 

The  materials  of  this  crust  are  not  thrown  together  confusedly ;  but 
distinct  mineral  masses,  called  rocks,  are  found  to  occupy  definite  spaces, 
and  to  exhibit  a  certain  order  of  arrangement.  The  term  rock  is  applied 
indifferently  by  geologists  to  all  these  substances,  whether  they  be  soft  or 
stony,  for  clay  and  sand  are  included  in  the  term,  and  some  have  even 
brought  peat  under  this  denomination.  Our  older  writers  endeavored 
to  avoid  offering  such  violence  to  our  language,  by  speaking  of  the  com- 
ponent materials  of  the  earth  as  consisting  of  rocks  and  soils.  But  there 
is  often  so  insensible  a  passage  from  a  soft  and  incoherent  state  to  that 
of  stone,  that  geologists  of  all  countries  have  found  it  indispensable  to 
have  one  technical  term  to  include  both,  and  in  this  sense  we  find  roche 
applied  in  French,  rocca  in  Italian,  andfelsart  in  German.  The  beginner, 
however,  must  constantly  bear  in  mind,  that  the  term  rock  by  no  means 
implies  that  a  mineral  mass  is  in  an  indurated  or  stony  condition. 

The  most  natural  and  convenient  mode  of  classifying  the  various  rocks 
which  compose  the  earth's  crust,  is  to  refer,  in  the  first  place,  to  their 
origin,  and  in  the  second  to  their  relative  age.  I  shall  therefore  begin 
by  endeavoring  briefly  to  explain  to  the  student  how  all  rocks  may  be 
divided  into  four  great  classes  by  reference  to  their  different  origin,  or,  in 
other  words,  by  reference  to  the  different  circumstances  and  causes  by 
which  they  have  been  produced. 

The  first  two  divisions,  which  will  at  once  be  understood  as  natural, 
are  the  aqueous  and  volcanic,  or  the  products  of  watery  and  those  of 
igneous  action  at  or  near  the  surface. 

Aqueous  rocks. — The  aqueous  rocks,  sometimes  called  the  sedimentary, 
or  fossiliferous,  cover  a  larger  part  of  the  earth's  surface  than  any  others. 
These  rocks  are  stratified,  or  divided  into  distinct  layers,  or  strata.  The 
term  stratum  means  simply  a  bed,  or  any  thing  spread  out  or  strewed 
over  a  given  surface  ;  and  we  infer  that  these  strata  have  been  generally 
spread  out  by  the  action  of  water,  from  what  we  daily  see  taking  place 
near  the  mouths  of  rivers,  or  on  the  land  during  temporary  inundations. 


CH.  I]  AQUEOUS  ROCKS.  3 

For,  whenever  a  running  stream  charged  with  mud  or  sand,  has  its  ve- 
locity checked,  as  when  it  enters  a  lake  or  sea,  or  overflows  a  plain,  the 
sediment,  previously  held  in  suspension  by  the  motion  of  the  water 
sinks,  by  its  own  gravity,  to  the  bottom.  In  this  manner  layers  of  mud 
and  sand  are  thrown  down  one  upon  another. 

If  we  drain  a  lake  which  has  been  fed  by  a  small  stream,  we  frequently 
find  at  the  bottom  a  series  of  deposits,  disposed  with  considerable  regu- 
larity, one  above  the  other ;  the  uppermost,  perhaps,  may  be  a  stratum 
of  peat,  next  below  a  more  dense  and  solid  variety  of  the  same  material ; 
still  lower  a  bed  of  shell-marl,  alternating  with  peat  or  sand,  and  then 
other  beds  of  marl,  divided  by  layers  of  clay.  Now,  if  a  second  pit  be 
sunk  through  the  same  continuous  lacustrine  formation,  at  some  distance 
from  the  first,  nearly  the  same  series  of  beds  is  commonly  met  with,  yet 
with  slight  variations  ;  some,  for  example,  of  the  layers  of  sand,  clay,  or 
marl,  may  be  wanting,  one  or  more  of  them  having  thinned  out  and 
given  place  to  others,  or  sometimes  one  of  the  masses  first  examined  is 
observed  to  increase  in  thickness  to  the  exclusion  of  other  beds. 

The  term  "formation"  which  I  have  used  in  the  above  explanation, 
expresses  in  geology  any  assemblage  of  rocks  which  have  some  character 
in  common,  whether  of  origin,  age,  or  composition.  Thus  we  speak  of 
stratified  and  unstratified,  freshwater  and  marine,  aqueous  and  volcanic, 
ancient  and  modern,  metalliferous  and  non-metalliferous  formations. 

In  the  estuaries  of  large  rivers,  such  as  the  Ganges  and  the  Mississippi, 
we  may  observe,  at  low  water,  phenomena  analogous  to  those  of  the 
drained  lakes  above  mentioned,  but  on  a  grander  scale,  and  extending 
over  areas  several  hundred  miles  in  length  and  breadth.  When  the  pe- 
riodical inundations  subside,  the  river  hollows  out  a  channel  to  the  depth 
of  many  yards  through  horizontal  beds  of  clay  and  sand,  the  ends  of 
which  are  seen  exposed  in  perpendicular  cliffs.  These  beds  vary  in  their 
mineral  composition,  or  color,  or  in  the  fineness  or  coarseness  of  their 
particles,  and  some  of  them  are  occasionally  characterized  by  containing 
drift-wood.  At  the  junction  of  the  river  and  the  sea,  especially  in  la- 
goons nearly  separated  by  sand-bars  from  the  ocean,  deposits  are  often 
formed  in  which  brackish-water  and  salt-water  shells  are  included. 

In  Egypt,  where  the  Nile  is  always  adding  to  its  delta  by  filling  up 
part  of  the  Mediterranean  with  mud,  the  newly-deposited  sediment  is 
stratified,  the  thin  layer  thrown  down  in  one  season  differing  slightly 
in  color  from  that  of  a  previous  year,  and  being  separable  from  it,  as 
has  been  observed  in  excavations  at  Cairo,  and  other  places.* 

When  beds  of  sand,  clay,  and  marl,  containing  shells  and  vegetable 
matter,  are  found  arranged  in  a  similar  manner  in  the  interior  of  the 
earth,  we  ascribe  to  them  a  similar  origin ;  and  the  more  we  examine 
their  characters  in  minute  detail,  the  more  exact  do  we  find  the  resem- 
blance. Thus,  for  example,  at  various  heights  and  depths  in  the  earth, 
and  often  far  from  seas,  lakes,  and  rivers,  we  meet  with  layers  of  rounded 

*  See  Principles  of  Geology,  by  the  Author,  Index,  "Nile,"  "  Rivers,"  (fee. 


4  AQUEOUS  EOCKS.  [Cn.  1 

pebbles  composed  of  flint,  limestone,  granite,  or  other  rocks,  resembling 
the  shingles  of  a  sea-beach  or  the  gravel  in  a  torrent's  bed.  Such  layers 
of  pebbles  frequently  alternate  with  others  formed  of  sand  or  fine  sedi- 
ment, just  as  we  may  see  in  the  channel  of  a  river  descending  from  hills 
bordering  a  coast,  where  the  current  sweeps  down  at  one  season  coarse 
sand  and  gravel,  while  at  another,  when  the  waters  are  low  and  less  rapid, 
fine  mud  and  sand  alone  are  carried,seaward.* 

If  a  stratified  arrangement,  and  the  rounded  form  of  pebbles,  are  alone 
sufficient  to  lead  us  to  the  conclusion  that  certain  rocks  originated  under 
water,  this  opinion  is  farther  confirmed  by  the  distinct  and  independent 
evidence  of  fossils,  so  abundantly  included  in  the  earth's  crust.  By  a 
fossil  is  meant  any  body,  or  the  traces  of  the  existence  of  any  body, 
whether  animal  or  vegetable,  which  has  been  buried  in  the  earth  by 
natural  causes.  Now  the  remains  of  animals,  especially  of  aquatic  species, 
are  found  almost  everywhere  imbedded  in  stratified  rocks,  and  sometimes, 
in  the  case  of  limestone,  they  are  in  such  abundance  as  to  constitute  the 
entire  mass  of  the  rock  itself.  Shells  and  corals  are  the  most  frequent, 
and  with  them  are  often  associated  the  bones  and  teeth  of  fishes,  frag- 
ments of  wood,  impressions  of  leaves,  and  other  organic  substances.  Fossil 
shells,  of  forms  such  as  now  abound  in  the  sea,  are  met  with  far  inland, 
both  near  the  surface,  and  at  great  depths  below  it.  They  occur  at  all 
heights  above  the  level  of  the  ocean,  having  been  observed  at  elevations 
of  more  than  8000  feet  in  the  Pyrenees,  10,000  in  the  Alps,  13,000  in 
the  Andes,  and  above  18,000  feet  in  the  Himalaya.f 

These  shells  belong  mostly  to  marine  testacea,  but  in  some  places 
exclusively  to  forms  characteristic  of  lakes  and  rivers.  Hence  it  is  con- 
cluded that  some  ancient  strata  were  deposited  at  the  bottom  of  the  sea, 
and  others  in  lakes  and  estuaries. 

When  geology  was  first  cultivated,  it  was  a  general  belief,  that  these 
marine  shells  and  other  fossils  were  the  effects  and  proofs  of  the  deluge 
of  Noah  ;  but  all  who  have  carefully  investigated  the  phenomena  have 
long  rejected  this  doctrine.  A  transient  flood  might  be  supposed  to  leave 
behind  it,  here  and  there  upon  the  surface,  scattered  heaps  of  mud,  sand, 
and  shingle,  with  shells  confusedly  intermixed  ;  but  the  strata  containing 
fossils  are  not  superficial  deposits,  and  do  not  simply  cover  the  earth,  but 
constitute  the  entire  mass  of  mountains.  Nor  are  the  fossils  mingled 
without  reference  to  the  original  habits  and  natures  of  the  creatures  of 
which  they  are  the  memorials ;  those,  for  example,  being  found  associated 
together  which  lived  in  deep  or  in  shallow  water,  near  the  shore  or  far 
from  it,  in  brackish  or  in  salt  water. 

It  has,  moreover,  been  a  favorite  notion  of  some  modern  writers,  who 
were  aware  that  fossil  bodies  could  not  all  be  referred  to  the  deluge, 
that  they,  and  the  strata  in  which  they  are  entombed,  might  have  been 
deposited  in  the  bed  of  the  ocean  during  the  period  which  intervened 

*  See  p.  18,  fig.  7. 

f  Capt.  R.  J.  Strachey  found  oolitic  fossils  18,400  feet  high  in  the  Himalaya 


CH.  L]  VOLCANIC  ROCKS.  5 

between  the  creation  of  man  and  the  deluge.  They  have  imagined 
that  the  antediluvian  bed  of  the  ocean,  after  having  been  the  receptacle 
of  many  stratified  deposits,  became  converted,  at  the  time  of  the  flood, 
into  the  lands  which  we  inhabit,  and  that  the  ancient  continents  were  at 
the  same  time  submerged,  and  became  the  bed  of  the  present  seas. 
This  hypothesis,  although  preferable  to  the  diluvial  theory  before  alluded 
to,  since  it  admits  that  all  fossiliferous  strata  were  successively  thrown 
down  from  water,  is  yet  wholly  inadequate  to  explain  the  repeated  revo- 
lutions which  the  earth  has  undergone,  and  the  signs  which  the  existing 
continents  exhibit,  in  most  regions,  of  having  emerged  from  the  ocean  at 
an  era  far  more  remote  than  four  thousand  years  from  the  present  time. 
Ample  proofs  of  these  reiterated  revolutions  will  be  given  in  the  sequel, 
and  it  will  be  seen  that  many  distinct  sets  of  sedimentary  strata,  hundreds 
and  sometimes  thousands  of  feet  thick,  are  piled  one  upon  the  other  in 
the  earth's  crust,  each  containing  peculiar  fossil  animals  and  plants  of 
species  distinguishable  for  the  most  part  from  all  those  now  living. 
The  mass  of  some  of  these  strata  consists  almost  entirely  of  corals,  others 
are  made  up  of  shells,  others  of  plants  turned  into  coal,  while  some  are 
without  fossils.  In  one  set  of  strata  the  species  of  fossils  are  marine ; 
in  another,  lying  immediately  above  or  below,  they  as  clearly  prove 
that  the  deposit  was  formed  in  a  lake  or  brackish  estuary.  When  the 
student  has  more  fully  examined  into  these  appearances,  he  will  become 
convinced  that  the  time  required  for  the  origin  of  the  rocks  composing 
the  actual  continents  must  have  been  far  greater  than  that  which  is  con- 
ceded by  the  theory  above  alluded  to ;  and  likewise  that  no  one 
universal  and  sudden  conversion  of  sea  into  land  will  account  for  geo- 
logical appearances. 

We  have  now  pointed  out  one  great  class  of  rocks,  which,  however 
they  may  vary  in  mineral  composition,  color,  grain,  or  other  characters, 
external  and  internal,  may  nevertheless  be  grouped  together  as  having  a 
common  origin.  They  have  all  been  formed  under  water,  in  the  same 
manner  as  modern  accumulations  of  sand,  mud,  shingle,  banks  of  shells, 
reefs  of  coral,  and  the  like,  and  are  all  characterized  by  stratification  or 
fossils,  or  by  both. 

Volcanic  rocks. — The  division  of  rocks  which  we  may  next  consider 
are  the  volcanic,  or  those  which  have  been  produced  at  or  near  the  sur- 
face whether  in  ancient  or  modern  times,  not  by  water,  but  by  the  action 
of  fire  or  subterranean  heat.  These  rocks  are  for  the  most  part  unstrat- 
ified,  and  are  devoid  of  fossils.  They  are  more  partially  distributed  than 
aqueous  formations,  at  least  in  respect  to  horizontal  extension.  Among 
those  parts  of  Europe  where  they  exhibit  characters  not  to  be  mistaken, 
T  may  mention  not  only  Sicily  and  the  country  round  Naples,  but  Au- 
vergne,  Velay,  and  Vivarais,  now  the  departments  of  Puy  de  Dome, 
Haute  Loire,  and  Ard6che,  towards  the  centre  and  south  of  France,  in 
which  are  several  hundred  conical  hills  having  the  forms  of  modern  vol- 
canoes, with  craters  more  or  less  perfect  on  many  of  their  summits.  These 
cones  are  composed  moreover  of  lava,  sand,  and  ashes,  similar  to  those 


6  VOLCANIC  ROCKS.  [Cn.  1 

of  active  volcanoes.  Streams  of  lava  may  sometimes  be  traced  from  the 
cones  into  the  adjoining  valleys,  where  they  have  choked  up  the  ancient 
channels  of  rivers  with  solid  rock,  in  the  same  manner  as  some  modern 
flows  of  lava  in  Iceland  have  been  known  to  do,  the  rivers  either  flowing 
beneath  or  cutting  out  a  narrow  passage  on  one  side  of  the  lava,  Al- 
though none  of  these  French  volcanoes  have  been  in  activity  within  the 
period  of  history  or  tradition,  their  forms  are  often  very  perfect.  Some, 
however,  have  been  compared  to  the  mere  skeletons  of  volcanoes,  the 
rains  and  torrents  having  washed  their  sides,  and  removed  all  the  loose 
sand  and  scorise,  leaving  only  the  harder  and  more  solid  materials.  By 
this  erosion,  and  by  earthquakes,  their  internal  structure  has  occasionally 
been  laid  open  to  view,  in  fissures  and  ravines  ;  and  we  then  behold  not 
only  many  successive  beds  and  masses  of  porous  lava,  sand,  and  scorise, 
but  also  perpendicular  walls,  or  dikes,  as  they  are  called,  of  volcanic 
rock,  which  have  burst  through  the  other  materials.  Such  dikes  are 
also  observed  in  the  structure  of  Vesuvius,  Etna,  and  other  active 
volcanoes.  They  have  been  formed  by  the  pouring  of  melted  matter, 
whether  from  above  or  below,  into  open  fissures,  and  they  commonly 
traverse  deposits  of  volcanic  tuff,  a  substance  produced  by  the  show- 
ering down  from  the  air,  or  incumbent  waters,  of  sand  and  cinders, 
first  shot  up  from  the  interior  of  the  earth  by  the  explosions  of  volcanic 
gases. 

Besides  the  parts  of  France  above  alluded  to,  there  are  other  countries, 
as  the  north  of  Spain,  the  south  of  Sicily,  the  Tuscan  territory  of  Italy, 
the  lower  Rhenish  provinces,  and  Hungary,  where  spent  volcanoes  may 
be  seen,  still  preserving  in  many  cases  a  conical  form,  and  having  craters 
and  often  lava-streams  connected  with  them. 

There  are  also  other  rocks  in  England,  Scotland,  Ireland,  and  almost 
every  country  in  Europe,  which  we  infer  to  be  of  igneous  origin,  although 
they  do  not  form  hills  with  cones  and  craters.  Thus,  for  example,  we 
feel  assured  that  the  rock  of  Staffa,  and  that  of  the  Giants'  Causeway, 
called  basalt,  is  volcanic,  because  it  agrees  in  its  columnar  structure  and 
mineral  composition  with  streams  of  lava  which  we  know  to  have  flowed 
from  the  craters  of  volcanoes.  We  find  also  similar  basaltic  and  other 
igneous  rocks  associated  with  beds  of  tuff  in  various  parts  of  the  British 
Isles,  and  forming  dikes,  such  as  have  been  spoken  of ;  and  some  of  the 
strata  through  which  these  dikes  cut  are  occasionally  altered  at  the 
point  of  contact,  as  if  they  had  been  exposed  to  the  intense  heat  of 
melted  matter. 

The  absence  of  cones  and  craters,  and  long  narrow  streams  of  super- 
ficial lava,  in  England  and  many  other  countries,  is  principally  to  be 
attributed  to  the  eruptions  having  been  submarine,  just  as  a  considerable 
proportion  of  volcanoes  in  our  own  times  burst  out  beneath  the  sea. 
But  this  question  must  be  enlarged  upon  more  fully  in  the  chapters  on 
Igneous  Rocks,  in  which  it  will  also  be  shown,  that  as  different  sedi- 
mentary formations,  containing  each  their  characteristic  fossils,  have 
been  deposited  at  successive  periods,  so  also  volcanic  sand  and  scorise 


OH.  I]  FLUTOJN1U   BOOKS.  7 

have  been  thrown  out,  and  lavas  have  flowed  over  the  land  or  bed  of  the 
sea,  at  many  different  epochs,  or  have  been  injected  into  fissures;  so  that 
the  igneous  as  well  as  the  aqueous  rocks  may  be  classed  as  a  chronologi- 
cal series  of  monuments,  throwing  light  on  a  succession  of  events  in  the 
history  of  the  earth. 

Plutonic  rocks  (Granite,  &c.). — We  have  now  pointed  out  the  exist- 
ence of  two  distinct  orders  of  mineral  masses,  the  aqueous  and  the 
volcanic  :  but  if  we  examine  a  large  portion  of  a  continent,  especially  if 
it  contain  within  it  a  lofty  mountain  range,  we  rarely  fail  to  discover 
two  other  classes  of  rocks,  very  distinct  from  either  of  those  above 
alluded  to,  and  which  we  can  neither  assimilate  to  deposits  such  as 
are  now  accumulated  in  lakes  or  seas,  nor  to  those  generated  by 
ordinary  volcanic  action.  The  members  of  both  these  divisions  of 
rocks  agree  in  being  highly  crystalline  and  destitute  of  organic  remains. 
The  rocks  of  one  division  have  been  called  plutonic,  comprehending 
all  the  granites  and  certain  porphyries,  which  are  nearly  allied  in 
some  of  their  characters  to  volcanic  formations.  The  members  of  the 
other  class  are  stratified  and  often  slaty,  and  have  been  called  by 
some  the  crystalline  schists,  in  which  group  are  included  gneiss, 
micaceous-schist  (or  mica-slate),  hornblende-schist,  statuary  marble, 
the  finer  kinds  of  roofing  slate,  and  other  rocks  afterwards  to  be 
described. 

As  it  is  admitted  that  nothing  strictly  analogous  to  these  crystalline 
productions  can  now  be  seen  in  the  progress  of  formation  on  the  earth's 
surface,  it  will  naturally  be  asked,  on  what  data  we  can  find  a  place  for 
them  in  a  system  of  classification  founded  on  the  origin  of  rocks.  I 
cannot,  in  reply  to  this  question,  pretend  to  give  the  student,  in  a  few 
words,  an  intelligible  account  of  the  long  chain  of  facts  and  reasonings 
by  which  geologists  have  been  led  to  infer  the  analogy  of  the  rocks  in 
question  to  others  now  in  progress  at  the  surface.  The  result,  however, 
may  be  briefly  stated.  All  the  various  kinds  of  granite,  which  'consti- 
tute the  plutonic  family,  are  supposed  to  be  of  igneous  origin,  but  to 
have  been  formed  under  great  pressure,  at  a  considerable  depth  in  the 
earth,  or  sometimes,  perhaps,  under  a  certain  weight  of  incumbent 
water.  Like  the  lava  of  volcanoes,  they  have  been  melted,  and  have 
afterwards  cooled  and  crystallized,  but  with  extreme  slowness,  and  under 
conditions  very  different  from  those  of  bodies  cooling  in  the  open  air. 
Hence  they  differ  from  the  volcanic  rocks,  not  only  by  their  more  crys- 
talline texture,  but  also  by  the  absence  of  tuffs  and  breccias,  which  are 
the  products  of  eruptions  at  the  earth's  surface,  or  beneath  seas  of 
inconsiderable  depth.  They  differ  also  by  the  absence  of  pores  or  cel- 
lular cavities,  to  which  the  expansion  of  the  entangled  gases  gives  rise 
in  ordinary  lava. 

Although  granite  has  often  pierced  through  other  strata,  it  has  rarely, 
if  ever,  been  observed  to  rest  upon  them,  as  if  it  had  overflowed.  But 
as  this  is  continually  the  case  with  the  volcanic  rocks,  they  have 
been  styled,  from  this  peculiarity,  "overlying"  by  Dr.  MacCulloch : 


METAMOEPHIC  ROCKS.  [On.  1 

and  Mr.  Necker  has  proposed  the  term  "  underlying"  for  the  granites, 
to  designate  the  opposite  mode  in  which  they  almost  invariably  present 
themselves. 

Metamorphic,  or  stratified  crystalline  rocks. — The  fourth  and  last 
great  division  of  rocks  are  the  crystalline  strata  and  slates,  or  schists, 
called  gneiss,  mica-schist,  clay-slate,  chlorite-schist,  marble,  and  the  like, 
the  origin  of  which  is  more  doubtful  than  that  of  the  other  three 
classes.  They  contain  no  pebbles,  or  sand,  or  scoriae,  or  angular  pieces 
of  imbedded  stone,  and  no  traces  of  organic  bodies,  and  they  are  often 
as  crystalline  as  granite,  yet  are  divided  into  beds,  corresponding  in 
form  and  arrangement  to  those  of  sedimentary  formations,  and  are 
therefore  said  to  be  stratified.  The  beds  sometimes  consist  of  an  alter- 
nation of  substances  varying  in  color,  composition,  and  thickness,  pre- 
cisely as  we  see  in  stratified  fossiliferous  deposits.  According  to  the 
Huttonian  theory,  which  I  adopt  as  the  most  probable,  and  which  will  be 
afterwards  more  fully  explained,  the  materials  of  these  strata  were  origi- 
nally deposited  from  water  in  the  usual  form  of  sediment,  but  they  were 
subsequently  so  altered  by  subterranean  heat,  as  to  assume  a  new  texture. 
It  is  demonstrable,  in  some  cases  at  least,  that  such  a  complete  conversion 
has  actually  taken  place,  fossiliferous  strata  laving  exchanged  an  earthy  for 
a  highly  crystalline  texture  for  a  distance  of  a  quarter  of  a  mile  from  their 
contact  with  granite.  In  some  cases,  dark  limestones  replete  with  shells  and 
corals,  have  been  turned  into  white  statuary  marble,  and  hard  clays-,  contain- 
ing vegetable  or  other  remains,  into  slates  called  mica-schist  or  hornblende- 
schist,  every  vestige  of  the  organic  bodies  having  been  obliterated. 

Although  we  are  in  a  great  degree  ignorant  of  the  precise  nature  of 
the  influence  exerted  in  these  cases,  yet  it  evidently  bears  some  analogy 
to  that  which  volcanic  heat  and  gases  are  known  to  produce ;  and  the 
action  may  be  conveniently  called  plutonic,  because  it  appears  to  have 
been  developed  in  those  regions  where  plutonic  rocks  are  generated,  and 
under  similar  circumstances  of  pressure  and  depth  in  the  earth.  Whether 
hot  water  or  steam  permeating  stratified  masses,  or  electricity,  or  any 
other  causes  have  cooperated  to  produce  the  crystalline  texture,  may  be 
matter  of  speculation,  but  it  is  clear  that  the  plutonic  influence  has  some- 
times pervaded  entire  mountain  masses  of  strata. 

In  accordance  with  the  hypothesis  above  alluded  to,  I  proposed  in  the 
first  edition  of  the  Principles  of  Geology  (1833),  the  term  "  Metamorphic" 
for  the  altered  strata,  a  term  derived  from  /JUSTCC,  meta,  trans,  and  fxop(ptj, 
morphe,  forma. 

Hence  there  are  four  great  classes  of  rocks  considered  in  reference  to  their 
origin, — the  aqueous,  the  volcanic,  the  plutonic,  and  the  metamorphic.  In 
the  course  of  this  work  it  will  be  shown,  that  portions  of  each  of  these  four 
distinct  classes  have  originated  at  many  successive  periods.  They  have  all 
been  produced  contemporaneously,  and  may  even  now  be  in  the  progress 
of  formation  on  a  large  scale.  It  is  not  true,  as  was  formerly  supposed, 
that  all  granites,  together  with  the  crystalline  or  metamorphic  strata, 
were  first  formed,  and  therefore  entitled  to  be  called  "  primitive,"  and 


OH.  I]        FOUR  CLASSES  OF  ROCKS  CONTEMPORANEOUS.  9 

that  the  aqueous  and  volcanic  rocks  were  afterwards  superimposed,  and 
should,  therefore,  >rank  as  secondary  in  the  order  of  time.  This  idea 
was  adopted  in  the  infancy  of  the  science,  when  all  formations,  whether 
stratified  or  unstratified,  earthy  or  crystalline,  with  or  without  fossils, 
were  alike  regarded  as  of  aqueous  origin.  At  that  period  it  was  natu- 
rally argued,  that  the  foundation  must  be  older  than  the  superstructure ; 
but  it  was  afterwards  discovered,  that  this  opinion  was  by  no  means  in 
every  instance  a  legitimate  deduction  from  facts  ;  for  the  inferior  parts 
of  the  earth's  crust  have  often  been  modified,  and  even  entirely  changed, 
by  the  influence  of  volcanic  and  other  subterranean  causes,  while  super- 
imposed formations  have  not  been  in  the  slightest  degree  altered.  In 
other  words,  the  destroying  and  renovating  processes  have  given  birth 
to  new  rocks  below,  while  those  above,  whether  crystalline  or  fossilif- 
erous,  have  remained  in  their  ancient  condition.  Even  in  cities,  such  as 
Venice  and  Amsterdam,  it  cannot  be  laid  down  as  universally  true,  that 
the  upper  parts  of  each  edifice,  whether  of  brick  or  marble,  are  more 
modern  than  the  foundations  on  which  they  rest,  for  these  often  consist 
of  wooden  piles,  which  may  have  rotted  and  been  replaced  one  after 
the  other,  without  the  least  injury  to  the  buildings  above ;  meanwhile, 
these  may  have  required  scarcely  any  repair,  and  may  have  been  con- 
stantly inhabited.  So  it  is  with  the  habitable  surface  of  our  globe,  in 
its  relation  to  large  masses  of  rock  immediately  below  :  it  may  continue 
the  same  for  ages,  while  subjacent  materials,  at  a  great  depth,  are  passing 
from  a  solid  to  a  fluid  state,  and  then  reconsolidating,  so  as  to  acquire  a 
new  texture. 

As  all  the  crystalline  rocks  may,  in  some  respects,  be  viewed  as  be- 
longing to  one  great  family,  whether  they  be  stratified  or  unstratified. 
plutonic  or  metamorphic,  it  will  often  be  convenient  to  speak  of  them  by 
one  common  name.  It  being  now  ascertained,  as  above  stated,  that  they 
are  of  very  different  ages,  sometimes  newer  than  the  strata  called  second- 
ary, the  terms  primitive  and  primaiy,  which  were  formerly  used  for  the 
whole,  must  be  abandoned,  as  they  would  imply  a  manifest  contradiction. 
It  is  indispensable,  therefore,  to  find  a  new  name,  one  which  must  not  be 
of  chronological  import,  and  must  express,  on  the  one  hand,  some  pecu- 
liarity equally  attributable  to  granite  and  gneiss  (to  the  plutonic  as  well 
as  the  altered  rocks),  and,  on  the  other,  must  have  reference  to  characters 
in  which  those  rocks  differ,  both  from  the  volcanic  and  from  the  unal- 
tered sedimentary  strata.  I  proposed  in  the  Principles  of  Geology  (first 
edition,  vol.  iii.),  the  term  "hypogene"  for  this  purpose,  derived  from 
Ctfo,  under,  and  yivo/xai,  to  be,  or  to  be  born ;  a  word  implying  the 
theory  that  granite,  gneiss,  and  the  other  crystalline  formations  are  alike 
nether-formed  rocks,  or  rocks  which  have  not  assumed  their  present 
form  and  structure  at  the  surface.  They  occupy  the  lowest  place  in 
the  order  of  superposition.  Even  in  regions  such  as  the  Alps,  where 
some  masses  of  granite  and  gneiss  can  be  shown  to  be  of  comparatively 
modern  date,  belonging,  for  example,  to  the  period  hereafter  to  be 
described  as  tertiary,  they  are  still  underlying  rocks.  They  never  repose 


10  COMPONENTS  OF  STKATA.  [Off.  II 

on  the  volcanic  or  trappean  formations,  nor  on  strata  containing  organic 
remains.  They  are  hypogene,  as  "  being  under"  all  the  rest. 

From  what  has  now  been  said,  the  reader  will  understand  that  each 
of  the  four  great  classes  of  rocks  may  be  studied  under  two  distinct 
points  of  view  ;  first,  they  may  be  studied  simply  as  mineral  masses  de- 
riving their  origin  from  particular  causes,  and  having  a  certain  composi- 
tion, form,  and  position  in  the  earth's  crust,  or  other  characters  both 
positive  and  negative,  such  as  the  presence  or  absence  of  organic  re- 
mains. In  the  second  place,  the  rocks  of  each  class  may  be  viewed  as 
a  grand  chronological  series  of  monuments,  attesting  a  succession  oi 
events  in  the  former  history  of  the  globe  and  its  living  inhabitants. 

I  shall  accordingly  proceed  to  treat  of  each  family  of  rocks  ;  first,  in 
reference  to  those  characters  which  are  not  chronological,  and  then  in 
particular  relation  to  the  several  periods  when  they  were  formed 


CHAPTER  II. 

AQUEOUS    HOCKS THEIR    COMPOSITION    AND    FORMS    OF    STRATIFI- 
CATION. 

Mineral  composition  of  strata — Arenaceous  rocks — Argillaceous — Calcareous- 
Gypsum — Forms  of  stratification — Original  horizontally — Thinning  out — Diag- 
onal arrangement — Ripple  mark. 

IN  pursuance  of  the  arrangement  explained  in  the  last  chapter,  we  shall 
begin  by  examining  the  aqueous  or  sedimentary  rocks,  which  are  for 
the  most  part  distinctly  stratified,  and  contain  fossils.  "We  may  first 
study  them  with  reference  to  their  mineral  composition,  external  appear- 
ance, position,  mode  of  origin,  organic  contents,  and  other  characters 
which  belong  to  them  as  aqueous  formations,  independently  of  their  age, 
and  we  may  afterwards  consider  them  chronologically  or  with  reference 
to  the  successive  geological  periods  when  they  originated. 

I  have  already  given  an  outline  of  the  data  which  led  to  the  belief 
that  the  stratified  and  fossiliferous  rocks  were  originally  deposited  under 
water ;  but,  before  entering  into  a  more  detailed  investigation,  it  will  be 
desirable  to  say  something  of  the  ordinary  materials  of  which  such 
strata  are  composed.  These  may  be  said  to  belong  principally  to  three 
divisions,  the  arenaceous,  the  argillaceous,  and  the  calcareous,  which  are 
formed  respectively  of  sand,  clay,  and  carbonate  of  lime.  Of  these,  the 
arenaceous,  or  sandy  masses,  are  chiefly  made  up  of  siliceous  or  flinty 
grains ;  the  argillaceous,  or  clayey,  of  a  mixture  of  siliceous  matter, 
with  a  certain  proportion,  about  a  fourth  in  weight,  of  aluminous  earth ; 


CH.  II.]     MINERAL   COMPOSITION   OF  STRATIFIED   ROCKS.  11 

and,  lastly,  the  calcareous  rocks  or  limestones  consist  of  carbonic  acid 
and  lime. 

Arenaceous  or  siliceous  rocks. — To  speak  first  of  the  sandy  division  : 
beds  of  loose  sand  are  frequently  met  with,  of  which  .the  grains  consist 
entirely  of  silex,  which  term  comprehends  all  purely  siliceous  minerals, 
as  quartz  and  common  flint.  Quartz  is  silex  in  its  purest  form ;  flint 
usually  contains  some  admixture  of  alumine  and  oxide  of  iron.  The 
siliceous  grains  in  sand  are  usually  rounded,  as  if  by  the  action  of  running 
water.  Sandstone  is  an  aggregate  of  such  grains,  which  often  cohere  to- 
gether without  any  visible  cement,  but  more  commonly  are  bound  together 
by  a  slight  quantity  of  siliceous  or  calcareous  matter,  or  by  iron  or  clay. 

Pure  siliceous  rocks  may  be  known  by  not  effervescing  when  a  drop 
of  nitric,  sulphuric,  or  other  acid  is  applied  to  them,  or  by  the  grains 
not  being  readily  scratched  or  broken  by  ordinary  pressure.  In  nature 
there  is  every  intermediate  gradation,  from  perfectly  loose  sand,  to  the 
hardest  sandstone.  In  micaceous  sandstones  mica  is  very  abundant ; 
and  the  thin  silvery  plates  into  which  that  mineral  divides,  are  often  ar- 
ranged in  layers  parallel  to  the  planes  of  stratification,  giving  a  slaty  or 
laminated  texture  to  the  rock. 

When  sandstone  is  coarse-grained,  it  is  usually  called  grit.  If  the 
grains  are  rounded,  and  large  enough  to  be  called  pebbles,  it  becomes  a 
conglomerate,  or  pudding-stone,  which  may  consist  of  pieces  of  one  or  of 
many  different  kinds  of  rock.  A  conglomerate,  therefore,  is  simply 
gravel  bound  together  by  a  cement. 

Argillaceous  rocks. — Clay,  strictly  speaking,  is  a  mixture  of  silex  or 
flint  with  a  large  proportion,  usually  about  one-fourth,  of  alumine,  or 
argil ;  but,  in  common  language,  any  earth  which  possesses  sufficient 
ductility,  when  kneaded  up  with  water,  to  be  fashioned  like  paste  by 
the  hand,  or  by  the  potter's  lathe,  is  called  a  clay  ;  and  such  clays  vary 
greatly  in  their  composition,  and  are,  in  general,  nothing  more  than  mud 
derived  from  the  decomposition  or  wearing  down  of  rocks.  The  purest 
clay  found  in  nature  is  porcelain  clay,  or  kaolin,  which  results  from  the 
decomposition  of  a  rock  composed  of  felspar  and  quartz,  and  it  is  almost 
always  mixed  with  quartz.*  Shale  has  also  the  property,  like  clay,  of 
becoming  plastic  in  water  :  it  is  a  more  solid  form  of  clay,  or  argillaceous 
matter,  condensed  by  pressure.  It  usually  divides  into  laminae,  more  or 
less  regular. 

One  general  character  of  all  argillaceous  rocks  is  to  give  out  a  pe- 
culiar, earthy  odor  when  breathed  upon,  which  is  a  test  of  the  presence 
of  alumine,  although  it  does  not  belong  to  pure  alumine,  but,  apparently, 
to  the  combination  of  that  substance  with  oxide  of  iron.f 

*  The  kaolin  of  China  consists  of  7M5  parts  of  silex,  15'86  of  alumine,  1'92  of 
lime,  and  6'73  of  water  (W.  Phillips,  Mineralogy,  p.  33) ;  but  other  porcelain  clays 
differ  materially,  that  of  Cornwall  being  composed,  according  to  Boase,  of  nearly 
equal  parts  of  silica  and  alumine,  with  1  per  cent,  of  magnesia.  (Phil.  Mag.  voL 
x.  1837.) 

f  See  W.  Phillips's  Mineralogy,  "  Alumine." 


12  MINERAL  COMPOSITION  OF  STRATIFIED  ROCKS.        [On.  11 

Calcareous  rocks. — This  division  comprehends  those  rocks  which,  like 
chalk,  are  composed  chiefly  of  lime  and  carbonic  acid.  Shells  and  coral? 
are  also  formed  of  the  same  elements,  with  the  addition  of  animal  matter. 
To  obtain  pure  lime  it  is  necessary  to  calcine  these  calcareous  substances, 
that  is  to  say,  to  expose  them  to  heat  of  sufficient  intensity  to  drive  off 
the  carbonic  acid,  and  other  volatile  matter.  White  chalk  is  sometimes 
pure  carbonate  of  lime ;  and  this  rock,  although  usually  in  a  soft  and 
earthy  state,  is  occasionally  sufficiently  solid  to  be  used  for  building, 
and  even  passes  into  a  compact  stone,  or  a  stone  of  which  the  separate 
parts  are  so  minute  as  not  to  be  distinguishable  from  each  other  by  the 
naked  eye. 

Many  limestones  are  made  up  entirely  of  minute  fragments  of  shells 
and  coral,  or  of  calcareous  sand  cemented  together.  These  last  might 
be  called  "  calcareous  sandstones  ;"  but  that  term  is  more  properly  ap- 
plied to  a  rock  in  which  the  grains  are  partly  calcareous  and  partly  sili- 
ceous, or  to  quartzose  sandstones,  having  a  cement  of  carbonate  of  lime. 

The  variety  of  limestone  called  "  oolite"  is  composed  of  numerous 
small  egg-like  grains,  resembling  the  roe  of  a  fish,  each  of  which  has 
usually  a  small  fragment  of  sand  as  a  nucleus,  around  which  concentric 
layers  of  calcareous  matter  have  accumulated. 

Any  limestone  which  is  sufficiently  hard  to  take  a  fine  polish  is  called 
marble.  Many  of  these  are  fossiliferous ;  but  statuary  marble,  which  is 
also  called  saccharine  limestone,  as  having  a  texture  resembling  that  of 
loaf-sugar,  is  devoid  of  fossils,  and  is  in  many  cases  a  member  of  the 
metamorphic  series. 

Siliceous  limestone  is  an  intimate  mixture  of  carbonate  of  lime  and 
flint,  and  is  harder  in  proportion  as  the  flinty  matter  predominates. 

The  presence  of  carbonate  of  lime  in  a  rock  may  be  ascertained  by 
applying  to  the  surface  a  small  drop  of  diluted  sulphuric,  nitric,  or  mu- 
riatic acids,  or  strong  vinegar ;  for  the  lime,  having  a  greater  chemical 
affinity  for  any  one  of  these  acids  than  for  the  carbonic,  unites  imme- 
diately with  them  to  form  new  compounds,  thereby  becoming  a  sulphate, 
nitrate,  or  muriate  of  lime.  The  carbonic  acid,  when  thus  liberated 
from  its  union  with  the  lime,  escapes  in  a  gaseous  form,  and  froths  up 
or  effervesces  as  it  makes  its  way  in  small  bubbles  through  the  drop  of 
liquid.  This  effervescence  is  brisk  or  feeble  in  proportion  as  the  lime- 
stone is  pure  or  impure,  or,  in  other  words,  according  to  the  quantity  of 
foreign  matter  mixed  with  the  carbonate  of  lime.  Without  the  aid  of 
this  test,  the  most  experienced  eye  cannot  always  detect  the  presence  of 
carbonate  of  lime  in  rocks. 

The  above-mentioned  three  classes  of  rocks,  the  siliceous,  argillaceous, 
and  calcareous,  pass  continually  into  each  other,  and  rarely  occur  in  a 
perfectly  separate  and  pure  form.  Thus  it  is  an  exception  to  the  general 
rule  to  meet  with  a  limestone  as  pure  as  ordinary  white  chalk,  or  with 
clay  as  aluminous  as  that  used  in  Cornwall  for  porcelain,  or  with 
sand  so  entirely  composed  of  siliceous  grains  as  the  white  sand  of  Alum 
Bay  in  the  Isle  of  Wight,  or  sandstone  so  pure  as  the  grit  of  Fontaine 


CH.  II.]  FOKMS   OF   STKATIFICATION.  13 

bleau,  used  for  pavement  in  France,  More  commonly  we  find  sand  and 
clay,  or  clay  and  marl,  intermixed  in  tne  same  mass.  When  the  sand 
and  clay  are  each  in  considerable  quantity,  the  mixture  is  called  loam. 
If  there  is  much  calcareous  matter  in  clay  it  is  called  marl ;  but  this 
term  has  unfortunately  been  used  so  vaguely,  as  often  to  be  very  ambig- 
uous. It  has  been  applied  to  substances  in  which  there  is  no  lime ;  as, 
to  that  red  loam  usually  called  red  marl  in  certain  parts  of  England. 
Agriculturists  were  in  the  habit  of  calling  any  soil  a  marl,  which,  like 
true  marl,  fell  to  pieces  readily  on  exposure  to  the  air.  Hence  arose  the 
confusion  of  using  this  name  for  soils  which,  consisting  of  loam,  were 
easily  worked  with  the  plough,  though  devoid  of  lime. 

Marl  slate  bears  the  same  relation  to  marl  which  shale  bears  to  clay, 
being  a  calcareous  shale.  It  is  very  abundant  in  some  countries,  as  in 
the  Swiss  Alps.  Argillaceous  or  marly  limestone  is  also  of  common  oc- 
currence. 

There  are  few  other  kinds  of  rock  which  enter  so  largely  into  the 
composition  of  sedimentary  strata  as  to  make  it  necessary  to  dwell  here 
on  their  characters.  I  may,  however,  mention  two  others, — magnesian 
limestone  or  dolomite,  and  gypsum.  Magnesian  limestone  is  composed 
of  carbonate  of  lime  and  carbonate  of  magnesia  ;  the  proportion  of  the 
latter  amounting  in  some  cases  to  nearly  one-half.  It  effervesces  much 
more  slowly  and  feebly  with  acids  than  common  limestone.  In  England 
this  rock  is  generally  of  a  yellowish  color  ;  but  it  varies  greatly  in  min- 
eralogical  character,  passing  from  an  earthy  state  to  a  white  compact 
stone  of  great  hardness.  Dolomite,  so  common  in  many  parts  of  Ger- 
many and  France,  is  also  a  variety  o'f  magnesian  limestone,  usually  of  a 
granular  texture. 

Gypsum. — Gypsum  is  a  rock  composed  of  sulphuric  acid,  lime,  and 
water.  It  is  usually  a  soft  whitish-yellow  rock,  with  a  texture  resembling 
that  of  loaf-sugar,  but  sometimes  it  is  entirely  composed  of  lenticular 
crystals.  It  is  insoluble  in  acids,  and  does  not  effervesce  like  chalk  and 
dolomite,  because  it  does  not  contain  carbonic  acid  gas,  or  fixed  air,  the 
lime  being  already  combined  with  sulphuric  acid,  for  which  it  has  a 
stronger  affinity  than  for  any  other.  Anhydrous  gypsum  is  a  rare  vari- 
ety, into  which  water  does  not  enter  as  a  component  part.  Gypseous 
marl  is  a  mixture  of  gypsum  and  marl.  Alabaster  is  a  granular  and 
compact  variety  of  gypsum  found  in  masses  large  enough  to  be  used  in 
sculpture  and  architecture.  It  is  sometimes  a  pure  snow-white  substance, 
as  that  of  Volterra  in  Tuscany,  well  known  as  being  carved  for  works  of 
art  in  Florence  and  Leghorn.  It  is  a  softer  stone  than  marble,  and  more 
easily  wrought. 

Forms  of  stratification. — A  series  of  strata  sometimes  consists  of  one 
of  the  above  rocks,  sometimes  of  two  or  more  in  alternating  beds. 
Thus,  in  the  coal  districts  of  England,  for  example,  we  often  pass  through 
several  beds  of  sandstone,  some  of  finer,  others  of  coarser  grain,  some 
white,  others  of  a  dark  color,  and  below  these,  layers  of  shale  and  sand- 
stone or  beds  of  shale,  divisible  into  leaf-like  laminae,  and  containing 


14  ALTERNATIONS.  [Cu.  IL 

beautiful  impressions  of  plants.  Then  again  we  meet  with  beds  of  pure 
and  impure  coal,  alternating  with  shales  and  sandstones,  and  underneath 
the  whole,  perhaps,  are  calcareous  strata,  or  beds  of  limestone,  filled  with 
corals  and  marine  shells,  each  bed  distinguishable  from  another  by  cer- 
tain fossils,  or  by  the  abundance  of  particular  species  of  shells  oi 
zoophytes. 

This  alternation  of  different  kinds  of  rock  produces  the  most  distinct 
stratification ;  and  we  often  find  beds  of  limestone  and  marl,  conglom- 
erate and  sandstone,  sand  and  clay,  recurring  again  and  again,  in  nearly 
regular  order,  throughout  a  series  of  many  hundred  strata.  The  causes 
which  may  .produce  these  phenomena  are  various,  and  have  been  fully 
discussed  in  my  treatise  on  the  modern  changes  of  the  earth's  surface.* 
It  is  there  seen  that  rivers  flowing  into  lakes  and  seas  are  charged  with 
sediment,  varying  in  quantity,  composition,  color,  and  grain,  according  to 
the  seasons ;  the  waters  are  sometimes  flooded  and  rapid,  at  other  periods 
low  and  feeble ;  different  tributaries,  also,  draining  peculiar  countries  and 
soils,  and  therefore  charged  with  peculiar  sediment,  are  swollen  at  distinct 
periods.  It  was  also  shown  that  the  waves  of  the  sea  and  currents  un- 
dermine the  cliffs  during  wintry  storms,  and  sweep  away  the  materials 
into  the  deep,  after  which  a  season  of  tranquillity  succeeds,  when  nothing 
but  the  finest  mud  is  spread  by  the  movements  of  the  ocean  over  the 
same  submarine  area. 

It  is  not  the  object  of  the  present  work  to  give  a  description  of  these 
operations,  repeated  as  they  are,  year  after  year,  and  century  after  century ; 
but  I  may  suggest  an  explanation  of  the  manner  in  which  some  micaceous 
sandstones  have  originated,  namely,  those  in  which  we  see  innumerable 
thin  layers  of  mica  dividing  layers  of  fine  quartzose  sand.  I  observed  the 
same  arrangement  of  materials  in  recent  mud  deposited  in  the  estuary  oi 
La  Roche  St.  Bernard  in  Brittany,  at  the  mouth  of  the  Loire.  The  sur- 
rounding rocks  are  of  gneiss,  which,  by  its  waste,  supplies  the  mud :  when 
this  dries  at  low  water,  it  is  found  to  consist  of  brown  laminated  clay, 
divided  by  thin  seams  of  mica.  The  separation  of  the  mica  in  this  case,  or 
in  that  of  micaceous  sandstones,  may  be  thus  understood.  If  we  take  a 
handful  of  quartzose  sand,  mixed  with  mica,  and  throw  it  into  a  clear 
running  stream,  we  see  the  materials  immediately  sorted  by  the  water, 
the  grains  of  quartz  falling  almost  directly  to  the  bottom,  while  the  plates 
of  mica  take  a  much  longer  time  to  reach  the  bottom,  and  are  carried 
farther  down  the  stream.  At  the  first  instant  the  water  is  turbid,  but 
immediately  after  the  flat  surfaces  of  the  plates  of  mica  are  seen  all  alone 
reflecting  a  silvery  light,  as  they  descend  slowly,  to  form  a  distinct  mica- 
ceous lamina.  The  mica  is  the  heavier  mineral  of  the  two ;  but  it  re- 
mains a  longer  time  suspended  in  the  fluid,  owing  to  its  greater  extent  of 
surface.  It  is  easy,  therefore,  to  perceive  that  where  such  mud  is  acted 
upon  by  a  river  or  tidal  current,  the  thin  plates  of  mica  will  be  earned 

*  Consult  Index  to  Principles  of  Geology,  "Stratification,"  " Currents," 
11  Deltas,"  "Water,"  <fec. 


Ca  II]  HORIZONTALS  Y  OF  STRATA.  15 

farther,  and  not  deposited  in  the  same  places  as  the  grains  of  quartz ;  and 
since  the  force  and  velocity  of  the  stream  varies  from  time  to  time,  layers 
of  mica  or  of  sand  will  be  thrown  down  successively  on  the  same  area. 

Original  horizontality. — It  is  said  generally  that  the  upper  and 
under  surfaces  of  strata,  or  the  planes  of  stratification,  are  parallel. 
Although  this  is  not  strictly  true,  they  make  an  approach  to  paral- 
lelism, for  the  same  reason  that  sediment  is  usually  deposited  at  first 
in  nearly  horizontal  layers.  The  reason  of  this  arrangement  can  by 
no  means  be  attributed  to  an  original  evenness  or  horizontality  in  the 
bed  of  the  sea ;  for  it  is  ascertained  that  in  those  places  where  no 
matter  has  been  recently  deposited,  the  bottom  of  the  ocean  is  often  as 
uneven  as  that  of  the  dry  land,  having  in  like  manner  its  hills,  valleys, 
and  ravines.  Yet  if  the  sea  should  sink,  'or  the  water  be  removed  near 
the  mouth  of  a  large  river  where  a  delta  has  been  forming,  we  should 
see  extensive  plains  of  mud  and  sand  laid  dry,  which,  to  the  eye,  would 
appear  perfectly  level,  although,  in  reality,  they  would  slope  gently  from 
the  land  towards  the  sea. 

This  tendency  in  newly-formed  strata  to  assume  a  horizontal  position 
arises  principally  from  the  motion  of  the  water,  which  forces  along  par- 
ticles of  sand  or  mud  at  the  bottom,  and  causes  them  to  settle  in  hollows 
or  depressions,  where  they  are  less  exposed  to  the  force  of  a  current  than 
when  they  are  resting  on  elevated  points.  /  The  velocity  of  the  current 
and  the  motion  of  the  superficial  waves  diminish  from  the  surface 
downwards,  and  are  least  in  those  depressions  where  the  water  is 
deepest. 

A  good  illustration  of  the  principle  here  alluded  to  may  be  sometimes 
seen  in  the  neighborhood  of  a  volcano,  when  a  section,  whether  natural 
or  artificial,  has  laid  open  to  view  a  succession  of  various-colored  layers 
of  sand  and  ashes,  which  have  fallen  in  showers  upon  uneven  ground. 
Thus  let  A  B  (fig.  1)  be  two  ridges  with  an  intervening  valley.  These 
original  inequalities  of  the  surface  have  been  gradually  effaced  by  beds 
of  sand  and  ashes  c,  <£,  e,  the  surface  at  e  being  quite  level.  It  will  be 
seen  that  although  the  materials  of  the  first  layers  have  accommodated 

themselves  in  a  great  degree  to  the  shape 
of  the  ground  A  B,  yet  each  bed  is  thick- 
est at  the  bottom.  At  first  a  great  many 
particles  would  be  carried  by  their  ^own 
gravity  down  the  steep  sides  of  A  and  B, 
and  others  would  afterwards  be  blown  by  the  wind  as  they  fell  off"  the 
ridges,  and  would  settle  in  the  hollow,  which  would  thus  become  more 
and  more  effaced  as  the  strata  accumulated  from  c  to  e.  This  levelling 
operation  may  perhaps  be  rendered  more  clear  to  the  student  by  sup- 
posing a  number  of  parallel  trenches  to  be  dug  in  a  plain  of  moving 
sand,  like  the  African  desert,  in  which  case  the  wind  would  soon  cause 
all  signs  of  these  trenches  to  disappear,  and  the  surface  would  be  as 
uniform  as  before.  Now,  water  in  motion  can  exert  this  levelling  power 
on  similar  materials  more  easily  than  air,  for  almost  all  stones  lose  m 


16 


DIAGONAL   OK  CROSS  STRATIFICATION. 


[On.  11 


water  more  tlian'a  third  of  the  weight  which  they  have  in  air,  the  spe- 
cific gravity  of  rocks  being  in  general  as  2£  when  compared  to  that  of 
water,  which  is  estimated  at  1.  But  the  buoyancy  of  sand  or  mud 
would  be  still  greater  in  the  sea,  as  the  density  of  salt  water  exceeds 
that  of  fresh. 

Yet,  however  uniform  and  horizontal  may  be  the  surface  of  new  de- 
posits in  general,  there  are  still  many  disturbing  causes,  such  as  eddies 
in  the  water,  and  currents  moving  first  in  one  and  then  in  another 
direction,  which  frequently  cause  irregularities.  We  may  sometimes 
follow  a  bed  of  limestone,  shale,  or  sandstone,  for  a  distance  of  many 
hundred  yards  continuously ;  but  we  generally  find  at  length  that  each 
individual  stratum  thins  out,  and  allows  the  beds  which  were  previously 
above  and  below  it  to  meet.  If  the  materials  are  coarse,  as  in  grits  and 
conglomerates,  the  same  beds  can  rarely  be  traced  many  yards  without 
varying  in  size,  and  often  coming  to  an  end  abruptly.  (See  fig.  2.) 

Fig.  2. 


Section  of  strata  of  sandstone,  grit,  and  conglomerate. 

Diagonal  or  Cross  Stratification. — There  is  also  another  phenomenon 
of  frequent  occurrence.  We  find  a  series  of  larger  strata,  each  of  which 
is  composed  of  a  number  of  minor  layers  placed  obliquely  to  the  general 

Fig.  3. 


Section  of  sand  at  Sandy  Hill,  near  Biggleswade,  BecLfoTdshire. 
Height  20  feet.    (Green-sand  formation.) 

of  stratification.  To  this  diagonal  arrangement  the  name  of 
"  false  or  cross  stratification"  has  been  given.  Thus  in  the  annexed  sec- 
tion (fig.  3)  we  see  seven  or  eight  large  beds  of  loose  sand,  yellow  and 


OH.  IL] 


CAUSES   OF   DIAGONAL   STRATIFICATION. 


17 


brown,  and  the  lines  a,  6,  c,  mark  some  of  the  principal  planes  of  strati- 
fication, which  are  nearly  horizontal.  But  the  greater  part  of  the  sub- 
ordinate laminae  do  not  conform  to  these  planes,  but  have  often  a  steep 
slope,  the  inclination  being  sometimes  towards  opposite  points  of  the 
compass.  When  the  sand  is  loose  and  incoherent,  as  in  the  case  here 
represented,  the  deviation  from  parallelism  of  the  slanting  laminae  can- 
not possibly  be  accounted  for  by  any  rearrangement  of  the  particles  ac- 
quired during  the  consolidation  of  the  rock.  In  what  manner  then  can 
such  irregularities  be  due  to  original  deposition  ?  We  must  suppose 
that  at  the  bottom  of  the  sea,  as  well  as  in  the  beds  of  rivers,  the  mo- 
tions of  waves,  currents,  and  eddies  often  cause  mud,  sand,  and  gravel 
to  be  thrown  down  in  heaps  on  particular  spots,  instead  of  being  spread 
out  uniformly  over  a  wide  area.  Sometimes,  when  banks  are  thus 
formed,  currents  may  cut  passages  through  them,  just  as  a  river  forms 
its  bed.  Suppose  the  bank  A  (fig.  4)  to  be  thus  formed  with  a  steep 


Fif.4. 


0  D 

sloping  side,  and  the  water  being  in  a  tranquil  state,  the  layer  of  sedi- 
ment No.  1  is  thrown*  down  upon  it,  conforming  nearly  to  its  surface. 
Afterwards  the  other  layers,  2,  3,  4,  may  be  deposited  in  succession,  so 
that  the  bank  B  C  D  is  formed.  If  the  current  then  increases  in  ve- 
locity, it  may  cut  away  the  upper  portion  of  this  mass  down  to  the 
dotted  line  e  (fig.  4),  and  deposit  the  materials  thus  removed  farther  on, 
so  as  to  form  the  layers  5,  6,  7,  8.  We  have  now  the  bank  BODE 
(fig.  5),  of  which  the  surface  is  almost  level,  and  on  which  the  nearly 

Fig.  5. 


horizontal  layers,  9,  10,  11,  may  then  accumulate.  1  It  was  shown  in  fig. 
3  that  the  diagonal  layers  of  successive  strata  may  sometimes  have  an 
opposite  slope.  This  is  well  seen  in  some  cliffs  of  loose  sand  on  the 

Suffolk  coast.  A  portion  of  one  of 
these  is  represented  in  fig.  6,  where 
the  layers,  of  which  there  are  about 
six  in  the  thickness  of  an  inch,  are 
composed  of  quartzose  grains.  This 
arrangement  may  have  been  due  to 
the  altered  direction  of  the  tides  and 
Cliff  between  Mismer  and  Dunwich.  currents  in  the  same  place. 


18  CAUSES   OF   DIAGONAL   STRATIFICATION.  [On.  II 

The  description  above  given  of  the  slanting  position  of  the  minor 
layers  constituting  a  single  stratum  is  in  certain  cases  applicable  on  a 
much  grander  scale  to  masses  several  hundred  feet  thick,  and  many  miles 
in  extent.  A  fine  example  may  be  seen  at  the  base  of  the  Maritime 
Alps  near  Nice.  The  mountains  here  terminate  abruptly  in  the  sea,  so 
that  a  depth  of  many  hundred  fathoms  is  often  found  within  a  stone's 
throw  of  the  beach,  and  sometimes  a  depth  of  3000  feet  within  half  a 
mile.  But  at  certain  points,  strata  of  sand,  marl,  or  conglomerate,  in- 
tervene between  the  shore  and  the  mountains,  as  in  the  annexed  fig.  (7), 
where  a  vast  succession  of  slanting  beds  of  gravel  and  sand  may  be 

Monte  Cairo.  Fig.  7. 


Sea, 


Section  from  Monte  Calvo  to  tho  sea  by  the  valley  of  Magnan,  near  Nice. 
A.  Dolomite  and  sandstone.    (Green-sand  formation  ?) 
a,  &,  d.  Beds  of  gravel  and  sand. 
c.  Fine  marl  and  sand  of  St.  Madeleine,  with  marine  shells. 

traced  from  the  sea  to  Monte  Calvo,  a  distance -of  no  less  than  9  miles 
in  a  straight  line.  The  dip  of  these  beds  is  remarkably  uniform,  being 
always  southward  or  towards  the  Mediterranean,  at  an  angle  of  about 
25°.  They  are  exposed  to  view  in  nearly  vertical  precipices,  varying 
from  200  to  600  feet  in  height,  which  bound  the  valley  through  which 
the  river  Magnan  flows.  Although  in  a  general  view,  the  strata  appear 
to  be  parallel  and  uniform,  they  are  nevertheless  found,  when  examined 
closely,  to  be  wedge-shaped,  and  to  thin  out  when  followed  for  a  few 
hundred  feet  or  yards,  so  that  we  may  suppose  them  to  have  been 
thrown  down  originally  upon  the  side  of  a  steep  bank,  where  a  river  or 
alpine  torrent  discharged  itself  into  a  deep  and  tranquil  sea,  and  formed 
a  delta,  which  advanced  gradually  from  the  base  of  Monte  Cajvo  to  a 
distance  of  9  miles  from  the  original  shore.  If  subsequently  this  part  of 
the  Alps  and  bed  of  the  sea  were  raised  700  feet,  the  coast  would  acquire 
its  present  configuration,  the  delta  would  emerge,  and  a  deep  channel 
might  then  be  cut  through  it  by  a  river. 

It  is  well  known  that  the  torrents  and  streams,  which  now  descend 
from  the  alpine  declivities  to  the  shore,  bring  down  annually,  when  the 
snow  melts,  vast  quantities  of  shingle  and  sand,  and  then,  as  they  sub- 
side, fine  mud,  while  in  summer  they  are  nearly  or  entirely  dry ;  so  that 
it  may  be  safely  assumed,  that  deposits  like  those  of  the  valley  of  the 
Magnan,  consisting  of  coarse  gravel  alternating  with  fine  sediment,  are 
still  in  progress  at  many  points,  as,  for  instance,  at  the  mouth  of  the 
Var.  They  must  advance  upon  the  Mediterranean  in  the  form  of  great 
shoals  terminating  in  a  steep  talus  ;  such  being  the  original  mode  of  ac- 


CH.  II.]  KIPPLE   MAKE.  19 

cumulation  of  all  coarse  materials  conveyed  into  deep  water,  especially 
where  they  are  composed  in  great  part  of  pebbles,  which  cannot  be 
transported  to  indefinite  distances  by  currents  of  moderate  velocity.  By 
inattention  to  facts  and  inferences  of  this  kind,  a  very  exaggerated  esti- 
mate has  sometimes  been  made  of  the  supposed  depth  of  the  ancient 
ocean.  There  can  be  no  doubt,  for  example,  that  the  strata  a,  fig.  7, 
or  those  nearest  to  Monte  Calvo,  are  older  than  those  indicated  by  6,  and 
these  again  were  formed  before  c  ;  but  the  vertical  depth  of  gravel  and 
sand  in  any  one  place  cannot  be  proved  to  amount  even  to  1000  feet, 
although  it  may  perhaps  be  much  greater,  yet  probably  never  exceeding 
at  any  point '3 000  or  4000  feet.  But  were  we  to  assume  that  all  the 
strata  were  once  horizontal,  and  that  their  present  dip  or  inclination  was 
due  to  subsequent  movements,  we  should  then  be  forced  to  conclude, 
that  a  sea  9  miles  deep  had  been  filled  up  with  alternate  layers  of  mud 
and  pebbles  thrown  down  one  upon  another. 

In  the  locality  now  under  consideration,  situated  a  few  miles  to  the* 
west  of  Nice,  there  are  many  geological  data,  the  details  of  which  can- 
not be  given  in  this  place,  all  leading  to  the  opinion,  that  when  the 
deposit  of  the  Magnan  was  formed,  the  shape  and  outline  of  the  alpine 
declivities  and  the  shore  greatly  resembled  what  we  now  behold  at  many 
points  in  the  neighborhood.  That  the  beds,  a,  6,  c,  c?,  are  of  compara- 
tively modern  date  is  proved  by  this  fact,  that  in  seams  of  loamy  marl 
intervening  between  the  pebbly  beds  are  fossil  shells,  half  of  which  be- 
long to  species  now  living  in  the  Mediterranean. 

Ripple  mark. — The  ripple  mark,  so  common  on  the  surface  of  sand- 
stones of  all  ages  (see  fig.  8),  and  which  is  so  often  seen  on  the  sea-shore 

Fig.  8. 


Slab  of  ripple-marked  (new  red)  sandstone  from  Cheshire. 


20  RIPPLE  MAEK.  [On.  II. 

at  low  tide,  seeins  to  originate  in  the  drifting  of  materials  along  the 
bottom  of  the  water,  in  a  manner  very  similar  to  that  which  may  explain 
the  inclined  layers  above  described.  This  ripple  is  not  entirely  confined 
to  the  beach  between  high  and  low  water  mark,  but  is  also  produced  on 
sands  which  are  constantly  covered  by  water.  Similar  undulating  ridges 
and  furrows  may  also  be  sometimes  seen  on  the  surface  of  drift  snow  and 
blown  sand.  The  following  is  the  manner  in  which  I  once  observed  the 
motion  of  the  air  to  produce  this  effect  on  a  large  extent  of  level  beach, 
exposed  at  low  tide  near  Calais.  Clouds  of  fine  white  sand  were  blown 
from  the  neighboring  dunes,  so  as  to  cover  the  shore,  and  whiten  a  dark 
level  surface  of  sandy  mud,  and  this  fresh  covering  of  sand  was  beauti- 
fully rippled.  On  levelling  all  the  small  ridges  and  furrows  of  this  ripple 
over  an  area  of  several  yards  square,  I  saw  them  perfectly  restored  in 
about  ten  minutes,  the  general  direction  of  the  ridges  being  always  at 
right  angles  to  that  of  the  wind.  The  restoration  began  by  the  appear- 
-ance  here  and  there  of  small  detached  heaps  of  sand,  which  soon 
lengthened  and  joined  together,  so  as  to  form  long  sinuous  ridges  with 
intervening  furrows.  Each  ridge  had  one  side  slightly  inclined,  and  the 
other  steep  ;  the  lee-side  being  always  steep,  as  6,  c, — d,  e  ;  the  windward- 
side  a  gentle  slope,  as  a,  6, — c,  d,  fig.  9.  When  a  gust  of  wind  blew 

Fig.  9. 


with  sufficient  force  to  drive  along  a  cloud  of  sand,  all  the  ridges  were 
seen  to  be  in  motion  at  once,  each  encroaching  on  the  furrow  before  it, 
and,  in  the  course  of  a  few  minutes,  filling  the  place  which  the  furrows 
had  occupied.  The  mode  of  advance  was  by  the  continual  drifting  of 
grains  of  sand  up  the  slopes  a  b  and  c  d,  many  of  which  grains,  when 
they  arrived  at  b  and  d,  fell  over  the  scarps  b  c  and  d  e,  and  were  under 
shelter  from  the  wind ;  so  that  they  remained  stationary,  resting,  ac- 
cording to  their  shape  and  momentum,  on  different  parts  of  the  descent, 
and  a  few  only  rolling  to  the  bottom.  In  this  manner  each  ridge  was 
distinctly  seen  to  move  slowly  on  as  often  as  the  force  of  the  wind  aug- 
mented. Occasionally  part  of  a  ridge,  advancing  more  rapidly  than  the 
rest,  overtook  the  ridge  immediately  before  it,  and  became  confounded 
with  it,  thus  causing  those  bifurcations  and  branches  which  are  so  com 
mon,  and  two  of  which  are  seen  in  the  slab,  fig.  8.  We  may  observe 
this  configuration  in  sandstones  of  all  ages,  and  in  them  also,  as  now  on 
the  sea-coast,  we  may  often  detect  two  systems  of  ripples  interfering  with 
each  other ;  one  more  ancient  and  half-effaced,  and  a  newer  one,  in  which 
the  grooves  and  ridges  are  more  distinct,  and  in  a  different  direction. 
This  crossing  of  two  sets  of  ripples  arises  from  a  change  of  wind,  and  the 
new  direction  in  which  the  waves  are  thrown  on  the  shore. 

The  ripple  mark  is  usually  an  indication  of  a  sea-beach,  or  of  water 
from  6  to  10  feet  deep,  for  the  agitation  caused  by  waves  even  during 


CH.  III.]      GRADUAL  DEPOSITION  INDICATED  BY  FOSSILS.  21 

storms  extends  to  a  very  slight  depth.  To  this  rule,  however,  there  are 
some  exceptions,  and  recent  ripple-marks  have  been  observed  at  the  depth 
of  60  or  70  feet.  It  has  also  been  ascertained  that  currents  or  large 
bodies  of  water  in  motion  may  disturb  mud  and  sand  at  the  depth  of  300 
of  even  450  feet.*  Beach  ripple,  however,  may  usually  be  distinguished 
from  current  ripple  by  frequent  changes  in  its  direction.  In  a  slab  of 
sandstone,  not  more  than  an  inch  thick,  the  furrows  or  ridges  of  an  an- 
cient ripple  may  often  be  seen  in  several  successive  laminae  to  run  to- 
wards different  points  of  the  compass. 


CHAPTER  HI. 

ARRANGEMENT    OF    FOSSILS    IN    STRATA FRESHWATER   AND    MARINE. 

Successive  deposition  indicated  by  fossils — Limestones  formed  of  corals  and  shells 
— Proofs  of  gradual  increase  of  strata  derived  from  fossils — Serpula  attached 
to  spatangus — Wood  bored  by  teredina — Tripoli  and  semi-opal  formed  of  in- 
fusoria— Chalk  derived  principally  from  organic  bodies — Distinction  of  fresh- 
water from  marine  formations — Genera  of  freshwater  and  land  shells — Rules 
for  recognizing  marine  testacea — Gyrogonite  and  chara — Freshwater  fishes — 
Alternation  of  marine  and  freshwater  deposits — Lym-Fiord. 

HAVING  in  the  last  chapter  considered  the  forms  of  stratification  so 
far  as  they  are  determined  by  the  arrangement  of  inorganic  matter,  we 
may  now  turn  our  attention  to  the  manner  in  which  organic  remains  are 
distributed  through  stratified  deposits.  We  should  often  be  unable  to 
detect  any  signs  of  stratification  or  of  successive  deposition,  if  particular 
kinds  of  fossils  did  not  occur  here  and  there  at  certain  depths  in  the 
mass.  At  one  level,  for  example,  univalve  shells  of  some  one  or  more 
species  predominate  ;  at  another,  bivalve  shells ;  and  at  a  third,  corals  ; 
while  in  some  formations  we  find  layers  of  vegetable  matter,  commonly 
derive.*!  from  land  plants,  separating  strata. 

It  may  appear  inconceivable  to  a  beginner  how  mountains,  several 
thousand  feet  thick,  can  have  become  filled  with  fossils  from  top  to  bot- 
tom ;  but  the  difficulty  is  removed,  when  he  reflects  on  the  origin  of 
stratification,  as  explained  in  the  last  chapter,  and  allows  sufficient'  time 
for  the  accumulation  of  sediment.  He  must  never  lose  sight  of  the  fact 
that,  during  the  process  of  deposition,  each  separate  layer  was  once  the 
uppermost,  and  covered  immediately  by  the  water  in  which  aquatic  ani- 
mals lived.  Each  stratum  in  fact,  however  far  it  may  now  lie  beneath  the 
surface,  was  once  in  the  state  of  shingle,  or  loose  sand  or  soft  mud  at  the 
bottom  of  the  sea,  in  which  shells  and  other  bodies  easily  became  enveloped. 

By  attending  to  the  nature  of  these  remains,  we  are  often  enabled  to 
determine  whether  the  deposition  was  slow  or  rapid,  whether  it  took 
place  in  a  deep  or  shallow  sea,  near  the  shore  or  far  from  land,  and 
whether  the  water  was  salt,  brackish,  or  fresh.  Some  limestones  consist 

*    Edin.  New  Phil.  Journ.  vol.  xxxi.;  and  Darwin,  Vole.  Islands,  p.  134. 


22  GRADUAL  DEPOSITION  [On.  HI 

almost  exclusively  of  corals,  and  in  many  cases  it  is  evident  that  the  present 
position  of  each  fossil  zoophyte  has  been  determined  by  the  manner  in 
which  it  grew  originally.  The  axis  of  the  coral,  for  example,  if  its  nat- 
ural growth  is  erect,  still  remains  at  right  angles  to  the  plane  of  stratifi- 
cation. If  the  stratum  be  now  horizontal,  the  round  spherical  heads  of 
certain  species  continue  uppermost,  and  their  points  of  attachment  are 
directed  downwards.  This  arrangement  is  sometimes  repeated  through- 
out a  great  succession  -of  strata.  From  what  we  know  of  the  growth  of 
similar  zoophytes  in  modern  reefs,  we  infer  that  the  rate  of  increase  was 
extremely  slow,  and  some  of  the  fossils  must  have  flourished  for  ages  like 
forest  trees  before  they  attained  so  large  a  size.  During  these  ages,  the 
water  remained  clear  and  transparent,  for  such  corals  cannot  live  in  tur- 
bid water. 

In  like  manner,  when  we  see  thousands  of  full-grown  shells  dispersed 
everywhere  throughout  a  long  series  of  strata,  WQ  cannot  doubt  that 
time  was  required  for  the  multiplication  of  successive  generations  ;  and 
the  evidence  of  slow  accumulation  is  rendered  more  striking  from  the 
proofs,  so  often  discovered,  of  fossil  bodies  having  lain  for  a  time  on  the 
floor  of  the  ocean  after  death  before  they  were  imbedded  in  sediment. 
Nothing,  for  example,  is  more  common  than  to  see  fossil  oysters  in  clay, 
with  serpulae,  or  barnacles  (acorn-shells),  or  corals,  and  other  creatures, 
attached  to  the  inside  of  the  valves,  so  that  the  mollusk  was  certainly  not 
buried  in  argillaceous  mud  the  moment  it  died.  There  must  have  been 
an  interval  during  which  it  was  still  surrounded  with  clear  water,  when 
the  creatures  whose  remains  now  adhere  to  it,  grew  from  an  embryo  to  a 
mature  state.  Attached  shells  which  are  merely  external,  like  some  of  the 
Berpulse  (a)  in  the  annexed  figure  (fig.  10),  may  often  have  grown  upon 
Fte- 10-  an  oyster  or  other  shell  while  the  an- 

imal within  was  still  living;  but  if 
they  are  found  on  the  inside,  it  could 
only  happen  after  the  death  of  the 
inhabitant  of  the  shell  which  affords 
the  support.  Thus,  in  fig.  10,  it  will 
be  seen  that  two  serpulae  have  grown 
on  the  interior,  one  of  them  exactly 
on  the  place  where  the  adductor  mus- 
cle of  the  Gryphcea  (a  kind  of  oys- 
ter) was  fixed. 

Some  fossil  shells,  even  if  simply 
attached  to  the  outside  of  others,  bear 
full  testimony  to  the  conclusion  above 
alluded  to,  namely,  that  an  interval 
elapsed  between  the  death  of  the 
creature  to  whose  shell  they  adhere, 
and  the  burial  of  the  same  in  mud  or 
sand.  The  sea-urchins  or  Echini,  so 

Fossil  Gryphcea,  covered  both  on  the  outside     i         -,       ,  •        r  •-       i     n       /*•      i  i 

and  inside  with  fossil  serpniaj.  abundant  in  white  chalk,  afford  a  good 


CH.  III.] 


INDICATED   BY  FOSSILS. 


23 


illustration .  It  is  well  known  that  these  animals,  when  living,  are  inva- 
riably covered  with  numerous  suckers,  or  gelatinous  tubes,  called  "  ambu- 
lacral,"  because  they  serve  as  organs  of  motion.  They  are  also  armed  witt 
spines  supported  by  rows  of  tubercles.  These  last  are  only  seen  after  the 
death  of  the  sea-urchin,  when  the  spines  have  dropped  off.  In  fig.  12  a 
living  species  of  Spatangus,  common  on  our  coast,  is  represented  with 


Fig.  11. 


Serpula  attached  to 

a  fossil  Spatangus 

from  the  chalk. 


Eecent  Spatangus  with  the  spines 
removed  from  one  side. 

&.  Spine  and  tubercles,  nat  size. 
a.  The  same  magnified. 


one-half  of  its  shell  stripped  of  the  spines.  In  fig.  1 1  a  fossil  of  the 
same  genus  from  the  white  chalk  of  England  shows  the  naked  surface 
which  the  individuals  of  this  family  exhibit  when  denuded  of  their  bris- 
tles. The  full-grown  Serpula,  therefore,  which  now  adheres  externally, 
could  not  have  begun  to  grow  till  the  Spatangus  had  died,  and  the 
spines  were  detached. 

JSTow  the  series  of  events  here  attested  by  a  single  fossil  may  be  carried 
a  step  farther.  Thus,  for  example,  we  often  meet  with  a  sea-urchin  in 
the  chalk  (see  fig.  13),  which  has  fixed  to  it  the  lower  valve  of  a  Crania, 
Fig.  is.  a  genus  of  bivalve  mollusca.  The  upper  valve  (6,  fig. 

13)  is  almost  invariably  wanting,  though  occasionally 
found  in  a  perfect  state  of  preservation  in  white  chalk 
at  some  distance.    In  this  case,  we  see  clearly  that  the 
sea-urchin  first  lived  from  youth  to  age,  then  died  and 
lost  its  spines,  which  were  carried  away.     Then  the 
a.  Echinus'ltrom  the  young  Crania  adhered  to  the  bared  shell,  grew  and 
vafve'ofth?oFra«S  Pushed  ^n  its  turn ;  after  which  the  upper  valve  was 
attached.  separated-  from  the  lower  before  the  Echinus  became 

6.  Upper  valve  of  tha 

Crania  detached,      enveloped  in  chalky  mud. 

It  may  be  well  to  mention  one  more  illustration  of  the  manner  in 
which  single  fossils  may  sometimes  throw  light  on  a  former  state  of 
things,  both  in  the  bed  of  the  ocean  and  on  some  adjoining  land.  We 
meet  with  many  fragments  of  wood  bored  by  ship-worms,  at  various 
depths  in  the  clay  on  which  London  is  built.  Entire  branches  and  stems 
of  trees,  several  feet  in  length,  are  sometimes  dug  out,  drilled  all  over  by 
the  holes  of  these  borers,  the  tubes  and  shells  of  the  mollusk  still  re- 
maining in  the  cylindrical  hollows.  In  fig.  15  e,  a  representation  is 
given  of  a  piece  of  recent  wood  pierced  by  the  Teredo  navalis,  or  com- 
mon ship-worm,  which  destroys  wooden  piles  and  ships.  When  the 
cylindrical  tube  d  has  been  extracted  from  the  wood,  a  shell  is  seen  at 
the  larger  extremity,  composed  of  two  pieces,  as  shown  at  c.  In  like 


SLOW   DEPOSITION   OF   STKATA. 


[On.  Ill 


manner,  a  piece  of  fossil  wood  (a,  fig.  14)  has  been  perforated  by  an 
animal  of  a  kindred  but  extinct  genus,  called  Teredina  by  Lamarck. 
The  calcareous  tube  of  this  mollusk  was  united  and  as  it  were  soldered 


Fig.  14. 


Fig.  15. 


Fossil  and  recent  wood  drilled  by  perforating  Mollusca. 
Fig.  14  a.  Fossil  wood  from  London  clay,  bored  by  Teredina. 

&.  Shell  and  tube  of  Teredina personata,  the  right-hand  figure  the  ventral,  the  left  the 

dorsal  view. 
Fig.  15.  e.  Recent  wood  bored  by  Teredo. 

d.  Shell  and  tube  of  Teredo  navalis,  from  the  same. 

o.  Anterior  and  posterior  view  of  the  valves  of  same  detached  from  the  tube. 

on  to  the  valves  of  the  shell  (6),  which  therefore  cannot  be  detached 
from  the  tube,  like  the  valves  of  the  recent  Teredo.  The  wood  in  this 
fossil  specimen  is  now  converted  into  a  stony  mass,  a  mixture  of  clay 
and  lime  ;  but  it  must  once  have  been  buoyant  and  floating  in  the  sea, 
when  the  Teredince  lived  upon  it,  perforating  it  in  all  directions.  Again, 
before  the  infant  colony  settled  upon  the  drift-wood,  the  branch  of  a  tree 
must  have  been  floated  down  to  the  sea  by  a  river,  uprooted,  perhaps,  by 
a  flood,  or  torn  off  and  cast  into  the  waves,  by  the  wind  :  and  thus  our 
thoughts  are  carried  back  to  a  prior  period,  when  the  trel3  grew  for  years 
on  dry  Hnd,  enjoying  a  fit  soil  and  climate. 

It  has  been  already  remarked  that  there  are  rocks  in  the  interior  of 
continents,  at  various  depths  in  the  earth,  and  at  great  heights  above  the 
sea,  almost  entirely  made  up  of  the  remains  of  zoophytes  and  testacea. 
Such  masses  may  be  compared  to  modern  oyster-beds  and  coral  reefs ; 
and,  like  them,  the  rate  of  increase  must  have  been  extremely  gradual. 
But  there  are  a  variety  of  stony  deposits  in  the  earth's  crust,  now  proved 
to  have  been  derived  from  plants  and  animals,  of  which  the  organic  ori- 
gin was  not  suspected  until  of  late  years,  even  by  naturalists.  Great 
surprise  was  therefore  created  by  the  recent  discovery  of  Professor  Ehren- 
berg  of  Berlin,  that  a  certain  kind  of  siliceous  stone,  called  tripoli,  was 
entirely  composed  of  millions  of  the  remains  of  organic  beings,  which 
the  Prussian  naturalist  refers  to  microscopic  Infusoria,  but  which  most 
others  now  believe  to  be  plants.  They  abound  in  freshwater  lakes  and 
ponds  in  England  and  other  countries,  and  are  termed  Diatomacere  by 
those  naturalists  who  believe  in  their  vegetable  origin.  The  substance 


CH.  Ill] 


INFUSORIA  OF  TRIPOLI. 


25 


alluded  to  lias  long  been  well  known  in  the  arts,  being  used  in  the  form 
of  powder  for  polishing  stones  and  metals.  It  has  been  procured,  among 
other  places,  from  Bilin,  in  Bohemia,  where  a  single  stratum,  extending 
over  a  wide  area,  is  no  less  than  14  feet  thick.  This  stone,  when  exam- 
ined with  a  powerful  microscope,  is  found  to  consist  of  the  siliceous 
plates  or  frustules  of  the  above-mentioned  Diatomaceae,  united  together 


Fig.  16. 


Fig.  17. 


iljliiiiiiiili 


Fig.  18. 


L    ig.    *Vi 

D 


Baeittaria  GaUonella  Gallondla 

vulgaris  ?  distans.  ferruginea. 

These  figures  are  magnified  nearly  300  times,  except  the  lower  figure  of  G.  ferruginea  (fie.  18  a), 
which  is  magnified  2000  times. 

without  any  visible  cement.  It  is  difficult  to  convey  an  idea  of  their 
extreme  minuteness ;  but  Ehrenberg  estimates  that  in  the  Bilin  tripoli 
there  are  41,000  millions  of  individuals  of  the  Gaillonella  distans  (see 
fig.  17)  in  every  cubic  inch,  which  weighs  about  220  grains,  or  about 
18V  millions  in  a  single  grain.  At  every  stroke,  therefore,  that  we  make 
with  this  polishing  powder,  several  millions,  perhaps. tens  of  millions,  of 
perfect  fossils  are  crushed  to  atoms. 

The  remains  of  these  Diatomacese  are  of  pure  silex,  and  their  forms 
are  various,  but  very  marked  and  constant  in  particular  genera  and  spe- 
Fjg  20.  Fig.  19.       cies-    Thus,  in  the  family  Ba- 

cillaria  (see  fig.  16),  the  fos- 
sils preserved  in  tripoli  are 
seen  to  exhibit  the  same  di- 
visions and  transverse  lines 
which  characterize  the  living 
species  of  kindred  form.  With 
these,  also,  the  siliceous  spicu- 
Ia3  or  internal  supports  of  the 
freshwater  sponge,  or  Spon- 
gilla  of  Lamarck,  are  some- 
times intermingled  (see  the 
needle-shaped  bodies  in  fig. 
20).  These  flinty  cases  and 
spiculze,  although  hard,  are 
very  fragile,  breaking  like 
glass,  and  are  therefore  admi- 
rably adapted,  when  rubbed, 
for  wearing  down  into  a  fine 
powder  fit  for  polishing  the 
surface  of  metals. 

Fragment  of  sem.i-opal  from  the  great  bed  of  tripoli,  Bilin.  Besides  the  tripoli,  formed 
Fi|  20!  The  sTmc  raWnified,  showing  circular  articula-  exclusively  of  the  fossils  above 

Gallonella'  and  spicul*  described,  there  occurs  in  the 


26  FOSSIL  INFUSORIA.  [On.  IH 

upper  part  of  the  great  stratum  at  Bilin  another  heavier  and  more  compact 
stone,  a  kind  of  semi-opal,  in  which  innumerable  parts  of  Diatomacese 
and  spiculae  of  the  Spongilla  are  filled  with,  and  cemented  together  by, 
siliceous  matter.  It  is  supposed  that  the  siliceous  remains  of  the  most 
delicate  Diatomaceae  have  been  dissolved  by  water,  and  have  thus  given 
rise  to  this  opal  in  which  the  more  durable  fossils  are  preserved  like  in- 
sects in  amber.  This  opinion  is  confirmed  by  the  fact  that  the  organic 
bodies  decrease  in  number  and  sharpness  of  outline  in  proportion  as  the 
opaline  cement  increases  in  quantity. 

In  the  Bohemian  tripoli  above  described,  as  in  that  of  Planitz  in  Sax- 
ony, the  species  of  DiatomaceaB  (or  Infusoria,  as  termed  by  Ehrenberg) 
are  freshwater ;  but  in  other  countries,  as  in  the  tripoli  of  the  Isle  of 
France,  they  are  of  marine  species,  and  they  all  belong  to  formations  of 
the  tertiary  period,  which  will  be  spoken  of  hereafter. 

A  well-known  substance,  called  bog-iron  ore,  often  met  with  in  peat- 
mosses, has  also  been  shown  by  Ehrenberg  to  consist  of  innumerable  ar- 
ticulated threads,  of  a  yellow  ochre  color,  composed  partly  of  flint  and 
partly  of  oxide  of  iron.  These  threads  are  the  cases  of  a  minute  micro- 
scopic body,  called  Gaillonella  ferruginea  (fig.  18). 

It  is  clear  that  much  time  must  have  been  required  for  the  accumulation 
of  strata  to  which  countless  generations  of  Diatomacese  have  contributed 
their  remains ;  and  these  discoveries  lead  us  naturally  to  suspect  that  other 
deposits,  of  which  the  materials  have  usually  been  supposed  to  be  inorganic, 
may  in  reality  have  been  derived  from  microscopic  organic  bodies.  That 
this  is  the  case  with  the  white  chalk,  has  often  been  imagined,  this  rock 
having  been  observed  to  abound  in  a  variety  of  marine  fossils,  such  as 
echini,  testacea,  bryozoa,  corals,  sponges,  Crustacea,  and  fishes.  Mr.  Lons- 
dale,  on  examining,  Oct.,  1835,  in  the  museum  of  the  Geological  Society 
of  London,  portions  of  white  chalk  from  different  parts  of  England,  found, 
on  carefully  pulverizing  them  in  water,  that  what  appear  to  the  eye  simply 
as  white  grains  were,  in  fact,  well  preserved  fossils.  He  obtained  above 
a  thousand  of  these  from  each  pound  weight  of  chalk,  some  being  frag- 
ments of  minute  bryozoa  and  corallines,  others  entire  Foraminifera  and 
Cytheridse.  The  annexed  drawings  will  give  an  idea  of  the  beautiful 
forms  of  many  of  these  bodies.  The  figures  a  a  represent  their  natural 
size,  but,  minute  as  they  seem,  the  smallest  of  them,  such  as  a,  fig.  24, 

CytheridcK  and  Foraminifera  from  the  chalk. 
Fig.  21.  Fig.  22.  Fig.  23.  Fig.  24. 


§ 


Cythere,  Mull.  Portion  of  Cristellaria  Rosalina. 

Cytherina,  Lam.      Nodosaria,  rotulata. 

are  gigantic  in  comparison  with  the  cases  of  Diatomacese  before  men- 
tioned. It  has,  moreover,  been  lately  discovered  that  the  chambers  into 
which  these  Foraminifera  are  divided  are  actually  often  filled  with  thou- 


CH.  III.]  FRESHWATER  AND   MARINE  FOSSILS.  27 

sands  of  well-preserved  organic  bodies,  which  abound  in  every  minute 
grain  of  chalk,  and  are  especially  apparent  in  the  white  coaling  of 
flints,  often  accompanied  by  innumerable  needle-shaped  spiculse  of 
sponges.  After  reflecting  on  these  discoveries,  we  are  naturally  led  on 
to  conjecture  that,  as  the  formless  cement  in  the  semi-opal  of  Bilin 
has  been  derived  from  the  decomposition  of  animal  and  vegetable  re- 
mains, so  also  many  chalk  flints  in  which  no  organic  structure  can  be 
recognized  may  nevertheless  have  constituted  a  part  of  microscopic 
animalcules. 

"  The  dust  we  tread  upon  was  once  alive  !" — BYROX. 

How  faint  an  idea  does  this  exclamation  of  the  poet  convey  of  the 
real  wonders  of  nature  !  for  here  we  discover  proofs  that  the  calcareous 
and  siliceous  dust  of  which  hills  are  composed  has  not  only  been  once 
alive,  but  almost  every  particle,  albeit  invisible  to  the  naked  eye,  still 
retains  the  organic  structure  which,  at  periods  of  time  incalculably  re- 
mote, was  impressed  upon  it  by  the  powers  of  life. 

Freshwater  and  marine  fossils. — Strata,  whether  deposited  in  salt 
or  fresh  water,  have  the  same  forms ;  but  the  imbedded  fossils  are 
very  different  in  the  two  cases,  because  the  aquatic  animals  which  fre- 
quent lakes  and  rivers  are  distinct  from  those  inhabiting  the  sea.  In 
the  northern  part  of  the  Isle  of  Wight  formations  of  marl  and  lime- 
stone, more  than  50  feet  thick,  occur,  in  which  the  shells  are  prin- 
cipally, if  not  all,  of  extinct  species.  Yet  we  recognize  their  freshwater 
origin,  because  they  are  of  the  same  genera  as  those  now  abounding 
in  ponds  and  lakes,  either  in  our  own  country  or  in  warmer  latitudes. 

In  many  parts  of  France,  as  in  Auvergne,  for  example,  strata  of  lime- 
stone, marl,  and  sandstone  are  found,  hundreds  of  feet  thick,  which  con- 
tain exclusively  freshwater  and  land  shells,  together  with  the  remains  of 
terrestrial  quadrupeds.  The  number  of  land  shells  scattered  through 
some  of  these  freshwater  deposits  is  exceedingly  great ;  and  there  are 
districts  in  Germany  where  the  rocks  scarcely  contain  any  other  fossils 
except  snail-shells  (helices) ;  as,  for  instance,  the  limestone  on  the  left 
bank  of  the  Rhine,  between  Mayence  and  Worms,  at  Oppenheim,  Find- 
heim,  Budenheim,  and  other  places.  In  order  to  account  for  this  phe- 
nomenon, the  geologist  has  only  to  examine  the  small  deltas  of  torrents 
which  enter  the  Swiss  lakes  when  the  waters  are  low,  such  as  the  newly- 
formed  plain  where  the  Kander  enters  the  Lake  of  Thun.  He  there  sees 
sand  and  mud  strewed  over  with  innumerable  dead  land  shells,  which 
have  been  brought  down  from  valleys  in  the  Alps  in  the  preceding  spring, 
during  the  melting  of  the  snows.  Again,  if  we  search  the  sands  on  the 
borders  of  the  Rhine,  in  the  lower  part  of  its  course,  we  find  countless 
land  shells  mixed  with  others  of  species  belonging  to  lakes,  stagnant 
pools,  and  marshes.  These  individuals  have  been  washed  away  from 
the  alluvial  plains  of  the  great  river  and  its  tributaries,  some  from 
mountainous  regions,  others  from  the  low  country. 


28 


DISTINCTION   OF   FKESHWATEB 


[On.  Til 


Although  freshwater  formations  are  often  of  great  thickness,  yet  they 
are  usually  very  limited  in  area  when  compared  to  marine  deposits, 
just  as  lakes  and  estuaries  are  of  small  dimensions  in  comparison  with 
seas. 

We  may  distinguish  a  freshwater  formation,  first,  by  the  absence  of 
many  fossils  almost  invariably  met  with  in  marine  strata.  For  example, 
there  are  no  sea-urchins,  no  corals,  and  scarcely  any  zoophytes ;  no 
chambered  shells,  such  as  the  nautilus,  nor  microscopic  Foraminifera. 
But  it  is  chiefly  by  attending  to  the  forms  of  the  mollusca  that  we  are 
guided  in  determining  the  point  in  question.  In  a  freshwater  deposit, 
the  number  of  individual  shells  is  often  as  great,  if  not  greater,  than  in 
a  marine  stratum  ;  but  there  is  a  smaller  variety  of  species  and  genera. 
This  might  be  anticipated  from  the  fact  that  the  genera  and  species  of 
recent  freshwater  and  land  shells  are  few  when  contrasted  with  the  ma- 
rine. Thus,  the  genera  of  true  mollusca  according  to  Woodward's 
system,  excluding  those  altogether  extinct  and  those  without  shells, 
amount  to  446  in  number,  of  which  the  terrestrial  and  freshwater 
genera  scarcely  form  more  than  a  fifth.* 

Almost  all  bivalve  shells,  or  those  of  acephalous  mollusca,  are  marine, 


Fig.  25. 


Fig.  26. 


Cycla.8  obovata  ;  fossil.    Hants. 


Cyrena  consobrina  ;  fossil.    Grays,  Lssex. 


about  ten  only  out  of  ninety  genera  being  freshwater.     Among  these 
last,  the  four  most  common  forms,  both  recent  and  fossil,  are  Cyclas,  Cy 


Fig.  27. 


Fig.  28. 


Fig.  29. 


Anodonta  Cordierii; 
fossil.    Paris, 


Anodonta  laHmarginatus  ; 
recent.    Bahia. 


Unio  littoralis  ; 
recent    Auvergne. 


rena,  Unio,  and  Anodonta  (see  figures) ;  the  two  first  and  two  last  of 
which  are  so  nearly  allied  as  to  pass  into  each  other. 


»  See  Woodward's  Manual  of  the  Mollusca,  1856. 


CH.  III.] 


FROM  MARINE  FORMATIONS. 


29 


Lamarck  divided  the  bivalve  mollusca  into  Fig.  so. 

the  Dimyary,  or  those  having  two  large  mus- 
cular impressions  in  each  valve,  as  a  b  in  the 
Cyclas,  fig.  25,  and  the  Monomyary,  such  as 
the  oyster  and  scallop,  in  which  there  is  only 
one  of  these  impressions,  as  is  seen  in  fig.  30. 
Now,  as  none  of  these  last,  or  the  unimuscular 
bivalves,  are  freshwater,*  we  may  at  once  pre- 
sume a  deposit  in  which  we  find  any  of  them 

tO  be  marine.  Orypkaa  incurva,  Sow.  (G. 

The  univalve   shells  most   characteristic   of     ™ata>  Lam->  upPer  valve- 


fresh-water  deposits  are,  Planorbis,  Limncea, 

and  Paludina.     (See  figures.)     But  to  these  are  occasionally  added 


Fig.  81. 


Fig.  32. 


Fig.  33. 


Planorbis  euomphalus: 
fossil.    Isle  of  Wight. 


Limncea  longiscata  ; 
fossil.    Hants. 


Paludina  lenta  ; 
fossil.    Hants. 


Physa,  Succinea,  Ancylus,  Valvata,  Melanopsis,  Melania,  Potamides, 
and  Neritina.     (See  figures.) 


Fig.  34. 


Fig.  85. 


Fig.  87. 


Succinea  amphibia  ; 
fossil.    Loess.  Rhine. 


Fig.  38. 


Ancylus  elegans  ; 
fossil.    Hants. 


Fig.  39. 


Fig.  40. 


Fig.  36. 


Vahata  ;    Physa  Jvypnorum  , 

fossil.  recent. 

Grays,  Essex. 

Fig.  41. 


Auricula  ; 
recent.    Ava. 


Physa  colum- 
naris.    Paris 
Paris  basin.  basin. 


Melanopste  buc- 

cinoidea;  recent. 

Asia. 


*  The  freshwater  Mulleria,  which  has  two  muscular  impressions  when  young,  has 
only  one  in  the  adult  state,  thus  forming  a  single  exception  to  the  rule. 


30 


DISTINCTION  OF  FRESHWATER 


[Cn.  III. 


Some  naturalists  include  Neritina  (fig.  42)  and  the  marine  Nerita 
(fig.  43)  in  the  same  genus,  it  being  scarcely  possible  to  distinguish 

Fig.  42.  Tig.  43.  Fig.  44. 


Neritina  globulus.    Paris  basin.          Nerita  granulosa.    Paris  basin. 

the  two  by  good  generic  characters.  But,  as  a  general 
rule,  the  fluviatile  species  are  smaller,  smoother,  and  more 
globular  than  the  marine;  and  they  have  never,  like  the 
Neritce,  the  inner  margin  of  the  outer  lip  toothed  or  crenu- 
lated.  (See  fig.  43.) 

The  Potamides  inhabit  the  mouths  of  rivers  in  warm 
latitudes,  and  are  distinguished  from  the  marine  cerithia 
by  their  orbicular  and  multispiral  opercula.      The  genus   p0tamides 
auricula  (fig.  38)  is  amphibious,  frequenting  swamps  and  'p^TbosST' 
marshes  within  the  influence  of  the  tide. 

The  terrestrial  shells  are  all  univalves.  The  most  abundant  genera 
among  these,  both  in  a  recent  and  fossil  state,  are  Helix  (fig.  45),  Cy~ 
dostoma  (fig.  46),  Pupa  (fig.  47),  Clausilia  (fig.  48),  Bulimus  (fig.  49), 


Fig.  45. 


Fig.  46. 


Fig.  47.        Fig.  48.  Fig.  49. 


Turonensis. 
Faluns,  Touraine. 


Cyclostoma 

elegana, 

Loess. 


Pupa 
tridens. 
Loess, 


Clausilia 
Mdens. 
Loess. 


Eulimus  lubricus. 
Loess,  Ehine. 


Fig.  50. 


and  Achatina  ;  which  two  last  are  nearly  allied  and  pass  into  each  other. 
The  Ampullaria  (fig.  50)  is  another  genus  of  shells,  inhabiting  rivers 
and  ponds  in  hot  countries.  Many  fossil  species  have 
been  referred  to  this  genus,  but  they  have  been  found 
chiefly  in  marine  formations,  and  are  suspected  by 
some  oonchologiste  to  belong  to  Natica  and  other  ma- 
rine genera. 

All  univalve  shells  of  land  and  freshwater  species, 
with  the  exception  of  Melanopsis  (fig.  41),  and  Acha- 
tina,  which  has  a  slight  indentation,  have  entire 
mouths  ;  and  this  circumstance  may  often  serve  as 
a  convenient  rule  for  distinguishing  freshwater  from  marine  strata  ; 
since,  if  any  univalves  occur  of  which  the  mouths  are  not  entire,  we 
may  presume  that  the  formation  is  marine.  The  aperture  is  said  to  be 
entire  in  such  shells  as  the  Ampullaria  and  the  land  shells  (figs.  45  — 
49),  when  its  outline  is  not  interrupted  by  an  indentation  or  notch. 


from  the  Jumna. 


CH.  III.]  FKOM   MARINE   FORMATIONS.  31 

such  as  that  seen  at  b  in  Andllaria  (fig.  52) ;  or  is  not  prolonged  into 
a  canal,  as  that  seen  at  a  in  Pleurotoma  (fig.  51). 

The  mouths  of  a  large  proportion  of  the  marine  univalves  have  these 
notches  or  canals,  and  almost  all  such  species  are  carnivorous ;  whereas 

Fig.  51. 


Pleurotoma 

rotata, 

Subap.  bills, 

Italy. 


AncUlaria  subulata.     Barton  clay. 

nearly  all  testacea  having  entire  mouths,  are  plant-eaters  ;  whether  the 
species  be  marine,  freshwater,  or  terrestrial. 

There  is,  however,  one  genus  which  affords  an  occasional  exception  to 
one  of  the  above  rules.  The  Cerithium  (fig.  44),  although  provided  with 
a  short  canal,  comprises  some  species  which  inhabit  salt,  others  brackish, 
and  others  fresh  water,  and  they  are  said  to  be  all  plant-eaters. 

Among  the  fossils  very  common  in  freshwater  deposits  are  the  shells 
of  Cypris,  a  minute  crustaceous  animal,  having  a  shell  much  resembling 
that  of  the  bivalve  mollusca.*  Many  minute  living  species  of  this  genus 
swarm  in  lakes  and  stagnant  pools  in  Great  Britain  ;  but  their  shells  are 
not,  if  considered  separately,  conclusive  as  to  the  freshwater  origin  of  a 
deposit,  because  the  majority  of  species  in  another  kindred  genus  of  the 
same  order,  the  Cytkerina  of  Lamarck  (see  above,  fig.  21,  p.  26),  in- 
habit salt  water ;  and,  although  the  animal  differs  slightly,  the  shell  is 
scarcely  distinguishable  from  that  of  the  Cypris. 

The  seed-vessels  and  stems  of  Chara,  a  genus  of  aquatic  plants,  are 
very  frequent  in  freshwater  strata.  These  seed-vessels  were  called,  before 
their  true  nature  was  known,  gyrogonites,  and  were  supposed  to  be 
foraminiferous  shells.  (See  fig.  53  a.) 

The  Charce  inhabit  the  bottom  of  lakes  and  ponds,  and  flourish 
mostly  where  the  water  is  charged  with  carbonate  of  lime.  Their  seed- 
vessels  are  covered  with  a  very  tough  integument,  capable  of  resisting 
decomposition ;  to  which  circumstance  we  may  attribute  their  abundance 
in  a  fossil  state.  The  annexed  figure  (fig.  54)  represents  a  branch  of 
one  of  many  new  species  found  by  Professor  Amici  in  the  lakes  of 
northern  Italy.  The  seed-vessel  in  this  plant  is  more  globular  than  in 
the  British  Charce,  and  therefore  more  nearly  resembles  in  form  the  ex- 
tinct fossil  species  found  in  England,  France,  and  other  countries.  The 

*  For  figures  of  fossil  species  of  Purbeck,  see  below,  ch.  xx. 


32  FRESHWATER  AND  MARINE  FORMATIONS.  [On.  III. 

stems,  as  well  as  the  seed-vessels,  of  these  plants  occur  both  in  modern 
shell  marl  and  in  ancient  freshwater  formations.     They  are  generally 

Fig.  63.  Fig.  64. 


Chara  medicaginula  ;  Chara  elastica  ;  recent    Italy. 

fossil.    Upper  Eocene, 

Isle  of  Wight.  a.  Sessile  seed-vessel  between  the  divisions  of 

a.  Seed-vessel,  the  leaves  of  the  female  plant. 

magnified  20  &.  Magnified  transverse  section  of  a  branch, 

diameters.  with  five  seed-vessels,  seen  from  below 

&.  Stem,  magnified.  upwards. 

composed  of  a  large  tube  surrounded  by  smaller  tubes  ;  the  whole  stem 
being  divided  at  certain  intervals  by  transverse  partitions  or  joints. 
(See  6,  fig.  53.) 

It  is  not  uncommon  to  meet  with  layers  of  vegetable  matter,  impres- 
sions of  leaves,  and  branches  of  trees,  in  strata  containing  freshwater 
shells  ;  and  we  also  find  occasionally  the  teeth  and  bones  of  land  quad- 
rupeds, of  species  now  unknown.  The  manner  in  which  such  remains 
are  occasionally  carried  by  rivers  into  lakes,  especially  during  floods,  has 
been  fully  treated  of  in  the  "  Principles  of  Geology."* 

The  remains  of  fish  are  occasionally  useful  in  determining  the  fresh- 
water origin  of  strata.  Certain  genera,  such  as  carp,  perch,  pike,  and 
loach  ( Cyprinus,  Perca,  Esox,  and  Cobitis),  as  also  Lebias,  being  pe- 
culiar to  freshwater.  Other  genera  contain  some  freshwater  and  some 
marine  species,  as  Cottus,  Mugil,  and  Anguilla,  or  eel.  The  rest  are 
either  common  to  rivers  and  the  sea,  as  the  salmon  ;  or  are  exclusively 
characteristic  of  salt  water.  The  above  observations  respecting  fossil 
fishes  are  applicable  only  to  the  more  modern  or  tertiary  deposits ;  for 
in  the  more  ancient  rocks  the  forms  depart  so  widely  from  those  of  ex- 
isting fishes,  that  it  is  very  difficult,  at  least  in  the  present  state  of  sci- 
ence, to  derive  any  positive  information  from  icthyolites  respecting  the 
element  in  which  strata  were  deposited. 

The  alternation  of  marine  and  freshwater  formations,  both  on  a  small 
and  large  scale,  are  facts  well  ascertained  in  geology.  When  it  occurs 
on  a  small  scale,  it  may  have  arisen  from  the  alternate  occupation  of 
certain  spaces  by  river  water  and  the  sea ;  for  in  the  flood  season  the 
river  forces  back  the  ocean  and  freshens  it  over  a  large  area,  depositing 
at  the  same  time  its  sediment ;  after  which  the  salt  water  again  returns, 
and,  on  resuming  its  former  place,  brings  with  it  sand,  mud,  and  marine 
shells. 

*  See  Index  of  Principles,  "  Fossilization." 


CH.  IV.]  CONSOLIDATION   OF   STKATA.  33 

There  are  also  lagoons  at  the  mouths  of  many  rivers,  as  the  Nile  and 
Mississippi,  which  are  divided  off  by  bars  of  sand  from  the  sea,  and 
which  are  filled  with  salt  and  fresh  water  by  turns.  They  often  commu- 
nicate exclusively  with  the  river  for  months,  years,  or  even  centuries ; 
and  then  a  breach  being  made  in  the  bar  of  sand,  they  are  for  long  pe- 
riods filled  with  salt  water. 

The  Lym-Fiord  in  Jutland  offers  an  excellent  illustration  of  analogous 
changes  ;  for,  in  the  course  of  the  last  thousand  years,  the  western  ex- 
tremity of  this  long  frith,  which  is  120  miles  in  length,  including  its 
windings,  has  been  four  times  fresh  and  four  times  salt,  a  bar  of  sand 
between  it  and  the  ocean  having  been  as  often  formed  and  removed. 
The  last  irruption  of  salt  water  happened  in  1824,  when  the  North  Sea 
entered,  killing  all  the  freshwater  shells,  fish,  and  plants  ;  and  from  that 
time  to  the  present,  the  sea-weed  Fucus  vesiculosus,  together  with  oys- 
ters and  other  marine  mollusca,  have  succeeded  the  Cyclas,  Lymnea, 
Paludina,  and  Charce* 

But  changes  like  these  in  the  Lym-Fiord,  and  those  before  mentioned 
as  occurring  at  the  mouths  of  great  rivers,  will  only  account  for  some 
cases  of  marine  deposits  of  partial  extent  resting  on  freshwater  strata. 
When  we  find,  as  in  the  southeast  of  England,  a  great  series  of  fresh- 
water beds,  1000  feet  in  thickness,  resting  upon  marine  formations  and 
again  covered  by  other  rocks,  such  as  the  cretaceous,  more  than  1000 
feet  thick,  and  of  deep-sea  origin,  we  shall  find  it  necessary  to  seek  for  a 
different  explanation  of  the  phenomena.f 


CHAPTER  IV. 

CONSOLIDATION    OF    STRATA    AND    PETRIFACTION    OF    FOSSILS. 

Chemical  and  mechanical  deposits — Cementing  together  of  particles — Hardening 
by  exposure  to  air — Concretionary  nodules — Consolidating  effects  of  pressure — 
Mineralization  of  organic  remains — Impressions  and  casts  ho\v  formed — Fossil 
wood — Goppert's  experiments — Precipitation  of  stony  matter  most  rapid  where 
putrefaction  is  going  on — Source  of  lime  in  solution — Silex  derived  from  de- 
composition of  felspar — Proofs  of  the  lapidification  of  some  fossils  soon  after 
burial,  of  others  when  much  decayed. 

HAVING  spoken  in  the  preceding  chapters  of  the  characters  of  sedi- 
mentary formations,  both  as  dependent  on  the  deposition  of  inorganic 
matter  and  the  distribution  of  fossils,  I  may  next  treat  of  the  consolidation 
of  stratified  rocks,  and  the  petrifaction  of  imbedded  organic  remains. 

Chemical  and  mechanical  deposits. — A  distinction  has  been  made  by 

*  See  Principles,  Index,  "  Lym-Fiord." 

f  Sec  below,  Chap.  XVIIL,  on  the  Wealden. 


34  CONSOLIDATION   OF   STKATA.  [On.  IV. 

geologists  between  deposits  of  a  chemical,  and  those  of  a  mechanical, 
origin.  By  the  latter  name  are  designated  beds  of  mud,  sand,  or  peb- 
bles produced  by  the  action  of  running  water,  also  accumulations  of 
stones  and  scoriae  thrown  out  by  a  volcano,  which  have  fallen  into  their 
present  place  by  the  force  of  gravitation.  But  the  matter  which  forms 
a  chemical  deposit  has  not  been  mechanically  suspended  in  water,  but  in 
a  state  of  solution  until  separated  by  chemical  action.  In  this  manner 
carbonate  of  lime  is  often  precipitated  upon  the  bottom  of  lakes  and 
seas  in  a  solid  form,  as  may  be  well  seen  in  many  parts  of  Italy,  where 
mineral  springs  abound,  and  where  the  calcareous  stone,  called  travertin, 
is  deposited.  In  these  springs  the  lime  is  usually  held  in  solution  by  an 
excess  of  carbonic  acid,  or  by  heat  if  it  be  a  hot  spring,  until  the  water, 
on  issuing  from  the  earth,  cools  or  loses  part  of  its  acid.  The  calcareous 
matter  then  falls  down  in  a  solid  state,  incrusting  shells,  fragments  of 
wood  and  leaves,  and  binding  them  together.* 

In  coral  reefs,  large  masses  of  limestone  are  formed  by  the  stony  skel- 
etons of  zoophytes ;  and  these,  together  with  shells,  become  cemented 
together  by  carbonate  of  lime,  part  of  which  is  probably  furnished  to 
the  sea-water  by  the  decomposition  of  dead  corals.  Even  shells  of  which 
the  animals  are  still  living,  on  these  reefs,  are  very  commonly  found  to 
be  incrusted  over  with  a  hard  coating  of  limestone.f 

If  sand  and  pebbles  are  carried  by  a  river  into  the  sea,  and  these 
are  bound  together  immediately  by  carbonate  of  lime,  the  deposit 
may  be  described  as  of  a  mixed  origin,  partly  chemical,  and  partly 
mechanical. 

Now,  the  remarks  already  made  in  Chapter  II.  on  the  original  hori- 
zontality  of  strata  are  strictly  applicable  to  mechanical  deposits,  and 
only  partially  to  those  of  a  mixed  nature.  Such  as  are  purely  chemical 
may  be  formed  on  a  very  steep  slope,  or  may  even  incrust  the  vertical 
walls  of  a  fissure,  and  be  of  equal  thickness  throughout ;  but  such  de- 
posits are  of  small  extent,  and  for  the  most  part  confined  to  vein-stones. 

Cementing  of  particles. — It  is  chiefly  in  the  case  of  calcareous  rocks 
that  solidification  takes  place  at  the  time  of  deposition.  But  there  are 
many  deposits  in  which  a  cementing  process  comes  into  operation  long 
afterwards.  We  may  sometimes  observe,  where  the  water  of  ferruginous 
or  calcareous  springs  has  flowed  through  a  bed  of  sand  or  gravel,  that 
iron  or  carbonate  of  lime  has  been  deposited  in  the  interstices  between 
the  grains  or  pebbles,  so  that  in  certain  places  the  whole  has  been  bound 
together  into  a  stone,  the  same  set  of  strata  remaining  in  other  parts 
loose  and  incoherent. 

Proofs  of  a  similar  cementing  action  are  seen  in  a  rock  at  Kelloway 
in  Wiltshire.  A  peculiar  band  of  sandy  strata,  belonging  to  the  group 
called  Oolite  by  geologists,  may  be  traced  through  several  counties,  the 
sand  being  for  the  most  part  loose  and  unconsoli dated,  but  becoming 

*  See  Principles,  Index,  "  Calcareous  Springs,"  <fec. 
\  Ibid.     "  Travertin,"  "  Coral  Reefs,"  <fec. 


Cu.  IV.]  CONSOLIDATION   OF   STRATA.  35 

stony  near  Kelloway.  In  this  district  there  are  numerous  fossil  shells 
which  have  decomposed,  having  for  the  most  part  left  only  their  casts. 
The  calcareous  matter  hence  derived  has  evidently  served,  at  some  former 
period,  as  a  cement  to  the  siliceous  grains  of  sand,  and  thus  a  solid  sand- 
stone has  been  produced.  If  we  take  fragments  of  many  other  argilla- 
ceous grits,  retaining  the  casts  of  shells,  and  plunge  them  imto  dilute 
muriatic  or  other  acid,  we  see  them  immediately  changed  into  common 
sand  and  mud  ;  the  cement  of  lime  derived  from  the  shells,  having  been 
dissolved  by  the  acid.  * 

Traces  of  impressions  and  casts  are  often  extremely  faintj  In  some 
loose  sands  of  recent  date  we  meet  with  shells  in  so  advanced  a  stage  of 
decomposition  as  to  crumble  into  powder  when  touched.  It  is  clear  that 
water  percolating  such  strata  may  soon  remove  the  calcareous  matter  of 
the  shell ;  and,  unless  circumstances  cause  the  carbonate  of  lime  to  be 
again  deposited,  the  grains  of  sand  will  not  be  cemented  together ;  in 
which  case  no  memorial  of  the  fossil  will  remain.  The  absence  of  or- 
ganic remains  from  many  aqueous  rocks  may  be  thus  explained ;  but 
we  may  presume  that  in  many  of  them  no  fossils  were  ever  imbedded, 
as  there  are  extensive  tracts  on  the  bottoms  of  existing  seas  even  of 
moderate  depth  on  which  no  fragment  of  shell,  coral,  or  other  living 
creature  can  be  detected  by  dredging.  On  the  other  hand,  there  are 
parts  of  the  Mediterranean  (the  ^Egean  sea  for  example),  where,  ac- 
cording to  Prof.  E.  Forbes,  the  zero  of  animal  life  has  been  reached,  at 
the  depth  of  230  fathoms ;  a  deposit  of  yellowish  mud  of  very  uniform 
character,  and  devoid  of  organic  remains,  being  there  in  progress.* 
Later  experiments,  however,  have  proved  that  organic  beings  inhabit 
other  parts  of  the  same  sea  at  considerably  greater  depths. 

In  what  manner  silex  and  carbonate  of  lime  may  become  widely  dif- 
fused in  small  quantities  through  the  waters  which  permeate  the  earth's 
crust  will  be  spoken  of  presently,  when  the  petrifaction  of  fossil  bodies 
is  considered ;  but  I  may  remark  here  that  such  waters  are  always 
passing  in  the  case  of  thermal  springs  from  hotter  to  colder  parts  of  the 
interior  of  the  earth  ;  and  as  often  as  the  temperature  of  the  solvent  is 
lowered,  mineral  matter  has  a  tendency  to  separate  from  it  and  solidify. 
Thus  a  stony  cement  is  often  supplied  to  sand,  pebbles,  or  any  fragment- 
ary mixture.  In  some  conglomerates,  like  the  pudding-stone  of  Hertford- 
shire (a  Lower  Eocene  deposit),  pebbles  of  flint  and  grains  of  sand  are 
united  by  a  siliceous  cement  so  firmly,  that  if  a  block  be  fractured  the 
rent  passes  as  readily  through  the  pebbles  as  through  the  cement. 

It  is  probable  that  many  strata  became  solid  at  the  time  when  they 
emerged  from  the  waters  in  which  they  were  deposited,  and  when  they 
first  formed  a  part  of  the  dry  land.  A  well-known  fact  seems  to  con- 
firm this  idea  :  by  far  the  greater  number  of  the  stones  used  for  building 
and  road-making  are  much  softer  when  first  taken  from  the  quarry 
than  after  they  have  been  long  exposed  to  the  air ;  and  these,  when  once 

*  Report  Brit.  Ass.  1843,  p.  178. 


36  CONSOLIDATION  OF  STRATA.  [Ca  IV 

dried,  may  afterwards  be  immersed  for  any  length  of  time  in  water 
without  becoming  soft  again.  Hence  it  is  found  desirable  to  shape  the 
stones  which  are  to  be  used  in  architecture  while  they  are  yet  soft  and 
wet,  and  while  they  contain  their  "  quarry-water,"  as  it  is  called ;  also  to 
break  up  stone  intended  for  roads  when  soft,  and  then  leave  it  to  dry  in 
the  air  for  months  that  it  may  harden.  Such  induration  may  perhaps 
be  accounted  for  by  supposing  the  water,  which  penetrates  the  minutest 
pores  of  rocks,  to  deposit,  on  evaporation,  carbonate  of  lime,  iron,  silex, 
and  other  minerals  previously  held  in  solutipn,  and  thereby  to  fill  up  the 
pores  partially.  These  particles,  on  crystallizing,  would  not  only  be 
themselves  deprived  of  freedom  of  motion,  but  would  also  bind  together 
other  portions  of  the  rock  which  before  were  loosely  aggregated.  On 
the  same  principle  wet  sand  and  mud  become  as  hard  as  stone  when, 
frozen ;  because  one  ingredient  of  the  mass,  namely,  the  water,  has  crys- 
tallized, so  as  to  hold  firmly  together  all  the  separate  particles  of  which 
the  loose  mud  and  sand  were  composed. 

Dr.  MacCulloch  mentions  a  sandstone  in  Skye,  which  may  be  moulded 
like  dough  when  first  found ;  and  some  simple  minerals,  which  are  rigid 
and  as  hard  as  glass  in  our  cabinets,  are  often  flexible  ancl  soft  in  their 
native  beds ;  this  is  the  case  with  asbestos,  sahlite,  tremolite,  and 
chalcedony,  and  it  is  reported  also  to  happen  in  the  case  of  the 
beryl.* 

The  marl  recently  deposited  at  the  bottom  of  Lake  Superior,  in  North 
America,  is  soft,  and  often  filled  with  freshwater  shells ;  but  if  a  pieco 
be  taken  up  and  dried,  it  becomes  so  hard  that  it  can  only  be  broken  by 
a  smart  blow  of  the  hammer.  If  the  lake  therefore  was  drained,  such 
a  deposit  would  be  found  to  consist  of  strata  of  marlstone,  like  that 
observed  in  many  ancient  European  formations,  and  like  them  contain- 
ing freshwater  shells. 

It  is  probable  that  some  of  the  heterogeneous  materials  which  rivers 
transport  to  the  sea  may  at  once  set  under  water,  like  the  artificial  mix- 
ture called  pozzolana,  which  consists  of  fine  volcanic  sand  charged  with 
about  20  per  cent,  of  oxide  of  iron,  and  the  addition  of  a  small  quantity 
of  lime.  This  substance  hardens,  and  becomes  a  solid  stone  in  water, 
and  was  used  by  the  Romans  in  constructing  the  foundations  of  build- 
ings in  the  sea. 

Consolidation  in  these  cases  is  brought  about  by  the  action  of  chemical 
affinity  on  finely  comminuted  matter  previously  suspended  in  water. 
After  deposition  similar  particles  seem  to  exert  a  mutual  attraction  on 
each  other,  and  congregate  together  in  particular  spots,  forming  lumps, 
nodules,  and  concretions.  Thus  in  many  argillaceous  deposits  there  are 
calcareous  balls,  or  spherical  concretions,  ranged  in  layers  parallel  to  the 
general  stratification  ;  an  arrangement  which  took  place  after  the  shale 
or  marl  had  been  thrown  down  in  successive  laminae  ;  for  these  laminse 

*  Dr.  MacCulloch,  Syst.  of  Geol.  vol.  i.  p.  123. 


CH.  IV.] 


CONCRETIONARY   STRUCTURE. 


37 


Fig.  55. 


Calcareous  nodules  in  Lias. 


Fig.  56. 


Spheroidal  concretions  in  magnesian 
limestone. 


I 


are  often  traced  in  the  concretions,  remaining  parallel  to  those  of  the  sur- 
rounding unconsolidated  rock.  (See  fig.  55.)  Such  nodules  of  lime- 
stone have  often  a  shell  or  other  foreign 
body  in  the  centre.* 

Among  the  most  remarkable  exam- 
ples of  concretionary  structure  are  those 
described  by  Professor  Sedgwick  as 
abounding  in  the  magnesian  limestone 
of  the  north  of  England.  The  spherical  balls  are  of  various  sizes,  from 
that  of  a  pea  to  a  diameter  of  several  feet,  and  they  have  both  a  con- 
centric and  radiated  structure,  while  at  the  same  time  the  laminae  of 
original  deposition  pass  uninterruptedly  through  them.  In  some  cliffs 
this  limestone  resembles  a  great  irregular  pile  of  cannon  balls.  Some 
of  the  globular  masses  have  their  centre  in  one  stratum,  while  a  portion 
of  their  exterior  passes  through  to  the  stratum  above  or  below.  Thus 
the  larger  spheroid  in  the  annexed  section  (fig.  56)  passes  from  the 

stratum  b  upwards  into  a.  In  this  in- 
stance we  must  suppose  the  deposition  of 
a  series  of  minor  layers,  first  forming  the 
stratum  6,  and  afterwards  the  incumbent 
stratum  a  ;  then  a  movement  of  the  par- 
ticles took  place,  and  the  carbonates  of 
lime  and  magnesia  separated  from  the 
more  impure  and  mixed  matter,  forming  the  still  unconsolidated  parts  of 
the  stratum.  Crystallization,  beginning  at  the  centre,  must  have  gone 
on  forming  concentric  coats,  around  the  original  nucleus  without  inter- 
fering with  the  laminated  structure  of  the  rock. 

When  the  particles  of  rocks  have  been  thus  rearranged  by  chemical 
forces,  it  is  sometimes  difficult  or  impossible  to  ascertain  whether  certain 
lines  of  division  are  due  to  original  deposition  or  to  the  subsequent  ag- 
gregation of  similar  particles.  Thus  suppose  three  strata  of  grit,  A,  B, 

C,  are  charged  unequally  with  calcareous 
matter,  and  that  B  is  the  most  calcareous. 
If  consolidation  takes  place  in  B,  the  con- 
cretionary action  may  spread  upwards 
into  a  part  of  A,  where  the  carbonate  of 
lime  is  more  abundant  than  in  the  rest ;  so  that  a  mass  c?,  e,  /,  forming 
a  portion  of  the  superior  stratum,  becomes  united  with  B  into  one  solid 
mass  of  stone.  The  original  line  of  division  c?,  e,  being  thus  effaced,  the 
line  c?,  /,  would  generally  be  considered  as  the  surface  of  the  bed  B, 
though  not  strictly  a  true  plane  of  stratification. 

Pressure  and  heat. — When  sand  and  mud  sink  to  the  bottom  of  a 
deep  sea,  the  particles  are  not  pressed  down  by  the  enormous  weight  of 
the  incumbent  ocean  ;  for  the  water,  which  becomes  mingled  with  the 
and  mud,  resists  pressure  with  a  force  equal  to  that  of  the  column 

*  De  la  Beche,  Geol  Researches,  p.  95,  and  Geol.  Observer  (1851),  p.  686. 


Fig.  57. 


38  MINERALIZATION  OF  [On.  IV. 

of  fluid  above.  The  same  happens  in  regard  to  organic  remains  which 
are  filled  with  water  under  great  pressure  as  they  sink,  otherwise  they 
would  be  immediately  crushed  to  pieces  and  flattened.  Nevertheless,  il 
the  materials  of  a  stratum  remain  in  a  yielding  state,  and  do  not  set  or 
solidify,  they  will  be  gradually  squeezed  down  by  the  weight  of  other 
materials  successively  heaped  upon  them,  just '  as  soft  clay  or  loose  sand 
on  which  a  house  is  built  may  give  way.  By  such  downward  pressure 
particles  of  clay,  sand,  and  marl,  may  become  packed  into  a  smaller 
space,  and  be  made  to  cohere  together  permanently. 

Analogous  effects  of  condensation  may  arise  when  the  solid  parts  of 
the  earth's  crust  are  forced  in  various  directions  by  those  mechanical 
movements  afterwards  to  be  described,  by  which  strata  have  been  bent, 
broken,  and  raised  above  the  level  of  the  sea.  Rocks  of  more  yielding 
materials  must  often  have  been  forced  against  others  previously  consol- 
idated, and,  thus  compressed,  may  have  acquired  a  new  structure.  A 
recent  discovery  may  help  us  to  comprehend  how  fine  sediment  derived 
from  the  detritus  of  rocks  may  be  solidified  by  mere  pressure.  The 
graphite  or  "  black  lead"  of  commerce  having  become  very  scarce,  Mr. 
Brockedon  contrived  a  method  by  which  the  dust  of  the  purer  portions 
of  the  mineral  found  in  Borrowdale  might  be  recomposed  into  a  mass  as 
dense  and  compact  as  native  graphite.  The  powder  of  graphite  is  first 
carefully  prepared  and  freed  from  air,  and  placed  under  a  powerful  press 
on  a  strong  steel  die,  with  air-tight  fittings.  It  is  then  struck  several 
blows,  each  of  a  power  of  1000  tons  ;  after  which  operation  the  powdei 
is  so  perfectly  solidified  that  it  can  be  cut  for  pencils,  and  exhibits  when 
broken  the  same  texture  as  native  graphite. 

But  the  action  of  heat  at  various  depths  in  the  earth  is  probably  the 
most  powerful  of  all  causes  in  hardening  sedimentary  strata.  To  thie 
subject  I  shall  refer  again  when  treating  of  the  inetamorphic  rocks,  and 
of  the  slaty  and  jointed  structure. 

Mineralization  of  organic  remains. — The  changes  which  fossil  organic 
bodies  have  undergone  since  they  were  first  imbedded  in  rocks,  throw 
much  light  on  the  consolidation  of  strata.  Fossil  shells  in  some  modern 
deposits  have  been  scarcely  altered  in  the  course  of  centuries,  having 
simply  lost  a  part  of  their  animal  matter.  But  in  other  cases  the  shell 
has  disappeared,  and  left  an  impression  only  of  its  exterior,  or  a  cast  of 
its  interior  form,  or  thirdly,  a  cast  of  the  shell  itself,  the  original  matter 
of  which  has  been  removed.  These  different  forms  of  fossilization  may 
easily  be  understood  if  we  examine  the  mud  recently  thrown  out  from  a 
pond  or  canal  in  which  there  are  shells.  If  the  mud  be  argillaceous,  it 
acquires  consistency  on  drying,  and  on  breaking  open  a  portion  of  it  we 
find  that  each  shell  has  left  impressions  of  its  external  form.  If  we  then 
remove  the  shell  itself,  we  find  within  a  solid  nucleus  of  clay,  having  the 
form  of  the  interior  of  the  shell.  This  form  is  often  very  different  from 
that  of  the  outer  shell.  Thus  a  cast  such  as  a,  fig.  58,  commonly  called 
a  fossil  screw,  would  never  be  suspected  by  an  inexperienced  conchologist 
to  be  the  internal  shape  of  the  fossil  univalve,  6,  fig.  58.  Nor  should 


CH.  IV.]  ORGANIC   REMAINS.  39 

we  have  imagined  at  first  sight  that  the  shell  a  and  the  cast  6,  fig.  59, 
were  different  parts  of  the  same  fossil.     The  reader  will  observe,  in  the 

Fig.  59. 


Phasianella  ffeddingtonensM,  Pleurotomaria  Anglica  and 

and  cast  of  the  same.    Coral  Bag.  cast.    Lias. 

last-mentioned  figure  (6,  fig.  59),  that  an  empty  space  shaded  dark,  which 
the  shell  itself  once  occupied,  now  intervenes  between  the  enveloping 
stone  and  the  cast  of  the  smooth  interior  of  the  whorls.  In  such  cases 
the  shell  has  been  dissolved  and  the  component  particles  removed  by 
water  percolating  the  rock.  If  the  nucleus  were  taken  out  a  hollow 
mould  would  remain,  on  which  the  external  form  of  the  shell  with  its 
tubercles  and  striae,  as  seen  in  a,  fig.  59,  would  be  seen  embossed.  Now 
if  the  space  alluded  to  between  the  nucleus  and  the  impression,  instead 
of  being  left  empty,  has  been  filled  up  with  calcareous  spar,  flint,  py- 
rites, or  other  mineral,  we  then  obtain  from  the  mould  an  exact  cast  both 
of  the  external  and  internal  form  of  the  original  shell.  In  this  manner 
silicified  casts  of  shells  have  been  formed ;  and  if  the  mud  or  sand  of 
the  nucleus  happen  to  be  incoherent,  or  soluble  in  acid,  we  can  then  pro- 
cure in  flint  an  empty  shell,  which  in  shape  is  the  exact  counterpart  of 
the  original.  This  cast  may  be  compared  to  a  bronze  statue,  representing 
merely  the  superficial  form,  and  not  the  internal  organization  ;  but  there 
is  another  description  of  petrifaction  by  no  means  uncommon,  and  of  a 
much  more  wonderful  kind,  which  may  be  compared  to  certain  anatom- 
ical models  in  wax,  where  not  only  the  outward  forms  and  features,  but 
the  nerves,  blood-vessels,  and  other  internal  organs  are  also  shown. 
Thus  we  find  corals,  originally  calcareous,  in  which  not  only  the  general 
shape,  but  also  the  minute  and  complicated  internal  organization  are  re- 
tained in  flint. 

Such  a  process  of  petrifaction  is  still  more  remarkably  exhibited  in 
fossil  wood,  in  which  we  often  perceive  not  only  the  rings  of  annual 
growth,  but  all  the  minute  vessels  and  medullary  rays.  Many  of  the 
minute  cells  and  fibres  of  plants,  and  even  those  spiral  vessels  which  in 
the  living  vegetable  can  only  be  discovered  by  the  microscope,  are  pre- 
served. Among  many  instances,  I  may  mention  a  fossil  tree,  72  feet  in 
length,  found  at  Gosforth  near  Newcastle,  in  sandstone  strata  associated 
with  coal.  By  cutting  a  transverse  slice  so  thin  as  to  transmit  light, 
and  magnifying  it  about  fifty-five  times,  the  texture  seen  in  fig.  60  is  ex- 


40  MINEKALIZATION   OF  [On.  IV 

hibited.  A  texture  equally  minute  and  complicated  has  been  observed 
in  the  wood  of  large  trunks  of  fossil  trees  found 
in  the  Craigleith  quarry  near  Edinburgh,  where 
the  stone  was  not  in  the  slightest  degree  siliceous, 
but  consisted  chiefly  of  carbonate  of  lime,  with 
oxide  of  iron,  alumina,  and  carbon.  The  parallel 
rows  of  vessels  here  seen  are  the  rings  of  an- 
nual growth,  but  in  one  part  they  are  imperfectly 
tre  irmthe  preserved,  the  wood  having  probably  decayed 

coal  strata,  magnified.   (Wi-     before  the  mineralizing:  matter  had  penetrated  to 

tham.)    Transverse  section. 

that  portion  01  the  tree. 

In  attempting  to  explain  the  process  of  petrifaction  in  such  cases,  we 
may  first  assume  that  strata  are  very  generally  permeated  by  water 
charged  with  minute  portions  of  calcareous,  siliceous,  and  other  earths 
in  solution.  In  what  manner  they  become  so  impregnated  will  be  after- 
wards considered.  If  an  organic  substance  is  exposed  in  the  open  air 
to  the  action  of  the  sun  and  rain,  it  will  in  time  putrefy,  or  be  dissolved 
into  its  component  elements,  which  consist  chiefly  of  oxygen,  hydrogen, 
and  carbon.  These  will  readily  be  absorbed  by  the  atmosphere  or  be 
washed  away  by  rain,  so  that  all  vestiges  of  the  dead  animal  or  plant 
disappear.  But  if  the  same  substances  be  submerged  in  water,  they  de- 
compose more  gradually ;  and  if  buried  in  earth,  still  more  slowly,  as  in 
the  familiar  example  of  wooden  piles  or  other  buried  timber.  Now,  if 
as  fast  as  each  particle  is  set  free  by  putrefaction  in  a  fluid  or  gaseous 
state,  a  particle  equally  minute  of  carbonate  of  lime,  flint,  or  other  min- 
eral, is  at  hand  and  ready  to  be  precipitated,  we  may  imagine  this  inor- 
ganic matter  to  take  the  place  just  before  left  unoccupied  by  the  organic 
molecule.  In  this  manner  a  cast  of  the  interior  of  certain  vessels  may 
first  be  taken,  and  afterwards  the  more  solid  walls  of  the  same  may 
decay  and  suffer  a  like  transmutation.  Yet  when  the  whole  is  lapidified, 
it  may  not  form  one  homogeneous  mass  of  stone  or  metal.  Some  of  the 
original  ligneous,  osseous,  or  other  organic  elements  may  remain  mingled 
in  certain  parts,  or  the  lapidifying  substance  itself  may  be  differently 
colored  at  different  times,  or  so  crystallized  as  to  reflect  light  differj 
ently,  and  thus  the  texture  of  the  original  body  may  be  faithfully 
exhibited. 

The  student  may  perhaps  ask  whether,  on  chemical  principles,  we  have 
any  ground  to  expect  that  mineral  matter  will  be  thrown  down  precisely 
in  those  spots  where  organic  decomposition  is  in  progress  ?  The  following 
curious  experiments  may  serve  to  illustrate  this  point.  Professor  Gop- 
pert  of  Breslau  attempted  recently  to  imitate  the  natural  process  of  pet- 
rifaction. For  this  purpose  he  steeped  a  variety  of  animal  and  vegetable 
substances  in  waters,  some  holding  siliceous,  others  calcareous,  others 
metallic  matter  in  solution.  He  found  that  in  the  period  of  a  few  weeks, 
or  even  days,  the  organic  bodies  thus  immersed  were  mineralized  to  a 
certain  extent.  Thus,  for  example,  thin  vertical  slices  of  deal,  taken 
from  the  Scotch  fir  (Pinus  sylvestris),  were  immersed  in  a  moderately 


Ca.  IV.]  ORGANIC  REMAINS.  41 

strong  solution  of  sulphate  of  iron.  When  they  had  been  thoroughly 
soaked  in  the  liquid  for  several  days  they  were  dried  and  exposed  to  a 
red-heat  until  the  vegetable  matter  was  burnt  up  and  nothing  remained 
but  an  oxide  of  iron,  which  was  found  to  have  taken  the  form  of  the 
deal  so  exactly  that  casts  even  of  the  dotted  vessels  peculiar  to  this  fam- 
ily of  plants  were  distinctly  visible  under  the  microscope. 

Another  accidental  experiment  has  been  recorded  by  Mr.  Pepys  in  the 
Geological  Transactions.*  An  earthen  pitcher  containing  several  quarts 
of  sulphate  of  iron  had  remained  undisturbed  and  unnoticed  for  about  a 
twelvemonth  in  the  laboratory.  At  the  end  of  this  time  when  the  liquor 
was  examined  an  oily  appearance  was  observed  on  the  surface,  and  a 
yellowish  powder,  which  proved  to  be  sulphur,  together  with  a  quantity 
of  small  hairs.  At  the  bottom  were  discovered  the  bones  of  several  mice 
in  a  sediment  consisting  of  small  grains  of  pyrites,  others  of  sulphur, 
others  of  crystallized  green  sulphate  of  iron,  and  a  black  muddy  oxide 
of  iron.  It  was  evident  that  some  mice  had  accidentally  been  drowned  in 
the  fluid,  and  by  the  mutual  action  of  the  animal  matter  and  the  sulphate 
of  iron  on  each  other,  the  metallic  sulphate  had  been  deprived  of  its  ox- 
ygen ;  hence  the  pyrites  and  the  other  compounds  were  thrown  down. 
Although  the  mice  were  not  mineralized,  or  turned  into  pyrites,  the  phe- 
nomenon shows  how  mineral  waters,  charged  with  sulphate  of  iron,  may 
be  deoxydated  on  coming  in  contact  with  animal  matter  undergoing  pu- 
trefaction, so  that  atom  after  atom  of  pyrites  may  be  precipitated,  and 
ready,  under  favorable  circumstances,' to  replace  the  oxygen,  hydrogen, 
and  carbon  into  which  the  original  body  would  be  resolved. 

The  late  Dr.  Turner  observes,  that  when  mineral  matter  is  in  a 
"  nascent  state,"  that  is  to  say,  just  liberated  from  a  previous  state  of 
chemical  combination,  it  is  most  ready  to  unite  with  other  matter,  and 
form  a  new  chemical  compound.  Probably  the  particles  or  atoms  just 
set  free  are  of  extreme  minuteness,  and  therefore  move  more  freely,  and 
are  more  ready  to  obey  any  impulse  of  chemical  affinity.  Whatever  be 
the  cause,  it  clearly  follows,  as  before  stated,  that  where  organic  matter 
newly  imbedded  in  sediment  is  decomposing,  there  will  chemical  changes 
take  place  most  actively. 

An  analysis  was  lately  made  of  the  water  which  was  flowing  off  from 
the  rich  mud  deposited  by  the  Hooghly  river  in  the  Delta  of  the  Ganges 
after  the  annual  inundation.  This  water  was  found  to  be  highly  charged 
with  carbonic  acid  gas  holding  lime  in  solution.f  Now  if  newly- 
deposited  mud  is  thus  proved  to  be  permeated  by  mineral  matter  in  a 
state  of  solution,  it  is  not  difficult  to  perceive  that  decomposing  organic 
bodies,  naturally  imbedded  in  sediment,  may  as  readily  become  petrified 
as  the  substances  artificially  immersed  by  Professor  Goppert  in  various 
fluid  mixtures. 

Tt  is  well  known  that  the  water  of  springs,  or  that  which  is  continually 

*  Vol.  i.  p.  399,  first  series. 

\  Piddington,  Asiat.  Research,  vol.  xviii.  p.  226. 


42  FLINT  OF  SILICIFIED  FOSSILS.  [On.  IV. 

percolating  the  earth's  crust,  is  rarely  free  from  a  slight  admixture  either 
of  iron,  carbonate  of  lime,  sulphur,  silica,  potash,  or  some  other  earthy, 
alkaline,  or  metallic  ingredient.  Hot  springs  in  particular  are  copiously 
charged  with  one  or  more  of  these  elements ;  and  it  is  only  in  their 
waters  that  silex  is  found  in  abundance.  In  certain  cases,  therefore, 
especially  in  volcanic  regions,  we  may  imagine  the  flint  of  silicified 
wood  and  corals  to  have  been  supplied  by  the  waters  of  thermal  springs. 
In  other  instances,  as  in  tripoli,  it  may  have  been  derived  in  great  part,  if 
not  wholly,  from  the  decomposition  of  diatomaceae,  sponges,  and  other 
bodies.  But  even  if  this  be  granted,  we  have  still  to  inquire  whence  a  lake 
or  the  ocean  can  be  constantly  replenished  with  the  calcareous  and  siliceous 
matter  so  abundantly  withdrawn  from  it  by  the  secretions  of  living  beings. 

In  regard  to  carbonate  of  lime  there  is  no  difficulty,  because  not 
only  are  calcareous  springs  very  numerous,  but  even  rain-water,  when 
it  falls  on  ground  where  vegetable  matter  is  decomposing,  may  be- 
come so  charged  with  carbonic  acid  as  to  acquire  a  power  of  dis- 
solving a  minute  portion  of  the  Calcareous  rocks  over  which  it  flows. 
Hence  marine  corals  and  mollusca  may  be  provided  by  rivers  with 
the  materials  of  their  shells  and  solid  supports.  But  pure  silex,  even 
when  reduced  to  the  finest  powder  and  boiled,  is  insoluble  in  water, 
except  at  very  high  temperatures.  Nevertheless  Dr.  Turner  has  well  ex- 
plained, in  an  essay  on  the  chemistry  of  geology,*  how  the  decomposi- 
tion of  felspar  may  be  a  source  of  silex  in  solution.  He  has  remarked 
that  the  siliceous  earth,  which  constitutes  more  than  half  the  bulk  of 
felspar,  is  intimately  combined  with  alumine,  potash,  and  some  other 
elements.  The  alkaline  matter  of  the  felspar  has  a  chemical  affinity  for 
water,  as  also  for  the  carbonic  acid  which  is  more  or  less  contained  in 
the  waters  of  most  springs.  The  water  therefore  carries  away  alkaline 
matter,  and  leaves  behind  a  clay  consisting  of  alumine  and  silica.  But 
this  residue  of  the  decomposed  mineral,  which  in  its  purest  state  is  called 
porcelain  clay,  is  found  to  contain  a  part  only  of  the  silica  which  existed 
in  the  original  felspar.  The  other  part,  therefore,  must  have  been  dis- 
solved and  removed  ;  and  this  can  be  accounted  for  in  two  ways  ;  first, 
because  silica  when  combined  with  an  alkali  is  soluble  in  water ;  sec- 
ondly, because  silica  in  what  is  technically  called  its  nascent  state  is  also 
soluble  in  water.  Hence  an  endless  supply  of  silica  is  afforded  to  rivers 
and  the  waters  of  the  sea.  For  the  felspathic  rocks  are  universally  dis- 
tributed, constituting,  as  they  do,  so  large  a  proportion  of  the  volcanic, 
plutonic,  and  metamorphic  formations.  Even  where  they  chance  to  be 
absent  in  mass,  they  rarely  fail  to  occur  in  the  superficial  gravel  or  allu- 
vial deposits  of  the  basin  of  every  large  river. 

The  disintegration  of  mica  also,  another  mineral  which  enters  largely  in- 
to the  composition  of  granite  and  various  sandstones,  may  yield  silica  which 
may  be  dissolved  in  water,  for  nearly  half  of  this  mineral  consists  of  silica, 
combined  with  alumine,  potash,  and  about  a  tenth  part  of  iron.  The  ox- 
idation of  this  iron  in  the  air  is  the  principal  cause  of  the  waste  of  mica. 

*  Jam.  Ed.  New  Phil.  Journ.  No.  30,  p.  246. 


On.  IV.]  PROCESS  OF  PETRIFACTION.  43 

We  have  still,  however,  much  to  learn  before  the  conversion  of  fossil 
bodies  into  stone  is  fully  understood.  Some  phenomena  seem  to  imply 
that  the  mineralization  must  proceed  with  considerable  rapidity,  for 
stems  of  a  soft  and  succulent  character,  and  of  a  most  perishable  nature, 
are  preserved  in  flint ;  and  there  are  instances  of  the  complete  silicifica- 
tion  of  the  young  leaves  of  a  palm-tree  when  just  about  to  shoot  forth, 
and  in  that  state  which  in  the  West  Indies  is  called  the  cabbage  of  the 
palm.*  It  may,  however,  be  questioned  whether  in  such  cases  there 
may  not  have  been  some  antiseptic  quality  in  the  water  which  re- 
tarded putrefaction,  so  that  the  soft  parts  of  the  buried  substance  may 
have  remained  for  a  long  time  without  disintegration,  like  the  flesh  of 
bodies  imbedded  in  peat. 

Mr.  Stokes  has  pointed  out  examples  of  petrifactions  in  which  the 
more  perishable,  and  others  where  the  more  durable  portions  of  wood 
are  preserved.  These  variations,  he  suggests,  must  doubtless  have  de- 
pended on  the  time  when  the  lapidifying  mineral  was  introduced.  Thus, 
in  certain  silicified  stems  of  palm-trees,  the  cellular  tissue,  that  most  de- 
structible part,  is  in  good  condition,  while  all  signs  of  the  hard  woody 
fibre  have  disappeared,  the  spaces  once  occupied  by  it  being  hollow  or 
filled  with  agate.  Here,  petrifaction  must  have  commenced  soon  after 
the  wood  was  exposed  to  the  action  of  moisture,  and  the  supply  of  min- 
eral matter  must  then  have  failed,  or  the  water  must  have  become  too 
much  diluted  before  the  woody  fibre  decayed.  But  when  this  fibre  is 
alone  discoverable,  we  must  suppose  that  an  interval  of  time  elapsed  be- 
fore the  commencement  of  lapidification,  during  which  the  cellular  tissue 
was  obliterated.  When  both  structures,  namely,  the  cellular  and  the 
woody  fibre,  are  preserved,  the  process  must  have  commenced  at  an 
early  period,  and  continued  without  interruption  till  it  was  completed 
throughout.! 

*  Stokes,  GeoL  Trans.  voL  v.  p.  212,  second  series. 
Ibid. 


LAND  HAS  BEEN  EAISED,  \Ca.  V. 


CHAPTER  V. 

ELEVATION     OF     STRATA    ABOVE     THE     SEA HORIZONTAL    AND     INCLINED 

STRATIFICATION. 

Why  the  position  of  marine  strata,  above  the  level  of  the  sea,  should  be  referred 
to  the  rising  up  of  the  land,  not  to  the  going  down  of  the  sea — Upheaval  oi 
extensive  masses  of  horizontal  strata — Inclined  and  vertical  stratification — An- 
ticlinal and  synclinal  lines — Bent  strata  in  east  of  Scotland — Theory  of  folding 
by  lateral  movement — Creeps — Dip  and  strike — Structure  of  the  Jura — Vari- 
ous forms  of  outcrop — Rocks  broken  by  flexure — Inverted  position  of  disturbed 
strata — Unconformable  stratification — Button  and  Playfair  on  the  same — Frac- 
tures of  strata — Polished  surfaces — Faults — Appearance  of  repeated  alterna- 
tions produced  by  them — Origin  of  great  faults. 

LAND  has  been  raised,  not  the  sea  lowered. — It  has  been  already  stated 
that  the  aqueous  rocks  containing  marine  fossils  extend  over  wide  conti- 
nental tracts,  and  are  seen  in  mountain  chains  rising  to  great  heights 
above  the  level  of  the  sea  (p.  4).  Hence  it  follows,  that  what  is  now  dry 
land  was  once  under  water.  But  if  we  admit  this  conclusion,  we  must 
imagine,  either  that  there  has  been  a  general  lowering  of  the  waters  of  the 
ocean,  or  that  the  solid  rocks,  once  covered  by  water,  have  been  raised 
up  bodily  out  of  the  sea,  and  have  thus  become  dry  land.  The  earlier 
geologists,  finding  themselves  reduced  to  this  alternative,  embraced  the 
former  opinion,  assuming  that  the  ocean  was  originally  universal,  and 
had  gradually  sunk  down  to  its  actual  level,  so  that  the  present  islands 
and  continents  were  left  dry.  It  seemed  to  them  far  easier  to  conceive 
that  the  water  had  gone  down,  than  that  solid  land  had  risen  upwards 
into  its  present  position.  It  was,  however,  impossible  to  invent  any  sat- 
isfactory hypothesis  to  explain  the  disappearance  of  so  enormous  a  body 
of  water  throughout  the  globe,  it  being  necessary  to  infer  that  the  ocean 
had  once  stood  at  whatever  height  marine  shells  might  be  detected.  It 
moreover  appeared  clear,  as  the  science  of  Geology  advanced,  that  certain 
spaces  on  the  globe  had  been  alternately  sea,  then  land,  then  estuary, 
then  sea  again,  and,  lastly,  once  more  habitable  land,  having  remained 
in  each  of  these  states  for  considerable  periods.  In  order  to  account  for 
such  phenomena,  without  admitting  any  movement  of  the  land  itself,  we 
are  required  to  imagine  several  retreats  and  returns  of  the  ocean  ;  and 
even  then  our  theory  applies  merely  to  cases  where  the  marine  strata 
composing  the  dry  land  are  horizontal,  leaving  unexplained  those  more 
jommon  instances  where  strata  are  inclined,  curved,  or  placed  on  their 
edges,  and  evidently  not  in  the  position  in  which  they  were  first 
deposited. 

Geologists,  therefore,  were  at  last  compelled  to  have  recourse  to  the 
other  alternative,  namely,  the  doctrine  that  the  solid  land  has  been  re- 
peatedly moved  upwards  or  downwards,  so  as  permanently  to  change  its 


CH.  V.]  NOT  THE   SEA  LOWERED.  45 

position  relatively  to  the  sea.  There  are  several  distinct  grounds  for 
preferring  this  conclusion.  First,  it  will  account  equally  for  the  position 
of  those  elevated  masses  of  marine  origin  in  which  the  stratification  re- 
mains horizontal,  and  for  those  in  which  the  strata  are  disturbed,  broken, 
inclined,  or  vertical.  Secondly,  it  is  consistent  with  human  experience 
that  land  should  rise  gradually  in  some  places  and  be  depressed  in 
others.  Such  changes  have  actually  occurred  in  our  own  days,  and  are 
now  in  progress,  having  been  accompanied  in  some  cases  by  violent  con- 
vulsions, while  in  others  they  have  proceeded  so  insensibly,  as  to  have 
been  ascertainable  only  by  the  most  careful  scientific  observations,  made 
at  considerable  intervals  of  time.  On  the  other  hand,  there  is  no  evi- 
dence from  human  experience  of  a  lowering  of  the  sea's  level  in  any 
region,  and  the  ocean  cannot  sink  in  one  place  without  its  level  being 
depressed  all  over  the  globe. 

These  preliminary  remarks  will  prepare  the  reader  to  understand  the 
great  theoretical  interest  attached  to  all  facts  connected  with  the  position 
of  strata,  whether  horizontal  or  inclined,  curved  or  vertical. 

Now  the  first  and  most  simple  appearance  is  where  strata  of  marine 
origin  occur  above  the  level  of  the  sea  in  horizontal  position.  Such  are 
the  strata  which  we  meet  with  in  the  south  of  Sicily,  filled  with  shells 
for  the  most  part  of  the  same  species  as  those  now  living  in  the  Mediter- 
ranean. Some  of  these  rocks  rise  to  the  height  of  more  than  2000  feet 
above  the  sea.  Other  mountain  masses  might  be  mentioned,  composed 
of  horizontal  strata  of  high  antiquity,  which  contain  fossil  remains  of 
animals  wholly  dissimilar  from  any  now  known  to  exist.  In  the  south 
of  Sweden,  for  example,  near  Lake  Wener,  the  beds  of  one  of  the  oldest 
of  the  fossiliferous  deposits,  namely,  that  formerly  called  Transition,  and 
now  Silurian,  by  geologists,  occur  in  as  level  a  position  as  if  they  had 
recently  formed  part  of  the  delta  of  a  great  river,  and  been  left  dry  on 
the  retiring  of  the  annual  floods.  Aqueous  rocks  of  about  the  same  age 
extend  for  hundreds  of  miles  over  the  lake-district  of  North  America, 
and  exhibit  in  like  manner  a  stratification  nearly  undisturbed.  The 
Table  Mountain  at  the  Cape  of  Good  Hope  is  another  example  of  highly 
elevated  yet  perfectly  horizontal  strata,  no  less  than  3500  feet  in  thick- 
ness, and  consisting  of  sandstone  of  very  ancient  date. 

Instead  of  imagining  that  such  fossiliferous  rocks  were  always  at  their 
present  level,  and  that  the  sea  was  once  high  enough  to  cover  them,  we 
suppose  them  to  have  constituted  the  ancient  bed  of  the  ocean,  and  that 
they  were  gradually  uplifted  to  their  present  height.  This  idea,  how- 
ever startling  it  may  at  first  appear,  is  quite  in  accordance,  as  before 
stated,  with  the  analogy  of  changes  now  going  on  in  certain  regions  of 
the  globe.  Thus,  in  parts  of  Sweden,  and  the  shores  and  islands  of  the 
Gulf  of  Bothnia,  proofs  have  been  obtained  that  the  land  is  experiencing, 
and  has  experienced  for  centuries,  a  slow  upheaving  movement.  Play- 
fair  argued  in  favor  of  this  opinion  in  1802  ;  and  in  1807,  Von  Buch, 
after  his  travels  in  Scandinavia,  announced  his  conviction  that  a  rising 
of  the  land  was  in  progress.  Celsius  and  other  Swedish  writers  had. 


46  RISING  AND  SINKING  OF  LAND.  [On.  "V. 

a  century  before,  declared  their  belief  that  a  gradual  change  had,  foi 
ages,  been  taking  place  in  the  relative  level  of  land  and  sea.  They  at- 
tributed the  change  to  a  fall  of  the  waters  both  of  the  ocean  and  the 
Baltic.  This  theory,  however,  has  now  been  refuted  by  abundant  evi- 
dence ;  for  the  alteration  of  relative  level  has  neither  been  universal  nor 
everywhere  uniform  in  quantity,  but  has  amounted,  in  some  regions,  to 
several  feet  in  a  century,  in  others  to  a  few  inches  ;  while  in  the  south- 
ernmost part  of  Sweden,  or  the  province  of  Scania,  there  has  been  actu- 
ally a  loss  instead  of  a  gain  of  land,  buildings  having  gradually  sunk 
below  the  level  of  the  sea.* 

It  appears,  from  the  observations  of  Mr.  Darwin  and  others,  that  very 
extensive  regions  of  the  continent  of  South  America  have  been  under- 
going slow  and  gradual  upheaval,  by  which  the  level  plains  of  Patagonia, 
covered  with  recent  marine  shells,  and  the  Pampas  of  Buenos  Ayres, 
have  been  raised  above  the  level  of  the  sea.f  On  the  other  hand,  the 
gradual  sinking  of  the  west  coast  of  Greenland,  for  the  space  of  more 
than  600  miles  from  north  to  south,  during  the  last  four  centuries,  has 
been  established  by  the  observations  of  a  Danish  naturalist,  Dr.  Pingel. 
And  while  these  proofs  of  continental  elevation  and  subsidence,  by  slow 
and  insensible  movements,  have  been  recently  brought  to  light,  the  evi- 
dence has  been  daily  strengthened  of  continued  changes  of  level  effected 
by  violent  convulsions  in  countries  where  earthquakes  are  frequent.  There 
the  rocks  are  rent  from  time  to  time,  and  heaved  up  or  thrown  down 
several  feet  at  once,  and  disturbed  in  such  a  manner,  that  the  original 
position  of  strata  may,  in  the  course  of  centuries,  be  modified  to  any 
amount. 

It  has  also  been  shown  by  Mr.  Darwin,  that,  in  those  seas  where  cir- 
cular coral  islands  and  barrier  reefs  abound,  there  is  a  slow  and  continued 
sinking  of  the  submarine  mountains  on  which  the  masses  of  coral  are 
based  ;  while  there  are  other  areas  of  the  South  Sea,  where  the  land  is 
on  the  rise,  and  where  coral  has  been  upheaved  far  above  the  sea-level. 

It  would  require  a  volume  to  explain  to  the  reader  the  various  facts 
which  establish  the  reality  of  these  movements  of  land,  whether  of  ele- 
vation or  depression,  whether  accompanied  by  earthquakes  or  accom- 
plished slowly  and  without  local  disturbance.  Having  treated  fully  of 
these  subjects  in  the  Principles  of  Geology,J  I  shall  assume,  in  the  present 
work,  that  such  changes  are  part  of  the  actual  course  of  nature ;  and 
when  admitted,  they  will  be  found  to  afford  a  key  to  the  interpretation 
of  a  variety  of  geological  appearances,  such  as  the  elevation  of  horizon- 
tal, inclined,  or  disturbed  marine  strata,  and  the  superposition  of  fresh- 

*  In  the  first  three  editions  of  my  Principles  of  Geology,  I  expressed  many 
doubts  as  to  the  validity  of  the  alleged  proofs  of  a  gradual  rise  of  land  in  Sweden ; 
but  after  visiting  that  country,  in  1834,  I  retracted  these  objections,  and  published 
a  detailed  statement  of  the  observations  which  led  me  to  alter  my  opinion  in  the 
Phil.  Trans.  1835,  Part  I.  See  also  the  Principles,  4th  and  subsequent  editions. 

f  See  his  Journal  of  a  Naturalist  in  Voyage  of  the  Beagle,  and  his  work  on 
Coral  Reefs. 

\  See  chapters  xxvii.  to  xxxii.  inclusive,  and  chap.  1. 


Ca  Y.J 


INCLINED   STRATIFICATION. 


47 


.  61. 


water  to  marine  deposits,  afterwards  to  be  described.  It  will  also  appear, 
in  the  sequel,  how  much  light  the  doctrine  of  a  continued  subsidence  of 
land  may  throw  on  the  manner  in  which  a  series  of  strata,  formed  in 
shallow  water,  may  have  accumulated  to  a  great  thickness.  The  exca- 
vation of  valleys  also,  and  other  effects  of  denudation,  of  which  I  shall 
presently  treat,  can  alone  be  understood  when  we  duly  appreciate  the 
proofs,  now  on  record,  of  the  prolonged  rising  and  sinking  of  land, 
throughout  wide  areas. 

To  conclude  this  subject,  I  may  remind  the  reader,  that  were  we  to 
embrace  the  doctrine  which  ascribes  the  elevated  position  of  marine 
formations,  and  the  depression  of  certain  freshwater  strata,  to  oscillations 
in  the  level  of  the  waters  instead  of  the  land,  we  should  be  compelled  to 
admit  that  the  ocean  has  been  sometimes  everywhere  much  shallower 
than  at  present,  and  at  others  more  than  three  miles  deeper. 

Inclined  stratification. — The  most  unequivocal  evidence  of  a  change 
in  the  original  position  of  strata  is  afforded  by  their  standing  up  perpen- 
dicularly on  their  edges,  which  is  by  no  means  a  rare  phenomenon,  es- 
pecially in  mountainous  countries.  Thus  we  find  in  Scotland,  on  the 
southern  skirts  of  the  Grampians,  beds  of  pudding-stone  alternating 
with  thin  layers  of  fine  sand,  all  placed  vertically  to  the  horizon.  When 
Saussure  first  observed  certain  conglomer- 
ates in  a  similar  position  in  the  Swiss  Alps, 
he  remarked  that  the  pebbles,  being  for  the 
most  part  of  an  oval  shape,  had  their 
longer  axes  parallel  to  the  planes  of  strati- 
fication (see  fig.  61).  From  this  he  in- 
ferred, that  such  strata  must,  at  first,  have 
been  horizontal,  each  oval  pebble  having 

Originally    settled    at    the    bottom    of    the    Vertical  conglomerate  and  sandstone. 

water,  with  its  flatter  side  parallel  to  the  horizon,  for  the  same  reason 
that  an  egg  will  not  stand  on  either  end  if  unsupported.  Some  few,  in- 
deed, of  the  rounded  stones  in  a  conglomerate  occasionally  afford  an 
exception  to  the  above  rule,  for  the  same  reason  that  we  see  on  a  shingle 
beach  some  oval  or  flat-sided  pebbles  resting  on  their  ends  or  edges ; 
these  having  been  forced  along  the  bottom  and  against  each  other  by  a 
wave  or  current  so  as  to  settle  in  this  position. 

Vertical  strata,  when  they  can  be  traced  continuously  upwards  or 
downwards  for  some  depth,  are  almost  invariably  seen  to  be  parts  of 
great  curves,  which  may  have  a  diameter  of  a  few  yards,  or  of  several 
miles.  I  shall  first  describe  two  curves  of  considerable  regularity,  which 
occur  in  Forfarshire,  extending  over  a  country  twenty  miles  in  breadth, 
from  the  foot  of  the  Grampians  to  the  sea  near  Arbroath. 

The  mass  of  strata  here  shown  may  be  nearly  2000  feet  in  thickness, 
consisting  of  red  and  white  sandstone,  and  various  colored  shales,  the 
beds  being  distinguishable  into  four  principal  groups,  namely,  No.  l,red 
marl  or  shale  ;  No.  2,  red  sandstone,  used  for  building ;  No.  3,  conglom- 
erate ;  and  No.  4,  gray  paving-stone,  and  tile-stone,  with  green  and  red- 


CUEVED   STKATA. 


tt  V. 


dish  shale,  containing  peculiar  organic  re- 
mains. A  glance  at  the  section  will  show 
that  each  of  the  formations  2,  3,  4,  are  re- 
peated thrice  at  the  surface,  twice  with  a 
southerly,  and  once  with  a  northerly  indi- 
cation or  dip,  and  the  beds  in  No.  1,  which 
are  nearly  horizontal,  are  still  brought  up 
twice  by  a  slight  curvature  to  the  surface, 
once  on  each  side  of  A.  Beginning  at  the 
northwest  extremity,  the  tile-stones  and 
conglomerates  No.  4  and  No.  3  are  verti- 
cal, and  they  generally  form  a  ridge  par- 
allel to  the  southern  skirts  of  the  Grampi- 
ans. The  superior  strata  Nos.  2  and  1  be- 
come less  and  less  inclined  on  descending 
to  the  valley  of  Strathmore,  where  the 
strata,  having  a  concave  oend,  are  said  by 
geologists  to  lie  in  a  "  trough"  or  "  basin." 
Through  the  centre  of  this  valley  runs  an 
imaginary  line  A,  called  technically  a 
"  synclinal  line,"  where  the  beds,  which 
are  tilted  in  opposite  directions,  may  be 
supposed  to  meet.  It  is  most  important 
for  the  observer  to  mark  such  lines,  for  he 
will  perceive  by  the  diagram,  that  in  trav- 
elling from  the  north  to  the  centre  of  the 
basin,  he  is  always  passing  from  older  to 
newer  beds;  whereas,  after  crossing  the 
line  A,  and  pursuing  his  course  in  the  same 
southerly  direction,  he  is  continually  leav- 
ing the  newer,  and  advancing  upon  older 
strata.  All  the  deposits  which  he  had  be- 
fore examined  begin  then  to  recur  in  re- 
versed order,  until  he  arrives  at  the  central 
axis  of  the  Sidlaw  hills,  where  the  strata 
are  seen  to  form  an  arch  or  saddle,  having 
an  anticlinal  line  B,  in  the  centre.  On  passing  this  line,  and  continuing 
towards  the  S.  E.,  the  formations  4,  3,  and  2,  are  again  repeated,  in  the 
same  relative  order  of  superposition,  but  with  a  southerly  dip.  At  White- 
ness (see  diagram)  it  will  be  seen  that  the  inclined  strata  are  covered  by 
a  newer  deposit,  a,  in  horizontal  beds.  These  are  composed  of  red  conglom- 
erate and  sand,  and  are  newer  than  any  of  the  groups,  1,  2,  3,  4,  before  de- 
scribed, and  rest  unconformably  upon  strata  of  the  sandstone  group,  No.  2. 
An  example  of  curved  strata,  in  which  the  bends  or  convolutions  of 
the  rock  are  sharper  and  far  more  numerous  within  an  equal  space,  has 
been  well  described  by  Sir  James  Hall.*  It  occurs  near  St.  Abb's  Head, 
*  Edin.  Trans,  vol.  vii.  pi.  8 


CK.  V.]  EXPERIMENTS  TO  ILLUSTRATE  CURVED  STRATA.     49 

on  the  east  coast  of  Scotland,  where  the  rocks  consist  principally  of  a 
bluish  slate,  having  frequently  a  ripple-marked  surface.  The  undulations 
of  the  beds  reach  from  the  top  to  the  bottom  of  cliffs  from  200  to  300 

Fig.  63. 


Curved  strata  of  slate  near  St.  Abb's  Head,  Berwickshire.    (Sir  J.  Hall.) 

feet  in  height,  and  there  are  sixteen  distinct  bendings  in  the  course  of 
about  six  miles,  the  curvatures  being  alternately  concave  and  convex  up- 
wards. 

An  experiment  was  made  by  Sir  James  Hall,  with  a  view  of  illus- 
trating the  manner  in  which  such  strata,  assuming  them  to  have  been 
originally  horizontal,  may  have  been  forced  into  their  present  position.  A 
set  of  layers  of  clay  were  placed  under  a  weight,  and  their  opposite  ends 
pressed  towards  each  other  with  such  force  as  to  cause  them  to  approach 
more  nearly  together.  On  the  removal  of  the  weight,  the  layers  of  clay 
were  found  to  be  curved  and  folded,  so  as  to  bear  a  miniature  resemblance 
to  the  strata  in  the  cliffs.  We  must,  however,  bear  in  mind,  that  in  the 
natural  section  or  sea-cliff  we  only  see  the  foldings  imperfectly,  one  part 
being7  invisible  beneath  the  sea,  and  the  other,  or  upper  portion,  being 
supposed  to  have  been  carried  away  by  denudation,  or  that  action  of 

Fig.  64 


water  which  will  be  explained  in  the  next  chapter.  The  dark  lines  in 
the  accompanying  plan  (fig.  64)  represent  what  is  actually  seen  of  the 
strata  in  part  of  the  line  of  cliff  alluded  to  ;  the  fainter  lines,  that  por- 

4 


50  CURVED   STEATA.  [On  V. 

tion  which  is  concealed  beneath  the  sea-level,  as  also  that  which  is  sup- 
posed to  have  once  existed  above  the  present  surface. 

We  may  still  more  easily  illustrate  the  effects  which  a  lateral  thrust 
might  produce  on  flexible  strata,  by  placing  several  pieces  of  differently 
Colored  cloths  upon  a  table,  and  when  they  are  spread  out  horizontally, 

Fig.  65. 


cover  them  with  a  book.  Then  apply  other  books  to  each  end,  and  force 
them  towards  each  other.  The  folding  of  the  cloths  will  exactly  imitate 
those  of  the  bent  strata.  (See  fig.  65.) 

Whether  the  analogous  flexures  in  stratified  rocks  have  really  been 
due  to  similar  sideway  movements  is  a  question  of  considerable  difficulty. 
It  will  appear  when  the  volcanic  and  granitic  rocks  are  described,  that 
some  of  them  have,  when  melted,  been  injected  forcibly  into  fissures, 
while  others,  already  in  a  solid  state,  have  been  protruded  upwards 
through  the  incumbent  crust  of  the  earth,  by  which  a  great  displace- 
ment of  flexible  strata  must  have  been  caused. 

But  we  also  know  by  the  study  of  regions  liable  to  earthquakes,  that 
there  are  causes  at  work  in  the  interior  of  the  earth  capable  of  producing 
a  sinking  in  of  the  ground,  sometimes  very  local,  but  sometimes  extend- 
ing over  a  wide  area.  The  frequent  repetition,  or  continuance  throughout 
long  periods,  of  such  downward  movements  seems  to  imply  the  formation 
and  renewal  of  cavities  at  a  certain  depth  below  the  surface,  whether  by 
the  removal  of  matter  by  volcanoes  and  hot  springs,  or  by  the  contrac- 
tion of  argillaceous  rocks  by  heat  and  pressure,  or  any  other  combination 
of  circumstances.  Whatever  conjectures  we  may  indulge  respecting  the 
causes,  it  is  certain  that  pliable  beds  may,  in  consequence  of  unequal 
degrees  of  subsidence,  become  folded  to  any  amount,  and  have  all  the 
appearance  of  having  been  compressed  suddenly  by  a  lateral  thrust. 

The  "  Creeps,"  as  they  are  called  in  coal-mines,  afford  an  excellent  il- 
lustration of  this  fact. — First,  it  may  be  stated  generally,  that  the  exca- 
vation of  coal  at  a  considerable  depth  causes  the  mass  of  overlying  strata 
to  sink  down  bodily,  even  when  props  are  left  to  support  the  roof  of  the 
mine.  "In  Yorkshire,"  says  Mr.  Buddie,  "three  distinct  subsidences 
were  perceptible  at  the  surface,  after  the  clearing  out  of  three  seams  of 
coal  below,  and  innumerable  vertical  cracks  were  caused  in  the  incum- 
bent mass  of  sandstone  and  shale,  which  thus  settled  down."*  The  ex- 

*  Proceedings  of  Geol.  Soc.  vol.  iii.  p.  148. 


OH.  V.] 


CEEEPS  IN   COAL-MINES. 


51 


act  amount  of  depression  in  these  cases  can  only  be  accurately  measured 
where  water  accumulates  on  the  surface,  or  a  railway  traverses  a  coal-field. 
When  a  bed  of  coal  is  worked  out,  pillars  or  rectangular  masses  of 
coal  are  left  at  intervals  as  props  to  support  the  roof  and  protect  the 
colliers.  Thus  in  fig.  66,  representing  a  section  at  Wallsend,  Newcastle, 


the  galleries  which  have  been  excavated  are  represented  by  the  white 
spaces  a  6,  while  the  adjoining  dark  portions  are  parts  of  the  original 
coal-seam  left  as  props,  beds  of  sandy  clay  or  shale  constituting  the  floor 
of  the  mine.  "When  the  props  have  been  reduced  in  size,  they  are  pressed 


52  CURVED  STEATA.  [On.  V 

down  by  the  weight  of  overlying  rocks  (no  less  than  630  feet  thick) 
upon  the  shale  below,  which  is  thereby  squeezed  and  forced  up  into  the 
open  spaces. 

Now  it  might  have  been  expected,  that  instead  of  the  floor  rising  up, 
the  ceiling  would  sink  down,  and  this  effect,  called  a  "Thrust,"  does,  in 
fact,  take  place  where  the  pavement  is  more  solid  than  the  roof.  But  it 
usually  happens,  in  coal-mines,  that  the  roof  is  composed  of  hard  shale, 
or  occasionally  of  sandstone,  more  unyielding  than  the  foundation,  which 
often  consists  of  clay.  Even  where  the  argillaceous  substrata  are  hard 
at  first,  they  soon  become  softened  and  reduced  to  a  plastic  state  when 
exposed  to  the  contact  of  air  and  water  in  the  floor  of  a  mine. 

The  first  symptom  of  a  "  creep,"  says  Mr.  Buddie,  is  a  slight  curvature 
at  the  bottom  of  each  gallery,  as  at  a,  fig.  66  ;  then  the  pavement  con- 
tinuing to  rise,  begins  to  open  with  a  longitudinal  crack,  as  at  b :  then 
the  points  of  the  fractured  ridge  reach  the  roof,  as  at  c  ;  and,  lastly,  the 
upraised  beds  close  up  the  whole  gallery,  and  the  broken  portions  of  the 
ridge  are  reunited  and  flattened  at  the  top,  exhibiting  the  flexure  seen  at 
d.  Meanwhile  the  coal  in  the  props  has  become  crushed  and  cracked  by 
pressure.  It  is  also  found,  that  below  the  creeps  a,  6,  c,  c?,  an  inferior 
stratum,  called  the  "  metal  coal,"  which  is  3  feet  thick,  has  been  fractured 
at  the  points  e,  /,  #,  A,  and  has  risen,  so  as  to  prove  that  the  upward 
movement,  caused  by  the  working  out  of  the  "main  coal,"  has  been 
propagated  through  a  thickness  of  54  feet  of  argillaceous  beds,  which 
intervene  between  the  two  coal  seams.  This  same  displacement  has  also 
been  traced  downwards  more  than  150  feet  below  the  metal  coal,  but  it 
grows  continually  less  and  less  until  it  becomes  imperceptible. 

No  part  of  the  process  above  described  is  more  deserving  of  our  no- 
tice than  the  slowness  with  which  the  change  in  the  arrangement  of  the 
beds  is  brought  about.  Days,  months,  or  even  years,  will  sometimes 
elapse  between  the  first  bending  of  the  pavement  and  the  time  of  its 
reaching  the  roof.  Where  the  movement  has  been  most  rapid,  the  curv- 
ature of  the  beds  is  most  regular,  and  the  reunion  of  the  fractured  ends 
most  complete ;  whereas  the  signs  of  displacement  or  violence  are  great- 
est in  those  creeps  which  have  required  months  or  years  for  their  entire 
accomplishment.  Hence  we  may  conclude  that  similar  changes  may 
have  been  wrought  on  a  larger  scale  in  the  earth's  crust  by  partial  and 
gradual  subsidences,  especially  where  the  ground  has  been  undermined 
throughout  long  periods  of  time ;  and  we  must  be  on  our  guard  against 
inferring  sudden  violence,  simply  because  the  distortion  of  the  beds  is 
excessive. 

Between  the  layers  of  shale,  accompanying  coal,  we  sometimes  see 
the  leaves  of  fossil  ferns  spread  out  as  regularly  as  dried  plants  between 
sheets  of  paper  in  the  herbarium  of  a  botanist.  These  fern-leaves,  01 
fronds,  must  have  rested  horizontally  on  soft  mud,  when  first  deposited. 
If,  therefore,  they  and  the  layers  of  shale  are  now  inclined,  or  standing 
on  end,  it  is  obviously  the  effect  of  subsequent  derangement.  The  proof 
becomes,  if  possible,  still  more  striking  when  these  strata,  including 


CH.  V.]  DIP  AND  STRIKE.  53 

vegetable  remains,  are  curved  again  and  again,  and  even  folded  into  the 
form  of  the  letter  Z,  so  that  the  same  continuous  layer  of  coal  is  cut 
through  several  times  in  the  same  perpendicular  shaft.  Thus,  in  the 
coal-field  near  Mons,  in  Belgium,  these  zigzag  bendings  are  repeated  four 

Fig.  67. 


Fig.  68. 


Zigzag  flexures  of  coal  near  Mons. 

or  five  times,  in  the  manner  represented  in  fig.  67,  the  black  lines  repre- 
senting seams  of  coal.* 

Dip  and  strike. — In  the  above  remarks,  several  technical  terms  have 
been  used,  such  as  dip,  the  unconformable  position  of  strata,  and  the 
anticlinal  and  synclinal  lines,  which,  as  well  as  the  strike  of  the  beds,  I 
shall  now  explain.  If  a  stratum  or  bed  of  rock,  instead  of  being  quite 
level,  be  inclined  to  one  side,  it  is  said  to  dip;  the  point  of  the  compass 
to  which  it  is  inclined  is  called  the  point  of  dip,  and  the  degree  of  devi- 
ation from  a  level  or  horizontal  line  is  called  the  amount  of  dip,  or  the 

angle  of  dip.  Thus,  in  the  annexed 
diagram  (fig.  68),  a  series  of  strata 
are  inclined,  and  they  dip  to  the  north 
at  an  angle  of  forty-five  degrees.  The 
strike,  or  line  of  bearing,  is  the  pro- 
longation or  extension  of  the  strata 
in  a  direction  at  right  angles  to  the  dip ;  and  hence  it  is  sometimes  called 
the  direction  of  the  strata.  Thus,  in  the  above  instance  of  strata  dipping 
to  the  north,  their  strike  must  necessarily  be  east  and  west.  We  have 
borrowed  the  word  from  the  German  geologists,  streichen  signifying  to 
extend,  to  have  a  certain  direction.  Dip  and  strike  may  be  aptly  illus- 
trated by  a  row  of  houses  running  east  and  west,  the  long  ridge  of 
the  roof  representing  the  strike  of  the  stratum  of  slates,  which  dip  on 
one  side  to  the  north,  and  on  the  other  to  the  south. 

A  stratum  which  is  horizontal,  or  quite  level  in  all  directions,  has 
neither  dip  nor  strike. 

It  is  always  important  for  the  geologist,  who  is  endeavoring  to  com- 
prehend the  structure  of  a  country,  to  learn  how  the  beds  dip  in  every 
part  of  the  district ;  but  it  requires  some  practice  to  avoid  being  occa- 
sionally deceived,  both  as  to  the  point  of  dip  and  the  amount  of  it. 

*  See  plan  by  M.  Chevalier,  Burat's  D'Aubuisson,  torn,  ii  p.  884. 


54  DIP  AND  STKIKE.  [On.  V. 

If  the  upper  surface  of  a  hard  stony  stratum  be  uncovered,  whether 
artificially  in  a  quarry,  or  by  the  waves  at  the  foot  of  a  cliff,  it  is  easy 
to  determine  towards  what  point  of  the  compass  the  slope  is  steepest,  or 
in  what  direction  water  would  flow,  if  poured  upon  it.  This  is  the  true 
dip.  But  the  edges  of  highly  inclined  strata  may  give  rise  to  perfectly 
horizontal  lines  in  the  face  of  a  vertical  cliff,  if  the  observer  see  the 
strata  in  the  line  of  their  strike,  the  dip  being  inwards  from  the  face  of 
the  cliff.  If,  however,  we  come  to  a  break  in  the  cliff,  which  exhibits  a 
section  exactly  at  right  angles  to  the  line  of  the  strike,  we  are  then  able 
to  ascertain  the  true  dip.  In  the  annexed  drawing  (fig.  69),  we  may 
suppose  a  headland,  one  side  of  which  faces  to  the  north,  where  the 


Apparent  horizontality  of  inclined  strata. 

beds  would  appear  perfectly  horizontal  to  a  person  in  the  boat ;  while  in 
the  other  side  facing  the  west,  the  true  dip  would  be  seen  by  the  person 
on  shore  to  be  at  an  .angle  of  40°.  If,  therefore,  our  observations  are 
confined  to  a  vertical  precipice  facing  in  one  direction,  we  must  endeavor 
to  find  a  ledge  or  portion  of  the  plane  of  one  of  the  beds  projecting  be- 
yond the  others,  in  order  to  ascertain  the  true  dip. 

It  is  rarely  important  to  determine  the  angle  of  inclination  with  such 
minuteness  as  to  require  the  aid  of  the  instrument  called  a  clinometer. 
We  may  measure  the  angle  within  a  few  degrees  by  standing  exactly 

opposite  to  a  cliff  where  the  true  dip  is 
exhibited,  holding  the  hands  immediately 
before  the  eyes,  and  placing  the  fingers  of 
one  in  a  perpendicular,  and  of  the  other  in 
a  horizontal  position,  as  in  fig.  70.  It  is 
thus  easy  to  discover  whether  the  lines  of 
the  inclined  beds  bisect  the  angle  of  90°, 
formed  by  the  meeting  of  the  hands,  so  as 
to  give  an  angle  of  45°,  or  whether  it 
would  divide  the  space  into  two  equal  or 
unequal  portions.  The  upper  dotted  line 
may  express  a  stratum  dipping  to  the  north ;  but  should  the  beds  dip 
precisely  to  the  opposite  point  of  the  compass  as  in  the  lower  dotted 


OH.  V.] 


DIP   AND   STRIKE. 


55 


line,  it  will  be  seen  that  the  amount  of  inclination  may  still  be  measured 
by  the  hands  with  equal  facility. 

It  has  been  already  seen,  in  describing  the  curved  strata  on  the  east 
coast  of  Scotland,  in  Forfarshire  and  Berwickshire,  that  a  series  of  con- 
cave and  convex  bendings  are  occasionally  repeated  several  times.  These 
usually  form  part  of  a  series  of  parallel  waves  of  strata,  which  are  pro- 
longed in  the  same  direction  throughout  a  considerable  extent  of  country. 
Thus,  for  example,  in  the  Swiss  Jura,  that  lofty  chain  of  mountains  has 
been  proved  to  consist  of  many  parallel  ridges,  with  intervening  longi- 
tudinal valleys,  as  in  fig.  71,  the  ridges  being  formed  by  curved  fossilif- 
erous  strata,  of  which  the  nature  and  dip  are  occasionally  displayed  in 
deep  transverse  gorges,  called  "  cluses,"  caused  by  fractures  at  right  angles 
to  the  direction  of  the  chain.*  Now  let  us  suppose  these  ridges  and 
parallel  valleys  to  run  north  and  south,  we  should  then  say  that  the 
strike  of  the  beds  is  north  and  south,  and  the  dip  east  and  west.  Lines 
drawn  along  the  summits  of  the  ridges,  A,  B,  would  be  anticlinal  lines, 
and  one  following  the  bottom  of  the  adjoining  valleys  a  synclinal  line. 

Fig.  71. 


Fig.  72. 


Fig.  73. 


Section  illustrating  the  structure  of  the  Swiss  Jura. 

It  will  be  observed  that  some  of  these  ridges,  A,  B,  are  unbroken  on  the 
summit,  whereas  one  of  them,  C,  has  been  fractured  along  the  line  of 
strike,  and  a  portio  i  of  it  carried  away  by  denudation,  so  that  the  ridges 
of  the  beds  in  the  formations  a,  b,  c,  come  out  to  the  day,  or,  as  the 

miners  say,  crop  out,  on  the  sides 
of  a  valley.     The  ground  plan  of 
|  such  a  denuded  ridge  as  0,  as  given 
1  in  a  geological  map,  may  be  ex- 
|  pressed  by  the  diagram  fig.  72,  and 
|  the  cross  section  of  the  same  by 
|  fig.  73.     The  line  D  E,  fig.  72,  is 
the  anticlinal  line,  on  each  side  of 

Ground  plan  of  the  denuded  ridge  C,  fig.  71.         which  the  dip  IS  in  opposite  direc- 

*  See  M.  Thurmann's  work,  "  Essai  sur  les  Soulevemens  Jurassiques  du  Por- 
rentruy,  Paris,  1832,"  with  whom  I  examined  part  of  these  mountains  in  1836. 


56 


OUTCROP  OF  STRATA. 


[On.  V. 


tions,  as  expressed  by  the  arrows.     The  emergence  of  strata  at  the  sur- 
face is  called  by  miners  their  outcrop  or  basset. 

If,  instead  of  being  folded  into  parallel  ridges,  the  beds  form  a  boss 
or  dome-shaped  protuberance,  and  if  we  suppose  the  summit  of  the 
dome  carried  off,  the  ground  plan  would  exhibit  the  edges  of  the  strata 
forming  a  succession  of  circles,  or  ellipses,  round  a  common  centre. 
These  circles  are  the  lines  of  strike,  and  the  dip  being  always  at  right 
angles  is  inclined  in  the  course  of  the  circuit  to  every  point  of  the  com- 
pass, constituting  what  is  termed  a  qua-quaversal  dip — that  is,  turning 
each  way. 

There  are  endless  variations  in  the  figures  described  by  the  basset- 
edges  of  the  strata,  according  to  the  different  inclination  of  the  beds, 
and  the  mode  in  which  they  happen  to  have  been  denuded.  One 
of  the  simplest  rules  with  which  every  geologist  should  be  acquainted, 
relates  to  the  V-like  form  of  the  beds  as  they  crop  out  in  an  ordinary 
valley.  First,  if  the  strata  be  horizontal,  the  V-like  form  will  be 
also  on  a  level,  and  the  newest  strata  will  appear  at  the  greatest 
heights. 

Secondly,  if  the  beds  be  inclined  and  intersected  by  a  valley  sloping 
in  the  same  direction,  and  the  dip  of  the  beds  be  less  steep  than  the 
slope  of  the  valley,  then  the  V's,  as  they  are  often  termed  by  miners, 
will  point  upwards  (see  fig.  74),  those  formed  by  the  newer  beds  appear- 
ing in  a  superior  position, 
and  extending  highest  up 
the  valley,  as  A  is  seen 
above  B. 

Thirdly,  if  the  dip  of  the 
beds  be  steeper  than  the 
slope  of  the  valley,  then 
the  V's  will  point  down- 
wards (see  fig.  75),  and 
those  formed  of  the  older 
beds  will  now  appear  up- 
permost, as  B  appears  above 
A. 

Fourthly,  in  every  case 
where  the  strata  dip  in  a 
contrary  direction  to  the 
slope  of  the  valley,  what- 
ever be  the  angle  of  incli- 
nation, the  newer  beds  will 
appear  the  highest,  as  in 
the  first  and  second  cases. 
This  is  shown  by  the  draw- 
ing (fig.  76),  which  exhib- 
its strata  nsmg  at  an  angle 

Slope  of  valley  20°,  dip  of  strata  5QO.  of    20°,      and      Crossed      by 


Slope  of  valley  400,  dip  of  strata  20°. 
Fig.  T5. 


CH.  V.]  ANTICLINAL  AND   SYNCLINAL   LINES. 

Fig.  76. 


57 


Slope  of  valley  20°,  dip  of  strata  20°,  in  opposite 
directions. 


Fig.  77. 


a  valley,  which  declines  in  an 
opposite  direction  at  20°.* 

These  rules  may  often  be  of 
great  practical  utility;  for 
the  different  degrees  of  dip 
occurring  In  the  two  cases 
represented  in  figures  74  and 
75,  may  occasionally  be  en- 
countered in  following  the 
same  line  of  flexure  at  points 
a  few  miles  distant  from 
each  other.  A  miner  un- 
acquainted with  the  rule, 

who  had  first  explored  the  valley  (fig.  74),  may  have  sunk  a  vertical 
shaft  below  the  coal-seam  A,  until  he  reached  the  inferior  bed  B.  He 
might  then  pass  to  the  valley  fig.  75,  and  discovering  there  also  the  out- 
crop of  two  coal-seams,  might  begin  his  workings  in  the  uppermost  in  the 
expectation  of  coming  down  to  the  other  bed  A,  which  would  be  observed 
cropping  out  lower  down  the  valley.  But  a  glance  at  the  section  will 
demonstrate  the  futility  of  such  hopes. 

In  the  majority  of  cases,  an  anticlinal  axis  forms  a  ridge,  and  a  syn- 
clinal axis  a  valley,  as  in  A,  B,  fig.  62,  p.  48  ;  but  there  are  exceptions 
to  this  rule,  the  beds  sometimes  sloping  in- 
wards from  either  side  of  a  mountain,  as  in 
fig.  77. 

On  following  one  of  the  anticlinal  ridges 
of  th.e  Jura,  before  mentioned,  A,  B,  C,  fig. 
71,  we  often  discover  longitudinal  cracks  and 
sometimes  large  fissures  along  the  line  where 
the  flexure  was  greatest.  Some  of  these,  as  above  stated,  have  been  en- 
larged by  denudation  into  valleys  of  considerable  width,  as  at  C,  fig.  71, 
which  follow  the  line  of  strike,  and  which  we  may  suppose  to  have  been 
hollowed  out  at  the  time  when  these  rocks  were  still  beneath  the  level  of 
the  sea,  or  perhaps  at  the  period  of  their  gradual  emergence  from  be- 
neath the  waters.  The  existence  of  such  cracks  at  the  point  of  the 
sharpest  bending  of  solid  strata  of  limestone  is  precisely  what  we  should 
have  expected ;  but  the  occasional  want  of  all  similar  signs  of  fracture, 
even  where  the  strain  has  been  greatest,  as  at  a,  fig.  71,  is  not  always 
easy  to  explain.  We  must  imagine  that  many  strata  of  limestone,  chert, 
and  other  rocks  which  are  now  brittle,  were  pliant  when  bent  into  their 
present  position.  They  may  have  owed  their  flexibility  in  part  to  the 

*  I  am  indebted  to  the  kindness  of  T.  Sopwith,  Esq.,  for  three  models  which  I 
have  copied  in  the  above  diagrams ;  but  the  beginner  may  find  it  by  no  means 
easy  to  understand  such  copies,  although,  if  he  were  to  examine  and  handle  the 
originals,  turning  them  about  in  different  ways,  he  -would  at  once  comprehend 
their  meaning,  as  well  as  the  import  of  others  far  more  complicated,  which  the 
same  engineer  has  constructed  to  illustrate  faults. 


58 


REVERSED   DIP   OF  STRATA. 


[On.  V. 


fluid  matter  which  they  contained  in  their  minute  pores,  as  before 
described  (p.  35),  and  in  part  to  the  permeation  of  sea-water  while  they 
were  yet  submerged. 

At  the  western  extremity  of  the  Pyrenees,  great  curvatures  of  the 
strata  are  seen  in  the  sea  cliffs,  where  the  rocks  consist  of  marl,  grit,  and 
chert.  At  certain  points,  as  at  a,  fig.  78,  some  of  the  bendings  of  the 


Fig.  T8. 


Fig.  79. 


Strata  of  chert,  grit,  and  marl,  near  St.  Jean  de  Luz. 

flinty  chert  are  so  sharp,  that  specimens  might  be  broken  off,  well  fitted 
to  serve  as  ridge-tiles  on  the  roof  of  a  house.  Although  this  chert 
could  not  have  been  brittle  as  now,  when  first  folded  into  this  shape,  it 
presents,  nevertheless,  here  and  there  at  the  points  of  greatest  flexure 
small  cracks,  which  show  that  it  was  solid,  and  not  wholly  incapable  of 
breaking  at  the  period  of  its  displacement.  The  numerous  rents  alluded 
to  are  not  empty,  but  filled  with  chalcedony  and  quartz. 

Between  San  Caterina  and  Castrogiovanni,  in  Sicily,  bent  and  undu- 
lating gypseous  marls  occur,  with  here  and  there  thin  beds  of  solid 

gypsum  interstratified.  Sometimes  these 
solid  layers  have  been  broken  into  detached 
fragments,  still  preserving  their  sharp  edges 
(ff  9i  %•  *79),  while  the  continuity  of  the 
more  pliable  and  ductile  marls,  m  m,  has 
not  been  interrupted. 

I  shall  conclude  my  remarks  on  bent 
strata  by  stating,  that,  in  mountainous  re- 

g.  gypsum,  m.  man.  gions  like  the  Alps,  it  is  often  difficult  for 
an  experienced  geologist  to  determine  correctly  the  relative  age  of  beds 
by  superposition,  so  often  have  the  strata  been  folded  back  upon  them- 
selves, the  upper  parts  of  the  curve  having  been  removed  by  denudation. 
Thus,  if  we  met  with  the  strata  seen  in  the  section  fig.  80,  we  should 

naturally  suppose  that  there  were  twelve 
distinct  beds,  or  sets  of  beds,  No.  1  being 
the  newest,  and  No.  12  the  oldest  of  the 
series.  But  this  section  may,  perhaps, 
exhibit  merely  six  beds,  which  have  been 

folded  in  the  manner  seen  in  fig.  81,  so  that  each  of  them  is  twice  re- 
peated, the  position  of  one-half  being  reversed,  and  part  of  No.  1,  origi- 
nally the  uppermost,  having  now  become  the  lowest  of  the  series.  These 
phenomena  are  often  observable  on  a  magnificent  scale  in  certain  regions 
in  Switzerland  in  precipices  from  2000  to  3000  feet  in  perpendicular 
height.  In  the  Iselten  Alp,  in  the  valley  of  the  Lutechine,  between 


m.  marl. 


Fig. 


Ca  V.] 


CURVED   STRATA   IN  THE  ALPS. 
Fig.  81. 


59 


Unterseen  and  Grindelwald,  curves  of  calcareous  shale  are  seen  from 
1000  to  1500  feet  in  height,  in  which  the  beds  sometimes  plunge  down 
vertically  for  a  depth  of  1000  feet  and  more,  before  they  bend  round 

Fig.  82. 


Curved  strata  of  the  Iselten  Alp. 


again.     There  are  many  flexures  not  inferior  in  dimensions  in  the  Pyre- 
nees, as  those  near  Gavarnie,  at  the  base  of  Mount  Perdu. 

Unconformable  stratification. — Strata  are  said  to  be  unconformable, 
when  one  series  is  so  placed  over  another,  that  the  planes  of  the  superior 
repose  on  the  edges  of  the  inferior  (see  fig.  83).  In  this  case  it  is  evi- 

Fig.  83. 


Unconformable  junction  of  old  red  sandstone  and  Silurian  schist  at  the  Siccar  Point,  near  St  Abb's 
Head,  Berwickshire.    See  also  Frontispiece. 

dent  that  a  period  had  elapsed  between  the  production  of  the  two  sets 
of  strata,  and  that,  during  this  interval,  the  older  series  had  been  tilted 


60  UNCONFORMABLE  STRATIFICATION.  [On.  V. 

and  disturbed.  Afterwards  the  upper  series  was  thrown  down  in  hori- 
zontal strata  upon  it.  If  these  superior  beds,  as  d,  d,  fig.  83,  are  also 
inclined,  it  is  plain  that  the  lower  strata,  a,  a,  have  been  twice  displaced ; 
first,  before  the  deposition  of  the  newer  beds,  d,  d,  and  a  second  time 
when  these  same  strata  were  thrown  out  of  the  horizontal  position. 

Play  fair  has  remarked*  that  this  kind  of  junction,  which  we  now  call 
unconformable,  had  been  described  before  the  time  of  Hutton,  but  that 
he  was  the  first  geologist  who  appreciated  its  importance,  as  illustrating 
the  high  antiquity  and  great  revolutions  of  the  globe.  He  had  observed 
that  where  such  contacts  occur,  the  lowest  beds  of  the  newer  series  very 
generally  consist  of  a  breccia  or  conglomerate  consisting  of  angular  and 
rounded  fragments,  derived  from  the  breaking  up  of  the  more  ancient 
rocks.  On  one  occasion  the  Scotch  geologist  took  his  two  distinguished 
pupils,  Playfair  and  Sir  James  Hall,  to  the  cliffs  on  the  east  coast  of 
Scotland,  near  the  village  of  Eyemouth,  not  far  from  St.  Abb's  Head, 
where  the  schists  of  the  Lammermuir  range  are  undermined  and  dis- 
sected by  the  sea.  Here  the  curved  and  vertical  strata,  now  known  to 
be  of  Silurian  age,  and  which  often  exhibit  a  ripple-marked  surface,  are 
well  exposed  at  the  headland  called  the  Siccar  Point,  penetrating  with 
their  edges  into  the  incumbent  beds  of  slightly  inclined  sandstone,  in 
which  large  pieces  of  the  schist,  some  round  and  others  angular,  are 
united  by  an  arenaceous  cement.  "  What  clearer  evidence,"  exclaims 
Playfair,  "  could  we  have  had  of  the  different  formation  of  these  rocks, 
and  of  the  long  interval  which  separated  their  formation,  had  we  actually 
seen  them  emerging  from  the  bosom  of  the  deep  ?  We  felt  ourselves 
necessarily  carried  back  to  the  time  when  the  schistus  on  which  we  stood 
was  yet  at  the  bottom  of  the  sea,  and  when  the  sandstone  before  us  was 
only  beginning  to  be  deposited  in  the  shape  of  sand  or  mud,  from  the 
waters  of  a  superincumbent  ocean.  An  epoch  still  more  remote  pre- 
sented itself,  when  even  the  most  ancient  of  these  rocks,  instead  of 
standing  upright  in  vertical  beds,  lay  in  horizontal  planes  at  the  bottom 
of  the  sea,  and  was  not  yet  disturbed  by  that  immeasurable  force  which 
has  burst  asunder  the  solid  pavement  of  the  globe.  Revolutions  still 
more  remote  appeared  in  the  distance  of  this  extraordinary  perspective. 
The  mind  seemed  to  grow  giddy  by  looking  so  far  into  the  abyss  of 
time ;  and  while  we  listened  with  earnestness  and  admiration  to  the 
philosopher  who  was  now  unfolding  to  us  the  order  and  series  of  these 
wonderful  events,  we  became  sensible  how  much  farther  reason  may 
sometimes  go  than  imagination  can  venture  to  follow."! 

In  the  frontispiece  of  this  volume  the  reader  will  see  a  view  of  this 
classical  spot,  reduced  from  a  large  picture,  faithfully  drawn  and  colored 
from  nature  by  the  youngest  son  of  the  late  Sir  James  Hall.  It  was  im- 
possible, however,  to  do  justice  to  the  original  sketch,  in  an  engraving,  as 
the  contrast  of  the  red  sandstone  and  the  light  fawn-colored  vertical  schists 

*  Biographical  account  of  Dr.  Hutton. 

f  Playfair,  ibid. ;  see  his  Works,  Edin.  1822,  vol.  iv.  p.  81. 


CH.  V.]  FISSUKES  IN  STEATA.  61 

could  not  be  expressed.  From  the  point  of  view  here  selected,  the  under- 
lying beds  of  the  perpendicular  schist,  a,  are  visible  at  b  through  a  small 
opening  in  the  fractured  beds  of  the  covering  of  red  sandstone,  d  d,  while 
on  the  vertical  face  of  the  old  schist  at  a'  a"  a  conspicuous  ripple-mark 
is  displayed. 

It  often  happens  that  in  the  interval  between  the  deposition  of  two  sets 
of  unconformable  strata,  the  inferior  rock  has  not  only  been  denuded,  but 
drilled  by  perforating  shells.  Thus,  for  example,  at  Autreppe  and  Gusigny, 
near  Mons,  beds  of  an  ancient  (primary  or  paleozoic)  limestone,  highly 

Fig.  84, 


Junction  of  unconformable  strata  near  Mons,  in  Belgium. 

inclined,  and  often  bent,  are  covered  with  horizontal  strata  of  greenish 
and  whitish  marls  of  the  Cretaceous  formation.  The  lowest  and  there- 
fore the  oldest  bed  of  the  horizontal  series  is  usually  the  sand  and  con- 
glomerate, a,  in  which  are  rounded  fragments  of  stone,  from  an  inch  to 
two  feet  in  diameter.  These  fragments  have  often  adhering  shells  at- 
tached to  them,  and  have  been  bored  by  perforating  mollusca.  The 
solid  surface  of  the  inferior  limestone  has  also  been  bored,  so  as  to  ex- 
hibit cylindrical  and  pear-shaped  cavities,  as  at  c,  the  work  of  saxicavous 
mollusca ;  and  many  rents,  as  at  5,  which  descend  several  feet  or  yards 
into  the  limestone,  have  been  filled  with  sand  and  shells,  similar  to  those 
in  the  stratum  a. 

Fractures  of  the  strata  and  faults. — Numerous  rents  may  often  be 
seen  in  rocks  which  appear  to  have  been  simply  broken,  the  separated 
parts  remaining  in  the  same  places  ;  but  we  often  find  a  fissure,  several 
inches  or  yards  wide,  intervening  between  the  disunited  portions.  These 
fissures  are  usually  filled  with  fine  earth  and  sand,  or  with  angular  frag- 
ments of  stone,  evidently  derived  from  the  fracture  of  the  contiguous 
rocks. 

It  is  not  uncommon  to  find  the  mass  of  rock,  on  one  side  of  a  fissure, 
thrown  up  above  or  down  below  the  mass  with  which  it  was  once  in 
contact  on  the  other  side.  This  mode  of  displacement  is  called  a  shift, 
slip,  or  fault.  "  The  miner,"  says  Playfair,  describing  a  fault,  "  is  often 
perplexed,  in  his  subterraneous  journey,  by  a  derangement  in  the  strata, 
which  changes  at  once  all  those  lines  and  bearings  which  had  hitherto 
directed  his  course.  When  his  mine  reaches  a  certain  plane,  which  is 
sometimes  perpendicular,  as  in  A  B,  fig.  85,  sometimes  oblique  to  the 
horizon  (as  in  C  D,  ibid.),  he  finds  the  beds  of  rock  broken  asunder, 
those  on  the  one  side  of  the  plane  having  changed  their  place,  by  sliding 
in  a  particular  direction  along  the  face  of  the  others.  In  this  motion 
they  have  sometimes  preserved  their  parallelism,  as  in  fig.  85,  so  that 


62 


FAULTS. 
Fig.  85. 


[OH.  V 


\ 


Faults.    A  B  perpendicular,  0  D  oblique  to  the  horizon. 

the  strata  on  each  side  of  the  faults  A  B,  C  D,  continue  parallel  to  one 
another ;  in  other  cases,  the  strata  on  each  side  are  inclined,  as  in  a,  5,  c,  d 

Fig.  86. 


F  a       c     h  a 

E  F,  fault  or  fissure  filled  with  rubbish,  on  each  side  of  which  the  shifted 
strata  are  not  parallel. 

(fig.  86),  though  their  identity  is  still  to  be  recognized  by  their  possessing 
the  same  thickness,  and  the  same  internal  characters."* 

In  Coalbrook  Dale,  says  Mr.  Prestwich,f  deposits  of  sandstone,  shale, 
and  coal,  several  thousand  feet  thick,  and  occupying  an  area  of  many 
miles,  have  been  shivered  into  fragments,  and  the  broken  remnants  have 
been  placed  in  very  discordant  positions,  often  at  levels  differing  several 
hundred  feet  from  each  other.  The  sides  of  the  faults,  when  perpendicu- 
lar, are  commonly  separated  several  yards,  but  are  sometimes  as  much 
as  50  yards  asunder,  the  interval  being  filled  with  broken  debris  of  the 
strata.  In  following  the  course  of  the  same  fault,  it  is  sometimes  found 
to  produce  in  different  places  very  unequal  changes  of  level,  the  amount 
of  shift  being  in  one  place  300,  and  in  another  700  feet,  which  arises,  in 
some  cases,  from  ;he  union  of  two  or  more  faults.  In  other  words,  the 
disjointed  strata  have  in  certain  districts  been  subjected  to  renewed  move- 
ments, which  they  have  not  suffered  elsewhere. 

We  may  occasionally  see  exact  counterparts  of  these  slips,  on  a  small 
scale,  in  pits  of  loose  sand  and  gravel,  many  of  which  have  doubtless 
been  caused  by  the  drying  and  shrinking  of  argillaceous  and  other  beds? 
slight  subsidences  having  taken  place  from  failure  of  support.  Sometimes, 
however,  even  these  small  slips  may  have  been  produced  during  earth- 
quakes ;  for  land  has  been  moved,  and  its  level,  relatively  to  the  sea, 
considerably  altered,  within  the  period  when  much  of  the  alluvial  sand 
and  gravel  now  covering  the  surface  of  continents  was  deposited. 

*  Playfair,  Illust.  of  Hutt.  Theory,  §  42. 
f  Geol.  Trans,  second  series,  vol.  v.  p.  452. 


CH.  V.I 


FAULTS. 


I  have  already  stated  that  a  geologist  must  be  on  his  guard,  in  a  region 
of  disturbed  strata,  against  inferring  repeated  alternations  of  rocks,  when, 
in  fact,  the  same  strata,  once  continuous,  have  been  bent  round  so  as  to 
recur  in  the  same  section,  and  with  the  same  dip.  A  similar  mistake  has 
often  been  occasioned  by  a  series  of  faults. 

If,  for  example,  the  dark  line  A  H  (fig.  87)  represent  the  surface  of  a 
country  on  which  the  strata  a  b  c  frequently  crop  out,  an  observer,  who 


Apparent  alternations  of  strata  caused  by  vertical  faults. 

is  proceeding  from  H  to  A,  might  at  first  imagine  that  at  every  step  he 
was  approaching  new  strata,  whereas  the  repetition  of  the  same  beds  has 
been  caused  by  vertical  faults,  or  downthrows.  Thus,  suppose  the  origi- 
nal mass,  A,  B,  C,  D,  to  have  been  a  set  of  uniformly  inclined  strata,  and 
that  the  different  masses  under  E  F,  F  G,  and  G  D,  sank  down  success- 
ively, so  as  to  leave  vacant  the  spaces  marked  in  the  diagram  by  dotted 
lines,  and  to  occupy  those  marked  by  the  continuous  lines ;  then  let  de- 
nudation take  place  along  the  line  A  H,  so  that  the  protruding  masses 
indicated  by  the  fainter  lines  are  swept  away, — a  miner,  who  has  not  dis- 
covered the  faults,  finding  the  mass  a,  which  we  will  suppose  to  be  a  bed 
of  coal  four  times  repeated,  might  hope  to  find  four  beds,  workable  to  an 
indefinite  depth,  but  first  on  arriving  at  the  fault  G  he  is  stopped  sud- 
denly in  his  workings,  upon  reaching  the  strata  of  sandstone  c,  or  on  ar- 
riving at  the  line  of  fault  F,  he  comes  partly  upon  the  shale  6,  and  partly 
on  the  sandstone  c,  and  on  reaching  E  he  is  again  stopped  by  a  wall  com- 
posed of  the  rock  d. 

The  very  different  levels  at  which  the  separated  parts  of  the  same  strata 
are  found  on  the  different  sides  of  the  fissure,  in  some  faults,  is  truly 
astonishing.  One  of  the  most  celebrated  in  England  is  that  called  the 
"  ninety-fathom  dike,"  in  the  coal-field  of  Newcastle.  This  name  has 
been  given  to  it,  because  the  same  beds  are  ninety  fathoms  lower  on  the 
northern  than  they  are  on  the  southern  side.  The  fissure  has  been  filled 
by  a  body  of  sand,  which  is  now  in  the  state  of  sandstone,  and  is  called 
the  dike,  which  is  sometimes  very  narrow,  but  in  other  places  more  than 
twenty  yards  wide.*  The  walls  of  the  fissure  are  scored  by  grooves,  such 

*  Conybeare  and  Phillips,  Outlines,  <fec.  p.  376. 


64:  ORIGIN  OF  GREAT  FAULTS.  [On.  V. 

as  would  have  been  produced  if  the  broken  ends  of  the  rock  had  been 
rubbed  along  the  plane  of  the  fault.*  In  the  Tynedale  and  Craven  faults, 
in  the  north  of  England,  the  vertical  displacement  is  still  greater,  and  the 
fracture  has  extended  in  a  horizontal  direction  for  a  distance  of  thirty 
miles  or  more.  Some  geologists  consider  it  necessary  to  imagine  that  the 
upward  or  downward  movement  in  these  cases  was  accomplished  at  a 
single  stroke,  and  not  by  a  series  of  sudden  but  interrupted  movements. 
This  idea  appears  to  have  been  derived  from  a  notion  that  the  grooved 
walls  have  merely  been  rubbed  in  one  direction.  But  this  is  so  far  from 
being  a  constant  phenomenon  in  faults,  that  it  has  often  been  objected  to 
the  received  theory  respecting  those  polished  surfaces  called  "slicken- 
sides,"  that  the  striae  are  not  always  parallel,  but  often  curved  and  ir- 
regular. It  has,  moreover,  been  remarked,  that  not  only  the  walls  of 
the  fissure  or  fault,  but  its  earthy  contents,  sometimes  present  the  same 
polished  and  striated  faces.  Now  these  facts  seem  to  indicate  partial 
changes  in  the  direction  of  the  movement,  and  some  slidings  subsequent 
to  the  first  filling  up  of  the  fissure.  Suppose  the  mass  of  rock  A,  B,  C, 
to  overlie  an  extensive  chasm  d  e,  formed  at  the  depth  of  several  miles, 


whether  by  the  gradual  contraction  in  bulk  of  a  melted  mass  passing  into 
a  solid  or  crystalline  state,  or  the  shrinking  of  argillaceous  strata,  baked 
by  a  moderate  heat,  or  by  the  subtraction  of  matter  by  volcanic  action,  or 
any  other  cause.  Now,  if  this  region  be  convulsed  by  earthquakes,  the 
fissures  /#,  and  others  at  right  angles  to-  them,  may  sever  the  mass  B 
from  A  and  from  C,  so  that  it  may  move  freely,  and  begin  to  sink  into 
the  chasm.  A  fracture  may  be  conceived  so  clean  and  perfect  as  to 
allow  it  to  subside  at  once  to  the  bottom  of  the  subterranean  cavity ;  but 
it  is  far  more  probable  that  the  sinking  will  be  effected  at  successive 
periods  during  different  earthquakes,  the  mass  always  continuing  to  slide 
in  the  same  direction  along  the  planes  of  the  fissures  f  <7,  and  the  edges 
of  the  falling  mass  being  continually  more  broken  and  triturated  at  each 
convulsion.  If,  as  is  not  improbable,  the  circumstances  which  have  caused 
the  failure  of  support  continue  in  operation,  it  may  happen  that  when  the 
mass  B  has  filled  the  cavity  first  formed,  its  foundations  will  again  give 
way  under  it,  so  that  it  will  fall  again  in  the  same  direction.  But,  if  the 
direction  should  change,  the  fact  could  not  be  discovered  by  observing 
the  slickensides,  because  the  last  scoring  would  efface  the  lines  of  previous 
friction.  In  the  present  state  of  our  ignorance  of  the  causes  of  subsidence, 
an  hypothesis  which  can  explain  the  great  amount  of  displacement  in 

*  Phillips,  Geology,  Lardner's  Cyclop,  p.  41. 


Os.  V.]  OBIGIN   OF   GREAT   FAULTS.  05 

some  faults,  on  sound  mechanical  principles,  by  a  succession  of  move- 
ments, is  far  preferable  to  any  theory  which  assumes  each  fault  to  have 
been  accomplished  by  a  single  upcast  or  downthrow  of  several  thousand 
feet.  For  we  know  that  there  are  operations  now  in  progress,  at  great 
depths  in  the  interior  of  the  earth,  by  which  both  large  and  small  tracts 
of  ground  are  made  to  rise  above  and  sink  below  their  former  level,  some 
slowly  and  insensibly,  others  suddenly  and  by  starts,  a  few  feet  or  yards 
at  a  time ;  whereas  there  are  no  grounds  for  believing  that,  during  the 
last  3000  years  at  least,  any  regions  have  been  either  upheaved  or  de- 
pressed, at  a  single  stroke,  to  the  amount  of  several  hundred,  much  less 
several  thousand  feet.  When  some  of  the  ancient  marine  formations  are 
described  in  the  sequel,  it  will  appear  that  their  structure  and  organic 
contents  point  to  the  conclusion,  that  the  floor  of  the  ocean  was  slowly 
sinking  at  the  time  of  their  origin.  The  downward  movement  was  very 
gradual,  and  in  Wales  and  the  contiguous  parts  of  England  a  maximum 
thickness  of  32,000  feet  (more  than  six  miles)  of  Carboniferous,  Devonian, 
and  Silurian  rock  was  formed,  whilst  the  bed  of  the  sea  was  all  the  time 
continuously  and  tranquilly  subsiding.*  Whatever  may  have  been  the 
changes  which  the  solid  foundation  underwent,  whether  accompanied  by 
the  melting,  consolidation,  crystallization,  or  desiccation  of  subjacent  min- 
eral matter,  it  is  clear  from  the  fact  of  the  sea  having  remained  shallow 
all  the  while  that  the  bottom  never  sank  down  suddenly  to  the  depth  of 
many  hundred  feet  at  once. 

It  is  by  assuming  such  reiterated  variations  of  level,  each  separately  of 
small  vertical  amount,  but  multiplied  by  time  till  they  acquire  importance 
in  the  aggregate,  that  we  are  able  to  explain  the  phenomena  of  denuda- 
tion, which  will  be  treated  of  in  the  next  chapter.  By  such  movements 
every  portion  of  the  surface  of  the  land  becomes  in  its  turn  a  line  of  coast, 
and  is  exposed  to  the  action  of  the  waves  ar,d  tides.  A  country  which  is 
undergoing  such  movement  is  never  allowed  to  settle  into  a  state  of  equi- 
librium, therefore  the  force  of  rivers  and  torrents  to  remove  or  excavate 
soil  and  rocky  masses  is  sustained  in  undiminished  energy. 

*  See  the  results  of  the  "Geological  Survey  of  Great  Britain;"  Memoirs,  vola 
L  and  ii.  by  Sir  H.  de  la  Beche,  Mr.  A.  C.  Ramsay,  and  Mr.  John  Phillips. 

5 


66  DENUDATION  OF  KOCKS.  [On.  VI 


CHAPTER  VI. 


DENUDATION. 

Denudation  defined — Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in 
the  earth's  crust — Horizontal  sandstone  denuded  in  Ross-shire — Levelled  sur- 
face of  countries  in  which  great  faults  occur — Coalbrook  Dale — Denuding  power 
of  the  ocean  during  the  emergence  of  land — Origin  of  Valleys — Obliteration  of 
sea-cliffs — Inland  sea-cliffs  and  terraces  in  the  Morea  and  Sicily — Limestone 
pillars  at  St.  Mihiel,  in  France — In  Canada — In  the  Bermudas. 

DENUDATION,  which  has  been  occasionally  spoken  of  in  the  preceding 
chapters,  is  the  removal  of  solid  matter  by  water  in  motion,  whether  of 
rivers  or  of  the  waves  and  currents  of  the  sea,  and  the  consequent  laying 
bare  of  some  inferior  rock.  Geologists  have  perhaps  been  seldom  in  the 
habit  of  reflecting  that  this  operation  has  exerted  an  influence  on  the 
structure  of  the  earth's  crust  as  universal  and  important  as  sedimentary 
deposition  itself;  for  denudation  is  the  inseparable  accompaniment  of 
the  production  of  all  new  strata  of  mechanical  origin.  The  formation 
of  every  new  deposit  by  the  transport  of  sediment  .and  pebbles  necessa- 
rily implies  that  there  has  been,  somewhere  else,  a  grinding  down  of  rock 
into  rounded  fragments,  sand,  or  mud,  equal  in  quantity  to  the  new 
strata.  All  deposition,  therefore,  except  in  the  case  of  a  shower  of  vol- 
canic ashes,  is  the  sign  of  superficial  waste  going  on  contemporaneously, 
and  to  an  equal  amount  elsewhere.  The  gain  at  one  point  is  no  more 
than  sufficient  to  balance  the  loss  at  some  other.  Here  a  lake  has  grown 
shallower,  there  a  ravine  has  been  deepened.  The  bed  of  the  sea  has  in 
one  region  been  raised  by  the  accumulation  of  new  matter,  in  another 
its  depth  has  been  augmented  by  the  abstraction  of  an  equal  quantity. 

When  we  see  a  stone  building,  we  know  that  somewhere,  far  or  near, 
a  quarry  has  been  opened.  The  courses  of  stone  in  the  building  may  be 
compared  to  successive  strata,  the  quarry  to  a  ravine  or  valley  which  has 
suffered  denudation.  As  the  strata,  like  the  courses  of  hewn  stone,  have 
been  laid  one  upon  another  gradually,  so  the  excavation  both  of  the 
valley  and  quarry  have  been  gradual.  To  pursue  the  comparison  still 
farther,  the  superficial  heaps  of  mud,  sand,  and  gravel,  usually  called 
alluvium,  may  be  likened  to  the  rubbish  of  a  quarry  which  has  been  re- 
jected as  useless  by  the  workmen,  or  has  fallen  upon  the  road  between 
the  quarry  and  the  building,  so  as  to  lie  scattered  at  random  over  the 
ground. 


CH.  VI] 


DENUDATION   OF   STKATIFIED   KOCKS. 


67 


Fig.  89. 


If,  then,  the  entire  mass  of  stratified  deposits  in  the  earth's  crust  is  at 
once  the  monument  and  measure  of  the  denudation  which  has  taken 
place,  on  how  stupendous  a  scale  ought  we  to  find  the  signs  of  this  re- 
moval of  transported  materials  in  past  ages!  Accordingly,  there  are 
different  classes  of  phenomena,  which  attest  in  a  most  striking  manner 
the  vast  spaces  left  vacant  by  the  erosive  power  of  water.  I  may  allude, 
first,  to  those  valleys  on  both  sides  of  which  the  same  strata  are  seen 
following  each  other  in  the  same  order,  and  having  the  same  mineral 
composition  and  fossil  contents.  We  may  observe,  for  example,  several 
formations,  as  Nos.  1,  2,  3,  4,  in  the  accom- 
panying diagram  (fig.  89) ;  No.  1  conglom- 
erate, No.  2  clay,  No.  3  grit,  and  No.  4 
limestone,  each  repeated  in  a  series  of  hills 
separated  by  valleys  varying  in  depth. 
When  we  examine  the  subordinate  parts  of 
these  four  formations,  we  find,  in  like  man- 
ner, distinct  beds  in  each,  corresponding,  on  the  opposite  sides  of  the 
valleys,  both  in  composition  and  order  of  position.  No  one  can  doubt 
that  the  strata  were  originally  continuous,  and  that  some  cause  has 
swept  away  the  portions  which  once  connected  the  whole  series.  A 
torrent  on  the  side  of  a  mountain  produces  similar  interruptions;  and 
when  we  make  artificial  cuts  in  lowering  roads,  we  expose,  in  like  man- 
ner, corresponding  beds  on  either  side.  But  in  nature,  these  appearances 
occur  in  mountains  several  thousand  feet  high,  and  separated  by  inter- 
vals of  many  miles  or  leagues  in  extent,  of  which  a  grand  exemplifica- 
tion is  described  by  Dr.  MacCulloch,  on  the  northwestern  coast  of  Koss- 
shire,  in  Scotland.* 

Fig.  90. 
Sail  Veinn.  Conl  beg.  Coul  more. 


Yalleys  of  denudation. 
a.  alluvium. 


Denudation  of  red  sandstone  on  northwest  coast  of  Boss-shire.     (MacCulloch.) 

The  fundamental  rock  of  that  country  is  gneiss,  in  disturbed  strata,  on 
which  beds  of  nearly  horizontal  red  sandstone  rest  unconformably.  The 
latter  are  often  very  thin,  forming  mere  flags,  with  their  surfaces  dis- 
tinctly ripple-marked.  They  end  abruptly  on  the  declivities  of  many 
insulated  mountains,  which  rise  up  at  once  to  the  height  of  about  2000 
feet  above  the  gneiss  of  the  'surrounding  plain  or  table- land,  and  to  an 
average  elevation  of  about  3000  feet  above  the  sea,  which  all  their  sum- 
mits generally  attain.  The  base  of  gneiss  varies  in  height,  so  that  the 
lower  portions  of  the  sandstone  occupy  different  levels,  and  the  thickness 
of  the  mass  is  various,  sometimes  exceeding  3000  feet.  It  is  impossible 
to  compare  these  scattered  and  detached  portions  without  imagining 
that  the  whole  country  has  once  been  covered  with  a  great  body  of  sand- 
stone, and  that  masses  from  1000  to  more  than  3000  feet  in  thickness  have 
been  removed. 

*  Western  Islands,  vol.  ii.  p.  93,  pi.  31,  fig.  4. 


68  DENUDATION.  [Cu.  VI 

In  the  "  Survey  of  Great  Britain"  (vol.  i.),  Professor  Ramsay  has  shown 
that  the  missing  beds,  removed  from  the  summit  of  the  Mendips,  must  have 
been  nearly  a  mile  in  thickness ;  and  he  has  pointed  out  considerable  areas 
in  South  Wales  and  some  of  the  adjacent  counties  of  England,  where 
a  series  of  primary  (or  palaeozoic)  strata,  not  less  than  11,000  feet  in 
thickness,  have  been  stripped  off.  All  these  materials  have  of  course 
been  transported  to  new  regions,  and  have  entered  into  the  composition 
of  more  modern  formations.  On  the  other  hand,  it  is  shown  by  obser- 
vations in  the  same  "  Survey."  that  the  palaeozoic  strata  are  from  20,000 
to  30,000  feet  thick.  It  is  clear  that  such  rocks,  formed  of  mud  and 
sand,  now  for  the  most  part  consolidated,  are  the  monuments  of  denuding 
operations,  which  took  place  on  a  grand  scale  at  a  very  remote  period  in 
the  earth's  history.  For,  whatever  has  been  given  to  one  area  must  al- 
ways have  been  borrowed  from  another ;  a  truth  which,  obvious  as  it 
may  seem  when  thus  stated,  must  be  repeatedly  impressed  on  the  stu- 
dent's mind,  because  in  many  geological  speculations  it  is  taken  for 
granted  that  the  external  crust  of  the  earth  has  been  always  growing 
thicker,  in  consequence  of  the  accumulation,  period  after  period,  of  sedi- 
mentary matter,  as  if  the  new  strata  were  not  always  produced  at  the 
expense  of  pre-existing  rocks,  stratified  or  unstratified.  By  duly  reflect- 
ing on  the  fact,  that  all  deposits  of  mechanical  origin  imply  the  trans- 
portation from  some  other  region,  whether  contiguous  or  remote,  of  an 
equal  amount  of  solid  matter,  we  perceive  that  the  stony  exterior  of  the 
planet  must  always  have  grown  thinner  in  one  place  whenever,  by  acces- 
sions of  new  strata,  it  was  acquiring  density  in  another.  No  doubt  the 
vacant  space  left  by  the  missing  rocks,  after  extensive  denudation,  is  less 
imposing  to  the  imagination  than  a  vast  thickness  of  conglomerate  or 
sandstone,  or  the  bodily  presence  as  it  were  of  a  mountain-chain,  with 
all  its  inclined  and  curved  strata.  But  the  denuded  tracts  speak  a  clear 
and  emphatic  language  to  our  reason,  and,  like  repeated  layers  of  fossil 
nummulites,  corals  or  shells,  or  like  numerous  seams  of  coal,  each  based 
on  its  under  clay  full  of  the  roots  of  trees,  still  remaining  in  their  natural 
position,  demand  an  indefinite  lapse  of  time  for  their  elaboration. 

No  one  will  maintain  that  the  fossils  entombed  in  these  rocks  did  not 
belong  to  many  successive  generations  of  plants  and  animals.  In  like 
manner,  each  sedimentary  deposit  attests  a  slow  and  gradual  action,  and 
the  strata  not  only  serve  as  a  measure  of  the  amount  of  denudation 
simultaneously  effected  elsewhere,  but  are  also  a  correct  indication  of  the 
rate  at  which  the  denuding  operation  was  carried  on. 

Perhaps  the  most  convincing  evidence  of  denudation  on  a  magnificent 
scale  is  derived  from  the  levelled  surfaces  of  districts  where  large  faults 
occur.  I  have  shown,  in  fig.  87,  p.  63,  and  in  fig.  91,  how  angular  and 
protruding  masses  of  rock  might  naturally  have  been  looked  for  on  the 
surface  immediately  above  great  faults,  although  in  fact  they  rarely 
exist.  This  phenomenon  may  be  well  studied  in  those  districts  where 
coal  has  been  extensively  worked,  for  there  the  former  relation  of  the 
beds  which  have  shifted  their  position  may  be  determined  with  great  ac- 


On.  VI] 


OF  STRATIFIED  ROCKS. 


69 


curacy.     Thus  in  the  coal  field  of  Ashby  de  la  Zouch,  in  Leicestershire 
(see  fig.  91),  a  fault  occurs,  on  one  side  of  which  the  coal  beds  abed 

Fig.  91. 


Faults  and  denuded  coal  strata,  Ashby  de  la  Zouch.    (Mammat.) 

rise  to  the  height  of  500  feet  above  the  corresponding  beds  on  the  other 
side.  But  the  uplifted  strata  do  not  stand  up  500  feet  above  the  general 
surface  ;  on  the  contrary,  the  outline  of  the  country,  as  expressed  by  the 
line  z  2,  is  uniformly  undulating  without  any  break,  and  the  mass  indicated 
by  the  dotted  outline  must  have  been  washed  away.*  There  are  proofs 
of  this  kind  in  some  level  countries,  where  dense  masses  of  strata  have 
been  cleared  away  from  areas  several  hundred  square  miles  in  extent. 

In  the  Newcastle  coal  district  it  is  ascertained  that  faults  occur  in 
which  the  upward  or  downward  movement  could  not  have  been  less  than 
140  fathoms,  which,  had  they  affected  the  configuration  of  the  surface  to 
an  equal  amount,  would  produce  mountains  with  precipitous  escarpments 
nearly  1000  feet  high,  or  chasms  of  the  like  depth;  yet  is  the  actual  level 
of  the  country  absolutely  uniform,  affording  no  trace  whatever  of  subter- 
ranean movements.f 

The  ground  from  which  these  materials  have  been  removed  is  usually 
overspread  with  heaps  of  sand  and  gravel,  formed  out  of  the  ruins  of 
the  very  rocks  which  have  disappeared.  Thus,  in  the  districts  above  re- 
ferred to,  they  consist  of  rounded  and  angular  fragments  of  hard  sand- 
stone, limestone,  and  ironstone,  with  a  small  quantity  of  the  more 
destructible  shale,  and  even  rounded  pieces  of  coal. 

Allusion  has  been  already  made  to  the  shattered  state  and  discordant 
position  of  the  carboniferous  strata  in  Coalbrook  Dale  (p.  62).  The 
collier  cannot  proceed  three  or  four  yards  without  meeting  with  small 
slips,  and  from  time  to  time  he  encounters  faults  of  considerable  magni- 
tude, which  have  thrown  the  rocks  up  or  down  several  hundred  feet. 
Yet  the  superficial  inequalities  to  which  these  dislocated  masses  origi- 
nally gave  rise  are  no  longer  discernible,  and  the  comparative  flatness  of 
the  existing  surface  can  only  be  explained,  as  Mr.  Prestwich  has  observed, 
by  supposing  the  fractured  portions  to  have  been  removed  by  water.  It 
is  also  clear  that  strata  of  red  sandstone,  more  than  1000  feet  thick, 
which  once  covered  the  coal,  in  the  same  region,  have  been  carried  away 


*  See  Mammat's  Geological  Facts,  <fcc.,  p.  90,  and  plate. 
f  Conybeare's  Report  to  Brit.  Assoc.  1842,  p.  381. 


70  ORIGIN  OF  VALLEYS.  [On.  VI 

from  large  areas.  That  water  has,  in  this  case,  been  the  denuding  agent, 
we  may  infer  from  the  fact  that  the  rocks  have  yielded  according  to  their 
different  degrees  of  hardness ;  the  hard  trap  of  the  Wrekin,  for  example, 
and  other  hills,  having  resisted  more  than  the  softer  shale  and  sandstone, 
so  as  now  to  stand  out  in  bold  relief.* 

Origin  of  valleys. — Many  of  the  earlier  geologists,  and  Dr.  Hutton 
among  them,  taught  that  "  rivers  have  in  general  hollowed  out  their  val- 
leys." This  is  no  doubt  true  of  rivulets  and  torrents  which  are  the  feeders 
of  the  larger  streams,  and  which,  descending  over  rapid  slopes,  are  most 
subject  to  temporary  increase  and  diminution  in  the  volume  of  their 
waters.  It  must  also  be  admitted  that  the  quantity  of  mud,  sand,  and 
pebbles  constituting  many  a  modern  delta  is  so  considerable,  as  to  prove 
that  a  very  large  part  of  the  inequalities  now  existing  on  the  earth's 
surface  are  due  to  fluviatile  action ;  but  the  principal  valleys  in  almost 
every  great  hydrographical  basin  in  the  world,  are  of  a  shape  and  magni- 
tude which  imply  that  they  have  been  due  to  other  causes  besides  the 
mere  excavating  power  of  rivers. 

Some  geologists  have  imagined  that  a  deluge,  or  succession  of  deluges, 
may  have  been  the  chief  denuding  agency,  and  they  have  speculated  on  a 
series  of  enormous  waves  raised  by  the  instantaneous  upthrow  of  continents 
or  mountain  chains  out  of  the  sea.  But  even  were  we  disposed  to  grant 
such  sudden  upheavals  of  the  floor  of  the  ocean,  and  to  assume  that  great 
waves  would  be  the  consequence  of  each  convulsion,  it  is  not  easy  to  ex- 
plain the  observed  phenomena  by  the  aid  of  so  gratuitous  an  hypothesis. 

On  the  other  hand,  a  machinery  of  a  totally  different  kind  seems  capa- 
ble of  giving  rise  to  effects  of  the  required  magnitude.  It  has  now  been 
ascertained  that  the  rising  and  sinking  of  extensive  portions  of  the  earth's 
crust,  whether  insensibly  or  by  a  repetition  of  sudden  shocks,  is  part  of 
the  actual  course  of  nature,  and  we  may  easily  comprehend  how  the 
land  may  have  been  exposed  during  these  movements  to  abrasion  by  the 
waves  of  the  sea.  In  the  same  manner  as  a  mountain  mass  may,  in  the 
course  of  ages,  be  formed  by  sedimentary  deposition,  layer  after  layer,  so 
masses  equally  voluminous  may  in  time  waste  away  by  inches  ;  as,  for 
example,  if  beds  of  incoherent  materials  are  raised  slowly  in  an  open  sea 
where  a  strong  current  prevails.  It  is  well  known  that  some  of  these 
oceanic  currents  have  a  breadth  of  200  miles,  and  that  they  sometimes 
run  for  a  thousand  miles  or  more  in  one  direction,  retaining  a  considera- 
ble velocity  even  at  the  depth  of  several  hundred  feet.  Under  these  cir- 
cumstances, the  flowing  waters  may  have  power  to  clear  away  each 
stratum  of  incoherent  materials  as  it  rises  and  approaches  the  surface, 
where  the  waves  exert  the  greatest  force ;  and  in  this  manner  a  volu- 
minous deposit  may  be  entirely  swept  away,  so  that,  in  the  absence  of 
faults,  no  evidence  may  remain  of  the  denuding  operation.  It  may  in- 
deed be  affirmed  that  the  signs  of  waste  will  usually  be  least  obvious 
\\  here  the  destruction  has  been  most  complete ;  for  the  annihilation 

*  Prestwich,  Geol.  Trans,  second  series,  vol.  v.  pp.  452,  473. 


CH.  VI.]  INLAND  SEA-CLIFFS.  71 

may  have  proceeded  so  far,  that  no  ruins  are  left  of  the  dilapidated 
rocks. 

Although  denudation  has  had  a  levelling  influence  on  some  countries 
of  shattered  and  disturbed  strata  (see  fig.  87,  p.  63,  and  fig.  91,  p.  69), 
it  has  more  commonly  been  the  cause  of  superficial  inequalities,  espe- 
cially in  regions  of  horizontal  stratification.  The  general  outline  of  these 
regions  is  that  of  flat  and  level  platforms,  interrupted  by  valleys  often  of 
considerable  depth,  and  ramifying  in  various  directions.  These  hollows 
may  once  have  formed  bays  and  channels  between  islands,  and  the 
steepest  slope  on  the  sides  of  each  valley  may  have  been  a  sea-cliff,  which 
was  undermined  for  ages,  as  the  land  emerged  gradually  from  the  deep. 
We  may  suppose  the  position  and  course  of  each  valley  to  have  been 
originally  determined  by  differences  in  the  hardness  of  the  rocks,  and  by 
rents  and  joints  which  usually  occur  even  in  horizontal  strata.  In  mountain 
chains,  such  as  the  Jura  before  described  (see  fig.  71,  p.  55),  we  perceive 
at  once  that  the  principal  valleys  have  not  been  due  to  aqueous  excava- 
tion, but  to  those  mechanical  movements  which  have  bent  the  rocks  into 
their  present  form.  Yet  even  in  the  Jura  there  are  many  valleys,  such 
as  C  (fig.  71),  which  have  been  hollowed  out  by  water  ;  and  it  may  be 
stated  that  in  every  part  of  the  globe  the  unevenness  of  the  surface  of 
the  land  has  been  due  to  the  combined  influence  of  subterranean  move- 
ments and  denudation. 

I  may  now  recapitulate  a  few  of  the  conclusions  to  which  we  have  ar- 
rived :  first,  all  the  mechanical  strata  have  been  accumulated  gradually, 
and  the  concomitant  denudation  has  been  no  less  gradual :  secondly,  the 
dry  land  consists  in  great  part  of  strata  formed  originally  at  the  bottom 
of  the  sea,  and  has  been  made  to  emerge  and  attain  its  present  height 
by  a  force  acting  from  beneath  :  thirdly,  no  combination  of  causes  has 
yet  been  conceived  so  capable  of  producing  extensive  and  gradual  denu- 
dation, as  the  action  of  the  waves  and  currents  of  the  ocean  upon  land 
slowly  rising  out  of  the  deep. 

Now,  if  we  adopt  these  conclusions,  we  shall  naturally  be  led  to  look 
everywhere  for  marks  of  the  former  residence  of  the  sea  upon  the  land, 
especially  near  the  coasts  from  which  the  last  retreat  of  the  waters  took 
place,  and  it  will  be  found  that  such  signs  are  not  wanting. 

I  shall  have  occasion  to  speak  of  ancient  sea-cliffs,  now  far  inland,  in 
the  southeast  of  England,  when  treating  in  Chapter  XIX.  of  the  denu- 
dation of  the  chalk  in  Surrey,  Kent,  and  Sussex.  Lines  of  upraised 
sea-beaches  of  more  modern  date  are  traced,  at  various  levels  from  20  to 
100  feet  and  upwards  above  the  present  sea-level,  for  great  distances  on 
the  east  and  west  coasts  of  Scotland,  as  well  as  in  Devonshire,  and  othei 
counties  in  England.  These  ancient  beach-lines  often  form  terraces  of 
sand  and  gravel,  including  littoral  shells,  some  broken,  others  entire,  and 
corresponding  with  species  now  living  on  the  adjoining  coast.  But  it 
would  be  unreasonable  to  expect  to  meet  everywhere  with  the  signs  of 
ancient  shores,  since  no  geologist  can  have  failed  to  observe  how  soon  all 
recent  marks  of  the  kind  above  alluded  to  are  obscured  or  entirely  ef- 


72  INLAND  SEA-CLIFFS.  [On.  VI 

faced,  wherever,  in  consequence  of  the  altered  state  of  the  tides  and  cur- 
rents, the  sea  has  receded  for  a  few  centuries.  We  see  the  cliffs  crumble 
down  in  a  few  years  if  composed  of  sand  or  clay,  and  soon  reduced  to  a 
gentle  slope.  If  there  were  shells  on  the  beach  they  decompose,  and 
their  materials  are  washed  away,  after  which  the  sand  and  shingle  may 
resemble  any  other  alluviums  scattered  over  the  interior. 

The  features  of  an  ancient  shore  may  sometimes  be  concealed  by  the 
growth  of  trees  and  shrubs,  or  by  a  covering  of  blown  sand,  a  good  ex- 
ample of  which  occurs  a  few  miles  west  from  Dax,  near  Bourdeaux,  in 
the  south  of  France.  About  twelve  miles  inland,  a  steep  bank  may  be 
traced  running  in  a  direction  nearly  northeast  and  southwest,  or  parallel 
to  the  contiguous  coast.  This  sudden  fall  of  about  50  feet  conducts  us 
from  the  higher  platform  of  the  Landes  to  a  lower  plain  which  extends 

Fig.  92. 


Section  of  inland  cliff  at  Abesse,  near  Dax. 
a.  Sand  of  the  Landes.  I.  Limestone.  c.  Clay. 

to  the  sea.  The  outline  of  the  ground  suggested  to  me,  as  it  would  do 
to  every  geologist,  the  opinion  that  the  bank  in  question  was  once  a  sea- 
cliff,  when  the  whole  country  stood  at  a  lower  level.  But  this  is  no 
longer  matter  of  conjecture,  for,  in  making  excavations  in  1830  for  the 
foundation  of  a  building  at  Abesse,  a  quantity  of  loose  sand,  which 
formed  the  slope  d  e,  was  removed  ;  and  a  perpendicular  cliff,  about  50 
feet  in  height,  which  had  hitherto  been  protected  from  the  agency  of  the 
elements,  was  exposed.  At  the  bottom  appeared  the  limestone  6,  con- 
taining tertiary  shells  and  corals,  immediately  below  it  the  clay  c,  and 
above  it  the  usual  tertiary  sand  a,  of  the  department  of  the  Landes.  At 
the  base  of  the  precipice  were  seen  large  partially  rounded  masses  of 
rock,  evidently  detached  from  the  stratum  6.  The  face  of  the  limestone 
was  hollowed  out  and  weathered  into  such  forms  as  are  seen  in  the  cal- 
careous cliffs  of  the  adjoining  coast,  especially  at  Biaritz,  near  Bayonne. 
It  is  evident  that,  when  this  country  stood  at  a  somewhat  lower  level,  the 
sea  advanced  along  the  surface  of  the  argillaceous  stratum  c,  which,  from 
its  yielding  nature,  favored  the  waste  by  allowing  the  more  solid  super- 
incumbent stone  b  to  be  readily  undermined.  Afterwards,  when  the 
country  had  been  elevated,  part  of  the  sand,  a,  fell  down,  or  was  drifted 
by  the  winds,  so  as  to  form  the  talus,  d  e,  which  masked  the  inland  cliff 
until  it  was  artificially  laid  open  to  view.  ' 

When  we  are  considering  the  various  causes  which,  in  the  course  of 
ages,  may  efface  the  characters  of  an  ancient  sea-coast,  earthquakes  must 
not  be  forgotten.  During  violent  shocks,  steep  and  overhanging  cliffs 
are  often  thrown  down  and  become  a  heap  of  ruins.  Sometimes  une- 
qual movements  of  upheaval  or  depression  entirely  destroy  that  horizon- 


CH.  VI]  INLAND  SEA-CLIFFS  AND  TERRACES.  7g 

tality  of  the  base-line  which  constitutes  the  chief  peculiarity  of  an 
ancient  sea-cliff'. 

It  is,  however,  in  countries  where  hard  limestone  rocks  abound,  that 
inland  cliffs  retain  faithfully  the  characters  which  they  acquired  when 
they  constituted  the  boundary  of  land  and  sea.  Thus,  in  the  Morea,  no 
less  than  three,  or  even  four,  ranges  of  what  were  once  sea-cliff's  are  well 
preserved.  These  have  been  described,  by  MM.  Boblaye  and  Virlet,  as 
rising  one  above  the  other  at  different  distances  from  the  actual  shore, 
the  summit  of  the  highest  and  oldest  occasionally  exceeding  1000  feet 
in  elevation.  At  the  base  of  each  there  is  usually  a  terrace,  which  is  in 
some  places  a  few  yards,  in  others  above  300  yards  wide,  so  that  we  are 
conducted  from  the  high  land  of  the  interior  to  the  sea  by  a  succession 
of  great  steps.  These  inland  cliffs  are  most  perfect,  and  most  exactly  re- 
semble those  now  washed  by  the  waves  of  the  Mediterranean,  where 
they  are  formed  of  calcareous  rock,  especially  if  the  rock  be  a  hard  crys- 
talline marble.  The  following  are  the  points  of  correspondence  observed 
between  the  ancient  coast  lines  and  the  borders  of  the  present  sea: — 1.  A 
range  of  vertical  precipices,  with  a  terrace  at  their  base.  2.  A  weathered 
state  of  the  surface  of  the  naked  rock,  such  as  the  spray  of  the  sea  pro- 
duces. 3.  A  line  of  littoral  caverns  at  the  foot  of  the  cliffs.  4.  A  con- 
solidated beach  or  breccia  with  occasional  marine  shells,  found  at  the 
base  of  the  cliff's,  or  in  the  caves.  5.  Lithodomous  perforations. 

In  regard  to  the  first  of  these,  it  would  be  superfluous  to  dwell  on  the 
evidence  afforded  of  the  undermining  power  of  waves  and  currents  by 
perpendicular  precipices.  The  littoral  caves,  also,  will  be  familiar  to 
those  who  have  had  opportunities  of  observing  the  manner  in  which  the 
waves  of  the  sea,  when  they  beat  against  rocks,  have  power  to  scoop  out 
caverns.  As  to  the  breccia,  it  is  composed  of  pieces  of  limestone  and 
rolled  fragments  of  thick  solid  shell,  such  as  Strombus  and  Spondylus, 
all  bound  together  by  a  crystalline  calcareous  cement.  Similar  aggrega- 
tions are  now  forming  on  the  modern  beaches  of  Greece,  and  in  caverns 
on  the  sea-side ;  and  they  are  only  distinguishable  in  character  from 
those  of  more  ancient  date,  by  including  many  pieces  of  pottery.  In 
regard  to  the  lithodomi  above  alluded  to,  these  bivalve  mollusks  are  well 
known  to  have  the  power  of  excavating  holes  in  the  hardest  limestones, 
the  size  of  the  cavity  keeping  pace  with  the  growth  of  the  shell.  When 
living  they  require  to  be  always  covered  by  salt  water,  but  similar  pear- 
shaped  hollows,  containing  the  dead  shells  of  these  creatures,  are  found 
at  different  heights  on  the  face  of  the  inland  cliff's  above  mentioned. 
Thus,  for  example,  they  have  been  observed  near  Modon  and  Navarino 
on  cliff's  in  the  interior  125  feet  high  above  the  Mediterranean.  As  to 
the  weathered  surface  of  the  calcareous  rocks,  all  limestones  are  known 
to  suffer  chemical  decomposition  when  moistened  by  the  spray  of  the 
salt  water,  and  are  corroded  still  more  deeply  at  points  lower  down  where 
they  are  just  reached  by  the  breakers.  By  this  action  the  stone  acquires 
a  wrinkled  and  furrowed  outline,  and  very  near  the  sea  it  becomes  rough 
and  branching,  as  if  covered  with  corals.  Such  effects  are  traced  not 


74  INLAND   SEA-CLIFFS  [Cn.  VI 

only  on  the  present  shore,  but  at  the  base  of  the  ancient  cliffs  far  in  the 
interior.  Lastly,  it  remains  only  to  speak  of  the  terraces,  which  extend 
with  a  gentle  slope  from  the  base  of  almost  all  the  inland  cliffs,  and  are 
for  the  most  part  narrow  where  the  rock  is  hard,  but  sometimes  half  a 
mile  or  more  in  breadth  where  it  is  soft.  They  are  the  effects  of  the 
encroachment  of  the  ancient  sea  upon  the  shore  at  those  levels  at  which 
the  land  remained  for  a  long  time  stationary.  The  justness  of  this  view 
is  apparent  on  examining  the  shape  of  the  modern  shore  wherever  the 
sea  is  advancing  upon  the  land,  and  removing  annually  small  portions 
of  undermined  rock.  By  this  agency  a  submarine  platform  is  produced 
on  which  we  may  walk  for  some  distance  from  the  beach  in  shallow 
water,  the  increase  of  depth  being  very  gradual,  until  we  reach  a  point 
where  the  bottom  plunges  down  suddenly.  This  platform  is  widened 
with  more  or  less  rapidity  according  to  the  hardness  of  the  rocks,  and 
when  upraised  it  constitutes  an  inland  terrace. 

But  the  four  principal  lines  of  cliff  observed  in  the  Morea  do  not 
imply,  as  some  have  imagined,  four  great  eras  of  sudden  upheaval ;  they 
simply  indicate  the  intermittance  of  the  upheaving  force.  Had  the  rise 
of  the  land  been  continuous  and  uninterrupted,  there  would  have  been 
no  one  prominent  line  of  cliff ;  for  every  portion  of  the  surface  having 
been,  in  its  turn,  and  for  an  equal  period  of  time,  a  sea-shore,  would 
have  presented  a  nearly  similar  aspect.  But  if  pauses  occur  in  the  pro- 
cess of  upheaval,  the  waves  and  currents  have  time  to  sap,  throw  down, 
and  clear  away  considerable  masses  of  rock,  and  to  shape  out  at  several 
successive  levels  lofty  ranges  of  cliffs  with  broad  terraces  at  their  base. 

There  are  some  levelled  spaces,  however,  both  ancient  and  modern,  in 
the  Morea,  which  are  not  due  to  denudation,  although  resembling  in 
outline  the  terraces  above  described.  They  may  be  called  Terraces  of 
Deposition,  since  they  have  resulted  from  the  gain  of  land  upon  the  sea 
where  rivers  and  torrents  have  produced  deltas.  If  the  sedimentary 
matter  has  filled  up  a  bay  or  gulf  surrounded  by  steep  mountains,  a  flat 
plain  is  formed  skirting  the  inland  precipices ;  and  if  these  deposits*  are 
upraised,  they  form  a  feature  in  the  landscape  very  similar  to  the  areas 
of  denudation  before  described. 

I  have  seen  on  the  northern  coast  of  Sicily  one  of  these  terraces 
of  deposition  in  the  environs  of  Palermo,  where,  as  in  Greece,  a  line 
of  limestone  cliffs  with  caverns  at  their  base  bounds  a  seaward- 
sloping  plain.  Proceeding  from  the  shore  inland,  we  find  the  plat- 
form, c,  fig.  93,  a  mile  wide,  composed  of  marine  calcareous  strata,  the 
majority  of  the  embedded  shells  and  corals  being  of  living  species. 
We  next  arrive  at  a  precipitous  cliff  of  hippurite  limestone,  a,  in 
which  the  well-known  cave  of  San  Giro,  6,  occurs,  130  feet  long,  50 
high,  and  30  wide.  Its  entrance  is  now  180  feet  above  the  sea ;  but 
the  salt  water  must  at  one  time  have  entered  it,  for  the  walls  are 
drilled  for  a  height  of  several  yards  by  perforating  molluscs,  and  the 
bottom  of  the  cave  is  strewed  over  with  a  thin  layer  of  sand,  in  which 
more  than  forty  species  of  sea-shells,  nearly  all  of  species  now  living 


CH.  VI.] 


IN  THE  ISLAND  OF  SICILY. 


in  the  Mediterranean  have  been  found.  Since  the  sea  retired  a  con- 
siderable thickness  of  breccia  has  accumulated  over  the  sand,  so  as  to 
conceal  from  view  the  lithodomous  perforations,  except  in  places 

Fig.  93. 


a.  Monte  Grifone.  b.  Cave  of  San  Ciro.* 

c.  Plain  of  Palermo,  in  which  are  Newer  Pliocene  strata  of 
limestone  and  sand.  d.  Bay  of  Palermo. 

where  these  have  been  exposed  to  view  by  artificial  excavations. 
The  breccia  is  composed  of  pieces  of  limestone,  quartz,  and  schist  in 
a  matrix  of  brown  marl  through  which  land  shells  are  dispersed 
together  with  bones  of  two  species,  as  we  learn  from  Dr.  Falconer, 
of  extinct  hippopotamus,  in  such  numbers  that  they  must  have  be- 
longed to  several  hundred  individuals.  With  these  are  associated  the 
remains  of  Elephas  antiquus  (as  determined  by  the  same  osteologist),, 
and  the  osseous  remains  of  Bos,  Cervus,  Sus,  Ursus,  Canis,  and  a 
large  Felis.  Some  of  these  bones  have  been  rolled  as  if  partially 
subjected  to  the  action  of  water,  and  the  whole  seem  to  have  been 
introduced  (perhaps  by  engulfed  streams)  both  in  this  and  some  neigh- 
boring caverns  through  rents  in  the  hippurite  limestone,  which  must 
once  have  been  connected  with  the  surface  of  the  country  above,  at  a 
time  when  the  physical  geography  of  the  region  was  extremely  dif- 
ferent from  what  it  now  is,  and  when  rivers  frequented  by  the  hippo- 
potamus existed  where  now  no  running  water  is  to  be  found. 

Besides  terraces  of  deposition  such  as  c,  fig.  93,  above  alluded  to, 
there  are  also  in  Sicily  others  of  denudation.  One  of  these  occurs 
on  the  east  coast  to  the  north  of  Syracuse,  and  the  same  is  resumed 
to  the  south  beyond  the  town  of  Noto,  where  it  may  be  traced  form- 
ing a  continuous  and  lofty  precipice,  a  5,  fig.  94,  facing  toward  the 
sea,  and  constituting  the  abrupt  termination  of  a  calcareous  for- 
mation, which  extends  in  horizontal  strata  far  inland.  This  preci- 
pice varies  in  height  from  500  to  TOO  feet,  and  between  its  base 
and  the  sea  is  an  inferior  platform,  c  5,  consisting  of  similar  white 
limestone.  All  the  beds  dip  toward  the  sea,  but  are  usually  in- 
clined at  a  very  slight  angle :  they  are  seen  to  extend  uninterrupt- 
edly from  the  base  of  the  escarpment  into  the  platform,  showing 
distinctly  that  the  lofty  cliff  was  not  produced  by  a  fault  or  ver- 
tical shift  of  the  beds,  but  by  the  removal  of  a  considerable  mass 
of  rock.  Hence  we  may  conclude  that  the  sea,  which  is  now 
undermining  the  cliffs  of  the  Sicilian  coast,  reached  at  some  for- 
mer period  the  base  of  the  precipice  a  5,  at  which  time  the  sur- 

*  Dr.  Christie,  Edin.  New  Phil.  Jour. 


76 


INLAND  SEA-CLIFFS  AND 


[On.  VI. 


face  of  the  terrace  c  b  must  have  been  covered  by  the  Mediterranean. 
There  was  a  pause,  therefore,  in  the  upward  movement,  when  the  waves 


Fig.  94. 


Sea 


of  the  sea  had  time  to  carve  out  the  platform  c  b ;  but  there  may  have 
been  many  other  stationary  periods  of  minor  duration.  Suppose,  for 
example,  that  a  series  of  escarpments  e,  /,  <7,  A,  once  existed,  and  that 
the  sea,  during  a  long  interval  free  from  subterranean  movements, 
advances  along  the  line  c  6,  all  preceding  cliffs  must  have  been 
swept  away  one  after  the  other,  and  reduced  to  the  single  precipice 
a  b. 

That  such  a  series  of  smaller  cliffs,  as  those  represented  at  <?,  /,  #,  A, 
fig.  94,  did  really  once  exist  at  intermediate  heights  in  place  of  the  single 
precipice  a  6,  is  rendered  highly  probable  by  the  fact,  that  in  certain 
bays  and  inland  valleys  opening  towards  the  east  coast  of  Sicily,  and  not 
far  from  the  section  given  in  fig.  94,  the  solid  limestone  is  shaped  out 
into  a  great  succession  of  ledges,  separated  from  each  other  by  small 
vertical  cliffs.  These  are  sometimes  so  numerous,  one  above  the  other. 


Fig.  95. 


Valley  called  Gozzo  degli  Martiri,  below  Melilli,  Val  di  Note. 

that  where  there  is  a  bend  at  the  head  of  a  valley,  they  produce  an  ef- 
fect singularly  resembling  the  seats  of  a  Roman  amphitheatre.     A  good 


CH.  VI] 


TERRACES  IN  SICILY. 


77 


example  of  this  configuration  occurs  near  the  town  of  Melilli,  as 
seen  in  the  annexed  view  (fig.  95).  In  the  south  of  the  island,  near 
Spaccaforno,  Scicli,  and  Mod'ica,  precipitous  rocks  of  white  limestone, 
ascending  to  the  height  of  500  feet,  have  been  carved  out  into  similar 
forms. 

This  appearance  of  a  range  of  marble  seats  circling  round  the  head  of 
a  valley,  or  of  great  flights  of  steps  descending  from  the  top  to  the  bot- 
tom, on  the  opposite  sides  of  a  gorge,  may  be  accounted  for,  as  already 
hinted,  by  supposing  the  sea  to  have  stood  successively  at  many  different 
levels,  as  at  a  a,  b  6,  c  c,  in  the  accompanying  fig.  96.  But  the  causes 
of  the  gradual  contraction  of  the  valley  from  above  downwards  may 

Fig.  96. 


still  be  matter  of  speculation.  Such  contraction  may  be  due  to  the 
greater  force  exerted  by  the  waves  when  the  land  at  its  first  emergence 
was  smaller  in  quantity,  and  more  exposed  to  denudation  in  an  open 
sea  ;  whereas  the  wear  and  tear  of  the  rocks  might  diminish  in  propor 
tion  as  this  action  became  confined  within  bays  or  channels  closed  in  on 
two  or  three  sides.  Or,  secondly,  the  separate  movements  of  elevation 
may  have  followed  each  other  more  rapidly  as  the  land  continued  to  rise, 
so  that  the  times  of  those  pauses,  during  which  the  greatest  denudation 
was  accomplished  at  certain  levels,  were  always  growing  shorter.  It 
should  be  remarked,  that  the  cliffs  and  small  terraces  are  rarely  found  on 
the  opposite  sides  of  the  Sicilian  valleys  at  heights  so  precisely  answering 
to  each  other  as  those  given  in  fig.  96,  and  this  might  have  been  ex- 
pected, to  whichever  of  the  two  hypotheses  above  explained  we  incline  ; 
for,  according  to  the  direction  of  the  prevailing  winds  and  currents,  the 
waves  may  beat  with  unequal  force  on  different  parts  of  the  shore,  so 
that  while  no  impression  is  made  on  one  side  of  a  bay,  the  sea  may 
encroach  so  far  on  the  other  as  to  unite  several  smaller  cliffs  into 
one. 

Before  quitting  the  subject  of  ancient  sea-cliffs,  carved  out  of  lime- 
stone, I  shall  mention  the  range  of  precipitous  rocks,  composed  of  a 
white  marble  of  the  Oolitic  period,  which  I  have  seen  near  the  northern 
gate  of  St.  Mihiel  in  France.  They  are  situated  on  the  right  bank  of 
the  Meuse,  at  a  distance  of  200  miles  from  the  nearest  sea,  and  they 
present  on  the  precipice  facing  the  river  three  or  four  horizontal  grooves, 
one  above  the  other,  precisely  resembling  those  which  are  scooped  out 
by  the  undermining  waves.  The  summits  of  several  of  these  masses  are 
detached  from  the  adjoining  hill,  in  which  case  the  grooves  pass  all 


78 


ROCKS  WORN  BY  THE  SEA. 


[On.  VI 


round  them,  facing  towards  all  points  of  the  compass,  as  if  they  had 
once  formed  rocky  islets  near  the  shore.* 

Captain  Bayfield,  in  his  survey  of  the  Gulf  of  St.  Lawrence,  discov- 
ered in  several  places,  especially  in  the  Mingan  islands,  a  counterpart  of 
the  inland  cliffs  of  St.  Mihiel,  and  traced  a  succession  of  shingle  beaches, 
one  above  the  other,  which  agreed  in  their  level  with  some  of  the  prin- 
cipal grooves  scooped  out  of  the  limestone  pillars.  These  beaches  con- 
sisted of  calcareous  shingle,  with  shells  of  recent  species,  the  farthest 
irom  the  shore  being  60  feet  above  the  level  of  the  highest  tides.  In 
addition  to  the  drawings  of  the  pillars  called  the  flower-pots,  which  he 
has  published,!  I  have  been  favored  with  other  views  of  rocks  on  the 
same  coast,  drawn  by  Lieut.  A.  Bowen,  K.  1ST.  (See  fig.  97.) 

Fig.  97. 


Limestone  columns  in  Niaplsca  Island,  in  the  Gulf  of  St.  Lawrence.   Height 
of  the  second  column  on  the  left,  60  feet. 

In  the  North- American  beaches  above  mentioned  rounded  fragments 
of  limestone  have  been  found  perforated  by  lithodomi ;  and  holes  drilled 
by  the  same  mollusks  have  been  detected  in  the  columnar  rocks  or 
"  flower-pots,"  showing  that  there  has  been  no  great  amount  of  atmos- 
pheric decomposition  on  the  surface,  or  the  cavities  alluded  to  would 
have  disappeared. 

Fig.  98. 


-  feS'  Bermuda,  lying  outside  the  great  coral  reef. 

A.  16  feet  high,  and  B.  12  feet.  c.  c.  Hollows  worn  by  the  sea. 

*  I  was  directed  by  M.  Deshayes  to  this  spot,  which  I  visited  in  June,  1838. 
f  See  Trans,  of  Geol.  Soc.  second  series,  vol.  v.  plate  v. 


CH.  VII.  1  ALLUVIUM.  79 

We  have  an  opportunity  of  seeing  in  the  Bermuda  islands  the  mannei 
in  which  the  waves  of  the  Atlantic  have  worn,  and  are  now  wearing  out, 
deep  smooth  hollows  on  every  side  of  projecting  masses  of  hard  limestone. 
In  the  annexed  drawing,  communicated  to  me  by  Capt.  Nelson,  R.  E.,  the 
excavations  c,  c,  c,  have  been  scooped  out  by  the  waves  in  a  stone  of  very 
modern  date,  which,  although  extremely  hard,  is  full  of  recent  corals  and 
shells,  some  of  which  retain  their  color. 

When  the  forms  of  these  horizontal  grooves,  of  which  the  surface  is 
sometimes  smooth  and  almost  polished,  and  the  roofs  of  which  often 
overhang  to  the  extent  of  5  feet  or  more,  have  been  carefully  studied  by 
geologists,  they  will  serve  to  testify  the  former  action  of  the  waves  at 
innumerable  points  far  in  the  interior  of  the  continents.  But  we  must 
learn  to  distinguish  the  indentations  due  to  the  original  action  of  the  sea, 
and  those  caused  by  subsequent  chemical  decomposition  of  calcareous 
rocks,  to  which  they  are  liable  in  the  atmosphere. 

I  shall  conclude  with  a  warning  to  beginners  not  to  feel  surprise  if  they 
can  detect  no  evidence  of  the  former  sojourn  of  the  sea  on  lands  which 
we  are  nevertheless  sure  have  been  submerged  at  periods  comparatively 
modern ;  for  notwithstanding  the  enduring  nature  of  the  marks  left  by 
littoral  action  on  calcareous  rocks,  we  can  by  no  means  detect  sea-beaches 
and  inland  cliffs  everywhere,  even  in  Sicily  and  the  Morea.  On  the  con 
trary,  they  are,  upon  the  whole,  extremely  partial,  and  are  often  entirely 
wanting  in  districts  composed  of  argillaceous  and  sandy  formations,  which 
must,  nevertheless,  have  been  upheaved  at  the  same  time,  and  by  the  same 
intermittent  movements,  as  the  adjoining  calcareous  rocks. 


CHAPTER  VE. 

ALLUVIUM. 

Alluvium  described — Due  to  complicated  causes — Of  various  ages,  as  shown  in 
Auvergne — How  distinguished  from  rocks  in  situ — Sand-pipes  in  chalk — Allu- 
vial terraces  caused  by  oscillations  in  the  level  of  land. 

BETWEEN  the  superficial  covering  of  vegetable  mould  and  the  subjacent 
rock  there  usually  intervenes  in  every  district  a  deposit  of  loose  gravel, 
sand,  and  mud,  to  which  the  name  of  alluvium  has  been  applied.  The 
term  is  derived  from  alluvio,  an  inundation,  or  alluo,  to  wash,  because  the 
pebbles  and  sand  commonly  resemble  those  of  a  river's  bed  or  the  mud 
and  gravel  washed  over  low  lands  by  a  flood. 

A  partial  covering  of  such  alluvium  is  found  alike  in  all  climates,  from 
the  equatorial  to  the  polar  regions ;  but  in  the  higher  latitudes  of  Europe 
and  North  America  it  assumes  a  distinct  character,  being  very  frequently 
devoid  of  stratification,  and  containing  huge  fragments  of  rock,  some  an- 
gular and  others  rounded,  which  have  been  transported  to  great  distances 
from  their  parent  mountains.  When  it  presents  itself  in  this  form,  it  has 
been  called  "  diluvium,"  "  drift,"  or  the  "  boulder  formation ;"  and  its  prob- 


80 


ALLUVIUM  IN  AUVERGNE. 


[On.  VII. 


able  connection  with  the  agency  of  floating  ice  and  glaciers  will  be  treated 
of  more  particularly  in  the  eleventh  and  twelfth  chapters. 

The  student  will  be  prepared,  by  what  I  have  said  in  the  last  chapter 
on  denudation,  to  hear  that  loose  gravel  and  sand  are  often  met  with, 
not  only  on  the  low  grounds  bordering  rivers,  but  also  at  various  points 
on  the  sides  or  even  summits  of  mountains.  For,  in  the  course  of  those 
changes  in  physical  geography  which  may  take  place  during  the  gradual 
emergence  of  the  bottom  of  the  sea  and  its  conversion  into  dry  land, 
any  spot  may  either  have  been  a  sunken  reef,  or  a  bay,  or  estuary,  or 
sea-shore,  or  the  bed  of  a  river.  The  drainage,  moreover,  may  have  been 
deranged  again  and  again  by  earthquakes,  during  which  temporary  lakes 
are  caused  by  landslips,  and  partial  deluges  occasioned  by  the  bursting 
of  the  barriers  of  such  lakes.  For  this  reason  it  would  be  unreason- 
able to  hope  that  we  should  ever  be  able  to  account  for  all  the  alluvial 
phenomena  of  each  particular  country,  seeing  that  the  causes  of  their 
origin  are  so  various.  Besides,  the  last  operations  of  water  have  a 
tendency  to  disturb  and  confound  together  all  pre-existing  alluviums. 
Hence  we  are  always  in  danger  of  regarding  as  the  work  of  a  single 
era,  and  the  effect  of  one  cause,  what  has  in  reality  been  the  result  of  a 
variety  of  distinct  agents,  during  a  long  succession  of  geological  epochs. 
Much  useful  instruction  may  therefore  be  gained  from  the  exploration  of 
a  country  like  Auvergne,  where  the  superficial  gravel  of  very  different 
eras  happens  to  have  been  preserved  by  sheets  of  lava,  which  were 
poured  out  one  after  the  other  at  periods  when  the  denudation,  and 
probably  the  upheaval,  of  rocks  were  in  progress.  That  region  had  al- 
ready acquired  in  some  degree  its  present  configuration  before  any  volca- 
noes were  in  activity,  and  before  any  igneous  matter  was  superimposed 
upon  the  granitic  and  fossiliferous  formations.  The  pebbles  therefore  in 
the  older  gravels  are  exclusively  constituted  of  granite  and  other  aborigi- 
nal rocks ;  and  afterwards,  when  volcanic  vents  burst  forth  into  eruption, 


Fig.  99, 


Lavas  of  Auvergne  resting  on  alluviums  of  different  ages. 

those  earlier  alluviums  were  covered  by  streams  of  lava,  which  protected 
them  from  intermixture  with  gravel  of  subsequent  date.  In  the  course 
of  ages,  a  new  system  of  valleys  was  excavated,  so  that  the  rivers  ran 
at  lower  levels  than  those  at  which  the  first  alluviums  and  sheets  of  lava 
were  formed.  When,  therefore,  fresh  eruptions  gave  rise  to  new  lava, 
the  melted  matter  was  poured  out  over  lower  grounds ;  and  the  gravel 


CH.  VII.] 


ALLUVIUM. 


of  these  plains  differed  from  the  first  or  upland  alluvium,  by  containing 
in  it  rounded  fragments  of  various  volcanic  rocks,  and  often  bones  be- 
longing to  distinct  groups  of  land  animals  which  flourished  in  the  country 
in  succession. 

The  annexed  drawing  will  explain  the  different  heights  at  which  beds  of 
lava  and  gravel,  each  distinct  from  the  other  in  composition  and  age,  are 
observed,  some  on  the  flat  tops  of  hills,  700  or  800  feet  high,  others  on 
the  slope  of  the  same  hills,  and  the  newest  of  all  in  the  channel  of  the 
existing  river  where  there  is  usually  gravel  alone,  but  in  some  cases  a  nar- 
row stripe  of  solid  lava  sharing  the  bottom  of  the  valley  with  the  river. 
In  all  these  accumulations  of  transported  matter  of  different  ages,  the  bones 
of  extinct  mammalia  have  been  found  belonging  to  assemblages  of  land 
quadrupeds  which  flourished  in  the  country  in  succession,  and  which 
vary  specifically,  the  one  set  from  the  other,  in  a  greater  or  less  degree, 
in  proportion  as  the  time  which  separated  their  entombment  has  been 
more  or  less  protracted.  The  streams  in  the  same  district  are  still  under- 
mining their  banks  and  grinding  down  into  pebbles  or  sand,  columns 
of  basalt  and  fragments  of  granite  and  gneiss;  but  portions  of  the 
older  alluviums,  with  the  fossil  remains  belonging  to  them,  are  prevented 
from  being  mingled  with  the  gravel  of  recent  date  by  the  cappings  of 
lava  before  mentioned.  But  for  the  accidental  interference,  therefore,  of 
this  peculiar  cause,  all  the  alluviums  might  have  passed  so  insensibly  the 
one  into  the  other,  that  those  formed  at  the  remotest  era  might  have 
appeared  of  the  same  date  as  the  newest,  and  the  whole  formation  might 
have  been  regarded  by  some  geologists  as  the  result  of  one  sudden  and 
violent  catastrophe. 

In  almost  every  country,  the  alluvium  consists  in  its  upper  part  of 
transported  materials,  but  it  often  passes  downwards  into  a  mass  of 
broken  and  angular  fragments  derived  from  the  subjacent  rock.  To  this 
mass  the  provincial  name  of  "  rubble,"  or  "  brash,"  is  given  in  many 
parts  of  England.  It  may  be  referred  to  the  weathering  or  disintegra- 
tion of  stone  on  the  spot,  the  effects  of  air  and  water,  sun  and  frost,  and. 
chemical  decomposition. 

The  inferior  surface  of  alluvial  deposits  is  often  very  irregular,  con- 
forming to  all  the  inequalities  of  the  fundamental  rocks  (fig.  100).  Oc- 
casionally, a  small  mass,  as  at  c,  appears 
detached,  and  as  if  included  in  the  subja- 
cent formation.  Such  isolated  portions  are 
usually  sections  of  winding  subterranean 
hollows  filled  up  with  alluvium.  They 
may  have  been  the  courses  of  springs  or 
subterranean  streamlets,  which  have  flowed 
through  and  enlarged-  natural  rents  ;  or, 
when  on  a  small  scale  and  in  soft  strata, 
they  may  be  spaces  which  the  roots  of  large 
trees  have  once  occupied,  gravel  and  sano 
having  been  introduced  after  their  decay. 


Fig.  100. 


82  SAND-PIPES.  [Cn.  VII 

But  there  are  other  deep  hollows  of  a  cylindrical  form  found  in  Eng- 
land, France,  and  elsewhere,  penetrating  the  white  chalk,  and  filled  with 
sand  and  gravel,  which  are  not  so  readily  explained.  They  are  some- 
times called  "sand-pipes,"  or  "sand-galls,"  and  "puits  naturels,"  in 
France.  Those  represented  in  the  annexed  cut  were  observed  by  me  in 


Band-pipes  in  the  chalk  at  Eaton,  near  Norwich. 

1839,  laid  open  in  a  large  chalk-pit  near  Norwich.  They  were  of  very 
symmetrical  form,  the  largest  more  than  12  feet  in  diameter,  and  some 
of  them  had  been  traced,  by  boring,  to  the  depth  of  more  than  60  feet. 
The  smaller  ones  varied  from  a  few  inches  to  a  foot  in  diameter,  and 
seldom  descended  more  than  12  feet  below  the  surface.  Even  where 
three  of  them  occurred,  as  at  a,  fig.  101,  very  close  together,  the  parting 
walls  of  soft  white  chalk  were  not  broken  through.  They  all  taper 
downwards  and  end  in  a  point.  As  a  general  rule,  sand  and  pebbles 
occupy  the  central  parts  of  each  pipe,  while  the  sides  and  bottom  are 
lined  with  clay. 

Mr.  Trimmer,  in  speaking  of  appearances  of  the  same  kind  in  the 
Kentish  chalk,  attributes  the  origin  of  such  "  sand-galls"  to  the  action 
of  the  sea  on  a  beach  or  shoal,  where  the  waves,  charged  with  shingle 
and  sand,  not  only  wear  out  longitudinal  furrows,  such  as  may  be  ob- 
served on  the  surface  of  the  above-mentioned  chalk  near  Norwich  when 
the  incumbent  gravel  is  removed,  but  also  drill  deep  circular  hollows  by 
the  rotatory  motion  imparted  to  sand  and  pebbles.  Such  furrows,  as  well 
as  vertical  cavities,  are  now  formed,  he  observes,  on  the  coast  where  the 
shores  are  composed  of  chalk.* 

That  the  commencement  of  many  of  the  tubular  cavities  now  under 
consideration  has  been  due  to  the  cause  here  assigned,  I  have  little  doubt, 
But  such  mechanical  action  could  not  have  hollowed  out  the  whole  of 
the  sand-pipes  c  and  cZ,  fig.  101,  because  several  large  chalk-flints  seen 
protruding  from  the  walls  of  the  pipes  have  not  been  eroded,  while  sand 
and  gravel  have  penetrated  many  feet  below  them.  In  other  cases,  as 

*  Trimmer,  Proceedings  of  Geol.  Soc.  vol.  iv.  p.  7,  1842. 


CH.  VII.]  ALLUVIUM.  33 

at  b  b,  similar  unrounded  nodules  of  flint,  still  preserving  their  irregular 
form  and  white  coating,  are  found  at  various  depths  in  the  midst  of  the 
loose  materials  filling  the  pipe.  These  have  evidently  been  detached 
from  regular,  layers  of  flints  occurring  above.  It  is  also  to  be  remarked 
that  the  course  of  the  same  sand-pipe,  b  b,  is  traceable  above  the  level 
of  the  chalk  for  some  distance  upwards,  through  the  incumbent  gravel 
and  sand,  by  the  obliteration  of  all  signs  of  stratification.  Occasionally, 
also,  as  in  the  pipe  c?,  the  overlying  beds  of  gravel  bend  downwards  into 
the  mouth  of  the  pipe,  so  as  to  become  in  part  vertical,  as  would  happen 
if  horizontal  layers  had  sunk  gradually  in  consequence  of  a  failure  of 
support.  All  these  phenomena  may  be  accounted  for  by  attributing  the 
enlargement  and  deepening  of  the  sand-pipes  to  the  chemical  action  of 
water  charged  with  carbonic  acid,  derived  from  the  vegetable  soil  and 
the  decaying  roots  of  trees.  Such  acid  might  corrode  the  chalk,  and 
deepen  indefinitely  any  previously  existing  hollow,  but  could  not  dissolve 
the  flints.  The  water,  after  it  had  become  saturated  with  carbonate  of 
lime,  might  freely  percolate  the  surrounding  porous  walls  of  chalk,  and 
escape  through  them  and  from  the  bottom  of  the  tube,  so  as  to  carry 
away  in  the  course  of  time  large  masses  of  dissolved  calcareous  rock,* 
and  leave  behind  it  on  the  edges  of  each  tubular  hollow  a  coating  of  fine 
clay,  which  the  white  chalk  contains. 

I  have  seen  tubes  precisely  similar  and  from  1  to  5  feet  in  diameter 
traversing  vertically  the  upper  half  of  the  soft  calcareous  building-stone, 
or  chalk  without  flints,  constituting  St.  Peter's  Mount,  Maestricht.  These 
hollows  are  filled  with  pebbles  and  clay,  derived  from  overlying  beds  of 
gravel,  and  all  terminate  downwards  like  those  of  Norfolk.  I  was  in- 
formed that,  6  miles  from  Maestricht,  one  of  these  pipes,  2  feet  in  diam- 
eter, was  traced  downwards  to  a  bed  of  flattened  flints,  forming  an  almost 
continuous  layer  in  the  chalk.  Here  it  terminated  abruptly,  but  a  few 
small  root-like  prolongations  of  it  were  detected  immediately  below, 
probably  where  the  dissolving  substance  had  penetrated  at  some  points 
through  openings  in  the  siliceous  mass. 

It  is  not  so  easy  as  may  at  first  appear  to  draw  a  clear  line  of  distinc- 
tion between  the  fixed  rocks,  or  regular  strata  (rocks  in  situ  or  in  place), 
and  alluvium.  If  the  bed  of  a  torrent  or  river  be  dried  up,  we  call  the 
gravel,  sand,  and  mud  left  in  their  channels,  or  whatever,  during  floods, 
they  may  have  scattered  over  the  neighboring  plains,  alluvium.  The 
very  same  materials  carried  into  a  lake,  where  they  become  sorted  by 
water  and  arranged  in  more  distinct  layers,  especially  if  they  inclose  the 
remains  of  plants,  shells,  or  other  fossils,  are  termed  regular  strata. 

In  like  manner  we  may  sometimes  compare  the  gravel,  sand,  and 
broken  shells,  strewed  along  the  path  of  a  rapid  marine  current,  with  a 
deposit  formed  contemporaneously  by  the  discharge  of  similar  materials, 
year  after  year,  into  a  deeper  and  more  tranquil  part  of  the  sea.  In 
such  cases,  when  we  detect  marine  shells  or  other  organic  remains  en- 

*  See  Lyell  on  Sand-pipes,  Ac.  Phil.  Mag.  third  series,  vol.  xv.  p.  257,  Oct.  1839. 


84  ALLUVIUM.  [On.  VII 

tombed  in  the  strata,  which  enable  us  to  determine  their  age  and 
mode  of  origin,  we  regard  them  as  part  of  the  regular  series  of  fos- 
siliferous  formations,  whereas,  if  there  are  no  fossils,  we  have  frequently 
no  power  of  separating  them  from  the  general  mass  of  superficial  al- 
luvium. 

The  usual  rarity  of  organic  remains  in  beds  of  loose  gravel  is  partly 
owing  to  the  friction  which  originally  ground  down  rocks  into  pebbles  or 
sand,  and  organic  bodies  into  small  fragments,  and  it  is  partly  owing  to 
the  porous  nature  of  alluvium  when  it  has  emerged,  which  allows  the  free 
percolation  through  it  of  rain-water,  and  promotes  the  decomposition  and 
solution  of  fossil  remains. 

It  has  long  been  a  matter  of  common  observation  that  most  rivers 
are  now  cutting  their  channels  through  alluvial  deposits  of  greater  depth 
and  extent  than  could  ever  have  been  formed  by  the  present  streams. 
From  this  fact  a  rash  inference  has  sometimes  been  drawn,  that  rivers  in 
general  have  grown  smaller,  or  become  less  liable  to  be  flooded  than  for- 
merly. But  such  phenomena  would  be  a  natural  result  of  considerable 
oscillations  in  the  level' of  the  land  experienced  since  the  existing  valleys 
originated. 

Suppose  part  of  a  continent,  comprising  within  it  a  large  hydrographical 
basin  like  that  of  the  Mississippi,  to  subside  several  inches  or  feet  in  a 
century,  as  the  west  coast  of  Greenland,  extending  600  miles  north  and 
south,  has  been  sinking  for  three  or  four  centuries,  between  the  latitudes 
60°  and  69°  K*  It  will  rarely  happen  that  the  rate  of  subsidence  will 
be  everywhere  equal,  and  in  many  cases  the  amount  of  depression  in  the 
interior  will  regularly  exceed  that  of  the  region  nearer  the  sea.  Whenever 
this  happens,  the  fall  of  the  waters  flowing  from  the  upland  country  will 
be  diminished,  and  each  tributary  stream  will  have  less  power  to  carry  its 
sand  and  sediment  into  the  main  river,  and  the  main  river  less  power  to 
convey  its  annual  burden  of  transported  matter  to  the  sea.  All  the  rivers, 
therefore,  will  proceed  to  fill  up  partially  their  ancient  channels,  and, 
during  frequent  inundations,  will  raise  their  alluvial  plains  by  new  deposits. 
If  then  the  same  area  of  land  be  again  upheaved  to  its  former  height,  the 
fall,  and  consequently  the  velocity,  of  every  river  would  begin  to  aug- 
ment. Each  of  them  would  be  less  given  to  overflow  its  alluvial  plain  ; 
and  their  power  of  carrying  earthy  matter  seaward,  and  of  scouring  out 
and  deepening  their  channels,  will  be  sustained  till,  after  a  lapse  of  many 
thousand  years,  each  of  them  has  eroded  a  new  channel  or  valley  through 
a  fluviatile  formation  of  comparatively  modern  date.  The  surface  of  what 
was  once  the  river-plain  at  the  period  of  greatest  depression,  will  then 
remain  fringing  the  valley  sides  in  the  form  of  a  terrace  apparently  flat, 
but  in  reality  sloping  down  with  the  general  inclination  of  the  river. 
Everywhere  this  terrace  will  present  cliffs  of  gravel  and  sand,  facing 
the  river.  That  such  a  series  of  movements  has  actually  taken  place  in 
the  main  valley  of  the  Mississippi  and  in  its  tributary  valleys  during 

*  Principles  of  Geology,  7th  ed.  p.  506,  8th  ed.  p.  509. 


CH.  VIII.]  CHRONOLOGY  OF  ROCKS. 


85 


oscillations  of  level,  I  have  endeavored  to  show  in  my  description  of 
that  country ;  *  and  the  freshwater  shells  of  existing  species  and  bones 
of  land  quadrupeds,  partly  of  extinct  races,  preserved  in  the  terraces 
of  fluviatile  origin,  attest  the  exclusion  of  the  sea  during  the  whole 
process  of  filling  up  and  partial  re-excavation. 

Such  terraces  are  the  converse  of  those  mentioned  at  p.  80,  fig.  99, 
where  the  uppermost  of  the  series  is  formed  of  alluvium  of  oldest 
date,  which  originated  long  before  the  valley  had  attained  its  actual 
width  and  depth. 


CHAPTER  VIII. 

CHRONOLOGICAL    CLASSIFICATION    OF   ROCKS. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically — 
Lehman's  division  into  primitive  and  secondary — Werner's  addition  of  a  tran- 
sition class — Neptunian  theory — Hutton  on  igneous  origin  of  granite — How  the 
name  of  primary  was  still  retained  for  granite — The  term  "transition,"  why 
faulty — The  adherence  to  the  old  chronological  nomenclature  retarded  the 
progress  of  geology — New  hypothesis  intended  to  reconcile  the  igneous  origin 
of  granite  to  the  notion  of  its  high  antiquity — Explanation  of  the  chronological 
nomenclature  adopted  in  this  work,  so  far  as  regards  primary,  secondary,  and 
tertiary  periods. 

IN  the  first  chapter  it  was  stated  that  the  four  great  classes  of  rocks, 
the  aqueous,  the  volcanic,  the  plutonic,  and  the  metamorphic,  would 
each  be  considered  not  only  in  reference  to  their  mineral  characters, 
and  mode  of  origin,  but  also  to  their  relative  age.  In  regard  to  the 
aqueous  rocks,  we  have  already  seen  that  they  are  stratified,  that 
some  are  calcareous,  others  argillaceous  or  siliceous,  some  made  up 
of  sand,  others  of  pebbles ;  that  some  contain  freshwater,  others  ma- 
rine fossils,  and  so  forth ;  but  the  student  has  still  to  learn  which 
rocks,  exhibiting  some  or  all  of  these  characters,  have  originated  at 
one  period  of  the  earth's  history,  and  which  at  another. 

To  determine  this  point  in  reference  to  the  fossiliferous  formations 
is  more  easy  than  in  any  other  class,  and  it  is  therefore  the  most  con- 
venient and  natural  method  to  begin  by  establishing  a  chronology  for 
these  strata,  and  then  to  refer  as  far  as  possible  to  the  same  divisions 
the  several  groups  of  plutonic,  volcanic,  and  metamorphic  rocks. 
Such  a  system  of  classification  is  not  only  recommended  by  its  great- 
er clearness  and  facility  of  application,  but  is  also  best  fitted  to 
strike  the  imagination  by  bringing  into  one  view  the  contempora- 
neous revolutions  of  the  inorganic  and  organic  creations  of  former 
times.  For  the  sedimentary  formations  are  most  readily  distin- 
guished by  the  different  species  of  fossil  animals  and  plants  which 

*  Second  Visit  to  the  U.  S.,  vol.  ii.,  chap.  34. 


80  CLASSIFICATION  OF  ROCKS.  [Cn.  VIII. 

they  inclose,  and  of  which  one  assemblage  after  another  has  flourished  and 
then  disappeared  from  the  earth  in  succession. 

But  before  entering  specially  on  the  subdivisions  of  the  aqueous  rocks 
arranged  according  to  the  order  of  time,  it  will  be  desirable  to  say  a  few 
words  on  the  chronology  of  rocks  in  general,  although  in  doing  so  we 
shall  be  unavoidably  led  to  allude  to  some  classes  of  phenomena  which 
the  beginner  must  not  yet  expect  fully  to  comprehend. 

It  was  for  many  years  a  received  opinion,  that  the  formation  of  entire 
families  of  rocks,  such  as  the  plutonic  and  those  crystalline  schists  spoken 
of  in  the  first  chapter  as  metamorphic,  began  and  ended  before  any  mem- 
bers of  the  aqueous  and  volcanic  orders  were  produced ;  and  although 
this  idea  has  long  been  modified,  and  is  nearly  exploded,  it  will  be  neces- 
sary to  give  some  account  of  the  ancient  doctrine,  in  order  that  beginners 
may  understand  whence  many  prevailing  opinions,  and  some  part  of  the 
nomenclature  of  geology,  still  partially  in  use,  was  derived. 

About  the  middle  of  the  last  century,  Lehman,  a  German  miner,  pro- 
posed to  divide  rocks  into  three  classes,  the  first  and  oldest  to  be  called 
primitive,  comprising  the  hypogene,  or  plutonic  and  metamorphic  rocks ; 
the  next  to  be  termed  secondary,  comprehending  the  aqueous  or  fossilif- 
erous  strata ;  and  the  remainder,  or  third  class,  corresponding  to  our 
alluvium,  ancient  and  modern,  which  he  referred  to  "  local  floods,  and 
the  deluge  of  Noah."  In  the  primitive  class,  he  said,  such  as  granite 
and  gneiss,  there  are  no  organic  remains,  nor  any  signs  of  materials  de- 
rived from  the  ruins  of  pre-existing  rocks.  Their  origin,  therefore,  may 
have  been  purely  chemical,  antecedent  to  the  creation  of  living  beings, 
and  probably  coeval  with  the  birth  of  the  world  itself.  The  secondary 
formations,  on  the  contrary,  which  often  contain  sand,  pebbles,  and  or- 
ganic remains,  must  have  been  mechanical  deposits,  produced  after  the 
planet  had  become  the  habitation  of  animals  and  plants.  This  bold 
generalization,  although  anticipated  in  some  measure  by  Steno,  a  century 
before,  in  Italy,  formed  at  the  time  an  important  step  in  the  progress  of 
geology,  and  sketched  out  correctly  some  of  the  leading  divisions  into 
which  rocks  may  be  separated.  About  half  a  century  later,  Werner,  so 
justly  celebrated  for  his  improved  methods  of  discriminating  the  minera- 
logical  characters  of  rocks,  attempted  to  improve  Lehman's  classification, 
and  with  this  view  intercalated  a  class,  called  by  him  "  the  transition 
formations/'  between  the  primitive  and  secondary.  Between  these  last 
he  had  discovered,  in  northern  Germany,  a  series  of  strata,  which  in  their 
mineral  peculiarities  were  of  an  intermediate  character,  partaking  in 
some  degree  of  the  crystalline  nature  of  micaceous  schist  and  clay-slate, 
and  yet  exhibiting  here  and  there  signs  of  a  mechanical  origin  and  or- 
ganic remains.  For  this  group,  therefore,  forming  a  passage  between 
Lehman's  primitive  and  secondary  rocks,  the  name  of  ubergang  or  transi- 
tion was  proposed.  They  consisted  principally  of  clay-slate  and  an  ar- 
gillaceous sandstone,  called  grauwacke,  and  partly  of  calcareous  beds. 
It  happened  in  the  district  which  Werner  first  investigated,  that  both  the 
primitive  and  transition  strata  were  highly  inclined,  while  the  beds  of 


CH.  VIII.]  NEPTUNIAN  THEORY.  g* 

the  newer  fossiliferous  roots,  the  secondary  of  Lehman,  were  horizontal. 
To  these  latter  therefore,  he  gave  the  name  of  /ote,  or  "  a  level  floor  •" 
and  every  deposit  more  modern  than  the  chalk,  which  was  classed  as  the 
uppermost  of  the  flotz  series,  was  designated  "  the  overflowed  land,"  an 
expression  which  may  be  regarded  as  equivalent  to  alluvium,  although 
under  this  appellation  were  confounded  all  the  strata  afterwards  called 
tertiary,  of  which  Werner  had  scarcely  any  knowledge.  As  the  followers 
of  Werner  soon  discovered  that  the  inclined  position  of  the  "  transition 
beds,"  and  the  horizontally  of  the  flotz,  or  newer  fossiliferous  strata,  were 
mere  local  accidents,  they  soon  abandoned  the  term  flotz ;  and  the  four 
divisions  of  the  Wernerian  school  were  then  named  primitive,  transition, 
secondary,  and  alluvial. 

As  to  the  trappean  rocks,  although  their  igneous  origin  had  been  al- 
ready demonstrated  by  Arduino,  Fortis,  Faujas,  and  others,  and  especially 
by  Desmarest,  they  were  all  regarded  by  Werner  as  aqueous,  and  as  mere 
subordinate  members  of  the  secondary  series.* 

The  theory  of  Werner's  was  called  the  "  Neptunian,"  and  for  many 
years  enjoyed  much  popularity.  It  assumed  that  the  globe  had  been  at 
first  invested  by  a  universal  chaotic  ocean,  holding  the  materials  of  all 
rocks  in  solution.  From  the  waters  of  this  ocean,  granite,  gneiss,  and 
other  crystalline  formations,  were  first  precipitated ;  and  afterwards,  when 
the  waters  were  purged  of  these  ingredients,  and  more  nearly  resembled 
those  of  our  actual  seas,  the  transition  strata  were  deposited.  These  were 
of  a  mixed  character,  not  purely  chemical,  because  the  waves  and  currents 
had  already  begun  to  wear  down  solid  land,  and  to  give  rise  to  pebbles, 
sand,  and  mud ;  nor  entirely  without  fossils,  because  a  few  of  the  first 
marine  animals  had  begun  to  exist.  After  this  period,  the  secondary  for- 
mations were  accumulated  in  waters  resembling  those  of  the  present  ocean, 
except  at  certain  intervals,  when,  from  causes  wholly  unexplained,  a  par- 
tial recurrence  of  the  "  chaotic  fluid"  took  place,  during  which  various 
trap  rocks,  some  highly  crystalline,  were  formed.  This  arbitrary  hypothe- 
sis rejected  all  intervention  of  igneous  agency,  volcanoes  being  regarded 
as  modern,  partial,  and  superficial  accidents,  of  trifling  account  among  the 
great  causes  which  have  modified  the  external  structure  of  the  globe. 

Meanwhile  Hutton,  a  contemporary  of  Werner,  began  to  teach,  in 
Scotland,  that  granite  as  well  as  trap  was  of  igneous  origin,  and  had  at 
various  periods  intruded  itself  in  a  fluid  state  into  different  parts  of  the 
earth's  crust.  He  recognized  and  faithfully  described  many  of  the  phe- 
nomena of  granitic  veins,  and  the  alterations  produced  by  them  on  the 
invaded  strata,  which  will  be  treated  of  in  the  thirty-third  chapter.  He, 
moreover,  advanced  the  opinion,  that  the  crystalline  strata  called  primi- 
tive had  not  been  precipitated  from  a  primaeval  ocean,  but  were  sediment- 
ary strata  altered  by  heat.  In  his  writings,  therefore,  and  in  those  of  his 
illustrator,  Playfair,  we  find  the  germ  of  that  metamorphic  theory  which 
has  been  already  hinted  at  in  the  first  chapter,  and  which  will  be  more 
fully  expounded  in  the  thirty-fourth  and  thirty-fifth  chapters. 

*  See  Principles  of  Geology,  vol.  i.  chap.  iv. 


88  ON  THE  TERM   "TRANSITION."  [Cn.  VIII. 

At  length,  after  much  controversy,  the  doctrine  of  the  igneous  origin  of 
trap  and  granite  made  its  way  into  general  favor ;  but  although  it  was,  in 
consequence,  admitted  that  both  granite  and  trap  had  been  produced  at 
many  successive  periods,  the  term  primitive  or  primary  still  continued  to 
be  applied  to  the  crystalline  formations  in  general,  whether  stratified,  like 
gneiss,  or  unstratified,  like  granite.  The  pupil  was  told  that  granite  was 
a  primary  rock,  but  that  some  granites  were  newer  than  certain  secondary 
formations ;  and  in  conformity  with  the  spirit  of  the  ancient  language,  to 
which  the  teacher  was  still  determined  to  adhere,  a  desire  was  naturally 
engendered  of  extenuating  the  importance  of  those  more  modern  granites, 
the  true  dates  of  which  new  observations  were  continually  bringing  to  light. 

A  no  less  decided  inclination  was  shown  to  persist  in  the  use  of  the 
term  "  transition,"  after  it  had  been  proved  to  be  almost  as  faulty  in  its 
original  application  as  that  of  flotz.  The  name  of  transition,  as  already 
stated,  was  first  given  by  Werner,  to  designate  a  mineral  character,  inter 
mediate  between  the  highly  crystalline  or  metamorphic  state  and  that  of 
an  ordinary  fossiliferous  rock.  But  the  term  acquired  also  from  the  first 
a  chronological  import,  because  it  had  been  appropriated  to  sedimentary 
formations,  which,  in  the  Hartz  and  other  parts  of  Germany,  were  more 
ancient  than  the  oldest  of  the  secondary  series,  and  were  characterized  by 
peculiar  fossil  zoophytes  and  shells.  When,  therefore,  geologists  found 
in  other  districts  stratified  rocks  occupying  the  same  position,  and  inclosing 
similar  fossils,  they  gave  to  them  also  the  name  of  transition,  according 
to  rules  which  will  be  explained  in  the  next  chapter ;  yet,  in  many  cases, 
such  rocks  were  found  not  to  exhibit  the  same  mineral  texture  which 
Werner  had  called  transition.  On  the  contrary,  many  of  them  were  not 
more  crystalline  than  different  members  of  the  secondary  class ;  while, 
on  the  other  hand,  these  last  were  sometimes  found  to  assume  a  semi- 
crystalline  and  almost  metamorphic  aspect,  and  thus,  on  lithological 
grounds,  to  deserve  equally  the  name  of  transition.  So  remarkably  was 
this  the  case  in  the  Swiss  Alps,  that  certain  rocks,  which  had  for  years 
been  regarded  by  some  of  the  most  skilful  disciples  of  Werner  to  be  tran- 
sition, were  at  last  acknowledged,  when  their  relative  position  and  fossils 
were  better  understood,  to  belong  to  the  newest  of  the  secondary  groups  ; 
nay,  some  of  them  have  actually  been  discovered  to  be  members  of  the 
lower  tertiary  series  !  If,  under  such  circumstances,  the  name  of  transition 
was  retained,  it  is  clear  that  it  ought  to  have  been  applied  without  refer- 
ence to  the  age  of  strata,  and  simply  as  expressive  of  a  mineral  peculiarity. 
The  continued  appropriation  of  the  term  to  formations  of  a  given  date,  in- 
duced geologists  to  go  on  believing  that  the  ancient  strata  so  designated 
bore  a  less  resemblance  to  the  Secondary  than  is  really  the  case,  and  to 
imagine  that  these  last  never  pass,  as  they  frequently  do,  into  metamor- 
phic rocks. 

The  poet  Waller,  when  lamenting  over  the  antiquated  style  of  Chaucer, 
complains  that — 

We  write  in  sand,  our  language  grows, 
And.  like  the  tide,  our  work  o'erflows. 


CH.  VIII.]  CHANGES  OF  NOMENCLATURE. 


89 


But  the  reverse  is  true  in  geology  ;  for  here  it  is  our  work  which  contin- 
ually outgrows  the  language.  The  tide  of  observation  advances  with  such 
speed  that  improvements  in  theory  outrun  the  changes  of  nomenclature  • 
and  the  attempt  to  inculcate  new  truths  by  words  invented  to  express  a 
different  or  opposite  opinion,  tends  constantly,  by  the  force  of  association 
to  perpetuate  error ;  so  that  dogmas  renounced  by  the  reason  still  retain 
a  strong  hold  upon  the  imagination. 

In  order  to  reconcile  the  old  chronological  views  with  the  new  doctrine 
of  the  igneous  origin  of  granite,  the  following  hypothesis  was  substituted 
for  that  of  the  Neptunists.  Instead  of  beginning  with  an  aqueous  men- 
struum or  chaotic  fluid,  the  materials  of  the  present  crust  of  the  earth 
were  supposed  to  have  been  at  first  in  a  state  of  igneous  fusion,  until  part 
of  the  heat  having  been  diffused  into  surrounding  space,  the  surface  of  the 
fluid  consolidated,  and  formed  a  crust  of  granite.  This  covering  of  crys- 
talline stone,  which  afterwards  grew  thicker  and  thicker  as  it  cooled,  was 
so  hot,  at  first^  that  no  water  could  exist  upon  it ;  but  as  the  refrigeration 
proceeded,  the  aqueous  vapor  in  the  atmosphere  was  condensed,  and,  fall- 
ing in  rain,  gave  rise  to  the  first  thermal  ocean.  So  high  was  the  tem- 
perature of  this  boiling  sea,  that  no  aquatic  beings  could  inhabit  its  waters, 
and  its  deposits  were  not  only  devoid  of  fossils,  but,  like  those  of  some 
hot  springs,  were  highly  crystalline.  Hence  the  origin  of  the  primary  or 
crystalline  strata, — gneiss,  mica-schist,  and  the  rest. 

Afterwards,  when  the  granitic  crust  had  been  partially  broken  up,  land 
and  mountains  began  to  rise  above  the  waters,  and  rains  and  torrents  to 
grind  down  rock,  so  that  sediment  was  spread  over  the  bottom  of  the 
seas.  Yet  the  heat  still  remaining  in  the  solid  supporting  substances 
was  sufficient  to  increase  the  chemical  action  exerted  by  the  water,  al- 
though not  so  intense  as  to  prevent  the  introduction  and  increase  of  some 
living  beings.  '  During  this  state  of  things  some  of  the  residuary  mineral 
ingredients  of  the  primaeval  ocean  were  precipitated,  and  formed  deposits 
(the  transition  strata  of  Werner),  half  chemical  and  half  mechanical,  and 
containing  a  few  fossils. 

By  this  new  theory,  which  was  in  part  a  revival  of  the  doctrine  of 
Leibnitz,  published  in  1680,  on  the  igneous  origin  of  the  planet,  the  old 
ideas  respecting  the  priority  of  all  crystalline  rocks  to  the  creation  of  or- 
ganic beings,  were  still  preserved  ;  and  the  mistaken  notion  that  all  the 
semi-crystalline  and  partially  fossiliferous  rocks  belonged  to  one  period, 
while  all  the  earthy  and  uncrystalline  formations  originated  at  a  subse- 
quent epoch,  was  also  perpetuated. 

It  may  or  may  not  be  true,  as  the  great  Leibnitz  imagined,  that  the 
whole  planet  was  once  in  a  state  of  liquefaction  by  heat ;  but  there  are  cer- 
tainly no  geological  proofs  that  the  granite  which  constitutes  the  founda- 
tion of  so  much  of  the  earth's  crust  was  ever  at  once  in  a  state  of  universal 
fusion.  On  the  contrary,  all  our  evidence  tends  to  show  that  the  formation 
of  granite,  like  the  deposition  of  the  stratified  rocks,  has  been  successive, 
and  that  different  portions  of  granite  have  been  in  a  melted  state  at  dis 
tinct  and  often  distant  periods.  One  mass  was  solid,  and  had  been  frac- 


90  CHRONOLOGICAL  ARRANGEMENT  [Cn.  VIII. 

tured,  before  another  body  of  granitic  matter  was  injected  into  it,  or  through 
it,  in  the  form  of  veins.  Some  granites  are  more  ancient  than  any  known 
fossiliferous  rocks ;  others  are  of  secondary ;  and  some,  such  as  that  of 
Mont  Blanc  and  part  of  the  central  axis  of  the  Alps,  of  tertiary  origin. 
In  short,  the  universal  fluidity  of  the  crystalline  foundations  of  the  earth's 
crust,  can  only  be  understood  in  the  same  sense  as  the  universality  of  the 
ancient  ocean.  All  the  land  has  been  under  water,  but  not  all  at  one 
time  ;  so  all  the  subterranean  unstratified  rocks  to  which  man  can  obtain 
access  have  been  melted,  but  not  simultaneously. 

In  the  present  work  the  four  great  classes  of  rocks,  the  aqueous,  plutonic, 
volcanic,  and  metamorphic,  will  form  four  parallel,  or  nearly  parallel,  col- 
umns in  one  chronological  table.  They  will  be  considered  as  four  sets  of 
monuments  relating  to  four  contemporaneous,  or  nearly  contemporaneous, 
series  of  events.  I  shall  endeavor,  in  a  subsequent  chapter  on  the  plutonic 
rocks,  to  explain  the  manner  in  which  certain  masses  belonging  to  each 
of  the  four  classes  of  rocks  may  have  originated  simultaneously  at  every 
geological  period,  and  how  the  earth's  crust  may  have  been  continually 
modelled,  above  and  below,  by  aqueous  and  igneous  causes,  from  times 
indefinitely  remote.  In  the  same  manner  as  aqueous  and  fossiliferous 
strata  are  now  formed  in  certain  seas  or  lakes,  while  in  other  places  vol- 
canic rocks  break  out  at  the  surface,  and  are  connected  with  reservoirs  of 
melted  matter  at  vast  depths  in  the  bowels  of  the  earth, — so,  at  every 
era  of  the  past,  fossiliferous  deposits  and  superficial  igneous  rocks  were  in 
progress  contemporaneously  with  others  of  subterranean  and  plutonic  ori- 
gin, and  some  sedimentary  strata  were  exposed  to  heat  and  made  to  as- 
sume a  crystalline  or  metamorphic  structure. 

It  can  by  no  means  be  taken  for  granted,  that  during  all  these  changes 
the  solid  crust  of  the  earth  has  been  increasing  in  thickness.  It  has  been 
shown,  that  so  far  as  aqueous  action  is  concerned,  the  gain  by  fresh  deposits, 
and  the  loss  by  denudation,  must  at  each  period  have  been  equal  (see  above, 
p.  68) :  and  in  like  manner,  in  the  inferior  portion  of  the  earth's  crust,  the 
acquisition  of  new  crystalline  rocks,  at  each  successive  era,  may  merely  have 
counterbalanced  the  loss  sustained  by  the  melting  of  materials  previously 
consolidated.  As  to  the  relative  antiquity  of  the  crystalline  foundations  of 
the  earth's  crust,  when  compared  to  the  fossiliferous  and  volcanic  rocks 
which  they  support,  I  have  already  stated,  in  the  first  chapter,  that  to  pro- 
nounce an  opinion  on  this  matter  is  as  difficult  as  at  once  to  decide  which 
of  the  two,  whether  the  foundations  or  superstructure  of  an  ancient  city  built 
on  wooden  piles,  may  be  the  oldest.  We  have  seen  that,  to  answer  this 
question,  we  must  first  be  prepared  to  say  whether  the  work  of  decay  and 
restoration  had  gone  on  most  rapidly  above  or  below,  whether  the  average 
duration  of  the  piles  has  exceeded  that  of  the  stone  buildings,  or  the  contrary. 
So  also  in  regard  to  the  relative  age  of  the  superior  and  inferior  portions 
of  the  earth's  crust ;  we  cannot  hazard  even  a  conjecture  on  this  point,  un- 
til we  know  whether,  upon  an  average,  the  power  of  water  above,  or  that 
of  heat  below,  is  most  efficacious  in  giving  new  forms  to  solid  matter. 

After  the  observations  which  have  now  been  made,  the  reader  will  per- 


CH.  VIII.]  OF  ROCKS  IN   GENEKAL. 


91 


ceive  that  the  term  primary  must  either  be  entirely  renounced,  or,  if  re- 
tained, must  be  differently  defined,  and  not  made  to  designate  a  set  of 
crystalline  rocks,  some  of  which  are  already  ascertained  to  be  newer  than 
all  the  secondary  formations.  In  this  work  I  shall  follow  most  nearly 
the  method  proposed  by  Mr.  Boue,  who  has  called  all  fossiliferous  rocks 
older  than  the  secondary  by  the  name  of  primary.  To  prevent  con- 
fusion, I  shall  sometimes  speak  of  these  last  as  the  primary  fossiliferous 
formations,  because  the  word  primary  has  hitherto  been  most  generally 
connected  with  the  idea  of  a  non-fossiliferous  rock.  Some  geologists,  to 
avoid  misapprehension,  have  introduced  the  term  Paleozoic  for  primary, 
from  tfaXcuov,  "  ancient,"  and  £wov,  "  an  organic  being,"  still  retaining  the 
terms  secondary  and  tertiary ;  Mr.  Phillips,  for  the  sake  of  uniformity,  has 
proposed  Mesozoic,  for  secondary,  from  fASrfof,  "  middle,"  &c. ;  and  Caino- 
zoic,  for  tertiary,  from  xaivo^,  "  recent,"  &c. ;  but  the  terms  primary,  sec- 
ondary, and  tertiary  are  synonymous,  and  have  the  claim  of  priority  in 
their  favor. 

If  we  can  prove  any  plutonic,  volcanic,  or  metamorphic  rocks  to  be 
older  than  the  secondary  formations,  such  rocks  will  also  be  primary,  ac- 
cording to  this  system.  Mr.  Boue,  having  with  propriety  excluded  the 
metamorphic  rocks,  as  a  class,  from  the  primary  formations,  proposed  to 
call  them  all  "  crystalline  schists." 

As  there  are  secondaiy  fossiliferous  strata,  so  we  shall  find  that  there 
are  plutonic,  volcanic,  and  metamorphic  rocks  of  contemporaneous  origin, 
which  I  shall  also  term  secondary. 

In  the  next  chapter  it  will  be  shown  that  the  strata  above  the  chalk 
have  been  called  tertiary.  If,  therefore,  we  discover  any  volcanic,  plutonic, 
or  metamorphic  rocks,  which  have  originated  since  the  deposition  of  the 
chalk,  these  also  will  rank  as  tertiary  formations. 

It  may  perhaps  be  suggested  that  some  metamorphic  strata,  and  some 
granites,  may  be  anterior  in  date  to  the  oldest  of  the  primary  fossilifer- 
ous rocks.  This  opinion  is  doubtless  true,  and  will  be  discussed  in  future 
chapters ;  but  I  may  here  observe,  that  when  we  arrange  the  four  classes 
of  rocks  in  four  parallel  columns  in  one  table  of  chronology,  it  is  by  no 
means  assumed  that  these  columns  are  all  of  equal  length ;  one  may 
begin  at  an  earlier  period  than  the  rest,  and  another  may  come  down  to 
a  later  point  of  time.  In  the  small  part  of  the  globe  hitherto  examined, 
it  is  hardly  to  be  expected  that  we  should  have  discovered  either  the 
oldest  or  the  newest  members  of  each  of  the  four  classes  of  rocks.  Thus, 
if  there  be  primary,  secondary,  and  tertiary  rocks  of  the  aqueous  or  fos- 
siliferous class,  and  in  like  manner  primary,  secondary,  and  tertiary  hypo- 
gene  formations,  we  may  not  be  yet  acquainted  with  the  most  ancient  of 
the  primary  fossiliferous  beds,  or  with  the  newest  of  the  hypogene. 


92  TESTS  OF  THE  DIFFERENT  AGES  [Cu.  IX. 


CHAPTER  IX. 

ON   THE    DIFFERENT   AGES    OF   THE    AQUEOUS    ROOKS. 

On  the  three  principal  tests  of  relative  age — Superposition,  mineral  character, 
and  fossils — Change  of  mineral  character  and  fossils  in  the  same  continuous 
formation — Proofs  that  distinct  species  of  animals  and  plants  have  lived  at  suc- 
cessive periods — Distinct  provinces  of  indigenous  species — Great  extent  of 
single  provinces — Similar  laws  prevailed  at  successive  geological  periods — 
Relative  importance  of  mineral  and  palseontological  characters — Test  of  age  by 
included  fragments — Frequent  absence  of  strata  of  intervening  periods — Prin- 
cipal groups  of  strata  in  western  Europe. 

IN  the  last  chapter  I  spoke  generally  of  the  chronological  relations  of 
tne  four  great  classes  of  rocks,  and  I  shall  now  treat  of  the  aqueous  rocks 
in  particular,  or  of  the  successive  periods  at  which  the  different  fossilif- 
erous  formations  have  been  deposited. 

There  are  three  principal  tests  by  which  we  determine  the  age  of  a 
given  set  of  strata ;  first,  superposition ;  secondly,  mineral  character ; 
and,  thirdly,  organic  remains.  Some  aid  can  occasionally  be  derived 
from  a  fourth  kind  of  proof,  namely,  the  fact  of  one  deposit  including  in 
it  fragments  of  a  pre-existing  rock,  by  which  the  relative  ages  of  the  two 
may,  even  in  the  absence  of  all  other  evidence,  be  determined. 

Superposition. — The  first  and  principal  test  of  the  age  of  one  aqueous 
deposit,  as  compared  to  another,  is  relative  position.  It  has  been  already 
stated,  that  where  strata  are  horizontal,  the  bed  which  lies  uppermost  is 
the  newest  of  the  whole,  and  that  which  lies  at  the  bottom  the  most 
ancient.  So,  of  a  series  of  sedimentary  formations,  they  are  like  vol- 
umes of  history,  in  which  each  writer  has  recorded  the  annals  of  his  own 
times,  and  then  laid  down  the  book,  with  the  last  written  page  upper- 
most, upon  the  volume  in  which  the  events  of  the  era  immediately  pre- 
ceding were  commemorated.  In  this  manner  a  lofty  pile  of  chronicles 
is  at  length  accumulated  ;  and  they  are  so  arranged  as  ,to  indicate,  by 


CH.  IX.]  OF  AQUEOUS  ROCKS.  go 

their  position  alone,  the  order  in  which  the  events  recorded  in  them  have 
occurred. 

In  regard  to  the  crust  of  the  earth,  however,  there  are  some  regions 
where,  as  the  student  has  already  been  informed,  the  beds  have  been  dis- 
turbed, and  sometimes  extensively  thrown  over  and  turned  upside  down. 
(See  pp.  58,  59.)  But  an  experienced  geologist  can  rarely  be  deceived 
by  these  exceptional  cases.  When  he  finds  that  the  strata  are  fractured, 
curved,  inclined,  or  vertical,  he  knows  that  the  original  order  of  superpo- 
sition must  be  doubtful,  and  he  then  endeavors  to  find  sections  in  some 
neighboring  district  where  the  strata  are  horizontal,  or  only  slightly  in- 
clined. Here  the  true  order  of  sequence  of  the  entire  series  of  deposits 
being  ascertained,  a  key  is  furnished  for  settling  the  chronology  of  those 
strata  where  the  displacement  is  extreme. 

Mineral  character. — The  same  rocks  may  often  be  observed  to  retain  for 
miles,  or  even  hundreds  of  miles,  the  same  mineral  peculiarities,  if  we  fol- 
low the  planes  of  stratification,  or  trace  the  beds,  if  they  be  undisturbed,  in 
a  horizontal  direction.  But  if  we  pursue  them  vertically,  or  in  any  direc- 
tion transverse  to  the  planes  of  stratification,  this  uniformity  ceases  almost 
immediately.  In  that  case  we  can  scarcely  ever  penetrate  a  stratified  mass 
for  a  few  hundred  yards  without  beholding  a  succession  of  extremely  dis- 
similar rocks,  some  of  fine,  others  of  coarse  grain,  some  of  mechanical,  others 
of  chemical  origin ;  some  calcareous,  others  argillaceous,  and  others  silice- 
ous. These  phenomena  lead  to  the  conclusion,  that  rivers  and  currents 
have  dispersed  the  same  sediment  over  wide  areas  at  one  period,  but  at 
successive  periods  have  been  charged,  in  the  same  region,  with  very  differ- 
ent kinds  of  matter.  The  first  observers  were  so  astonished  at  the  vast 
spaces  over  which  they  were  able  to  follow  the  same  homogeneous  rocks 
in  a  horizontal  direction,  that  they  came  hastily  to  the  opinion,  that  the 
whole  globe  had  been  environed  by  a  succession  of  distinct  aqueous  forma- 
tions, disposed  round  the  nucleus  of  the  planet,  like  the  concentric  coats  of 
an  onion.  But  although,  in  fact,  some  formations  may  be  continuous  over 
districts  as  large  as  half  of  Europe,  or  even  more,  yet  most  of  them  either 
terminate  wholly  within  narrower  limits,  or  soon  change  their  lithological 
character.  Sometimes  they  thin  out  gradually,  as  if  the  supply  of  sedi- 
ment had  failed  in  that  direction,  or  they  come  abruptly  to  an  end,  as  if 
we  had  arrived  at  the  borders  of  the  ancient  sea  or  lake  which  served  as 
their  receptacle.  It  no  less  frequently  happens  that  they  vary  in  mineral 
aspect  and  composition,  as  we  pursue  them  horizontally.  For  example, 
we  trace  a  limestone  for  a  hundred  miles,  until  it  becomes  more  arena-, 
ceous,  and  finally  passes  into  sand,  or  sandstone.  We  may  then  follow  this 
sandstone,  already  proved  by  its  continuity  to  be  of  the  same  age,  through 
out  another  district  a  hundred  miles  or  more  in  length. 

Organic  remains. — This  character  must  be  used  as  a  criterion  of  the 
age  of  a  formation,  or  of  the  contemporaneous  origin  of  two  deposits  in 
distant  places,  under  very  much  the  same  restrictions  as  the  test  of  min- 
eral composition. 

First,  the  same  fossils  may  be  traced  over  wide  regions,  if  we  examine 


94  TESTS  OF  THE  DIFFERENT  AGES  [Cn.  IX. 

strata  in  the  direction  of  their  planes,  although  by  no  means  for  indefi- 
nite distances. 

Secondly,  while  the  same  fossils  prevail  in  a  particular  set  of  strata 
for  hundreds  of  miles  in  a  horizontal  direction,  we  seldom  meet  with  the 
same  remains  for  many  fathoms,  and  very  rarely  for  several  hundred 
yards,  in  a  vertical  line,  or  a  line  transverse  to  the  strata.  This  fact  has 
now  been  verified  in  almost  all  parts  of  the  globe,  and  has  led  to  a  con- 
viction, that  at  successive  periods  of  the  past,  the  same  area  of  land  and 
water  has  been  inhabited  by  species  of  animals  and  plants  even  more 
distinct  than  those  which  now  people  the  antipodes,  or  which  now  co- 
exist in  the  arctic,  temperate,  and  tropical  zones.  It  appears,  that  from 
the  remotest  periods  there  has  been  ever  a  coming  in  of  new  organic 
forms,  and  an  extinction  of  those  which  pre-existed  on  the  earth ;  some 
species  having  endured  for  a  longer,  others  for  a  shorter,  time ;  while 
none  have  ever  reappeared  after  once  dying  out.  The  law  which  has 
governed  the  creation  and  extinction  of  species  seems  to  be  expressed  in 
the  verse  of  the  poet, — 

Natura  il  fece,  e  poi  ruppe  la  starapa.        ARIOSTO. 
Nature  made  him,  and  then  broke  the  die. 

And  this  circumstance  it  is  which  confers  on  fossils  their  highest  value  as 
chronological  tests,  giving  to  each  of  them,  in  the  eyes  of  the  geologist, 
that  authority  which  belongs  to  contemporary  medals  in  history. 

The  same  cannot  be  said  of  each  peculiar  variety  of  rock  ;  for  some 
of  these,  as  red  marl  and  red  sandstone,  for  example,  may  occur  at  once 
at  the  top,  bottom,  and  middle  of  the  entire  sedimentary  series ;  exhib- 
iting in  each  position  so  perfect  an  identity  of  mineral  aspect  as  to  be 
undistinguishable.  Such  exact  repetitions,  however,  of  the  same  mix- 
tures of  sediment  have  not  often  been  produced,  at  distant  periods,  in 
precisely  the  same  parts  of  the  globe ;  and  even  where  this  has  hap- 
pened, we  are  seldom  in  any  danger  of  confounding  together  the  monu- 
ments of  remote  eras,  when  we  have  studied  their  imbedded  fossils  and 
their  relative  position. 

It  was  remarked  that  the  same  species  of  organic  remains  cannot  be 
traced  horizontally,  or  in  the  direction  of  the  planes  of  stratification  for 
indefinite  distances.  This  might  have  been  expected  from  analogy ;  for 
when  we  inquire  into  the  present  distribution  of  living  beings,  we  find 
that  the  habitable  surface  of  the  sea  and  land  may  be  divided  into  a 
considerable  number  of  distinct  provinces,  each  peopled  by  a  peculiar 
assemblage  of  animals  and  plants.  In  the  Principles  of  Geology,  I  have 
endeavored  to  point  out  the  extent  and  probable  origin  of  these  separate 
divisions  ;  and  it  was  shown  that  climate  is  only  one  of  many  causes  on 
which  they  depend,  and  that  difference  of  longitude  as  well  as  latitude  is 
generally  accompanied  by  a  dissimilarity  of  indigenous  species. 

As  different  seas,  therefore,  and  lakes  are  inhabited  at  the  same  period, 
by  different  aquatic  animals  and  plants,  and  as  the  lands  adjoining  these 


CH.  IX.]  OF  AQUEOUS  ROCKS.  95 

may  be  peopled  by  distinct  terrestrial  species,  it  follows  that  distinct  fossils 

will  be  imbedded  in  contemporaneous  deposits.     If  it  were  otherwise if 

the  same  species  abounded  in  every  climate,  or  in  every  part  of  the  globe 
where,  so  far  as  we  can  discover,  a  corresponding  temperature  and  other 
conditions  favorable  to  their  existence  are  found — the  identification  of 
mineral  masses  of  the  same  age,  by  means  of  their  included  organic 
contents,  would  be  a  matter  of  still  greater  certainty. 

Nevertheless,  the  extent  of  some  single  zoological  provinces,  es- 
pecially those  of  marine  animals,  is  very  great;  and  our  geological 
researches  have  proved  that  the  same  laws  prevailed  at  remote  periods ; 
for  the  fossils  are  often  identical  throughout  wide  spaces,  and  in  de- 
tached deposits,  consisting  of  rocks  varying  entirely  in  their  mineral 
nature. 

The  doctrine  here  laid  down  will  be  more  readily  understood,  if  we 
reflect  on  what  is  now  going  on  in  the  Mediterranean.  That  entire  sea 
may  be  considered  as  one  zoological  province ;  for,  although  certain 
species  of  testacea  and  zoophytes  may  be  very  local,  and  each  region  has 
probably  some  species  peculiar  to  it,  still  a  considerable  number  are  com- 
mon to  the  whole  Mediterranean.  If,  therefore,  at  some  future  period, 
the  bed  of  this  inland  sea  should  be  converted  into  land,  the  geologist 
might  be  enabled,  by  reference  to  organic  remains,  to  prove  the  contem- 
poraneous origin  of  various  mineral  masses  scattered  over  a  space  equal 
in  area  to  half  of  Europe. 

Deposits,  for  example,  are  well  known  to  be  now  in  progress  in  this 
sea  in  the  deltas  of  the  Po,  Rhone,  Nile,  and  other  rivers,  which  differ 
as  greatly  from  each  other  in  the  nature  of  their  sediment  as  does  the 
composition  of  the  mountains  which  they  drain.  There  are  also  other 
quarters  of  the  Mediterranean,  as  off  the  coast  of  Campania,  or  near  the 
base  of  Etna,  in  Sicily,  or  in  the  Grecian  Archipelago,  where  another 
class  of  rocks  is  now  forming ;  where  showers  of  volcanic  ashes  occa- 
sionally fall  into  the  sea,  and  streams  of  lava  overflow  its  bottom  ;  and 
where,  in  the  intervals  between  volcanic  eruptions,  beds  of  sand  and  clay 
are  frequently  derived  from  the  waste  of  cliffs,  or  the  turbid  waters  of 
rivers.  Limestones,  moreover,  such  as  the  Italian  travertins,  are  here 
and  there  precipitated  from  the  waters  of  mineral  springs,  some  of  which 
rise  up  from  the  bottom  of  the  sea.  In  all  these  detached  formations, 
so  diversified  in  their  lithological  characters,  the  remains  of  the  same 
shells,  corals,  Crustacea,  and  fish  are  becoming  inclosed ;  or,  at  least,  a 
sufficient  number  must  be  common  to  the  different  localities  to  enable  the 
zoologist  to  refer  them  all  to  one  contemporaneous  assemblage  of 
species. 

There  are,  however,  certain  combinations  of  geographical  circum- 
stances which  cause  distinct  provinces  of  animals  and  plants  to  be  sepa- 
rated from  each  other  by  very  narrow  limits ;  and  hence  it  must  happen; 
that  strata  will  be  sometimes  formed  in  contiguous  regions,  differing 
widely  both  in  mineral  contents  and  organic  remains.  Thus,  for  exam- 
ple, the  testacea,  zoophytes,  and  fish  of  the  Red  Sea  are,  as  a  group,  ex- 


96  TESTS  OF  THE  DIFFERENT  AGES  [Cn.  IX. 

tremely  distinct  from  those  inhabiting  the  adjoining  parts  of  the  Mediter- 
ranean, although  the  two  seas  are  separated  only  by  the  narrow  isthmus 
of  Suez.  Of  the  bivalve  shells,  according  to  Philippi,  not  more  than  a 
fifth  are  common  to  the  Red  Sea  and  the  sea  around  Sicily,  while  the 
proportion  of  univalves  (or  Gasteropoda)  is  still  smaller,  not  exceeding 
eighteen  in  a  hundred.  Calcareous  formations  have  accumulated  on  a 
great  scale  in  the  Red  Sea  in  modern  times,  and  fossil  shells  of  existing 
species  are  well  preserved  therein  ;  and  we  know  that  at  the  mouth  of 
the  Nile  large  deposits  of  mud  are  amassed,  including  the  remains  of 
Mediterranean  species.  It  follows,  therefore,  that  if  at  some  future  pe- 
riod the  bed  of  the  Red  Sea  should  be  laid  dry,  the  geologist  might  ex- 
perience great  difficulties  in  endeavoring  to  ascertain  the  relative  age  of 
these  formations,  which,  although  dissimilar  both  in  organic  and  mineral 
characters,  were  of  synchronous  origin. 

But,  on  the  other  hand,  we  must  not  forget  that  the  northwestern 
shores  of  the  Arabian  Gulf,  the  plains  of  Egypt,  and  the  isthmus  of 
Suez,  are  all  parts  of  one  province  of  terrestrial  species.  Small  streams, 
therefore,  occasional  land-floods,  and  those  winds  which  drift  clouds  of 
sand  along  the  deserts,  might  carry  down  into  the  Red  Sea  the  same 
shells  of  fluviatile  and  land  testacea  which  the  Nile  is  sweeping  into  its 
delta,  together  with  some  remains  of  terrestrial  plants  and  the  bones  of 
quadrupeds,  whereby  the  groups  of  strata,  before  alluded  to,  might,  not- 
withstanding the  discrepancy  of  their  mineral  composition  and  marine 
organic  fossils,  be  shown  to  have  belonged  to  the  same  epoch. 

Yet  while  rivers  may  thus  carry  down  the  same  fluviatile  and  ter- 
restrial spoils  into  two  or  more  seas  inhabited  by  different  marine  species, 
it  will  much  more  frequently  happen,  that  the  coexistence  of  terrestrial 
species  of  distinct  zoological  and  botanical  provinces  will  be  proved  by 
the  identity  of  the  marine  beings  which  inhabited  the  intervening  space. 
Thus,  for  example,  the  land  quadrupeds  and  shells  of  the  south  of  Eu- 
rope, north  of  Africa,  and  northwest  of  Asia,  differ  considerably,  yet  their 
remains  are  all  washed  down  by  rivers  flowing  from  these  three  countries 
into  the  Mediterranean. 

In  some  parts  of  the  globe,  at  the  present  period,  the  line  of  demarca- 
tion between  distinct  provinces  of  animals  and  plants  is  not  very  strongly 
marked,  especially  where  the  change  is  determined  by  temperature,  as  it 
is  in  seas  extending  from  the  temperate  to  the  tropical  zone,  or  from  the 
temperate  to  the  arctic  regions.  Here  a  gradual  passage  takes  place 
from  one  set  of  species  to  another.  In  like  manner  the  geologist,  in 
studying  particular  formations  of  remote  periods,  has  sometimes  been 
able  to  trace  the  gradation  from  one  ancient  province  to  another,  by  ob- 
serving carefully  the  fossils  of  all  the  intermediate  places.  His  success 
in  thus  acquiring  a  knowledge  of  the  zoological  or  botanical  geography 
of  very  distant  eras  has  been  mainly  owing  to  this  circumstance,  that 
the  mineral  character  has  no  tendency  to  be  affected  by  climate.  A 
large  river  may  convey  yellow  or  red  mud  into  some  part  of  the  ocean, 
where  it  may  be  dispersed  by  a  current  over  an  area  several  hundred 


CH.  IX.]  OF  AQUEOUS  ROCKS. 


97 


leagues  in  length,  so  as  to  pass  from  the  tropics  into  the  temperate  zone, 
If  the  bottom  of  the  sea  be  afterwards  upraised,  the  organic  remains 
imbedded  in  such  yellow  or  red  strata  may  indicate  the  different  animals 
or  plants  which  once  inhabited  at  the  same  time  the  temperate  and 
equatorial  regions. 

It  may  be  true,  as  a  general  rule,  that  groups  of  the  same  species  of 
animals  and  plants  may  extend  over  wider  areas  than  deposits  of  homo- 
geneous composition  ;  and  if  so,  pala3ontological  characters  will  be  of 
more  importance  in  geological  classification  than  the  test  of  mineral  com- 
position ;  but  it  is  idle  to  discuss  the  relative  *  Bailie  of  these  tests,  as  the 
aid  of  both  is  indispensable,  and  it  fortunately  happens,  that  where  the 
one  criterion  fails,  we  can  often  avail  ourselves  of  the  other. 

Test  by  included  fragments  of  older  rocks. — It  was  stated,  that  inde- 
pendent proof  may  sometimes  be  obtained  of  the  relative  date  of  two 
formations,  by  fragments  of  an  older  rock  being  included  in  a  newer  one. 
This  evidence  may  sometimes  be  of  great  use,  where  a  geologist  is  at  a 
loss  to  determine  the  relative  age  of  two  formations  from  want  of  clear 
sections  exhibiting  their  true  order  of  position,  or  because  the  strata  of 
each  group  are  vertical.  In  such  cases  we  sometimes  discover  that  the 
more  modern  rock  has  been  in  part  derived  frorn  the  degradation  of  the 
older.  Thus,  for  example,  we  may  find  chalk  with  flints  in  one  part  of  a 
country ;  and,  in  another,  a  distinct  formation,  consisting  of  alternations 
of  clay,  sand,  and  pebbles.  If  some  of  these  pebbles  consist  of  similar 
flint,  including  fossil  shells,  sponges,  and  foraminiferae,  of  the  same  species 
as  those  in  the  chalk,  we  may  confidently  infer  that  the  chalk  is  the  oldest 
of  the  two  formations. 

Chronological  groups. — The  number  of  groups  into  which  the  fossil- 
iferous  strata  may  be  separated  are  more  or  less  numerous,  according  to 
the  views  of  classification  which  different  geologists  entertain  ;  but  when 
we  have  adopted  a  certain  system  of  arrangement,  we  immediately  find 
that  a  few  only  of  the  entire  series  of  groups  occur  one  upon-  the  other 
in  any  single  section  or  district. 

The  thinning  out  of  individual  strata  was  before  described  (p.  16). 

Fig.  102. 


But  let  the  annexed  diagram  represent  seven  fossiliferous  groups,  instead 
of  as  many  strata.  It  will  then  be  seen  that  in  the  middle  all  the  super- 
imposed formations  are  present ;  but  in  consequence  of  some  of  them 
thinning  out,  No.  2  and  No.  5  are  absent  at  one  extremity  of  the  sec- 
tion, and  No.  4  at  the  other. 

In  the  annexed  diagram,  fig.  103,  a  real  section  of  the  geological 
formations  in  the  neighborhood  of  Bristol  and  the  Mendip  Hills,  is  pre- 
7 


98 


CHRONOLOGICAL  ARRANGEMENT 


[OH.  IX. 


sented  to  the  reader,  as  laid  down  on  a  true  scale  by  Prof.  Ramsay, 
where  the  newer  groups  1, 2,  3, 4,  rest  uncomformably  on  the  formations 


Fig.  103. 
Dundry  Hill. 


Section  South  of  Bristol. 
Length  of  section,  4  miles.       a,  &.  Level  of  the  sea. 


A.  C.  Bamsay. 


1.  Inferior  oolite. 

2.  Lias. 

8.  New  red  sandstone. 

4.  Magnesian  conglomerate. 


5.  Coal  measures. 

6.  Carboniferous  limestone. 

7.  Old  red  sandstone. 


5  and  6.  Here  at  the  southern  end  of  the  line  of  section  we  meet  with 
the  beds  No.  3  (the  New  Red  Sandstone)  resting  immediately  on  No.  6, 
while  farther  north,  as  at  Dundry  Hill,  we  behold  six  groups  superim- 
posed one  upon  the  other,  comprising  all  the  strata  from  the  inferior 
oolite  to  the  coal  and  carboniferous  limestone.  The  limited  extension  of 
the  groups  1  and  2  is  owing  to  denudation,  as  these  formations  end  ab- 
ruptly, and  have  left  outlying  patches  to  attest  the  fact  of  their  having 
originally  covered  a  much  wider  area. 

In  many  instances,  however,  the  entire  absence  of  one  or  more  forma- 
tions of  intervening  periods  between  two  groups,  such  as  3  and  5  in  the 
same  section,  arises,  not  from  the  destruction  of  what  once  existed,  but 
because  no  strata  of  an  intermediate  age  were  ever  deposited  on  the  in- 
ferior rock.  They  were  not  formed  at  that  place,  either  because  the 
region  was  diy  land  during  the  interval,  or  because  it  was  part  of  a  sea 
or  lake  to  which  no  sediment  was  carried. 

In  order,  therefore,  to  establish  a  chronological  succession  of  fossilifer- 
ous  groups,  a  geologist  must  begin  with  a  single  section,  in  which  sev- 
eral sets  of  strata  lie  one  upon  the  other.  He  must  then  trace  these 
formations,  by  attention  to  their  mineral  character  and  fossils,  continu- 
ously, as  far  as  possible,  from  the  starting  point.  As  often  as  he  meets 
with  new  groups,  he  must  ascertain  by  superposition  their  age  relatively 
to  those  first  examined,  and  thus  learn  how  to  intercalate  them  in  a  tab- 
ular arrangement  of  the  whole. 

By  this  means  the  German,  French,  and  English  geologists  have  de- 
termined the  succession  of  strata  throughout  a  great  part  of  Europe,  and 
have  adopted  pretty  generally  the  following  groups,  almost  all  of  which 
have  their  representatives  in  the  British  Islands. 


Secondary,  or  Mesozoic. 


CH.  IX.]  OP  AQUEOUS  ROCKS.  99 

Groups  of  Fossiliferous  Strata  observed  in  Western  Europe,  arranged 
in  what  is  termed  a  descending  Series,  or  beginning  with  the  newest. 
(See  a  more  detailed  Tabular  view,  pp.  101-106.) 

1.  Post-Tertiary,    including    Recent    and  "1 

Post-Pliocene.  m    .. 

2.  Pliocene.  L  Tertiary,    Supracretaceous  * 

3.  Miocene.  or  Cainozoic.f 

4.  Eocene.  J 

6.  Chalk. 

6.  Greensand  and  Wealden. 

7.  Upper  Oolite,  including  the  Purbeck. 

8.  Middle  Oolite. 

9.  Lower  Oolite. 

10.  Lias. 

11.  Trias. 

.    12.  Permian. 

18.  Coal. 

14.  Old  Red  Sandstone,  or  Devonian.  I  ~  • 

16.  Upper  Silurian.  marv- 

16.  Lower  Silurian. 

17.  Cambrian  and  older  fossiliferous  strata. 

It  is  not  pretended  that  the  three  principal  sections  in  the  above  table, 
called  primary,  secondary,  and  tertiary,  are  of  equivalent  importance,  or 
that  the  eighteen  subordinate  groups  comprise  monuments  relating  to 
equal  portions  of  past  time,  or  of  the  earth's  history.  But  we  can  assert 
that  they  each  relate  to  successive  periods,  during  which  certain  animals 
and  plants,  for  the  most  part  peculiar  to  their  respective  eras,  have  flour- 
ished, and  during  which  different  kinds  of  sediment  were  deposited  in  the 
space  now  occupied  by  Europe. 

If  we  were  disposed,  on  palaeontological  grounds,];  to  divide  the  entire 
fossiliferous  series  into  a  few  groups  less  numerous  than  those  in  the  above 
table,  and  more  nearly  co-ordinate  in  value  than  the  sections  called  pri- 
mary, secondary,  and  tertiary,  we  might,  perhaps,  adopt  the  six  groups  or 
periods  given  in  the  next  table. 

At  the  same  time,  I  may  observe,  that,  in  the  present  state  of  the 
science,  when  we  have  not  yet  compared  the  evidence  derivable  from  all 
classes  of  fossils,  not  even  those  most  generally  distributed,  such  as 
shells,  corals,  and  fish,  such  generalizations  are  premature,  and  can  only 
be  regarded  as  conjectural  or  provisional  schemes  for  the  founding  of 
large  natural  groups. 

*  For  tertiary,  Sir  H.  De  la  Beche  has  used  the  term  "  supracretaceous," 
a  name  implying  that  the  strata  so  called  are  superior  in  position  to  th« 
chalk. 

f  For  an  explanation  of  Cainozoic,  see  p.  95. 

J  Palaeontology  is  the  science  which  treats  of  fossil  remains,  both  animal  and 
vegetable.  Etym.  itaXatos,  palaios,  ancient,  ovra,  onta,  beings,  and  Aoyof,  logos,  a 
discourse. 


100 


CHRONOLOGICAL  ARRANGEMENT. 


[Cn.  IX. 


Fossiliferous  Strata  of  Western  Europe  divided  into  Eight  Groups. 


1.  Post-Tertiary  and  Ter- 

tiary   - 

2.  Cretaceous 

3.  Oolitic     - 

4.  Triassic    - 

6.  Permian  and   Carboni- 
ferous - 

6.  Devonian  or  Old  Red 

Sandstone     - 

7.  Silurian   - 

8.  Cambrian 


from  the  Recent  to  the  Eocene  inclusive. 

from  the  Maestricht  Chalk  to  the  Wealden  inclu- 
sive. 

from  the  Purbeck  to  the  Lias  inclusive. 

including  the  Keuper,  Muschelkalk,  and  Bunter- 
Sandstein  of  the  Germans. 

including  Magnesian  Limestone,  Coal  Measures, 
and  Mountain  Limestone. 

from  the  Yellow  Sandstone  of  Fife  to  the  Forfar- 
shire  paving  stones  with  cephalaspis. 

from  the  Upper  Ludlow  to  the  Bala  Limestone, 
and  Graptolite  Schists. 

from  the  Lingula  flags  or  primordial  zone  of  Bar- 
rande  to  the  lowest  known  fossiliferous  rocks. 


But  the  following  more  detailed  list  of  fossiliferous  strata,  divided 
into  a  greater  number  of  sections,  will  be  found  useful  by  the  reader 
when  he  is  studying  our  descriptions  of  the  sedimentary  formations 
given  in  the  next  18  chapters. 


CH.  IX.]        ABRIDGED  TABLE  OF  FOSSILIFEROUo  STRATA. 


101 


ABRIDGED    GENERAL    TABLE    OF    FOSSILIFEROTJS 
STRATA. 


1  RECENT. 

2.  POST-PLIOCENE. 

8.  NEWER  PLIOCENE. 

4.  OLDEE  PLIOCENE. 

5.  UPPER  MIOCENE. 

6.  LOWER  MIOCENE. 

7.  UPPER  EOCENE. 

8.  MIDDLE  EOCENE. 

9.  LOWER  EOCENE. 

10.  MAESTRICHT  BEDS. 

11.  WHITE  CHALK. 

12.  UPPER  GREENSAND. 
18.  GAULT. 

14  LOWER  GREENSAND 

15.  WEALDEN. 

16.  PURBECK  BEDS. 
IT.  PORTLAND  STONE. 

18.  KIMMERIDGE  CLAY. 

19.  CORAL  RAG. 

20.  OXFORD  CLAY. 

21.  GREAT  OE  BATH  OOLITE. 

22.  INFERIOR  OOLITE. 

23.  LIAS. 

24.  UPPER  TRIAS. 

25.  MIDDLE  TRIAS. 
2&  LOWER  TRIAS. 

27.  PERMIAN. 

28.  COAL  MEASURES. 

29.  CARBONIFEROUS    LIME- 

STONE, 

30.  UPPER    I 

81.  MIDDLE  L  DEVONIAN. 

82.  LOWER  J 
38.  UPPER    -I 

84,  MIDDLE  I  SILURIAN. 

35.  LOWER  J 

36.  UPPER    ) 

(•CAMBRIAN. 
87.  LOWER    i 

*UWBB  I 

89  LOWER    j 


POST-TERTIARY. 
PLIOCENE. 

MIOCENE. 

>> 
EOCENE. 

CRETACEOUS. 


JURASSIC. 


[  CARBONIFEROUS. 
DEVONIAN. 

SILURIAN. 

CAMBRIAN. 
LAURENTIAN. 


102 


TABULAR  VIEW  OF  THE  FOSSILIFEROUS  STRATA.       [On.  IX. 


TABULAR  VIEW  OF  THE  FOSSILIFEROUS  STRATA, 

SHOWING  THE  ORDER  OP  SUPERPOSITION   OR   CHRONOLOGICAL  SUCCESSION  OP   THE  PRIN- 
CIPAL GROUPS,    WITH  REFERENCE  TO  THE  PAGES  WHERE  THEY 
ARE  DESCRIBED  IN  THIS  WORK. 


i. 

KECENT. 

s 

H 

1 

2 

2. 

POST- 

PLIOCENE 

3. 

NEWEB 
PLIOCENE. 


4. 

OLDER 
PLIOCENE. 


Shells  and 

mammalia,  all 

of  living 

species. 


Shells,  recem 

mammalia 

in  part 

extinct. 


POST-TERTIARY. 
(Terrains  contemporains  et  quaternaires.) 

EXAMPLES. 

British— Marine  strata,  with  human  remains 
on  coast  of  Cornwall  (p.  109). 

Marine  strata,  with  canoes,  in  the  estuary  of 

the  Clyde  (p.  109). 

Foreign— Danish  peat  (kitchen-middens),  with 
implements  of  bronze  and  stone  (p.  109). 

Lacustrine  mud,  with  remains  of  Swiss  lake- 
dwellings  and  implements  of  stone  and 
metal  (p.  110). 

Marine  strata  inclosing  Temple  of  Serapis,  at 
Puzzuoli  (p.  108). 

Lacustrine  strata  of  Cashmere  (p.  108). 
British — Loam    of  Brixham    cave,    with    flint 
knives  and  bones  of  extinct  and  living  quad- 
rupeds (p.  124). 

Yalley  gravels,  or  ancient  alluvium  of  the 
Thames  and  Ouse,  with  stone  implements 

Glacial  drift  of  Scotland,  with  marine  shells 
(p.  153). 

Boulder  formation  of  Norfolk  cliffs  (p.  162). 

Forest-bed  of  Norfolk  cliffs,  with  bones  of  ele- 
phant, &c.  (p.  161). 

Glacial  drift  of  "Wales  with  marine  fossil  shells 
nearly  1400  feet  high,  on  Moel  Tryfaen  (p. 
158). 

Foreign — Ancient  valley  gravels  of  Amiens,  with 
flint  implements  and  bones  of  extinct  mam- 
malia (p.  116). 

Loess  of  Ehine  (pp.  119, 120). 

Ancient  Nile-mud  forming  river-terraces  (p. 
118). 

Marine  strata  of  Sardinia,  300  feet  above  sea- 
level,  with  pottery  and  bones  of  extinct 
quadrupeds  (p.  121). 

Loam  and  breccia  of  Liege  caverns,  with  hu- 
man remains,  and  bones  of  extinct  and  re- 
cent mammalia  (p.  124). 

Australian  cave-breccias,  with  bones  of  extinct 
marsupials  (p.  126). 

Glacial  drift  of  Northern  Europe  (pp.  142-151). 

Post-glacial  freshwater  deposits  of  North  Amer- 
ica with  remains  of  Mastodon  (p.  166). 

TERTIARY. 

(Terrains  tertiaires.) 

British — Norwich  crag,  marine,  with  11  per  cent,  of  the  shells  of 
extinct  species,  bones  of  Mastodon  arvrenensis,  &c.  (p.  199). 

Chillesford  beds,  with  marine  shells,  9  per  cent,  extinct,  and 
those  of  living  species  chiefly  Arctic  (p.  199). 

Bridlington  beds,  marine  Arctic  fauna,  commencement  of  gla- 
cial epoch  (p.  199). 
Foreign— Tuffs  of  Ischia  (p.  189).  )  Marine  shells  of  which 

Cone  of  Monte  Somma  (p.  190).  V    1  to  7  per  cent,  of  the 

Eastern  base  of  Mount  Etna  (p.  190).   \     species  extinct. 

Calcareous  and  argillaceous  strata  and  volcanic  tuffs  of  Sicily, 
with  shells  from  10  to  80  per  cent  of  extinct  species  (p.  191). 

Lacustrine  strata  of  Upper  Val  d'Arno,  with  Mastodon  arver- 

nenais,  &c.  (p.  196). 

British— Bed  Crag  of  Suffolk,  marine  shells,  some  of  northern 
forms,  40  per  cent,  of  extinct  species  (pp.  200-205). 

White  or  coralline  crag  of  Suffolk,  testacea  less  northern,  48  per 

cent,  of  extinct  species  Cp.  202). 

Foreign—  Tipper  and  middle  Antwerp  crag,  shells  from  40  to  50 
per  cent,  extinct,  bones  of  cetacea  numerous  (p.  207). 

Subapennine  marls  and  sands  (p.  208). 

Aralo-Caspian  brackish-water  formations  (p.  211). 


CH.  IX.]       TABULAR  VIEW  OF  THE  FOSSILIFEROUS  STRATA. 


103 


EXAMPLES. 


British—  a.  Ferruginous  sands  of  North  DOWIJS?  (p.  285). 

Foreign—  a.  Edeghem  beds,  Antwerp,  with  shells  61  per  cent  of 
extinct  species  (p.  235). 

a.  Diest  sands  (p.  234). 

Bolderberg  beds  of  Belgium  (p.  235). 
Faluns  of  Touraine,  with  testacea  of  sub-tropical  character 
Dinotherium,  &c.  (p.  212). 

5. 

Faluns,  proper,  of  Bordeaux  (p.  231). 
Freshwater  strata  of  Gers,  with  remains  of  quadrumana  (p. 

Sands  of  Eppelsheim,  with  falunian  quadrupeds  (p.  244). 

UPPER 

Vienna  basin,  with  shells  four-fifths  extinct  species,  and  Dino- 

MIOCENE. 

therium  (p.  244). 
Beds  of  the  Superga  near  Turin  (p.  247). 
Deposit  at  Pikerme,  near  Athens,  with  fossil  pachyderms  and 
apes  (p.  247). 

_ 

Swiss  (Eningen  beds,  rich  in  plants  and  insects  (pp.  248-254). 
Marine  molasse,  Switzerland  (p.  258). 

Siwdlik  hills,  with  freshwater  shells  and  extinct  quadrupeds 

(p.  276). 

Marine  strata  of  the  Atlantic  border  in  the  United  States  (p. 

277). 

Volcanic  tuff  and  limestone  of  Madeira,  the  Canaries,  and  the 

Azores  (p.  268). 

British  —  Hempstead    beds,    marine   and  freshwater   strata   (p. 

Lignites  and  clays  of  Bovey  Tracey,  plants  of  sub-tropical 

character  (p.  240). 

Isle  of  Mull  leaf-bed,  volcanic  tuff  (p.  242). 

Foreign—  Calcaire  de  la  Beauce,  &c.  (p.  219). 

Grea  do  Fontainebleau  (p.  219). 
Lacustrine  strata  of  the  Limagne  d'Auvergne  (p.  222),  and  of 

the  Cantal  (p.  229). 

Lower  marine  and  brackish  strata  of  Bordeaux,  with  Cerithium 

plicatum,  &c.  (p.  232). 

Mayence  basin,  Littorinella  limestone,  and  marls  with  Cyrena. 

LOWER 

semistriata,  &c.  (p.  243). 
Eadaboj  beds  of  Croatia,  with  fossil   plants  and  insects  (p. 

MIOCENE. 

245). 

Brown  coal  of  Germany  (p.  246). 

Lower  molasse  of  Switzerland,  freshwater  and  brackish,  with 

sub-tropical  flora  (pp.  258-263). 

Eupelian  beds  of  Dumont,  with  Leda  Deshayesiana,  &c.  (p. 

236). 

Middle  Limburg  (Kleyn  Spawen)  beds  (Upper  Tongrian  of 
Dumont),  with  marine  and  freshwater  shells  (p.  237). 

Lower  Limburg  (Lower  Tongrian  of  Dumont)  with  marine 

shells,  one-third  common  to  Upper  Eocene  (p.  238). 
Nebraska  beds,  with  bones  of  extinct  quadrupeds  and  chelo- 

nians  (p.  279). 

British—  1.  Bembridge,  fluvio-marine  strata  with  Paleotherium, 

&c.  (p.  283). 

2.  Osborne  or  St.  Helen's  series  (p.  284). 

7. 
UPPER 

8.  Headon  series,  with  marine  and  freshwater  shells  (p.  284). 
4.  Barton  clay,  with  nummulites  (p.  287). 

EOCENE. 

Foreign—I.  Gypsum  of  Montmartre,  freshwater  with  PaUoihe- 
rium  (p.  299). 

2.  Calcaire  silicieux,  or  Travertin  inferieur  (p.  302). 

8.  Gres  de  Beauchamp  or  Sables  moyens  (p.  302). 

British—  I.  Bagshot  and  Bracklesham  beds  (p.  28S). 
2.  White  clays  of  Alum  Bay,  with  plants  of  tropical  genera 

8. 

(p.  290). 

MIDDLE 

Foreign  —  1.  Calcaire  grossier,  miliolitic  limestone  (p.  803). 
2.  Soissonnais    sands,  or   Lits   coquilliers,  with  NummuliteA 

EOCENE. 

planulata  (p.  804). 

3.  Claiborne  beds  of  United  States,  with  Orbitoidea  and  Zeug- 

lodon  (p.  310). 

British—  -1.  London  clay  proper,  shells,  flsh,  and  plants  of  sub- 

9. 

2.  Plastic   or^moUled   clays  of  Woolwich,  fluvio-marine   (p. 

LOWER 

3.  Thanet  sands,  with  Pholadomya,  &c.  (p.  297). 

EOCENE. 

I 

Foreign—  -1.  Argile  de  Londres  near  Dunkirk  (P-.298). 
2.  Argile  plastique,  with  Gastornis  parisieiws  (P-  805). 
3.  Sables  de  Bracheux,  with  Arctocyon  prtmcevus  (p.  3Ub) 

104 


TABULAR  VIEW  OF  THE  FOSS1LIFEROUS  STRATA.       [Cn.  IX. 


1 


O.I 


10. 

UPPER 
CRETACE- 
OUS. 


11. 

LOWER 
CRETACE- 
OUS, 

OB 

NEOCO- 
MIAN. 


12. 

UPPER 
OOLITE. 


13. 

MIDDLE 
OOLITE. 


14. 

LOWER 
OOLITE. 


15. 
LIAS. 


16. 

UPPER 
TRIAS. 


17. 

MIDDLE 
'IRIAS. 

18. 

LOWER 
TRIAS. 


SECONDARY. 

(Terrains  secondaires.) 

EXAMPLES. 

British— 1.  Wanting. 
2.  White  chalk  with  flints,  marine  (p.  321). 
8.  Chalk  marl,  marine  (p.  330). 

4.  Upper  Greensand — fire-stone  of  Surrey,  marine  (p.  831). 

5.  Gault — dark  blue  marl  of  southeast  of  England  (p.  831). 
Blackdown  beds  of  littoral  origin  (p.  332). 

Foreign— 1.  Maestricht  beds,  with  Motsasaurus  (p.  815). 

Faxoe  chalk  with  Nautilus  danicus,  &c.  (p.  316). 
2.  White  chalk  of  France,  Sweden  and  Eussia  (p.  818). 
8.  Planer-kalk  of  Saxony  (p.  325). 

2  and  3.  Sands  and  clays  of  Aix-la-Cliapelle,  with  preponder- 
ance of  dicotyledonous  angiosperms  (p.  333). 

4.  Quader  sandstein  of  Germany  (p.  334). 

5.  Gault  of  the  Loire  (p.  332). 

2  and  3.  Hippurite  limestone  of  South  of  France  (p.  336). 
2  to  5.  New  Jersey  (U.  8.)  sands  and  marls  (p.  338). 
2  to  5.  Siliceous  limestone  of  Texas  (p.  340). 
British— -1.  Ferruginous  and  green  sands  (p.  341). 
Kentish  raff,  or  calcareous  stone  (p.  342). 
Atherfield  beds,  marine,  with  Perna  Mulleti  (p.  342). 
2.  Weald  clay  of  Surrey,  Kent,  and  Sussex,  freshwater,  with 

Oypris  (p.  346). 
Hastings  sands  (Tunbridge  and  Ashburnham  beds),  fresh 

water,  Iguanodon  Mantelli  (p.  348). 
Foreign — 1.  Neocomian  of  Neufchatel  (p.  341). 

2.  Wealden  beds  of  Hanover  (p.  351). 
f  British — Upper  Purbeck  beds,  freshwater,  Purbeck  Marble  (p. 

379). 

Middle  Purbeck  fluvio-marine,  with  numerous  marsupial  quad- 
rupeds, &c.  (p.  380). 

Lower  Purbeck  freshwater,  with  intercalated  dirt-bed  (p.  389). 
Portland  stone  and  sand  (p.  894). 
Kimmeridge  clay,  bituminous  shale,  with  marine  shells,  24  per 

cent,  common  to  middle  oolite  (p.  394). 
Foreign— Marnes  a  gryphees  virgules  of  Argonne  (p.  895). 
[     Lithographic  stone  of  Solenhofen  with  Archceopteryx  (p.  395). 
British— Coral-rag  of  Berkshire,  Wilts,  and  Yorkshire  (p.  398). 
Oxford  clay,  with  belemnites  and  ammonites  (p.  399). 
Kelloway  rock  of  Wilts  and  Yorkshire,  with  shells,  21  per  cent. 

common  to  lower  oolite  (p.  400). 
Foreign — 1.  Nerinaean  limestone  of  the  Jura  (p.  399). 

Diceras  limestone  of  the  Alps  (p.  399). 

British — Cornbrash  and  forest  marble  of  Wilts  and  Gloucester- 
shire (p.  401). 

Great  oolite  of  Bradford,  with  encrinites,  &c.  (p.  402). 
Stonesfleld  slate  with  marsupials  and  Araucaria  (p.  405). 
Fuller's  earth  of  Bath  with  Ostrea  acuminata  (p.  412). 
Inferior  oolite,  with  24  per  cent,  of  shells  common  to  great 

oolite  (p.  412). 
Upper  lias,  argillaceous,  with  Ammonites  striatulus,  Spirifer, 

and  Leptoena  (p.  417). 

Shale  and  limestone,  with  Ammonites  bifrons  (p.  418). 
Marlstone  series,  or  middle  lias  divisible  into  three  zones  with 

characteristic  Ammonites  (p.  416). 

Lower  lias,  divisible  into  siz  zones,  Ammonites  Buclclandi  in 
the  lowest  but  one,  and  A.  planorbis  in  the  lowest  zone  (p. 
419). 
British — Penarth,  or  Amcula  contorta  beds — White  lias,  with 

fish  of  the  genera  Hybodus,  &c.  (p.  441). 
Dolomitic  conglomerate  of  Bristol,  with  Thecodontosaurus,  &c. 

Eed  clay,  with  thick  beds  of  salt,  at  Northwich,  in  Cheshire  (p. 

448). 
Foreign — Keuper  beds  of  Germany,  with  Microlestes  and  fish  of 

the  genera  Hybodus,  &c.  (p.  432). 

St.  Cassian  or  Hallstadt  beds,  with  rich  marine  fauna  (p.  434). 
Coalfield  of  Eichmond,  Virginia,  with   Estheria  ojcata   and 

plants  resembling  those  of  European  Keuper  (p.  451). 
Chatham  coalfield,  North  Carolina,  with  Dromatherium,  (p. 
I          457). 
(  British— Wanting. 
•<  Foreign— Muschelkalk  of  Germany,  with  Encrinus  liliiformis 

and  Placodus  gigas  (p.  438). 
British— New  red  sandstone  of  Lancashire  and  Cheshire,  with 

Labyrinthodon  and  footprints  of  C heirotherium  (p.  443). 
Foreign — Bunter-sandstein  of  Germany,  with  footsteps  of  Laby- 
rinthodon (p.  440). 

Eed  sandstone  of  Connecticut  Valley,  with  footprints  of  birds 
and  reptiles  (p.  452). 


CH.  IX.]       TABULAR  VIEW  OF  THE  FOSSILIFEROUS  STRATA. 


105 


19. 
PERMIAN. 


PRIMARY. 

(Terrains  paleozo'iques.) 
EXAMPLES. 

British— 1.  Concretionary  magnesian  limestone  of  Durham  and 
Yorkshire  (p.  459). 

2.  Brecciated  magnesian  limestone  of  Tynemouth  Cliff,  &c.  (p. 

459). 

3.  Fossiiiferous  magnesian  limestone,  with  Fenestella  retifor- 

mis  (p.  460). 

4.  Compact  magnesian  limestone  (p.  461). 

5.  Marl-slate  of  Durham,  with  heterocercal  fish  (461). 

6.  Inferior  sandstones,  wich  plants  resembling  those  of  the  coal, 

but  differing  in  species  (p.  462). 
Foreign— 1.  Stinkstein  of  Thuringia  (p.  458). 
2.  Eauchwacke,  ibid.  (p.  458). 
8.  Dolomite  or  Upper  Zechstein  (p.  463). 

4.  Zechstein  or  Lower  Zechstein  (p.  463). 

5.  Mergel-schiefer  or  Kupfer-schiefer,  with  Protorosauru*  (p. 


6  Eoth-'liegendes  of  Thuringia,  with  Psaronius  (p.  463). 
Magnesian  limestones,  &c.,  of  Kussia  (p.  463). 


CARBONIFEROUS. 

1 
20. 

UPPER 
CARBON- 
IFEROUS. 

21. 

LOWER 
CARBON- 
IFEROUS. 

ing  Stigmaria  (p.  466). 
Coal  measures  of  Coalbrook  Dale  (p.  493). 
Millstone  grit  (p.  466). 
Carboniferous  rocks  of  Ireland  (p.  466). 
J?oreignr-$t.  Etienne  coalfield,  with  erect  fossil  trees  (p.  482) 
Coalfield  of  Saarbriick  with  Archegosaivrvs  (p.  506). 
Carboniferous  strata  of  Nova  Scotia,  with  iossil  forests,  and 
land-shell  Pupa  vetusta  (p.  511). 
Appalachian  coalfield,  720  miles  long  and  180  miles  wide,  with 
footprints  of  Cheirotherium  (p.  509). 

,  British—  Mountain  limestone  of  Wales  and  South  of  England, 
with  marine  fossils,  chiefly  corals  and  crinoids  (p.  514). 
Same  in  Somersetshire  and  Ireland,  with  fish-beds  (p.  521). 
Carboniferous  limestone  of  Scotland  alternating  with  coal-bear- 
ing sandstones  (p.  466). 
Foreign-Mountain  limestone  of  Belgium  (p.  521). 
Kiesel-schiefer   and   Jungere    Grauwacke    of  Germany,  with 
Posldonomya  Becheri  (p.  522). 
Gypseous  beds  and  Encrinital  limestone,  Nova  Scotia  (p.  522). 

22. 

UPPER 
DEVO- 
NIAN. 


23. 

MIDDLE 
DEVO- 
NIAN. 


ttehr- Yellow  sandstone  of  Dura  Den,  with  Glyptolwmw  (p. 
524,  533) ;  and  of  Kilkenny  with  fossil  fish  (p.  524) 
Pilton  group  of  North  Devon,  with  Spirifer  diyunctua  (p. 

Petherwyn  group  of  Cornwall,  with  Clymenia  and  Cypridina 

(p.  53T). 
Foreign— Clymcnien  kalk  and  Cypridinen-schiefer  of  G 

Limestones  of  the  Fichtelgebirge,  with  trilobites  of  the  genera 
Catskill  and  Chemung  group  of  New  York,  U.  S.  (p.  544). 
.BH^-Sandstones  of  Forfarshire  and  Perthshire,  with  Holopty- 

BituSots  M?rf  Gamrie,  Caithness,  &c.,  with  numerous 
fish  (p.  531). 


LOWER 
DEVO- 
NIAN. 


with  many  trilobites  andTorals  ,  and  with  ce- 
phalopoda distinct  from  Upper  Devonian  (p.  538). 
Foreign-YAfel  limestone   with  underlying   echists  containing 
Co^Srous^ormSion  of  Western  Canada  and  New  York  (p. 

546) 
Devonian  strata  of  Eussia  (p.  542). 

.Br^A-Arbroath  paving-stones  with  Cephalaspis,  Pterygotua, 

Foreign-Son*  African  Devonian  strata  with  Homalorwtu*,  &c 
sandstone  of  Western  Canada  and  New  York  (p. 


546). 


106  TABULAR  VIEW  OF  THE  FOSSILIFEROUS  STRATA.       [On.  IX. 


EXAMPLES. 


British  —  "Upper  Ludlow   formation,  Downton   sandstone,  with 

bone-bed  in  the  upper  part;  gray  sandstone  with  Hhyncho- 

nella  amcula  (pp.  551-653). 

25. 

Lower  Ludlow  formation,  comprising  Aymestry  limestone  and 
Ludlow  shale,  with  oldest  known  fish  remains  (p.  553). 

UPPER 

Wenlock  limestone,  with  trilobites,  &c.  (p.  557). 

x-1* 

SILURIAN. 

Wenlock  shale,  with  graptolites  (p.  559). 
Woolhope  limestone  and  grit  (p.  560). 

.1 

Foreign  —  Niagara  limestone,  with  Calymene,  Homalonotus,  &c. 

fe 

(p.  571). 

§ 

British—  Upper  Llandovery,   comprising   Tarannon   shale    and 

g 

May-hill  sandstone  and  limestone,  with  Pentamerus  Ic&vis, 

tS 

26. 

&c.  (p.  560). 

1 

MIDDLE 

LowerLlandovery  slates  (p.  561). 

^ 

SILURIAN. 

Foreign—  Clinton  group  of  America,  with  Pentamerus  Iwvis,  &c. 

**^' 

(p.  571.) 

5 

Silurian  strata  of  Kussia,  with  Pentamerus  (p.  569). 

S 

British—  Caradoc  and  Bala  beds,  with  Trinucleus  Caractaci,  &c. 

B 

(p.  562). 

fj 

Llandeilo  flags,  with  graptolites  and   interstratifled  volcanic 

»—  » 
™ 

tuffs  (p.  565). 

27 

Lower  Llandeilo  or  Arenig  formation,  with  Didymograpaus 

<l  t  • 

geminus,  and  interstratified  volcanic  tuffs  (p.  567). 

LOWER 
SILURIAN. 

Foreign  —  Ungulite  or  Obolus  grit  of  Russia  (p.  569). 
Hudson  Elver  group  and  Trenton  limestone  of  North  America, 
with  Trinucleus,  &c.,  and  Black  Eiver  limestone,  with  large 

Orthoceras  (p.  571). 

Orthoceras  limestone  of  Sweden  (p.  572). 

oo 

'  British  —  Tremadoc  slates,  with  trilobites  of  genera,  partly  Silu- 

KB. 

UPPER 

rian,  partly  "  primordial  of  Barrande  "  (p.  576). 
Lingula  flags  with  Lingula  Davisii  (p.  577). 

CAMBRIAN 

Foreign  —  "  Primordial  "  zone  of  Bohemia,  with  trilobites  of  the 

AMBRIAN, 

(Primordial  zone 
of  Barrande). 

29. 

genera  Paradoxides,  &c.  (p.  573). 
Alum  schists  of  Sweden  and  Norway  (p.  581). 
Potsdam  sandstone,  with  Dikelocephalus  and  Obolella  (p.  581). 
Quebec  group  with  mixed  fauna,  resembling  that  of  Lower 
Llandeilo  and  Tremadoc  groups  (p.  583). 

o 

LOWER 
CAMBRIAN 

British—  Harlech  grits,  with  Arenicolites  sparsus,  &c.  (p.  578). 
Llanberis  slates,  with  zoophytes  (Oldhamid)  (p.  578). 

(Longmynd 

Foreign—  Rurovi&n  series  of  Canada  (p.  583). 

Group). 

9 


30. 

UPPER 

LAUREN- 

TIAN. 

31. 

LOWER 

LAUREN- 

TIAN. 


British— Funfament&l  gneiss  of  the  Hebrides  ?  (p.  585). 
Hypersthene  rocks  of  Skye  ?  (p.  579). 

Foreign — Labradorite  series  north  of  the  river  St.  Lawrence  in 

Canada  (p.  588). 
Adirondack  Mountains  of  New  York  (p.  584). 

British-Wanting? 

Foreign — Beds  of  gneiss  and  quartzite,  with  interstratified  lime- 
stones, in  one  of  which,  1000  feet  thick,  occurs  a  foraminifer, 
Eozoon  Canadense,  the  oldest  known  fossil  (p.  584). 


OH.  X.]  NOMENCLATURE. 


10T 


CHAPTER   X. 

RECENT    AND    POST-PLIOCENE    PERIODS. 

Recent  and  Post-pliocene  periods — Terms  defined — Formations  of  th«  Recent 
period — Modern  littoral  deposits  containing  works  of  art  near  Naples — Danish 
peat  and  shell  mounds — Swiss  lake-dwellings — Periods  of  stone,  bronze,  and 
iron — Form  of  human  skulls  of  the  Recent  period — Post-pliocene  formations — 
Coexistence  of  man  with  extinct  mammalia — Higher  and  Lower-level  Valley- 
gravels — Loess  or  inundation  mud  of  the  Nile,  Rhine,  &c. — Antiquity  of  Post- 
pliocene  Lake-terraces  in  Switzerland — Upraised  marine  strata  in  Sardinia — 
Origin  of  caverns — Remains  of  man  and  extinct  quadrupeds  in  cavern  deposits 
— Cave  of  Kirkdale — Reindeer  period  of  south  of  France — Australian  cave- 
breccias — Geographical  relationship  of  the  provinces  of  living  vertebrata  and 
those  of  extinct  Post-pliocene  species — Extinct  struthious  birds  of  New  Zealand 
— Fluctuations  of  climate  in  Post-glacial  period — Comparative  longevity  of 
species  in  the  mammalia  and  testacea — Teeth  of  recent  and  Post-pliocene  mam- 
malia. 

FROM  the  general  tables,  given  at  the  end  of  the  last  chapter,  the 
reader  will  have  learned  that  the  uppermost  or  newest  strata  are 
called  Post-tertiary,  as  being  more  modern  than  the  Tertiary.  It  will 
also  be  observed  that  the  Post-tertiary  formations  are  divided  into 
two  subordinate  groups:  the  Recent,  and  Post-pliocene.  In  the 
former,  or  the  Recent,  the  mammalia  as  well  as  the  shells  are  iden- 
tical with  species  now  living;  whereas  in  the  Post-pliocene  a  part, 
and  often  a  considerable  part,  of  the  mammalia  belong  to  extinct  spe- 
cies. To  this  nomenclature  it  may  be  objected  that  the  term  Post- 
pliocene  should  in  strictness  include  all  geological  monuments  poste- 
rior in  date  to  the  Pliocene ;  but  when  I  have  occasion  to  speak  of 
the  whole  collectively,  I  shall  call  them  Post-tertiary,  and  reserve  the 
term  Post-pliocene  for  the  older  Post-tertiary  formations,  while  the 
Upper  or  newer  ones  will  be  called  "  Recent." 

Cases  will  occur  where  it  may  be  scarcely  possible  to  draw  the 
boundary  line  between  the  Recent  and  Post-pliocene  deposits ;  and 
we  must  expect  these  difficulties  to  increase  rather  than  diminish 
with  every  advance  in  our  knowledge,  and  in  proportion  as  gaps  are 
filled  up  in  the  series  of  records. 

In  1839  I  proposed  the  term  Pleistocene  as  an  abbreviation  for 
Newer  Pliocene,  and  it  soon  became  popular,  having  beeq.  adopted  by 
the  late  Edward  Forbes  in  his  admirable  essay  on  "  The  Geological 
Relations  of  the  existing  Fauna  and  Flora  of  the  British  Isles ; "  but 
he  applied  the  term  almost  precisely  in  the  sense  in  which  I  shall  use 
Post-pliocene  in  this  volume,  and  not  as  short  for  Newer  Pliocene. 
In  order  to  prevent  confusion,  I  think  it  best  entirely  to  abstain  from 


108  RECENT  PERIOD.  [On.  X. 

the  use  of  Pleistocene  in  this  work,  for  I  find  that  the  introduction 
of  such  a  fourth  name  (unless  restricted  solely  to  the  older  Post- 
tertiary  formations)  must  render  the  use  of  Pliocene,  in  its  original 
extended  sense,  impossible,  and  it  is  often  almost  indispensable  to 
have  a  single  term  to  comprehend  both  divisions  of  the  Pliocene 
period.* 

RECENT    PERIOD. 

It  was  stated  in  the  sixth  chapter,  when  I  treated  of  denudation, 
that  the  dry  land,  or  that  part  of  the  earth's  surface  which  is  not 
covered  by  the  waters  of  lakes  or  seas,  is  generally  wasting  away  by 
the  incessant  action  of  rain  and  rivers,  and  in  some  cases  by  the 
undermining  and  removing  power  of  waves  and  tides  on  the  sea 
coast.  But  the  rate  of  waste  is  very  unequal,  since  the  level  and 
gently  sloping  lands,  where  they  are  protected  by  a  continuous  cov- 
ering of  vegetation,  escape  nearly  all  wear  and  tear,  so  that  they 
may  remain  for  ages  in  a  stationary  condition,  while  the  removal  of 
matter  is  constantly  widening  and  deepening  the  intervening  ravines 
and  valleys. 

The  materials,  both  fine  and  coarse,  carried  down  annually  by 
rivers  from  the  higher  regions  to  the  lower,  and  deposited  in  succes- 
sive strata  in  the  basins  of  seas  and  lakes,  must  be  of  enormous 
volume.  We  are  always  liable  to  underrate  their  magnitude,  because 
the  accumulation  of  strata  is  going  on  out  of  sight. 

There  are,  however,  causes  at  work  which,  in  the  course  of  centu- 
ries, tend  to  render  visible  these  modern  formations,  whether  of 
marine  or  lacustrine  origin.  For  a  large  portion  of  the  earth's  crust 
is  always  undergoing  a  change  of  level,  some  areas  rising  and  others 
sinking  at  the  rate  of  a  few  inches,  or  a  few  feet,  perhaps  sometimes 
yards,  in  a  century,  so  that  spaces  which  were  once  subaqueous  are 
gradually  converted  into  land,  and  others  which  were  high  and  dry 
become  submerged.  In  consequence  of  such  movements  we  find  in 
certain  regions,  as  in  Cashmere  for  example,  where  the  mountains  are 
often  shaken  by  earthquakes,  deposits  which  were  formed  in  lakes  in 
the  historical  period,  but  through  which  rivers  have  now  cut  deep 
and  wide  channels.  In  lacustrine  strata  thus  intersected,  works  of 
art  and  freshwater  shells  are  seen.  In  other  districts  on  the  borders 
of  the  sea,  usually  at  very  moderate  elevations  above  its  level,  raised 
beaches  occur,  or  marine  littoral  deposits,  such  as  those  in  which,  on 
the  borders  of  the  Bay  of  Baise,  near  Naples,  the  well-known  temple 
of  Serapis  was  embedded.  In  that  case  the  date  of  the  monuments 
buried  in  the  marine  strata  is  ascertainable,  but  in  many  other  in- 

*  If  geologists  still  think  it  convenient  to  retain  the  term  Pleistocene,  I  would 
recommend  them  to  use  it  not  in  the  sense  originally  proposed  by  me,  nor  in  thf 
somewhat  vague  manner  in  which  it  was  applied  by  Edward  Forbes,  but  in  place 
of  Post-pliocene  as  this  term  is  denned  in  the  present  work. 


CH.  X.]  DANISH  SHELL  MOUNDS. 


109 


stances,  the  exact  age  of  the  remains  of  human  workmanship  is 
uncertain,  as  in  the  estuary  of  the  Clyde  at  Glasgow,  where  many 
canoes  have  been  exhumed,  with  other  works  of  art,  all  assignable  to 
some  part  of  the  recent  period. 

On  the  coast  of  Cornwall,  at  Pentuan,  near  St.  Austell,  and  at 
Carnon  in  the  same  county,  at  the  depth  of  53  feet,  human  skulls 
have  been  met  with  beneath  marine  strata,  in  which  the  bones  of 
whales,  and  of  several  land  quadrupeds,  all  of  living  species,  were 
embedded. 

Danish  peat  and  shell  mounds,  or  kitchen-middens. — Sometimes 
we  obtain  evidence,  without  the  aid  of  a  change  of  level,  of  events 
which  took  place  in  pre-historic  times.  The  combined  labors,  for 
example,  of  the  antiquary,  zoologist,  and  botanist  have  brought  to 
light  many  monuments  of  the  early  inhabitants  buried  in  peat- 
mosses in  Denmark.  Their  geological  age  is  determined  by  the  fact 
that,  not  only  the  contemporaneous  freshwater  and  land  shells,  but 
all  the  quadrupeds,  found  in  the  peat,  agree  specifically  with  those 
now  inhabiting  the  same  districts,  or  which  are  known  to  have  been 
indigenous  in  Denmark  within  the  memory  of  man.  In  the  lower  beds 
of  peat  (a  deposit  vayring  from  20  to  30  feet  in  thickness),  weapons 
of  stone  accompany  trunks  of  the  Scotch  fir,  Pinus  sylvestris,  while 
in  the  higher  portions  of  the  same  bogs,  bronze  implements  are 
associated  with  trunks  and  acorns  of  the  common  oak.  It  appears 
that  the  pine  has  never  been  a  native  of  Denmark  in  historical  times, 
and  it  seems  to  have  given  place  to  the  oak  about  the  time  when 
articles  and  instruments  of  bronze  superseded  those  of  stone.  It  also 
appears  that,  at  a  still  later  period,  the  oak  itself  became  scarce,  and 
was  nearly  supplanted  by  the  beech,  a  tree  which  now  flourishes 
luxuriantly  in  Denmark.  Again,  at  the  still  later  epoch  when  the 
beech  tree  abounded,  tools  of  iron  were  introduced,  and  were  gradually 
substituted  for  those  of  bronze. 

On  the  coasts  of  the  Danish  islands  in  the  Baltic,  certain  mounds, 
called  in  those  countries  "  Kjokken-modding,"  or  "  kitchen-middens," 
occur,  consisting  chiefly  of  the  castaway  shells  of  the  oyster,  cockle, 
periwinkle,  and  other  eatable  kinds  of  mollusks.  These  mounds  are 
from  3  to  10  feet  high,  and  from  100  to  1000  feet  in  their  longest 
diameter.  They  greatly  resemble  heaps  of  shells  formed  by  the  Red 
Indians  of  North  America  along  the  eastern  shores  of  the  United 
States.  In  the  old  refuse-heaps,  recently  studied  by  the  Danish  anti- 
quaries and  naturalists  with  great  skill  and  diligence,  no  implements 
of  metal  have  ever  been  detected.  All  the  knives,  hatchets,  and  other 
tools,  are  of  stone,  horn,  bone,  or  wood.  With  them  are  often  inter- 
mixed fragments  of  rude  pottery,  charcoal  and  cinders,  and  the  bones 
of  quadrupeds  on  which  the  rude  people  fed.  These  bones  belong  to 
wild  species  still  living  in  Europe,  though  some  of  them,  like  the 
beaver,  have  long  been  extirpated  in  Denmark.  The  only  animal  which 
they  »eem  to  have  domesticated  was  the  dog. 


110  LAKE-DWELLINGS  OF  SWITZERLAND.  [Cu.  X 

As  there  is  an  entire  absence  of  metallic  tools,  these  refuse-heaps  are 
referred  to  what  is  called  the  age  of  stone,  which  immediately  preceded 
in  Denmark  the  age  of  bronze — a  race  more  advanced  in  civilization, 
armed  with  weapons  of  that  mixed  metal,  having  apparently  invaded 
Scandinavia,  and  ousted  the  aborigines.* 

Lacustrine  habitations  of  Switzerland. — In  Switzerland  a  different 
class  of  monuments,  illustrating  the  successive  ages  of  stone,  bronze, 
and  iron,  has  been  of  late  years  investigated  with  great  success,  and 
especially  since  1854,  in  which  year  Dr.  F.  Keller  explored  near  the 
shore  at  Meilen,  in  the  bottom  of  the  lake  of  Zurich,  the  ruins  of  an  old 
village,  originally  built  on  numerous  wooden  piles,  driven,  at  some 
unknown  period,  into  the  muddy  bed  of  the  lake.  Since  then  a  great 
many  other  localities,  more  than  a  hundred  and  fifty  in  all,  have  been 
detected  of  similar  pile-dwellings,  situated  near  the  borders  of  the 
Swiss  lakes,  at  points  were  the  depth  of  water  does  not  exceed  1 5 
feet.f  The  superficial  mud  in  such  cases  is  filled  with  various  articles, 
many  hundreds  of  them  being  often  dredged  up  from  a  very  limited 
area.  Thousands  of  piles,  decayed  at  their  upper  extremities,  are  often 
met  with  still  firmly  fixed  in  the  mud. 

Herodotus  relates  that  in  the  time  of  Darius  (about  520  B.C.)  there 
existed  a  similar  settlement  in  the  middle  of  Lake  Prasias  (probably 
now  Lake  Takinos),  in  Po3onia,  or  in  the  modern  Turkish  province  of 
Rounielia.  "  The  houses,"  he  says,  "  were  built  on  a  platform  of  wood 
supported  by  wooden  stakes,  and  a  narrow  bridge,  which  could  be 
withdrawn  at  pleasure,  communicated  with  the  shore." J  "When 
man,"  says  Morlot,§  "thus  stationed  his  dwellings  on  piles,  all  the 
refuse  of  his  industry  and  of  his  food  were  naturally  thrown  into  the 
lake,  and  were  often  well  preserved  in  the  mud  at  the  bottom.  If 
occasionally  such  establishments  were  burnt,  whether  intentionally  by 
the  enemy,  or  by  accident,  a  vast  quantity  and  variety  of  articles,  in- 
cluding some  of  great  value,  would  sink  to  the  botton  of  the  waters. 
Such  aquatic  sites  were  probably  selected  as  places  of  safety,  since, 
when  the  bridge  was  removed,  they  could  only  be  approached  by  boats, 
and  the  water  would  serve  for  protection  alike  against  wild  animals  and 
human  foes." 

As  the  ages  of  stone,  bronze,  and  iron  merely  indicate  successive 
stages  of  civilization,  they  may  all  have  coexisted  at  once  in  different 
parts  ot  the  globe,  and  even  in  contiguous  regions,  among  nations 
having  little  intercourse  with  each  other.  To  make  out,  therefore,  a 
distinct  chronological  series  of  monuments  is  only  possible  when  our 

*  See  the  works  of  Nilsson,  Thomsen,  Warsaae,  Steenstrup  aud  others. 

f  See  the  works  of  MM.  Troyon  and  Keller,  and  M.  Morlot's  sketch  of  these 
researches.  Bulletin  de  la  Socie'te  Vaudoise  des  Sci.  Nat.,  t.  vi.,  Lausanne,  1860 ; 
and  Antiquity  of  Man,  by  the  Author,  ch.  ii. 

\  Herod.,  v.  16. 

§  General  Views  of  Archaeology,  by  Morlot,  Memoirs  of  Smithsonian  Institution, 
1861. 


CH.  X.]  STONE  AND  BRONZE  PERIODS.  I-Q 

observations  are  confined  to  a  limited  district,  such  as  Switzerland  • 
and  the  distinctness  of  date  becomes  more  striking  when  a  settlement 
like  that  of  Moosseedorf,  near  Berne,  belonging  exclusively  to  the  age 
of  stone,  is  surrounded  by  a  great  many  others  all  referable  to  the 
period  of  bronze.  The  number  of  objects  found  at  Moosseedorf  exceeds 
two  thousand,  among  which  no  metallic  ones  were  observed.  At 
Wangen,  on  the  Lake  of  Constance,  more  than  1300  articles  of  stone, 
bone,  and  pottery  were  collected,  without  the  intermixture  of  a  single 
utensil,  instrument,  or  ornament  of  bronze.  In  other  lakes,  as  in  those 
of  Bienne  and  Geneva,  there  are  settlements  were  the  number  of  bronze 
articles  is  equally  numerous,  with  a  very  slight  admixture  of  weapons 
of  stone. 

The  relative  antiquity  of  the  pile-dwellings,  which  belong  respec- 
tively to  the  ages  of  stone  and  bronze,  is  also  clearly  illustrated  by 
the  association  of  the  tools  with  certain  groups  of  animal  remains. 
Where  the  tools  are  of  stone,  the  castaway  bones  which  served  for  the 
food  of  the  ancient  people  are  those  of  deer,  the  wild  boar,  and  wild 
ox,  which  abounded  when  society  was  in  the  hunter  state.  But  the 
bones  of  the  latter  or  bronze  epoch  were  chiefly  those  of  the  domestic 
ox,  goat,  and  pig,  indicating  progress  in  civilization.  Some  villages 
of  the  stone  age  are  of  later  date  than  others,  and  exhibit  signs  of  an 
inproved  state  of  the  arts.  Among  their  relics  are  discovered 
carbonized  grains  of  wheat  and  barley,  and  pieces  of  bread,  proving 
that  the  cultivation  of  cereals  had  begun.  In  the  same  settlements, 
also,  cloth  made  of  woven  flax  and  straw,  has  been  detected. 

To  the  Swiss  pile-buildings  of  the  bronze  age  belong  manufactured 
objects  which  display  a  very  decided  superiority  in  beauty  of  form, 
and  ornamentation,  when  contrasted  with  those  of  the  antecedent  age 
of  stone.  In  one  village  at  Mdau,  on  the  lake  of  Bienne,  a  great 
number  of  axes,  lances,  sickles,  fish-hooks,  and  bracelets,  altogether 
nearly  two  thousand  articles,  have  been  obtained,  and  with  them  some  few 
implements  of  stone.  These  last,  dredged  up  from  the  same  site,  may 
perhaps  have  been  used  simultaneously  ;  or  possibly  the  same  village, 
founded  in  the  age  of  stone,  may  have  continued  to  flourish  in  the 
succeeding  period  of  bronze.*  The  pottery  of  the  bronze  age  in 
Switzerland  is  of  a  finer  texture,  and  more  elegant  in  form,  than  that 
of  the  age  of  stone.  At  Nidau,  articles  of  iron  have  also  been  dis- 
covered, so  that  this  settlement  was  evidently  not  abandoned  till  that 
metal  had  come  into  use. 

At  La  Thene,  in  the  northern  angle  of  the  lake  of  Neufchatel,  a 
great  many  articles  of  iron  have  been  obtained,  which  in  form  and 
ornamentation  are  entirely  different  both  from  those  of  the  bronze 
period  and  from  those  used  by  the  Romans.  Gaulish  and  Celtic  coins 
have  also  been  found  there  by  MM.  Schwab  and  Desor.  They  agree 
in  character  with  remains,  including  many  iron  swords,  which  have 

*  Mr.  J.  Lubbock's  Lecture,  Royal  Institution,  Feb.  27th,  1863. 


112  BRONZE  OF  THE  ANCIENTS.  [Cn.  X. 

been  found  at  Tiefenau,  near  Berne,  in  ground  supposed  to  have  been 
a  battle-field ;  and  their  date  appears  to  have  been  anterior  to  the 
great  Roman  invasion  of  Northern  Europe,  though  perhaps  not  long 
before  that  event.* 

The  period  of  bronze  must  have  been  one  of  foreign  commerce,  as 
tin,  which  enters  into  this  metallic  mixture  in  the  proportion  of  about 
ten  per  cent,  to  the  copper,  was  obtained  by  the  ancients  chiefly  from 
Cornwall.  From  that  country  it  is  supposed  to  have  been  supplied  at 
one  time  by  the  Phoenicians  to  the  Greeks,  as  well  as  to  all  the  inhabi- 
tants of  the  eastern  shores  of  the  Mediterranean.  Even  the  tin  said 
to  have  come  from  Iberia,  or  Spain,  is  imagined  by  many  anti- 
quaries to  have  been  first  shipped  from  the  Cassiterides,  or  Cornwall, 
to  Cadiz.f  At  a  later  period  we  learn  from  Diodorus  that  ingots  of 
tin  were  shipped  from  Iktis,  or  St.  Michael's  Mount,  in  Cornwall,  and 
conveyed  over  the  channel  to  the  opposite  coast,  and  thence  on  the 
backs  of  horses  across  Gaul,  in  about  thirty  days,  to  Massilia  or  Mar- 
seilles, from  whence  the  Romans  obtained  it.| 

The  Greeks  are  described  by  Homer  in  the  Iliad  as  armed  with 
^aA/co^,  usually  translated  brass,  which  is  now  ascertained,  by  a  pre- 
cise analysis  of  ancient  Greek  armor  and  coins,  to  have  consisted  not 
of  copper  and  zinc,  but  of  copper  and  tin,  or  what  we  now  call  bronze. 
Contemporaneously  with  bronze,  iron  was  also  in  use  among  the 
ancients,  even  from  very  remote  times ;  but  so  long  as  the  art  of 
making  steel  by  blending  iron  in  certain  chemical  proportions  with 
carbon  was  unknown,  or  still  in  its  infancy,  bronze  seems  to  have 
competed  successfully  with  iron  in  the  construction  of  all  cutting  im- 
plements. The  best  definition,  perhaps,  of  the  age  of  iron  yet  pro- 
posed, is  that  which  describes  it  as  the  period  when  this  metal  had, 
for  the  most  part,  superseded  bronze  in  all  instruments  requiring  a 
sharp  cutting  edge.  It  is  remarkable  that  in  Herculaneum  and 
Pompeii,  which  was  buried  under  the  ashes  of  Vesuvius  in  the  year  79, 
nearly  a  thousand  years  after  Homer's  time,  the  prevailing  metal  of 
which  the  agricultural,  culinary,  and  even  the  surgical  instruments 
are  made  was  bronze  ;  although  articles  of  iron  are  by  no  means  want- 
ing among  the  relics  found  in  those  ancient  cities.  In  Transylvania 
and  Hungary,  according  to  Keller,  an  age  of  copper  instruments  inter- 
vened between  that  of  stone  and  bronze. 

In  estimating  the  degree  in  which  iron  and  bronze  prevailed  in 
prehistoric  ages,  we  are  in  some  danger  of  being  misled  by  the  great 
durability  of  the  one  metal,  and  the  facility  with  which  the  other,  or 
the  iron,  is  decomposed.  But  if  iron  be  corroded  in  large  quantities 
by  oxidation,  it  would  usually  betray  itself  to  the  geologist  by  acting 
as  a  cement,  and  binding  together  the  particles  of  sand,  gravel,  mud,  and 

*  Mr.  J.  Lubbock's  Lecture,  Royal  Institution,  Feb.  27th,  1863. 
f  Sir  G.  Cornwall  Lewis,  Astronomy  of  the  Ancients,  ch.  viii. 
\  Diodorus,  v.  21,  22,  and  Sir  H.  James,  Note  on  Block  of  Tin  dredged  up  in 
Falmouth  Harbor.     Royal  Institution  of  Cornwall,  1863. 


CH.  X.]  CRANIAL  TYPES  OF  THE   BRONZE  PERIOD. 


113 


shells  in  which  it  lay.  A  cylindrical  coating  of  such  materials  has 
sometimes  been  found  encircling  cannon  and  gun-barrels,  the  fur- 
ther corrosion  of  which  seems  to  have  been  arrested  by  such  an  en- 
velope.* 

Human  remains  of  the  recent  period. — Very  few  human  bones  of 
the  bronze  period  have  been  met  with  in  the  Danish  peat,  or  in  the  Swiss 
lake-dwellings,  and  this  scarcity  in  generally  attributed  by  archaeolo- 
gists to  the  custom  of  burning  the  dead,  which  prevailed  in  the  age 
of  bronze.  In  the  antecedent  era  of  stone,  the  primitive  population 
of  the  North  are  said  to  have  buried  their  dead  in  sepulchral  vaults, 
carefully  constructed  of  large  undressed  blocks  of  stone.  From  such 
burial-places  many  skulls  have  been  obtained  by  Scandinavian  ethnolo- 
gists, which  show  that  the  ancient  race  had  small  heads,  remarkably 
rounded  in  every  direction,  but  with  a  facial  angle  tolerably  large,  and 
a  well-developed  forehead.  (See  figure  104.)  Similar  skulls  have, 
according  to  Retzius,  been  discovered  in  France,  Ireland,  and  Scot- 
land, and  they  are  so  like  those  of  the  modern  Laplanders,  as  to  have 
suggested  the  idea  that  the  latter  were  the  last  survivors  of  the  stone 
period  in  the  north  of  Europe.  The  •  Laplanders  have  usually  been 
considered  as  an  extreme  branch  of  the  Mongolian  race. 

The  cranial  type  of  the  bronze  age  is  not  yet  well  known,  but  with 
the  introduction  of  iron,  the  custom  of  burying  the  dead  was  resumed, 
and  with  it  a  new  form  of  skulls  appears,  resembling  that  now-a-days 


Fig.  104. 


Fig.  105. 


Brach 


Dolichocephalous  type  of  the  beginning 
of  the  age  of  iron  in  Denmark. 


most  common  in  Europe.  As  seen  in  fig.  105,  it  is  elongated  fore  and 
aft,  has  a  forehead  somewhat  retreating,  and  corresponds  with  what  is 
often  called  the  Celtic  type.f 


./  POST-PLIOCENE    PERIOD. 

From  the  foregoing  observations  we  may  infer  that  the  ages  of  iron 
and  bronze  in  Northern  and  Central  Europe  were  preceded  by  a  stone 

*  See  LyelPs  Principles  of  Geology,  9th  ed.,  p.  760. 
f  Morlot,  ibid. 

8 


POST-PLIOCENE  PERIOD. 


[On.  X. 


age,  referable  to  the  recent  division  of  the  post-tertiary  epoch  as 
determined  by  the  organic  remains  which  accompany  the  stone  imple- 
ments. But  memorials  have  of  late  been  brought  to  light  of  a  still  older 
age  of  stone,  when  man  was  contemporary  in  Europe  with  the  ele- 
phant and  rhinoceros,  and  various  other  animals,  of  which  many  of 
the  most  conspicuous  have  long  since  died  out.  The  alluvial  and 
marine  deposits  of  this  remoter  age,  the  earliest  to  which  any  vestiges 
of  man  have  yet  been  traced  back,  belong  to  a  time  when  the  physi- 
cal geography  of  Europe  differed  in  a  more  marked  degree  from  that 
now  prevailing  than  during  the  latter  part  of  the  post-tertiary  period, 
when  the  valleys  and  rivers  coincided  almost  entirely  with  those  by 
which  the  present  drainage  of  the  land  is  carried  on,  and  when  the 
peat-mosses  were  the  same  as  those  now  growing.  So,  also,  the  situa- 
tion of  the  shell-mounds  and  lake-dwellings  above  alluded  to  is  such 
as  to  imply  that  the  topography  of  each  district  where  they  are 
observed  has  not  subsequently  undergone  any  material  alteration.  In 
some  exceptional  cases,  it  is  true,  a  marked  change  has  been  brought 
about  by  the  rising  or  sinking  of  the  earth's  crust  in  the  neighborhood 

Fig.  106. 


Eecent  and  Post-pliocene  alluvial  deposits. 


1.  Peat  of  the  recent  period. 

2.  Gravel  of  modern  river. 

V.  Loam  or  brick-earth  (loess)  of  same 
age  as  2,  formed  by  inundations  of 
the  river. 

3.  Lower-level  valley-gravel  with  extinct 

mammalia  (post-pliocene). 
&.  Loam  of  same  age. 


4.  Higher  level  valley-gravel  (post-plio- 

cene). 
4'.  Loam  of  same  age. 

5.  Upland  gravel  of  various  kinds  and 

periods,  consisting  in  some  places 
of  unstratified  boulder  clay  or  gla- 
cial drift. 

6.  Older  rocks. 


of  the  sea,  so  that  raised  beaches  occur  at  moderate  heights  rarely 
exceeding  twenty-five  feet  above  high-water  mark  ;  or  in  other  places 
submerged  forests  are  seen  at  low  water,  skirting  the  coasts ;  and  we 
may  take  for  granted  that  similar  or  even  greater  movements  have  been 
experienced  far  inland  within  the  same  era,  although  we  cannot  recog- 
nize them,  or  appreciate  their  magnitude,  for  want  of  a  standard  of 
measurement  such  as  that  which  the  contiguity  of  the  ocean  affords. 
These  movements,  whether  upward  or  downward,  have  affected  some- 
what uniformly  very  wide  areas,  so  as  not  greatly  to  derange  the 
local  features  of  such  an  extent  of  country  as  the  eye  can  embrace  at 
one  view.  But  we  no  sooner  examine  the  post-pliocene  formations  in 
which  the  remains  of  so  many  extinct  mammalia  are  found,  than  we 
at  once  perceive  a  more  decided  discrepancy  between  the  former  and 


CH.  X.]  MAN  COEVAL  WITH  EXTINCT  MAMMALIA.  ^5 

present  outline  of  the  surface.  Since  those  deposits  originated, 
changes  of  considerable  magnitude  have  been  effected  in  the  depth  and 
width  of  many  valleys,  also  in  the  direction  of  the  superficial  and  sub- 
terranean drainage,  and,  as  is  manifest  near  the  sea-coast,  in  the  relative 
position  of  land  and  water.  In  the  annexed  diagram  (fig.  106),  an 
ideal  section  is  given,  illustrating  the  different  position  which  the 
recent  and  post-pliocene  alluvial  deposits  occupy  in  many  European 
valleys. 

The  peat  No.  1  has  been  found  in  a  low  part  of  the  modern  allu- 
vial plain,  in  parts  of  which  gravel  No.  2  of  the  recent  period  is  seen. 
Over  this  gravel  the  loam  or  fine  sediment  2'  has  in  many  places  been 
deposited  by  the  river  during  floods  which  covered  nearly  the  whole 
alluvial  plain. 

No.  3  represents  an  older  alluvium,  composed  of  sand  and  gravel, 
formed  before  the  valley  had  been  excavated  to  its  present  depth.  It 
contains  the  remains  of  fluviatile  shells  of  living  species  associated 
with  the  bones  of  mammalia,  in  part  of  recent  and  in  part  of  extinct 
species.  Among  the  latter,  the  mammoth  (E.  primigenius]  and 
Siberian  rhinoceros  (R.  tichorhinus)  are  the  most  common  in  Europe. 
No.  3'  is  a  remnant  of  the  loam  or  brick  earth  by  which  No.  3  was 
overspread.  No.  4  is  a  still  older  and  more  elevated  terrace,  similar 
in  its  composition  and  organic  remains  to  No.  3,  and  covered  in  like 
manner  with  its  inundation  mud,  4'.  Often  there  is  only  one  of 
these  valley  gravels  of  older  date,  and  occasionally  there  are  more 
than  two,  marking  as  many  successive  stages,  in  the  excavation  of 
the  valley.  They  usually  occur  at  heights  varying  from  10  to  100 
feet,  sometimes  on  the  right  and  sometimes  on  the  left  side  of  the 
existing  river-plain,  but  rarely  in  great  strength  on  exactly  opposite 
sides  of  the  valley. 

Among  the  genera  of  extinct  quadrupeds  most  frequently  met  with 
in  England,  France,  Germany,  and  other  parts  of  Europe,  are  Elephas, 
Rhinoceros,  Hippopotamus,  Equus,  Megaceros,  Ursus,  Felis,  and 
Hyaena.  In  the  peat  No.  1  (fig.  106)  and  in  the  more  modern  gravel 
and  silt  (No.  2),  works  of  art  of  the  ages  of  iron  and  bronze,  and  of 
what  we  may  call  the  "  later  stone  period,"  already  described,  are  met 
with.  In  the  more  ancient  gravels,  3  and  4  (fig.  106),  there  have 
been  found  of  late  years  in  several  valleys  in  France  and  England,  as, 
for  example,  in  those  of  the  Seine  and  Somme,  and  of  the  Thames,  and 
Ouse,  near  Bedford,  stone  implements  of  a  rude  type,  showing  that 
man  coexisted  in  those  districts  with  the  elephant  and  other  extinct 
quadrupeds  of  the  genera  above  enumerated. 

Several  geologists  had  come  to  the  conclusion,  about  the  close  of 
the  last  and  beginning  of  the  present  century,  that  certain  human 
remains  embedded  in  the  mud  and  breccia  of  caves  were  as  old  as  the 
extinct  mammalia  with  which  they  were  associated.     But  the  evidenc 
of  such  high  antiquity  was  not  generally  received  as  satisfactory,  se 
ing  that  so  many  caves  had  been  inhabited  by  a  succession  of  tenants, 


DISCOVERIES  AT  AMIENS.  [Cn.  X. 

and  selected  by  man  as  places  both  of  domicile  and  of  sepulture, 
while  suites  of  caverns  have  also  served  as  the  channels  through  which 
underground  rivers  have  flowed ;  so  that  the  remains  of  living  beings 
which  peopled  the  district  at  more  than  one  era  may,  at  a  later  date, 
have  been  mingled  and  confounded  together  in  one  and  the  same 
deposit.  But  in  1847,  M.  Boucher  de  Perthes  observed  in  an  ancient 
alluvium  at  Abbeville,  in  Picardy,  the  bones  of  extinct  mammalia 
associated  in  such  a  manner  with  flint  implements  of  a  rude  type  as 
to  lead  him  to  infer  that  both  the  organic  remains  and  the  works  of 
art  were  referable  to  one  and  the  same  period.  This  inference, 
though  questioned  for  a  time,  was  soon  confirmed  by  fresh  observa- 
tions made  by  Dr.  Kigollot,  at  Amiens,  and  all  doubts  were  finally 
cleared  up  in  1859,  by  Mr.  Prestwich,  who  found  a  flint  tool  in  situ 
in  the  same  stratum  at  Amiens,  that  contained  the  remains  of  extinct 
mammalia.  Geologists  were,  moreover,  better  prepared  to  accept 
such  proofs  of  the  coexistence  of  man  with  the  ancient  fauna  in  conse- 
quence of  the  more  exact  data  obtained  from  the  exploration  of  the 
Brixham  cave  in  1860,  to  be  mentioned  in  the  sequel. 

The  flint  implements  found  at  Abbeville  and  Amiens  are  most  of 
them  considered  to  be  hatchets  and  spear-heads,  and  are  different 
from  those  commonly  called  "  Celts."  These  celts,  so  ofted  found  in 
the  recent  formations,  have  a  more  regular  oblong  shape,  the  result  of 
grinding,  by  which  also  a  sharp  edge  has  been  given  to  them.  The 
Abbeville  tools  found  in  gravel  at  different  levels,  as  in  Nos.  3  and  4, 
fig.  106,  in  which  the  bones  of  the  elephant,  rhinoceros,  and  other 
extinct  mammalia  occur,  are  always  unground,  having  evidently  been 
brought  into  their  present  form  simply  by  the  chipping  off  of  fragments 
of  flint  by  repeated  blows,  such  as  could  be  given  by  a  stone  ham- 
mer. 

Some  of  them  are  oval,  others  of  a  spear-headed  form,  no  two 
exactly  alike,  and  yet  the  greater  number  of  each  kind  are  obviously 
fashioned  after  the  same  general  pattern.  Their  outer  surface  is  often 
white,  the  original  black  flint  having  been  discolored  and  bleached  by 
exposure  to  the  air,  or  by  the  action  of  acids,  as  they  lay  in  the 
gravel.  They  are  most  commonly  stained  of  the  same  ochreous 
color  as  the  flints  of  the  gravel  in  which  they  are  embedded.  Occa- 
sionally their  antiquity  is  indicated  not  only  by  their  color  but  by 
superficial  incrustations  of  carbonate  of  lime,  or  by  dendrites  formed 
of  oxide  of  iron  and  manganese.  The  edges  also  of  most  of  them 
are  worn,  either  by  having  been  used  as  tools,  or  by  having  been  rolled 
in  the  river's  bed.  They  are  usually  found  at  depths  of  from  15  to  25 
feet  from  the  surface,  in  gravel,  covered  by  loam,  and  most  of  them 
near  the  bottom  of  the  gravel,  and  not  far  from  its  contact  with  the 
subjacent  chalk.  They  are  met  with  not  only  in  the  lower-level  gravels, 
as  in  No.  3,  fig.  106,  but  also  in  No.  4,  or  the  higher  gravels,  as  at 
St.  Acheul,  in  the  suburbs  of  Amiens,  where  the  old  alluvium  lies  at  an 
elevation  of  about  100  feet  above  the  level  of  the  river  Somme.  At 


CH.  X.]  LOESS  OR  INUNDATION  MUD.  -Q* 

both  levels  fluviatile  and  land-shells  are  met  with  in  the  loam  as  well 
as  in  the  gravel,  but  there  are  no  marine  shells  associated,  except  at 
Abbeville,  in  the  lowest  part  of  the  gravel,  near  the  sea,  and  a  fow 
feet  only  above  the  present  high-water  mark.  Here  with  fossil  shells 
of  living  species  are  mingled  the  bones  of  Elephas  primigenius  and 
E.  antiquus,  Rhinoceros  tichorhinus,  Hippopotamus,  Felis  spelcea, 
Hyaena  spelcea,  reindeer,  and  many  others,  the  bones  accompanying 
the  flint  implements  in  such  a  manner  as  to  show  that  both  were 
buried  in  the  old  alluvium  at  the  same  period. 

Nearly  the  entire  skeleton  of  a  rhinoceros  was  found  at  one  point, 
namely,  in  the  Menchecourt  drift  at  Abbeville,  the  bones  being  in 
such  juxtaposition  as  to  show  that  the  cartilage  must  have  held  them 
together  at  the  time  of  their  inhumation. 

The  general  absence  here  and  elsewhere  of  human  bones  from 
gravel  and  sand  in  which  flint  tools  are  discovered,  may  in  some 
degree  be  due  to  the  present  limited  extent  of  our  researches.  But  it 
may  also  be  presumed  that  when  a  hunter  population,  always  scanty 
in  numbers,  ranged  over  this  region,  they  were  too  wary  to  allow 
themselves  to  be  overtaken  by  the  floods  which  swept  away  many 
herbivorous  animals  from  the  low  river-plains  where  they  may  have 
been  pasturing  or  sleeping.  Beasts  of  prey  prowling  about  the  same 
alluvial  flats  in  search  of  food  may  also  have  been  surprised  more 
readily  than  the  human  tenant  of  the  same  region,  to  whom  the  signs 
of  a  coming  tempest  were  better  known. 

In  the  very  few  instances  in  which  we  have  good  evidence  in 
Europe  of  the  occurrence  of  human  remains  in  post-pliocene  deposits, 
exclusive  of  those  in  caves,  the  fossil  relics  have  been  found  at  or  near 
the  line  of  junction  of  the  superficial  loam  (3',  4',  fig.  106)  with  the 
underlying  gravel.  Thus  M.  Ami  Bone",  an  experienced  observer, 
disinterred  with  his  own  hands,  in  the  valley  of  the  Rhine  in  1853, 
parts  of  a  human  skeleton  from  the  lower  portion  of  a  deposit  of  loam 
or  loess  80  feet  thick.  This  discovery  was  made  at  Lahr,  a  small 
town  in  the  Grand  Duchy  of  Baden,  nearly  opposite  Strasburg,  on  the 
right  side  of  the  valley  of  the  Rhine.  They  were  shown  at  the  time 
to  Cuvier,  and  recognized  by  him  as  human.*  One  of  them,  a  femur, 
first  attracted  notice  as  it  projected  from  a  perpendicular  cliff  of 
loess,  forming  the  lowest  of  a  succession  of  terraces,  which  had  been 
excavated  in  the  loam  by  the  denuding  power  of  the  Schutter,  a 
small  tributary  which  at  Lahr  joins  the  great  alluvial  plain  of  the 
Rhine.  The  loam  in  which  the  bones  were  embedded  is  similar 
in  mineral  character  to  that  of  the  great  adjoining  plain,  and  so 
continuous  as  to  imply  that  the  Rhine  once  flowed  up  into  the  valley 
of  its  tributary,  and  filled  it  to  a  considerable  height  with  its 
muddy  sediment,  at  the  time  when  the  skeleton  was  enveloped  in  it. 

Inundation-mud  of  rivers. — Brick-earth. — Fluviatile  loam,  or  loess. 

*  Lyell,  Antiquity  of  Man.     Appendix  2d  and  3d  ed. 


118  FLUVIATILE  DEPOSITS  OF  THE  NILE.  [Cn.  X. 

— As  a  general  rule,  the  fluviatile  alluvia  of  different  ages  (Nos.  2,  3, 
4,  fig.  106)  are  severally  made  up  of  coarse  materials  in  their  lower 
portions,  and  of  fine  silt  or  loam  in  their  upper  parts.  For  rivers  are 
constantly  shifting  their  position  in  the  valley-plain,  encroaching 
gradually  on  one  bank,  near  which  there  is  deep  water,  and  deserting 
the  other  or  opposite  side,  where  the  channel  is  growing  shallower, 
being  destined  eventually  to  be  converted  into  land.  Where  the  cur- 
rent runs  strongest,  coarse  gravel  is  swept  along,  and  where  its  veloci- 
ty is  slackened,  first  sand,  and  then  only  the  finest  mud,  is  thrown 
down.  A  thin  film  of  this  fine  sediment  is  spread,  during  floods,  over 
a  wide  area,  on  one,  or  sometimes  on  both  sides,  of  the  main  stream, 
often  reaching  as  far  as  the  base  of  the  bluff's  or  higher  grounds  which 
bound  the  valley.  Of  such  a  description  are  the  well-known  annual 
deposits  of  the  Nile,  to  which  Egypt  owes  its  fertility.  So  thin  are 
they,  that  the  aggregate  amount  accumulated  in  a  century  is  said 
rarely  to  exceed  five  inches,  although  in  the  course  of  thousands  of 
years  it  has  attained  a  vast  thickness,  the  bottom  not  having  been 
reached  by  borings  extending  to  a  depth  of  60  feet  towards  the  cen- 
tral parts  of  the  valley.  Everywhere  it  consists  of  the  same 
homogeneous  mud,  destitute  of  stratification — the  only  signs  of  suc- 
cessive accumulation  being  where  the  Nile  has  silted  up  its  channel, 
or  where  the  blown  sands  of  the  Libyan  desert  have  invaded  the  plain, 
and  given  rise  to  alternate  layers  of  sand  and  mud. 

The  general  absence  of  lamination  in  the  loam  of  the  Egyptian 
river-plain  is  probably  owing  to  the  thinness  of  the  layer  thrown 
down  in  a  single  year,  and  to  its  being  exposed  for  eight  months  to 
drying  winds,  or  the  rays  of  a  hot  sun.  Parts  of  it  are  often  swept 
in  the  form  of  dust  from  one  region  to  another,  and  almost  every- 
where the  soil  is  pierced  by  worms,  insects,  and  the  roots  of  plants. 
Many  geologists  have  been  disposed  to  refer  the  absence  of  stratifica- 
tion in  such  formations  to  the  sudden  and  tumultuous  action  of 
floods,  by  which  dense  masses  of  mud  were  thrown  down  rapidly  and 
uninterruptedly ;  but  I  believe  that  the  absence  of  divisional  planes 
or  marks  of  successive  deposition  has  arisen,  not  from  the  want  of 
intermittent  action,  but  because  the  amount  of  annual  deposit  has 
been  so  slight,  and  because  it  has  taken  place  on  ground  not 
permanently  submerged.  There  may  be  found  in  deposits  of  this  class 
examples  of  every  gradation,  from  a  stratified  to  an  unstratified  con- 
dition. 

In  European  river-loams  we  occasionally  observe  isolated  pebbles 
and  angular  pieces  of  stone  which  have  been  floated  by  ice  to  the 
places  where  they  now  occur ;  but  no  such  coarse  materials  are  met 
with  in  the  plains  of  Egypt.  Above  and  below  the  first  cataract,  an- 
cient river  terraces  composed  of  fluviatile  deposits  have  been  observed 
by  Dr.  Adams  and  others  at  various  elevations  above  the  present  allu- 
vial plain  of  the  Nile.  In  these  old  river-formations — some  of  which 
are -30,  others  100,  and  others  several  hundred  feet  above  the  river — 


OH.  X.]  LOESS  FOSSILS  OF  THE  RHINE. 


119 


fossil  shells,  identical  with  species  now  living  in  the  Nile,  have  been 
found.  The  probable  causes  of  such  alterations  in  the  level  of  tho 
river,  and  the  successive  filling  up  and  re-excavation  of  the  same 
hydrographical  basin  at  different  periods,  will  be  presently  spoken  of. 
They  are  changes  of  a  kind  that  cannot  fail  to  result  from  great  conti- 
nental movements  of  subsidence  and  upheaval,  such  as  we  may  safely 
assume  that  Egypt  has  undergone  in  the  post-tertiary  epoch,  because 
the  eastern  shore  of  the  Red  Sea  on  one  side,  and  the  great  desert  of 
the  Sahara  on  the  other,  have  been  converted  from  sea  into  land  since 
the  commencement  of  the  Post-pliocene  period. 

In  some  parts  of  the  valley  of  the  Rhine  the  accumulation  of  similar 
loam,  called  in  Germany  "  loess,"  has  taken  place  on  an  enormous  scale. 
Its  color  is  yellowish-gray,  and  very  homogeneous ;  and  Professor 
Bischoff  has  ascertained,  by '  analysis,  that  it  agrees  in  composition 
with  the  mud  of  the  Nile.  Although  for  the  most  part  unstratified, 
it  betrays  in  some  places  marks  of  stratification,  especially  where  it 
contains  calcareous  concretions,  or  in  its  lower  part  where  it  rests  on 
subjacent  gravel  and  sand  which  alternate  with  each  other  near  the 
junction.  About  a  sixth  part  of  the  whole  mass  is  composed  of  car- 
bonate of  lime,  and  there  is  usually  an  intermixture  of  fine  quartzose 
and  micaceous  sand. 

Although  this  loam  of  the  Rhine  is  unsolidified,  it  usually  termi- 
nates where  it  has  been  undermined  by  running  water  in  a  vertical 
cliff,  from  the  face  of  which  shells  of  terrestrial,  freshwater  and 
amphibious  mollusks  project  in  relief.  These  shells  do  not  imply  the 
permanent  sojourn  of  a  body  of  fresh  water  on  the  spot,  for  the  most 
aquatic  of  them,  the  Succinea,  inhabits  marshes  and  wet  grassy  meadows. 
The  Succinea  elongata,  (or  S.  oblonga,)  fig.  107,  is  very  characteristic 
both  of  the  loess  of  the  Rhine  and  of  some  other  European  river- 
loams. 

Among  the  land-shells  of  the  Rhenish  loess,  Helix  plebeia  and  Pupa 
muscorum  are  very  common. 

Fig.  107.  Fig.  108,  Fig.  109. 


4.41 


Succinea  elongata.          Pupa,  muscorum.  ffeliat  plebeia. 

Both  the  terrestrial  and  aquatic  shells  are  of  most  fragile  and  deli- 
cate structure,  and  yet  they  are  almost  invariably  perfect  and  uninjured. 
They  must  have  been  broken  to  pieces  had  they  been  swept  along  by 
a  violent  inundation.  Even  the  color  of  some  of  the  land-shells,  as 
that  of  Helix  nemoralis,  is  occasionally  preserved. 

I  observed  the  three  fossils  above  figured  in  the  upper  fluviatile 
loam  of  the  Saale,  near  Rudolstadt,  in  Thuringia,  a  river  which  falls 
into  the  Ilm,  and  belongs  to  the  basin  of  the  Elbe.  I  have  also  seen 


120  POST-PLIOCENE  LAKE  TERRACES.  [Cn.  X. 

loam  like  that  of  the  Ehine  at  the  Porta  Westphalica,  near  Minden,  at 
the  height  of  500  feet  above  the  river-plain  of  the  Weser,  in  which  the 
same  three  shells  were  conspicuous. 

If  in  some  places  mollusks  of  purely  aquatic  species  of  such  genera 
as  Lymnea,  Planorbis,  and  Paludina,  occur  near  the  base  of  the  loess,  they 
probably  indicate  ancient  ponds  and  lakes  marking  the  course  of  old  de- 
serted river  channels,  which  were  afterwards  silted  up. 

In  parts  of  the  valley  of  the  Rhine,  between  Bingen  and  Basle,  the 
fluviatile  loam  or  loess  now  under  consideration  is  several  hundred  feet 
thick,  and  contains  here  and  there  throughout  that  thickness  land  and 
amphibious  sheEs.  As  it  is  seen  in  masses  fringing  both  sides  of  the 
great  plain,  and  as  occasionally  remnants  of  it  occur  in  the  centre  of  the 
valley,  forming  hills  several  hundred  feet  in  height,  it  seems  necessary 
to  suppose,  first,  a  time  when  it  slowly  accumulated ;  and  secondly,  a 
later  period,  when  large  portions  of  it  were  removed,  or  when  the 
original  valley,  which  had  been  partially  filled  up  with  it,  was  re- 
excavated. 

Such  changes  may  have  been  brought  about  by  a  great  movement 
of  oscillation,  consisting  first  of  a  general  depression  of  the  land,  and 
then  of  a  gradual  re-elevation  of  the  same.  The  amount  of  continen- 
tal depression  which  first  took  place  in  the  interior,  must  be  imagined 
to  have  exceeded  that  of  the  region  near  the  sea,  in  which  case  the 
higher  part  of  the  great  valley  would  have  its  alluvial  plain  gradually 
raised  by  an  accumulation  of  sediment,  which  would  only  cease  when 
the  subsidence  of  the  land  was  at  an  end.  If  the  direction  of  the 
movement  was  then  reversed,  and,  during  the  re-elevation  of  the  con- 
tinent, the  inland  region  nearest  the  mountains  should  rise  more  rap- 
idly than  that  near  the  coast,  the  river  would  acquire  a  denuding 
power  sufficient  to  enable  it  to  sweep  away  gradually  nearly  all  the 
loam  and  gravel  with  which  parts  of  its  basin  had  been  filled  up. 
Terraces  and  hillocks  of  mud  and  sand  would  then  alone  remain  to 
attest  the  various  levels  at  which  the  river  had  thrown  down  and  after- 
wards removed  alluvial  matter. 

Post-pliocene  lake-terraces  in  Switzerland. — In  Switzerland  terraces 
of  drift  are  found  at  different  levels  above  the  present  rivers  and  lakes, 
which  correspond  to  the  older  gravels  (Nos.  3  and  4,  fig.  106),  and 
they  contain  the  remains  of  the  mammoth,  reindeer,  and  other 
mammalia,  many  of  them  extinct  or  no  longer  inhabitants  of  Europe  ; 
together  with  shells,  all  of  them  of  species  still  living.  Skirting  the 
Lake  of  Geneva  are  the  deltas  of  numerous  torrents  which  bring 
down  mud,  sand,  and  pebbles  to  the  lake,  so  as  to  make  annual  addi- 
tions to  the  littoral  accumulations.  "  If,"  says  M.  Morlot,  "  we  follow 
up  the  course  of  any  of  these  streams  to  the  height  of  150  feet  above 
the  lake,  we  encounter  another  and  more  ancient  delta,  about  ten 
times  as  large,  evidently  the  monument  of  a  more  protracted  period, 
when  the  water  stood  for  ages  at  that  higher  level,  and  when  the  physi- 
cal geography  of  the  country  differed  considerably  from  that  now  estab- 
lished." 


CH.  X.]  UPRAISED  MARINE  STRATA. 

One  of  the  deltas  of  transported  matter,  or,  as  M.  Morlot  styles 
them,  flattened  cones,  is  seen  at  the  mouth  of  the  Tiniere,  a  torrent 
which  enters  the  lake  on  its  south  side,  near  Villeneuve.  Its  internal 
structure  has  been  laid  open  by  a  railway  cutting,  which  has  exposed 
to  view  three  layers  of  vegetable  soil,  each  of  which  has  once  formed 
the  surface  of  the  delta.  For  that  part  of  the  cone  which  is  above  the 
level  of  the  lake  is  for  the  most  part  covered  with  vegetation,  as  are 
generally  the  higher  and  unsubmerged  parts  of  all  river  deltas.  The 
uppermost  of  these  old  buried  soils,  about  five  feet  deep  from  the 
present  surface,  contained  Roman  tiles  and  a  coin ;  in  the  soil  next 
below,  six  inches  thick  and  ten  feet  from  the  surface,  were  found  pot- 
tery and  instruments  of  the  bronze  epoch  ;  and  in  the  third  soil,  which 
was  half  a  foot  thick  and  nineteen  feet  deep,  pottery,  pieces  of  char- 
coal, bones,  and  a  human  skeleton  having  a  small,  round,  and  very 
thick  skull,  of  the  brachycephalous  type  (fig.  104,  p.  113)  M.  Mor- 
lot estimates  the  Roman  relics  as  about  seventeen  centuries  old,  those 
of  the  bronze  age  between  3000  and  4000  years,  and  those  of  the 
stone  period  from  5000  to  7000  years.  To  the  entire  delta  he  ascribes 
an  antiquity  of  about  10,000  years,  while  he  conjectures  that  the 
higher  cone  or  delta,  which  is  ten  times  as  large,  may  have  taken 
about  100,000  years  for  its  formation.  It  contains,  as  above  stated, 
the  remains  of  the  mammoth,  and  is  probably  contemporaneous,  in  the 
geological  sense  of  the  term,  with  the  gravels  of  Amiens  and  Abbe- 
ville, from  which  so  many  flint  implements  of  an  antique  type  have 
been  extracted.  The  above  calculation  does  not  pretend  to  be  more 
than  a  rude  approximation  to  the  truth.  Ancient  as  are  the  upper 
terraces  when  compared  to  historical  times,  they  are  certainly  post- 
glacial, or  more  modern  than  the  glacial  period,  which  will  be  treated 
of  in  the  next  chapter.  In  other  words,  the  Alpine  glaciers  had 
already  shrunk  nearly  into  their  present  contracted  limits  before  even 
the  higher  deltas,  containing  the  mammoth  bones,  were  formed. 

Upraised  marine  strata  with  pottery  in  Sardinia. — The  most  eleva- 
ted marine  strata  of  the  post-pliocene  period  in  Europe,  in  which 
articles  of  human  workmanship  have  yet  been  noticed,  are  those 
observed  on  the  south  coast  of  Sardinia,  near  Cagliari,  so  well  de- 
scribed by  Count  Albert  de  la  Marmora.  They  consist  of  a  breccia, 
containing  fragments  of  limestone  and  numerous  shells  of  living 
Mediterranean  species,  such  as  the  eatable  oyster  and  mussel,  with 
both  valves  united.  Among  these  shells,  pieces  of  pottery  of  a  very 
rude  kind  are  dispersed.  They  are  traceable  to  a  height  of  300  feet 
above  the  sea.  In  the  vegetable  soil  covering  such  marine  strata,  frag- 
ments of  a  more  modern  or  Roman  pottery  have  been  found.  There 
are  also  in  the  rocks  of  the  same  district  numerous  fissures  filled  with 
breccia,  containing  the  remains  of  terrestrial  quadrupeds,  some  of 
them  of  extinct  species.  These  breccias,  although  very  ancient,^ as 
shown  by  mammalian  bones,  are  more  modern  than  the  marine 
post-pliocene  strata  with  pottery  above  mentioned,  for  some  of  the 


122  CAVERNS  IN  LIMESTONE.  [Cn.  X. 

shells,  the  Mytilus  edulis  for  example,  washed  out  of  the  older 
formation,  have  been  mingled  in  the  fissures  with  bones  of  the  extinct 
quadrupeds.* 

There  are  examples  in  Europe  of  marine  strata  characterized  in  like 
manner  by  embedded  shells  of  living  species  which  reach  elevations 
far  exceeding  those  of  Cagliari,  but  in  which  no  human  bones  or  works 
of  art  have  yet  been  discovered. 


CAVERN   DEPOSITS    CONTAINING   HUMAN    REMAINS    AND    BONES    OF 
EXTINCT    ANIMALS. 

In  England,  and  in  almost  all  countries  where  limestone  rocks  abound 
caverns  are  found,  usually  consisting  of  cavities  of  large  dimensions, 
connected  together  by  low,  narrow,  and  sometines  tortuous  galleries  or 
tunnels.  These  subterranean  vaults  are  usually  filled  in  part  with  mud, 
pebbles,  and  breccia,  in  which  bones  occur  belonging  to  the  same 
assemblage  of  animals  as  those  characterizing  the  post-pliocene  alluvia 
above  described.  Some  of  these  bones  are  referable  to  extinct  and 
others  to  living  species,  and  they  are  occasionally  intermingled,  as  in 
the  valley  gravels,  with  implements  of  one  or  other  of  the  great 
divisions  of  the  stone  age,  and  these  are  not  unfrequently  accompanied 
by  human  bones,  which  are  much  more  common  in  cavern  deposits 
than  in  valley  alluvium. 

Each  suite  of  caverns,  and  the  passages  by  which  they  communi- 
cate the  one  with  the  other,  afford  memorials  to  the  geologists  of  at 
least  three  successive  phases  through  which  the  physical  geography 
of  the  country  where  they  occur  must  have  passed.  First  there  was 
a  period  when  limestone  rocks  were  dissolved  on  a  great  scale,  and 
when  the  carbonate  of  lime  was  carried  out  gradually  by  springs  from 
the  interior  of  the  earth ;  secondly,  an  era  when  engulfed  rivers 
or  occasional  floods  swept  organic  and  inorganic  debris  into  the 
subterranean  hollows  previously  formed  ;  and  thirdly,  there  were  such 
changes  in  the  configuration  of  the  region  as  caused  the  engulfed 
rivers  to  be  turned  into  new  channels,  and  springs  to  be  dried  up, 
after  which  the  cave-mud,  breccia,  gravel,  and  fossil  bones  would 
bear  the  same  kind  of  relation  to  the  existing  drainage  of  the 
country  as  the  older  valley  drifts  with  their  extinct  mammalian 
remains  and  works  of  art  bear  to  the  present  rivers  and  alluvial 
plains. 

In  the  first  of  the  periods  above  supposed  the  operations  are  en- 
tirely subterranean.  We  know  that  in  every  limestone  district  the 
rain  water  is  soft  or  free  from  earthy  ingredients  when  it  falls  upon 
the  soil,  and  when  it  enters  the  rocks  below,  whereas  it  is  hard,  or 
charged  with  carbonate  of  lime,  when  it  issues  again  to  the  sur- 
face in  springs,  which,  by  failing  after  long  droughts,  and  by  in- 

*  LyelTs  Antiquity  of  Man,  p.  177. 


CH.  X.]  ORIGIN  OF  THE  STALACTITE. 

creasing  in  volume  after  rainy  seasons,  betray  their  dependence  for  a 
supply  of  water  on  atmospheric  sources.  The  rain  derives  some  of 
its  carbonic  acid  from  the  air,  but  much  more  from  the  decay  of 
vegetable  matter  in  the  soil  which  it  percolates,  and  by  the  excess 
of  this  acid,  limestone  is  dissolved,  and  the  water  becomes  charged 
with  carbonate  of  lime.  The  mass  of  solid  matter  silently  and  un- 
ceasingly subtracted  in  this  way  from  the  rocks  in  every  century  is 
considerable,  and  must  in  the  course  of  thousands  of  years  be  so  vast 
that  the  space  it  once  occupied  may  well  be  expressed  by  a  long  suite 
of  caverns.  The  varying  size  and  shape  of  these  will  be  determined 
by  innumerable  local  accidents,  such  as  the  direction  of  pre-existing 
rents  and  faults,  or  the  unequal  purity  and  consequent  solubility  of 
the  limestone  in  different  strata,  or  in  different  parts  of  the  same 
stratum. 

If  there  be  a  series  of  convulsions  and  movements  of  upheaval  and 
depression,  during  which  old  valleys  are  gradually  deepened  and 
widened,  or  new  ones  formed,  accompanied  by  the  rending  of  rocks 
in  many  places,  the  surface  drainage  may  in  time  be  so  altered  that 
streams  sweeping  along  angular  and  rounded  stones  may  break  into 
cavities  once  having  no  such  connexion  with  the  surface.  Such 
streams  may  introduce  fine  mud,  or  angular  and  rounded  pebbles  and 
land-shells,  with  portions  of  skeletons  of  various  quadrupeds,  or  of 
man,  together  with  fragments  of  works  of  art,  and  fill  up  a  large  part 
of  the  underground  rents,  galleries,  and  chambers  with  heterogeneous 
materials.  The  whole  of  these  may  sometimes  be  united  into  solid 
breccias  and  conglomerates  by  stalactitic  infiltrations. 

In  the  descriptions  given  of  violent  earthquakes  we  read  of  the 
sudden  appearance  of  new  fissures  several  feet  wide,  often  of  great 
depth,  and  some  of  which  remain  permanently  open.  Wild  animals 
chased  by  beasts  of  prey  fall  into  such  natural  pit-falls  ;  the  pursued 
and  the  pursuer  perishing  together.  Their  bones,  during  the  slow 
decay  of  the  carcase,  may  be  carried  separately  into  subterranean 
vaults,  or  many  of  them  still  bound  together  by  ligaments ;  even 
entire  skeletons  may  sometimes  be  washed  into  caves  and  be  there 
preserved. 

The  quarrying  away  of  large  masses  of  Carboniferous  and  Devo- 
nian limestone,  near  Liege,  in  Belgium,  has  afforded  the  geologist 
magnificent  sections  of  some  of  these  caverns,  and  the  former  com- 
munication of  cavities  in  the  interior  of  the  rocks  with  the  old  sur- 
face of  the  country  by  means  of  vertical  or  oblique  fissures,  has  been 
demonstrated  in  places  where  it  would  not  otherwise  have  been 
suspected,  so  completely  have  the  upper  extremities  of  these  fissures 
been  concealed  by  superficial  drift,  while  their  lower  ends,  which 
extended  into  the  roofs  of  the  caves,  are  masked  by  stalactitic  incrus- 
tations. 

The  origin  of  the  stalactite  is  thus  explained  by  the  eminent 
chemist  Liebig.  On  the  surface  of  Franconia,  where  the  limestone 


124:  'CAVES  AT  ENGIHOUL  AND  BRIXHAM.  [Cn.  X. 

abounds  in  caverns,  is  a  fertile  soil,  in  which  vegetable  matter  is  con- 
tinually decaying.  This  mould  or  humus,  being  acted  on  by  moisture 
and  air,  evolves  carbonic  acid,  which  is  dissolved  by  rain.  The  rain 
water,  thus  impregnated,  permeates  the  porous  limestone,  dissolves  a 
portion  of  it,  and  afterwards,  when  the  excess  of  carbonic  acid  evap- 
orates in  the  caverns,  parts  with  the  calcareous  matter,  and  forms 
stalactite.  Even  while  caverns  are  still  liable  to  be  occasionally  flooded 
such  calcareous  incrustations  accumulate,  but  it  is  generally  when  they 
are  no  longer  in  the  line  of  drainage  that  a  solid  floor  of  hard  stalag- 
mite is  found  on  the  bottom.  On  the  whole,  the  circumstances  under 
which  an  organic  body  is  usually  introduced  into  a  cave  are  far 
more  favourable  to  its  preservation  than  those  which  accompany  its 
envelopment  in  valley-alluvium  ;  for  where  the  mud  or  stones  are 
connected  together  by  carbonate  of  line,  the  free  percolation  of 
water,  and  consequent  decay  and  removal  of  the  bones  or  shells,  are 
arrested. 

The  late  Dr.  Schmerling  examined  forty  caves  near  Liege,  and  found 
in  all  of  them  the  remains  of  the  same  fauna,  comprising  the  mam- 
moth tichorhine  rhinoceros,  cave-bear,  cave-hya3na,  cave-lion,  and  many 
others,  some  of  extinct  and  some  of  living  species,  and  in  all  of  them 
flint  implements.  In  four  or  five  caves  only  parts  of  human  skeletons 
were  met  with,  comprising  sometimes  skulls  with  a  few  other  bones, 
sometimes  nearly  every  part  of  the  skeleton  except  the  skull.  In  one 
of  the  caves,  that  of  Engihoul,  where  Schmerling  had  found  the  re- 
mains of  at  least  three  human  individuals,  they  were  mingled  in  such 
a  manner  with  bones  of  extinct  mammalia,  as  to  leave  no  doubt  on  his 
mind  of  man  having  coexisted  with  them. 

In  1860,  Professor  Malaise,  of  Liege,  explored  with  me  this  same 
cave  of  Engihoul,  and  beneath  a  hard  floor  of  stalagmite  we  found 
mud  full  of  the  bones  of  extinct  and  living  animals,  such  as  Schmer- 
ling had  described,  and  my  companion,  persevering  in  his  researches 
after  I  had  returned  to  England,  extracted  from  the  same  deposit  two 
human  lower  jaw-bones  retaining  their  teeth.  The  skulls  from  these 
Belgian  caverns  display  no  marked  deviation  from  the  normal  Euro- 
pean type  of  the  present  day.  One  of  them,  for  example,  obtained 
by  Schmerling  from  the  Engis  cave,  situated  on  the  left  bank  of  the 
Meuse,  is  now  preserved  in  the  museum  of  the  University  of  Liege, 
and  agrees  with  the  long-headed  type  (fig.  105,  p.  113),  and  not  with 
the  short  round  form  which  seems,  in  Scandinavia  at  least,  to  have 
been  the  more  ancient  of  the  two. 

The  careful  investigations  carried  on  by  Dr.  Falconer,  Mr.  Pengelly, 
and  others,  in  the  Brixham  cave  near  Torquay,  in  1858,  demonstrated 
that  flint  knives  were  there  embedded  in  such  a  manner  in  loam 
underlying  a  floor  of  stalagmite  as  to  prove  that  man  had  been  an 
inhabitant  of  that  region  when  the  cave-bear  and  other  members  of 
the  ancient  post-pliocene  fauna  were  also  in  existence. 

The  certainty  of  the  data  on  which  this  conclusion  was  founded 


CH.  X.]  REINDEER  PERIOD  IN  FRANCE. 

had  no  small  influence  in  inducing  many  English  and  French  geolo- 
gists to  appreciate  more  justly  the  opinion  at  which  M.  Boucher  de 
Perthes  had  arrived  after  his  researches  at  Abbeville  before  men- 
tioned, which  were  still  regarded  by  the  scientific  public  in  general 
with  skepticism  and  suspicion. 

The  absence  of  gnawed  bones  had  led  Dr.  Schmerling  to  infer  that 
none  of  the  Belgian  caves  which  he  explored  had  served  as  the  dens 
of  wild  beasts ;  but  there  are  many  caves  in  Germany  and  England 
which  have  certainly  been  so  inhabited,  especially  by  the  extinct 
hyaena  and  bear. 

A  fine  example  of  a  hyaena's  den  was  afforded  by  the  cave  of  Kirk- 
dale,  so  well  described  by  the  late  Dr.  Buckland  in  his  Reliquiae  Dilu- 
viance.  In  that  cave,  about  twenty-five  miles  N.N.E.  of  York,  the 
remains  of  about  300  hyaenas,  belonging  to  individuals  of  every  age, 
were  detected.  The  species  (Hyaena  spelcea)  is  extinct,  and  was 
larger  than  the  fierce  Hycena  crocuta  of  South  Africa,  which  it  most 
resembled.  Dr.  Buckland,  after  carefully  examining  the  spot,  proved 
that  the  hyaenas  must  have  lived  there ;  a  fact  attested  by  the  quan- 
tity of  their  dung,  which,  as  in  the  case  of  the  living  hyaena,  is  of 
nearly  the  same  composition  as  bone,  and  almost  as  durable.  In  the 
cave  were  found  the  remains  of  the  ox,  young  elephant,  hippopota- 
mus, rhinoceros,  horse,  bear,  wolf,  hare,  water-rat,  and  several  birds. 
All  the  bones  have  the  appearance  of  having  been  broken  and  gnawed 
by  the  teeth  of  the  hyaenas ;  and  they  occur  confusedly  mixed  in  loam 
or  mud,  or  dispersed  through  a  crust  of  stalagmite  which  covers  it. 
In  these  and  many  other  cases  it  is  supposed  that  portions  of  herbiv- 
orous quadrupeds  have  been  dragged  into  caverns  by  beasts  of  prey, 
and  have  served  as  their  food — an  opinion  quite  consistent  with  the 
known  habits  of  the  living  hyaena. 

Reindeer  period  in  South  of  France. — In  the  larger  number  of  the 
caves  of  Europe,  as  for  example  in  those  of  England,  Belgium,  Ger- 
many, and  many  parts  of  France,  the  animal  remains  agree  specifi- 
cally with  the  fauna  of  the  oldest  division  of  the  age  of  stone,  or  that 
to  which  belongs  the  drift  of  Amiens  and  Abbeville  already  men- 
tioned, containing  flint  implements  of  a  very  antique  type.  But 
there  are  some  caves  in  the  departments  of  Dordogne,  Aude,  and 
other  parts  of  the  south  of  France,  which  are  believed  by  M.  Lartet 
to  be  of  intermediate  date  between  that  ancient  division  of  the  stone 
age  and  the  more  modern  one  which  is  represented  by  the  Swiss 
lake-dwellings.  To  this  intermediate  era  M.  Lartet  gave,  in  1863,  the 
name  of  the  "  reindeer  period,"  because  vast  quantities  of  the  bones 
and  horns  of  that  deer  have  been  met  with  in  those  French  caverns. 
In  some  cases  separate  plates  of  molars  of  the  mammoth,  and  several 
teeth  of  the  great  Irish  deer,  Cervus  Megaceros,  have  been  found 
mixed  up  with  cut  and  carved  bones  of  reindeer ;  but  whether  these 
extinct  quadrupeds  were  really  contemporaneous  at  the  era  in  ques- 
tion with  man  and  the  reindeer,  is  not  yet  clearly  made  out.  Al- 


126  AUSTRALIAN   CAVE-BRECCIAS.  [Cn.  X. 

though  the  mammalian  fauna  consists  of  living  species,  the  presence 
of  the  reindeer,  marmot,  and  some  other  northern  animals,  seems  to 
imply  a  colder  climate  than  that  of  the  Swiss  lake-dwellings,  in  which 
no  remains  of  reindeer  have  as  yet  been  discovered.  The  absence  of 
these  in  the  old  lacustrine  habitations  of  Switzerland  is  the  more  sig- 
nificant, because  in  a  cave  in  the  neighborhood  of  the  Lake  of  Ge- 
neva, namely,  that  of  Mont  Saleve,  bones  of  the  reindeer  occur  with 
flint  implements  similar  to  those  of  the  caverns  of  Dordogne  and 
Perigord. 

The  state  of  the  arts,  as  exemplified  by  the  instruments  found  in 
these  caverns  of  the  reindeer  period,  is  somewhat  more  advanced 
than  that  which  characterizes  the  tools  of  the  Amiens  drift,  but  is 
nevertheless  more  rude  than  that  of  the  Swiss  lake-dwellings.  No 
metallic  articles  occur,  and  the  stone  hatchets  are  not  ground  after 
the  fashion  of  celts ;  but  some  of  the  bones  are  artistically  carved,  so 
as  to  represent  animals ;  and  the  needles  of  bone  are  shaped  in  a 
workmanlike  style,  having  their  eyes  drilled  with  consummate  skill. 

Australian  cave-breccias. — Ossiferous  breccias  are  not  confined  to 
Europe,  but  occur  in  all  parts  of  the  globe ;  and  those  discovered  in 
fissures  and  caverns  in  Australia  correspond  closely  in  character  with 
what  has  been  called  the  bony  breccia  of  the  Mediterranean,  in  which 
the  fragments  of  bone  and  rock  are  firmly  bound  together  by  a  red 
ochreous  cement. 

Some  of  these  caves  were  examined  by  the  late  Sir  T.  Mitchell  in 
the  Wellington  Valley,  about  210  miles  west  of  Sidney,  on  the  river 
Bell,  one  of  the  principal  sources  of  the  Macquarie,  and  on  the  Mac- 
quarie  itself.  The  caverns  often  branch  off  in  different  directions 
through  the  rock,  widening  and  contracting  their  dimensions,  and 
the  roofs  and  floors  are  covered  with  stalactite.  The  bones  are 
often  broken,  but  do  not  seem  to  be  water-worn.  In  some  places 
they  lie  imbedded  in  loose  earth,  but  they  are  usually  included  in  a 
breccia. 

,  The  remains  found  most  abundantly  are  those  of  the  kangaroo,  of 
which  there  are  four  species,  besides  which  the  genera  Hypsiprym- 
nus,  Phalangista,  Phascolomys,  and  Dasyurus,  occur.  There  are  also 
bones,  formerly  conjectured  by  some  osteologists  to  belong  to  the 
hippopotamus,  and  by  others  to  the  dugong,  but  which  are  now  re- 
ferred by  Mr.  Owen  to  a  marsupial  genus,  allied  to  the  Wombat. 

In  the  fossils  above  enumerated,  several  species  are  larger  than 
the  largest  living  ones  of  the  same  genera  now  known  in  Australia. 
The  preceding  figure  of  the  right  side  of  a  lower  jaw  of  a  kangaroo 
(Macropus  atlas,  Owen)  will  at  once  be  seen  to  exceed  in  magnitude 
the  corresponding  part  of  the  largest  living  kangaroo,  which  is  repre- 
sented in  fig.  111.  In  both  these  specimens  part  of  the  substance  of 
the  jaw  has  been  broken  open,  so  as  to  show  the  permanent  false 
molar  (a,  fig.  110)  concealed  in  the  socket.  From  the  fact  of  this 
molar  not  having  been  cut,  we  learn  that  the  individual  was  young, 


CH.  X.] 


GEOGRAPHICAL  RELATIONS  OF  FOSSILS. 


127 


and  had  not  shed  its  first  teeth.     In  fig.  112  a  front  tooth  of  the 
same  species  of  kangaroo  is  represented. 

Fig.  110. 


Part  of  lower  jaw  of  Macropus  atlas.    Owen.    A  young  individual  of  an  extinct  species. 
a.  Permanent  false  molar,  in  the  alveolus. 


Fig.  111. 


Lower  jaw  of  largest  living  species  of  kangaroo. 
(Macropus  major.) 


Fig.  112. 


The  reader  will  observe  that  these  extinct  quadrupeds 
of  Australia  belong  to  the  marsupial  family,  or,  in  other 
words,  that  they  are  referable  to  the  same  peculiar  type 
of  organization  which  now  distinguishes  the  Australian 
mammalia  from  those  of  other  parts  of  the  globe.  This 
fact  is  one  of  many  pointing  to  a  general  law  deducible 
from  the  fossil  vertebrate  and  invertebrate  animals  of 
times  immediately  antecedent  to  our  own,  namely,  that 
the  present  geographical  distribution  of  organic  forms 
dates  back  to  a  period  anterior  to  the  origin  of  existing 
species;  in  other  words,  the  limitation  of  particular 
genera  or  families  of  quadrupeds,  mollusca,  &c.,  to  cer- 
tain existing  provinces  of  land  and  sea,  began  before  the 
larger  part  of  the  species  now  contemporary  with  man 
had  been  introduced  into  the  earth. 

Professor  Owen,  in  his  excellent  "History  of  British  Fossil  Mam- 


128  GEOGRAPHICAL  RELATIONS  OF  FOSSILS.  [Cn.  X. 

mals,"  has  called  attention  to  this  law,  remarking  that  the  fossil 
quadrupeds  of  Europe  and  Asia  differ  from  those  of  Australia  or 
South  America.  We  do  not  find,  for  example,  in  the  EuropaBO- 
Asiatic  province  fossil  kangaroos  or  armadillos,  but  the  elephant, 
rhinoceros,  horse,  bear,  hyaBna,  beaver,  hare,  mole,  and  others,  which 
still  characterize  the  same  continent. 

In  like  manner,  in  the  Pampas  of  South  America  the  skeletons  of 
Megatherium,  Megalonyx,  Glyptodon,  Mylodon,  Toxodon,  Macrau- 
chenia,  and  other  extinct  forms,  are  analogous  to  the  living  sloth, 
armadillo,  cavy,  capybara,  and  llama.  The  fossil  quadrumana,  also 
associated  with  some  of  these  forms  in  the  Brazilian  caves,  belong 
to  the  Platyrrhine  family  of  monkeys,  now  peculiar  to  South  Amer- 
ica. That  the  extinct  fauna  of  Buenos  Ayres  and  Brazil  was  very 
modern  has  been  shown  by  its  relation  to  deposits  of  marine  shells, 
agreeing  with  those  now  inhabiting  the  Atlantic ;  and  when  in 
Georgia,  in  1845,  I  ascertained  that  the  Megatherium,  Mylodon, 
Equus  curvidens,  and  other  quadrupeds  aHied  to  the  Pampean  type, 
collected  by  Mr.  Hamilton  Couper,  were  posterior  in  date  to  beds  con- 
taining marine  shells  belonging  to  forty-five  recent  species  of  the 
neighboring  sea. 

There  are  indeed  some  cosmopolite  genera,  such  as  the  Mastodon 
(a  genus  of  the  elephant  family)  and  the  horse,  which  were  simul- 
taneously represented  by  different  fossil  species  in  Europe,  North 
America,  and  South  America ;  but  these  few  exceptions  can  by  no 
means  invalidate  the  rule  which  has  been  thus  expressed  by  Professor 
Owen,  that  in  "  the  highest  organized  class  of  animals  the  same 
forms  were  restricted  to  the  same  great  provinces  at  the  Pliocene 
periods  (and  we  may  add  Post-pliocene)  as  they  are  at  the  present  day." 

However  modern,  in  a  geological  point  of  view,  we  may  consider 
the  Newer  Pliocene  and  Post-pliocene  epochs,  it  is  evident  that  causes 
more  general  and  powerful  than  the  intervention  of  man  have  occasioned 
the  disappearance  of  the  ancient  fauna  from  so  many  extensive  re- 
gions. Not  a  few  of  the  species  had  a  wide  range  ;  the  same  Mega- 
therium, for  instance,  extended  from  Patagonia  and  the  river  Plata  in 
South  America,  between  latitudes  31°  and  39°  south,  to  correspond- 
ing latitudes  in  North  America,  the  same  animal  being  also  an  inhabi- 
tant of  the  intermediate  country  of  Brazil,  where  its  fossil  remains 
have  been  met  with  in  caves.  The  mammoth  (Elephas  primigenius) 
has  been  likewise  found  fossil  in  North  America,  and  again  in  the 
'  eastern  hemisphere  from  Siberia  to  the  south  of  Europe.  If  it  be 
objected  that,  notwithstanding  the  adaptation  of  such  quadrupeds  to  a 
variety  of  climates  and  geographical  conditions,  their  great  size  ex- 
posed them  to  extermination  by  the  first  hunter  tribes,  we  may  observe 
that  the  investigations  of  Lund  and  Clausen  in  the  ossiferous  limestone 
caves  of  Brazil  have  demonstrated  that  these  large  mammalia  were 
associated  with  a  great  many  smaller  quadrupeds,  some  of  them  ab 
diminutive  as  field-mice,  which  have  all  died  out  together,  while  the 


CH.  X.]  LAW  OF  GEOGRAPHICAL   RELATIONSHIP. 


129 


land-shells  formerly  their  contemporaries  still  continue  to  exist 
in  the  same  countries.  As  we  may  feel  assured  that  these  minute 
quadrupeds  could  never  have  been  extirpated  by  man,  especially  in  a 
country  so  thinly  peopled  as  Brazil,  so  we  may  conclude  that  all  the 
species,  small  and  great,  have  been  annihilated  one  after  the  other,  in 
the  course  of  indefinite  ages,  by  those  changes  of  circumstances  in 
the  organic  and  inorganic  world  which  are  always  in  progress,  and  are 
capable  in  the  course  of  time  of  greatly  modifying  the  physical  geogra- 
phy, climate,  and  all  other  conditions  on  which  the  continuance  upon 
the  earth  of  any  living  being  must  depend.* 

The  law  of  geographical  relationship  above  alluded  to,  between  the 
living  vertebrata  of  every  great  zoological  providence  and  the  fossils 
of  the  period  immediately  antecedent,  even  where  the  fossil  species 
are  extinct,  is  by  no  means  confined  to  the  mammalia.  New  Zea- 
land, when  first  examined  by  Europeans,  was  found  to  contain  no  in- 
digenous land  quadrupeds,  no  kangaroos,  or  opossums,  like  Australia ; 
but  a  wingless  bird  abounded  there,  the  smallest  living  representative 
of  the  ostrich  family,  called  the  Kiwi  by  the  natives  (Apteryx).  In 
the  fossils  of  the  Post-pliocene  period  in  this  same  island,  there  is  the 
like  absence  of  kangaroos,  opossums,  wombats,  and  the  rest ;  but  in 
their  place  a  prodigious  number  of  well-preserved  specimens  of  gigan- 
tic birds  of  the  struthious  order,  called  by  Owen  Dinornis  and 
Palapteryx,  which  are  entombed  in  superficial  deposits.  These  genera 
comprehended  many  species,  some  of  which  were  four,  some  seven, 
others  nine,  and  others  eleven  feet  in  height !  It  seems  doubtful 
whether  any  contemporary  mammalia  shared  the  land  with  this  popu- 
lation of  gigantic  feathered  bipeds. 

Mr.  Darwin,  when  describing  the  recent  and  fossil  mammalia  of 
South  America,  has  dwelt  much  on  the  wonderful  relationship  of  the 
extinct  to  the  living  types  in  that  part  of  the  world,  inferring  from 
such  geographical  phenomena  that  the  existing  species  are  all  re- 
lated to  the  extinct  ones  which  preceded  them  by  a  bond  of  common 
descent. 

The  late  able  naturalist,  Edward  Forbes,  had  declared  in  1846  his 
conviction  that,  not  only  the  great  extinct  deer,  Cervus  megaceros,  but 
also  the  mammoth,  and  other  lost  pachyderms  and  carnivora,  lived  in 
Britain  after  the  extreme  cold  of  the  glacial  period  had  passed  away.f 
More  recent  observations  by  Mr.  Prestwich  and  Dr.  Falconer,  on  the 
fossil  contents  of  the  drift  and  cave  deposits  of  England,  have  confirmed 
this  opinion,  and  have  also  proved  that  a  larger  number  of  the  lost 
species  than  Forbes  probably  suspected  were  posterior  in  date  to  the 
submergence  of  central  England  beneath  the  waters  of  the  glacial  sea 
— an  event  which  will  be  spoken  of  in  the  twelfth  chapter.  Mr. 
Prestwich  has  pointed  out  that  there  are  some  contortions  of  the 

*  See  Principles  of  Geology,  chaps,  xli.  to  xliv. 
f  Memoirs  of  Geol.  Survey,  pp.  394,  397. 


130  RELATIONSHIP  OF  EXTINCT  TO  LIVING  TYPES         [On.  X. 

strata  in  the  higher  level  gravels  of  the  Seine  and  Somme  which  in- 
dicate ice-action,  such  as  might  be  caused  by  the  freezing  over  of  the 
rivers  in  winter,  as  now  happens  in  corresponding  latitudes  in  Canada. 
As  these  higher-level  gravels,  which  contain  human  implements 
mingled  with  remains  of  extinct  mammalia,  approach  in  age  to  the 
glacial  period  in  proportion  as  they  recede  to  a  greater  distance  from 
our  time,  it  is  natural  that  we  should  discover  in  them  some  indica- 
tions of  a  colder  climate.  Accordingly,  in  addition  to  the  disturbed 
stratification,  a  phenomenon  to  which  I  shall  again  allude  in  the 
sequel,  p.  156,  the  large  dimension  of  many  angular  fragments  of  rock 
buried  in  the  higher  gravel,  and  which  have  been  transported  from 
great  distances  in  the  same  hydrographical  basins,  afford  corrobora- 
tive indications  of  ice-action. 

If  it  be  asked  whether  the  character  of  the  fluviatile  and  land-shells 
of  the  same  post-pliocene  drifts  also  implies  a  colder  climate,  it  may 
be  said  that  they  are  generally  of  the  same  species  as  those  now  in- 
habiting the  same  districts,  but  most  of  them  have  now  so  wide  a 
northward  range  into  Norway  and  Finland,  that  they  may  perhaps 
have  nourished  when  the  cold,  especially  in  winter,  was  greater  than 
now.  But  Avhen  we  contemplate  the  whole  of  the  evidence  as  to 
climate  derived  from  a  wide  area  in  Europe,  we  find  it  to  be  very 
conflicting,  owing  possibly  to  post-glacial  fluctuations  in  temperature, 
occasioning  the  migrations  of  quadrupeds  from  north  to  south  and 
from  south  to  north,  during  different  seasons  of  the  same  year,  or 
during  successive  stages  of  the  same  era.  The  reindeer  and  the 
musk-buffalo,  JBubalus  moschatus,  are  well  known  as  living  inhabi- 
tants of  the  Arctic  regions,  and  they  both  occur  fossil  in  the  valley  of  the 
Thames,  and  in  that  of  the  Avon,  near  Batheaston,  as  well  as  in  the 
drift  of  the  valley  of  the  Oise,  a  tributary  of  the  Seine.  The  same 
buffalo  has  also  been  met  with  in  the  post-pliocene  drift  of  North 
Germany,  at  the  gates  of  Berlin,  where,  as  in  England,  it  accompanied 
the  mammoth,  Elephas  primigenius,  and  the  two-horned,  or  woolly 
rhinoceros,  R.  tichorhinus.  The  last-mentioned  mammalia  were  both 
of  them  found  by  Pallas  preserved  with  their  flesh  in  the  frozen  gravel 
of  Siberia,  and  they  have  also  been  met  with  in  the  drift  of  North 
Germany,  near  Quedlinburg,  associated  with  the  Norwegian  lemming, 
Myodes  lemmus,  and  another  species  of  the  same  family,  called  by 
Pallas  Myodes  torquatus  (by  Hensel  Misothermus  torquatus),  a  still 
more  Arctic  quadruped,  for  it  was  observed  by  Parry  in  lat.  82°  N., 
and  is  said  never  to  stray  farther  south  than  the  northern  borders  of 
the  woody  region. 

No  instance  has  yet  occurred  in  North  Germany  of  the  association 
of  these  lemmings,  reindeer,  and  musk-buffalos,  with  the  hippopotamus. 
When  the  latter  genus  occurs  in  England,  it  is  usually  accompanied 
by  JSlephas  antiquus,  and  Rhinoceros  hemitoechos  (Falc.),  or  sometimes 
with  Rhinoceros  leptorhinus. 

At  Gray's  Thurrock,  in  Essex,  on  the  left  or  north  bank  of  the 


CH.  X.]  FLUCTUATIONS  OF  CLIMATE. 


131 


Thames,  where  the  three  pachyderms  last  enumerated  are  found 
together,  a  fossil  shell,  Cyrena  fluminalis,  is  abundant,  which  no  longer 
lives  in  any  European  river,  but  still  inhabits  the  Nile  and  parts  of 
Asia.  With  it,  in  the  same  sand  and  gravel,  the  Unio  littoralis  occurs, 
now  extinct  in  Britain,  but  still  living  in  the  Seine  and  Loire  in 
France.  It  may  be  contended  that  when  the  Cyrena  fluminalis 
abounded  in  the  Thames,  the  hippopotamus  may  have  been  suited  to 
the  same  climate,  just  as  the  same  mollusk  and  the  living  hippo- 
potamus now  coexist  in  the  Nile.  We  may  doubtless  imagine  that 
during  the  countless  centuries  which  may  have  passed  away  since  the 
glacial  epoch,  there  have  been  oscillations  of  temperature,  in  the 
course  of  which  certain  members  of  a  m6*re  southern  fauna  migrated 
northwards,  and  then  retreated  again  when  a  succession  of  less  genial 
seasons  prevailed,  while  other  migrations  in  an  opposite  direction 
took  place  whenever  there  was  a  change  from  a  warmer  to  a  colder 
climate. 

In  the  valley  of  the  Somme  the  rude  flint  tools  before  mentioned, 
page  116,  have  been  found  at  Menchecourt,  near  Abbeville,  associated 
with  the  Cyrena  fluminalis,  and  with  the  Hippopotamus  major. 
These  were  met  with  in  the  lower  level  post-pliocene  gravel,  and  may 
be  referable,  as  Mr.  Prestwich  has  suggested,  to  a  period  when  the 
climate  was  somewhat  warmer  than  that  of  the  higher  level  drift  of 
this  same  valley.  It  is  in  that  higher  and  older  drift  at  St.  Acheul, 
near  Amiens,  that  flint  implements  have  been  found  in  the  greatest 
number,  together  with  the  bones  of  the  elephant  and  other  post- 
pliocene  quadrupeds,  so  that  man  must  have  existed  through  several 
successive  phases  of  the  geography  and  climate  of  that  region  in 
prehistoric  times. 

In  1863,  several  individuals  of  the  Greenland  lemming,  and  several 
of  a  new  species  of  Spermophilus,  an  Arctic  type  allied  to  the  mar- 
mot, were  found  by  Dr.  Blackmore  in  the  ancient  alluvium  of  the 
Wiley  near  Salisbury,  in  lower-level  drift,  rising  about  thirty  feet 
abpve  the  present  water  meadows.  They  were  associated  with  the 
mammoth,  tichorine  rhinoceros,  cave  hya3na,  reindeer,  and  many  other 
mammalia,  probably  suited,  like  them,  to  a  cold  climate.  In  the  im- 
mediate vicinity  occurs  a  higher  level  gravel,  ninety  feet  above  the 
Wiley,  from  which  flint  implements,  much  rolled  and  resembling 
some  of  those  at  Amiens,  have  been  obtained.  After  examining  the 
spot,  I  agree  with  Dr.  Blackmore,  that  these  flint  tools,  and  the  gravel 
in  which  they  are  embedded,  are  older  than  the  deposits  containing 
the  extinct  mammalia,  so  that  in  this  instance  we  cannot  suppose, 
as  in  the  case  of  Menchecourt  above  alluded  to,  that  the  fossils  of 
the  more  modern  or  lower-level  deposit  indicate  a  more  genial 
climate. 

Nearly  all  the  known  post-pliocene  quadrupeds  have   now    I 
found  either  in  valley  drifts  or  cave  deposits  in  England  or  on  the 
Continent,  accompanying  flint  knives  or  hatchets  in  such  a  way  as  to 


132  RELATIVE  LONGEVITY  OF  SPECIES.  [On.  X. 

imply  the  co-existence  of  the  same  mammalia  with  man.  The  antiquity, 
therefore,  of  the  human  race  may  be  inferred  from  the  concurrent 
testimony  of  several  independent  classes  of  geological  facts.  In  the 
first  place,  the  disappearance  of  many  wild  animals  from  a  large  con- 
tinent, even  where  man  has  been  an  active  agent  of  extermination, 
must  always  require  a  considerable  lapse  of  time  for  its  accomplish- 
ment ;  indeed,  before  the  invention  of  fire-arms,  it  is  hard  to  say  how 
many  centuries  it  would  take  to  bring  about  such  utter  extirpation.  Yet 
there  can  be  no  doubt  that  many  species  became  extinct  after  man 
was  a  denizen  of  the  earth,  and  before  the  Danish  shell-mounds  were 
formed,  or  the  oldest  of  the  Swiss  lake-dwellings  constructed.  Sec- 
ondly, thousands  of  years  mhst  have  been  required  to  enable  rivers  to 
deepen  and  widen  their  valleys,  and  to  grind  down  fragments  of  rock 
into  mud,  sand,  and  pebbles,  on  such  a  scale  as  to  produce  the  old 
valley  gravels,  both  higher  and  lower,  containing  flint  implements  and 
the  bones  of  extinct  mammalia.  Thirdly,  much  time  is  also  demand- 
ed to  enable  springs  and  engulfed  rivers  to  change  their  courses,  and 
for  caves  which  once  lay  in  the  line  of  a  great  subterranean  drainage 
to  become  dry,  and  to  have  their  floors  encrusted  over  with  a  hard 
covering  of  stalagmite.  Lastly,  ages  must  have  been  required  to 
bring  about  such  a  change  in  the  climate  of  a  wide  region  as  to  cause 
the  winters  to  be  less  severe,  and  the  geographical  distribution  of 
certain  species  of  mammalia  and  land  and  freshwater  shells  to  vary. 
The  length  of  the  historical  epoch,  even  if  assumed  to  be  3000  or 
4000  years,  does  not  furnish  us  with  any  appreciable  measure  for  cal- 
culating the  number  of  centuries  which  would  suffice  for  such  a  series 
of  changes,  which  are  by  no  means  of  a  local  character,  but  have 
already  been  traced  from  England  and  the  North-west  of  France  to 
Sardinia  and  Sicily. 

Relative  longevity  of  species  in  the  mammalia  and  testacea. — I  called 
attention,  in  1830,*  to  the  fact  which  had  not  at  that  time  attracted 
notice,  that  the  association  in  the  post-pliocene  deposits  of  shells, 
exclusively  of  living  species,  with  many  extinct  quadrupeds,  beto- 
kened a  longevity  of  species  in  the  testacea  far  exceeding  that  in  the 
mammalia.  Subsequent  researches  seem  to  show  that  this  greater 
duration  of  the  same  specific  forms  in  the  class  mollusca  is  dependent 
i  on  a  still  more  general  law,  namely,  that  the  lower  the  grade  of  ani- 
mals, or  the  greater  the  simplicity  of  their  structure,  the  more  per- 
sistent are  they  in  general  in  their  specific  characters  throughout  vast 
periods  of  time.  Not  only  have  the  invertebrata,  as  shown  by  geo- 
logical data,  altered  at  a  less  rapid  rate  than  the  vertebrata,  but  if  we 
take  one  of  the  classes  of  the  former,  as  for  example  the  mollusca,  we 
find  those  of  more  simple  structure  to  have  varied  at  a  slower  rate 
than  those  of  a  higher  and  more  complex  organization  ;  the  brachio- 
poda,  for  example,  more  slowly  than  the  lamellibranchiate  bivalves, 

*  Principles  of  Geology,  1st  ed.  vol.  iii.  p.  140. 


CH.  X.] 


TEETH  OF  EXTINCT  MAMMALIA. 


133 


while  the  latter  have  been  more  persistent  than  the  univalves,  whether 
gasteropoda  or  cephalopoda.  In  like  manner  the  specific  identity  of 
the  characters  of  the  foraminifera,  which  are  among  the  lowest  types 
of  the  invertebrata,  has  outlasted  that  of  the  mollusca  in  an  equally 
decided  manner. 

Teeth  of  post-pliocene  mammalia. — To  those  who  have  never  studied 

Fig.  112  a. 


Elephas  primigenius  (or  Mammoth) ;  molar  of  upper  jaw,  right  side ;  one  third  of  nat.  size. 
Post-pliocene.  a.  Grinding  surface.  6.  Side  view. 

comparative  anatomy,  it  may  seem  scarcely  credible  that  a  single 
bone  taken  from  any  part  of  the  skeleton  may  enable  a  skilful  oste- 
ologist  to  distinguish,  in  many  cases,  the  genus,  and  sometimes  the 
species,  of  quadruped  to  which  it  belonged.  Although  few  geologists 
can  aspire  to  such  knowledge,  which  must  be  the  result  of  long  prac- 
tice and  study,  they  will  nevertheless  derive  great  advantage  from 
learning,  what  is  comparatively  an  easy  task,  to  distinguish  the  prin- 
cipal divisions  of  the  mammalia  by  the  forms  and  characters  of  their 
teeth. 

The  annexed  figures  represent  the  teeth  of  some  of  the  more  com- 
mon species  and  genera  found  in  alluvial  and  cavern  deposits. 

Fig.  113. 


Elephas  diitiqitu?,  Falconer.     Fc-iiuitmi  i!e  molar,  one-third  of  nat.  size. 

Post-pi;  >ccne  and  pliocene. 


134 


TEETH  OF  EXTINCT  MAMMALIA. 
Fig.  114, 


[Cn.  X. 


Elephas  meridional/is,  Nesti.    Penultimate  molar,  one-third  of  nat.  size. 
Post-pliocene  aiid  pliocene. 


Fig.  115. 


Fig.  116. 


Fig.  117. 


Rhinoceros  leptorhinus,  Cu- 
vier  =  Rhin.  megarhinus, 
Christol;  fossil  from  fresh- 
water beds  of  Grays,  Essex 
(see  p.  130);  penultimate 
molar,  lower  jaw,  left  side ; 
two-thirds  of  nat.  size.  Post- 
pliocene  and  Newer  Plio- 


RMnoceros  tiehorhinus  ;  pen- 
ultimate molar,  lower  jaw, 
left  side ;  two- thirds  of  nat. 
size.  Post-pliocene. 


Hippopotamus ;  from  cave 
near  Palermo ;  molar  tooth ; 
two-thirds  of  nat.  size.  Post- 
pliocene. 


Fig.  118. 


Fig.  119 


Pig. 

Sus  scrofa,  L.  (common 
pig) ;  from  shell-marl.  For- 
farshire;  posterior  molar, 
lower  jaw,  nat.  size.  Ke- 
cent. 


Horse. 

Eqwus  caballus,  L.  (common  horse); 
from  the  shell-marl,  Forfarshire ;  sec- 
ond molar,  lower  jaw.  Eecent. 

a.  Grinding  surface,  two-thirds  nat.  size. 
&.  Side  view  of  same,  half  nat.  size. 


On  comparing  the  grinding  surfaces  of  the  corresponding  molars 


CH.  X.] 


TEETH   OF   EXTINCT   MAMMALIA. 


135 


of  the  three  species  of  elephants,  figs.  112  a,  113,  114,  it  will  be  seen 
that  the  folds  of  enamel  are  most  numerous  in  the  mammoth,  fewer 
and  wider,  or  more  open,  in  E.  antiquus,  and  most  open  and  fewest 
in  E.  meridionalis.  It  will  be  also  seen  that  the  enamel  in  the  molar 
of  the  rhinoceros  tichorhinus  (fig.  116)  is  much  thicker  than  in  that 
of  the  rhinoceros  leptorhinus  (fig.  115). 


Fig.  120. 


Fig.  121. 


a,  &.  Deer. 

Elk  (Cervus  alces,  L. ) ;  re- 
cent; molar  of  upper  jaw. 

a.  Grinding  surface. 
&.  Side  view ;  two-thirds  of 
nat.  size. 


Fig.  122. 


c,  d.  Ox. 

Ox,  common,  from  shell-marl,  Forfar- 
shire;  true  molar,  upper  jaw;  two- 
thirds  nat.  size.  Recent. 

c.  Grinding  surface. 

d.  Side  view;  fangs  uppermost. 

Fig.  128. 


a.  Canine  tooth  or  tusk  of  bear  ( Urms 
spelceus) ;  from  cave  near  Liege. 

6.  Molar  of  left  side,  upper  jaw;  one- 
third  of  nat.  size.  Post-pliocene. 


Tiger. 

c.  Canine  tooth  of  tiger  (Felis  tigris) ;  re- 

cent. 

d.  Outside  view  of  posterior  molar,  lower 

jaw ;  one-third  of  nat.  size ;  recent. 


Fig.  124. 


ffi/ama,  spelcea  ;  lower  jaw.    Kent's  Hole,  Torquay,  Devonshire. 
One-third  nat.  size.    Post-pliocene. 


136 


Fig.  125 


GLACIAL  EPOCH.  [Cn.  XI. 

Fig.  126. 


Hyaena  upelcea;  second  molar, 
left  side,  lower  .jaw;  nat  size. 
Cave  of  Kirkdale.  Post-plio- 
cene. 


Teeth  of  a  new  species  of  Arvicola,  field-mouse;  from 

the  Norwich  Crag.    Newer  Pliocene. 

a.  Grinding  surface.  &.  Side  view  of  same. 

c.  Nat.  size  of  a  and  &. 


Fig.  127. 


a.  Fourth  molar, 
gia,U 


ir,  right  side,  lower  jaw.    Megatherium  ;  Geor- 
.  S. ;  one-third  nat.  size.    Post-pliocene. 


&.  Crown  of  same. 


CHAPTER  XI. 


POST-PLIOCENE    PERIOD    CONTINUED. GLACIAL    EPOCH. 

Geographical  distribution,  form,  and  characters  of  glacial  drift — Fundamental  rocks, 
polished,  grooved,  and  scratched — Abrading  and  striating  action  of  glaciers — 
Moraines,  erratic  blocks,  and  "  Roches  Moutonnees  " — Alpine  blocks  on  the  Jura 
— Colossal  size  of  ancient  Swiss  glaciers — Continental  ice  of  Greenland — Ancient 
centres  of  the  dispersion  of  erratics — Transportation  of  drift  by  floating  ice- 
bergs— Bed  of  the  sea  furrowed  and  polished  by  the  running  aground  of  floating 
ice-islands — How  to  distinguish  glacial  drift  of  submarine  from  that  of  terrestrial 
origin. 

AMONG  the  different  kinds  of  alluvium  described  in  Chapter  VII., 
a  passing  allusion  was  made  (page  80)  to  the  "  boulder  formation " 
and  to  its  origin  as  probably  connected  with  the  agency  of  glaciers 
and  floating  ice.  This  formation,  to  which  many  names,  such  as 
"  diluvium,"  "  northern  drift,"  "  boulder  clay,"  and  "  glacial  deposits  " 
have  been  given,  is  abundant  in  Europe  north  of  the  50th,  and  in 
North  America  north  of  the  40th  parallel  of  latitude.  It  is  wanting 
in  the  warmer  and  equatorial  regions,  and  reappears  when  we  ex- 
amine the  lands  which  lie  south  of  the  40th  and  50th  parallels  in  the 
Southern  Hemisphere;  as,  for  example,  in  Patagonia,  Terra  del 
Fuego,  and  New  Zealand.  It  consists  of  sand  and  clay,  sometimes 
stratified,  but  often  wholly  devoid  of  stratification  for  a  depth  of  50, 
100,  or  even  a  greater  number  of  feet.  To  this  unstratified  form  of 


CH.  XI.]  CHARACTERISTICS  OF  GLACIAL  DRIFT. 

the  deposit  the  name  of  till  has  long  been  applied  in  Scotland.  It 
generally  contains  a  mixture  of  angular  and  rounded  fragments  of 
rock,  some  of  large  size,  having  occasionally  one  or  more  of  their 
sides  flattened  and  smoothed,  or  even  highly  polished.  The  smoothed 
surfaces  usually  exhibit  many  scratches  parallel  to  each  other,  one  set 
of  which  often  crosses  an  older  set.  The  till  is  almost  everywhere 
wholly  devoid  of  organic  remains,  except  those  washed  into  it  from 
older  formations,  though  in  some  places  it  contains  marine  shells  of 
arctic  species,  many  of  them  in  a  fragmentary  state.  The  bulk  of  the ' 
till  has  usually  been  derived  from  the  grinding  down  into  mud  of 
rocks  in  the  immediate  neighborhood,  so  that  it  is  red  in  a  region  of 
Red  Sandstone,  as  in  Strathmore  in  Forfarshire ;  gray  or  black  in  a 
district  of  coal  and  coal-shale,  as  around  Edinburgh ;  and  white  in  a 
chalk  country,  as  in  parts  of  Norfolk  and  Denmark.  The  stony  frag- 
ments dispersed  irregularly  through  the  till  usually  belong,  especially 
in  mountainous  countries,  to  rocks  found  in  some  parts  of  the  same 
hydrographical  basin ;  but  there  are  regions  where  the  whole  of  the 
boulder  clay  has  come  from  a  distance,  and  huge  blocks,  or  "  erra- 
tics," as  they  have  been  called,  many  feet  in  diameter,  have  not  unfre- 
quently  travelled  hundreds  of  miles  from  their  point  of  departure,  or 
from  the  parent  rocks  from  which  they  have  evidently  been  detached. 
These  are  commonly  angular,  and  have  often  one  or  more  of  their 
sides  polished  and  furrowed. 

The  fundamental  rock  on  which  the  boulder  formation  reposes,  if  it 
consists  of  granite,  gneiss,  marble,  or  other  hard  stone,  capable  of  per- 
manently retaining  any  superficial  markings  which  may  have  been  im- 
printed upon  it,  is  usually  smoothed  or  polished,  like  the  erratics  above 
described  ;  and  exhibits  parallel  striae  and  furrows  having  a  determinate 
direction.  This  direction,  both  in  Europe  and  North  America,  agrees 
generally  in  a  marked  manner  with  the  course  taken  by  the  erratic 
blocks  in  the  same  district. 

The  boulder  clay,  when  it  was  first  studied,  seemed  in  many  of  its 
characters  so  singular  and  anomalous,  that  geologists  despaired  of  ever 
being  able  to  interpret  the  phenomena  by  reference  to  causes  now  in 
diurnal  action.  In  those  exceptional  cases,  where  marine  shells  of 
the  same  date  as  the  boulder  clay  were  found,  nearly  all  of  them  were 
recognised  as  living  species — a  fact  conspiring  with  the  superficial 
position  of  the  drift  to  indicate  a  comparatively  modern  origin.  The 
recentness  of  the  date  caused  the  enigma  to  appear  only  the  more 
perplexing,  and  strengthened  the  belief  that  the  phenomena  were  the 
results  of  forces  distinct  both  in  kind  and  energy  from  those  now  op- 
erating in  the  ordinary  course  of  nature.  Notions  of  this  kind  were 
calculated  to  retard  the  progress  of  science,  by  diverting  attention 
from  such  every-day  operations  as  were  capable  of  producing  analogous 
effects. 

The  term  "  diluvium"  was  for  a  time  the  most  popular  name  of  the 
boulder  formation,  because  it  was  referred  by  many  to  the  deluge  of 


138  ABRADING  ACTION  OF  GLACIERS.  [Cn.  XI. 

Noah,  while  others  retained  the  name  as  expressive  of  their  opinion 
that  a  series  of  diluvial  waves  raised  by  hurricanes  and  storms,  or  by 
earthquakes,  or  by  the  sudden  upheaval  of  land  from  the  bed  of  the 
sea,  had  swept  over  the  continents,  carrying  with  them  vast  masses 
of  mud  and  heavy  stones,  and  forcing  these  stones  over  rocky  sur- 
faces so  as  to  polish  and  imprint  upon  them  long  furrows  and 
striae. 

But  geologists  were  not  long  in  seeing  that  the  boulder  formation 
was  characteristic  of  high  latitudes,  and  that  on  the  whole  the  size 
and  number  of  erratic  blocks  increases  as  we  travel  toward  the  arctic 
regions.  They  could  not  fail  to  be  struck  with  the  contrast  which 
the  countries  bordering  the  Baltic  presented  when  compared  with 
those  surrounding  the  Mediterranean.  The  multitude  of  travelled 
blocks  and  striated  rocks  in  the  one  region,  and  the  absence  of  such 
appearances  in  the  other,  were  too  obvious  to  be  overlooked.  Even  the 
great  development  of  the  boulder  formation,  with  large  erratics  so  far 
south  as  the  Alps,  offered  an  exception  to  the  general  rule  favorable 
to  the  hypothesis  that  there  was  some  intimate  connection  between  it 
and  accumulations  of  snow  and  ice. 

Abrading,  polishing,  scouring  and  transporting  power  of  glaciers. — 
-  li  is  well  known  that  those  parts  of  the  Alps  which  rise  to  heights  ex- 
ceeding 8500  feet  above  the  level  of  the  sea  are  covered  with  perpetual 
snow.  This  sriow,  as  it  receives  annual  additions,  would  increase  in- 
definitely in  altitude  were  not  its  accumulation  checked  by  the  constant 
descent  of  a  large  portion  of  it  by  gravitation.  As  it  glides  slowly 
down  the  principal  valleys  flanking  the  highest  mountains,  it  becomes 
converted  into  solid  ice,  and  forms  what  are  termed  glaciers,  or  rivers 
of  ice,  the  lower  extremities  of  which,  when  they  descend  into  warmer 
regions,  melt  and  give  rise  to  torrents  of  water.  On  the  borders  of 
every  glacier  are  seen  on  either  side  mounds,  or  taluses  of  rubbish, 
consisting  of  angular  fragments  of  rock,  with  large  heaps  of  sand  and 
mud.  At  certain  distances  from  each  side,  and  often  in  the  centre, 
ridges  composed  of  similar  debris  from  three  to  twelve  feet  in  height, 
are  observable.  Each  of  these  has  originated,  like  the  lateral  mounds, 
in  the  form  of  a  talus  accumulated  at  the  foot  of  a  steep  slope  or 
precipice.  Frost,  rain,  lightning,  and  avalanches  of  snow  are  con- 
stantly detaching  fragments  of  rock  and  soil  which  fall  or  roll  down 
to  the  bottom  of  such  precipices.  If  the  base  of  the  heap  of  loose 
materials  were  washed  by  a  river,  it  would  soon  be  undermined  and 
swept  away,  but  when  this  fallen  matter  reaches  the  edge  of  a  glacier, 
which  is  always  moving  onward  night  and  day  at  the  rate  of  several 
inches,  or  sometimes  a  foot  or  two  in  twenty-four  hours,  the  whole 
talus  becomes  locomotive,  and  is  changed  into  a  long  stream  of  blocks 
and  earthy  matter,  fringing  the  glacier  on  both  sides,  and  constitut- 
ing what  are  called  lateral  moraines.  As  often  as  glaciers  are  connu 
ent,  the  right  lateral  moraine  of  one  blends  with  the  left  moraine  of 
the  other,  and  both  are  then  carried  down  in  the  middle  of  the  mass 


CH.  XI.]  SMOOTHED  AND  STRIATED  ROCKS.  139 

of  ice  produced  by  the  union  of  the  two  glaciers,  forming  what  is  called 
a  medial  moraine.  The  number  and  position  of  these  moraines  will  de- 
pend on  the  number  and  size  of  the  tributary  glaciers  which  join  the 
main  one.  By  such  machinery,  not  only  small  stones  and  earth,  but 
erratic  blocks  of  the  largest  size,  are  carried  down  from  the  mountains 
to  the  lower  valleys  and  plains,  performing  a  journey  of  twenty  or 
thirty  miles  in  the  course  of  several  centuries,  and  usually  retaining 
their  edges  sharp  and  unworn  to  the  last. 

When  the  glacier  passes  over  uneven  ground,  it  becomes  rent,  and 
traversed  by  broad  and  deep  transverse  fissures,  into  which  portions 
of  the  lateral  or  medial  moraines  are  precipitated.  Rills  of  water  also, 
derived  from  the  liquefaction  of  the  ice  by  the  sun's  rays  in  summer, 
run  over  the  surface  of  the  glacier  until,  arriving  at  one  of  these 
fissures,  they  cascade  into  it.  From  this  source,  as  well  as  from  springs, 
which  must  occasionally  break  out  under  the  glacier,  are  derived 
torrents  which  flow  under  the  ice  in  tunnels,  where  the  angular  stones 
which  have  fallen  to  the  bottom  through  the  fissures  often  become 
rounded,  as  in  the  ordinary  bed  of  a  river.  Other  blocks  and  pebbles, 
being  fixed  in  the  ice,  and  firmly  frozen  into  it,  are  pushed  along  the 
bottom  of  the  glacier,  abrading,  polishing,  and  grooving  the  rocky  floor 
below,  while  each  stone  is  reciprocally  flattened,  polished,  and  striated 
on  its  lower  side.  As  the  forces  of  downward  pressure  and  onward 
propulsion  are  enormous,  each  small  grain  of  sand,  if  it  consists  of 
quartz  or  some  hard  mineral,  scratches  and  polishes  the  surface, 
whether  of  the  underlying  rock  or  of  the  boulder  which  impinges  on 
it,  as  a  diamond  cuts  glass  or  as  emery  powder  polishes  steel.  The 
striss  which  are  made,  and  the  deep  grooves  which  are  scooped  out  by 
this  action,  are  rectilinear  and  parallel  to  an  extent  never  seen  in 
those  produced  on  loose  stones  or  rocks,  where  shingle  is  hurried 
along  by  a  torrent,  or  by  the  waves  on  a  sea-beach. 

As  water  is  always  flowing  under  some  parts  of  a  glacier,  and  much 
melting  and  regelation  are  going  on  in  different  places,  stones  are  lia- 
ble to  change  their  position,  in  which  case  a  second  set  of  striae  and 
furrows  may  be  imprinted  in  a  new  direction,  or  another  side  of  the 
stone  becomes,  in  its  turn,  flattened,  striated,  and  polished.  In  like 
manner  the  solid  rock  underneath  the  glacier  may  exhibit  scratches 
and  grooves  in  more  than  one  direction.  The  furrows  will,  most  of 
them,  coincide  with  the  general  course  of  the  valley ;  but  as  the  ice 
in  different  seasons  varies  in  quantity,  the  direction  of  its  motion  at 
any  given  point  is  not  uniform,  so  that  the  grooves  and  scratches  will 
also  vary,  one  set  often  intersecting  another. 

"When  a  Swiss  glacier,  laden  with  mud  and  stones,  descends  so  far  as 
to  reach  a  region  about  3500  feet  above  the  level  of  the  sea,  the 
warmth  of  the  air  is  such  that  it  melts  rapidly  in  summer,  and  in  spite 
of  the  downward  movement  of  the  mass,  it  can  advance  no  farther. 
Its  precise  limits  are  variable  from  year  to  year,  and  still  more  so  from 
century  to  century ;  one  example  being  on  record  of  a  recession  of 


140  MORAINES  AND  ERRATIC  BLOCKS.  [CH.  XI. 

half  a  mile  in  a  single  year.  We  also  learn  from  M.  Yenetz,  that 
whereas,  between  the  eleventh  and  fifteenth  centuries,  all  the  Alpine 
glaciers  were  less  advanced  than  now,  they  began  in  the  seventeenth 


Fig.  128. 


Limestone  polished,  furrowed,  and  scratched  by  the  glacier  of  Kosenlaui,  in  Switzerland.  (Agassiz.) 

a  a.  White  streaks  or  scratches,  caused  by  small  grains  of  flint  frozen  into  the  ice. 
&  6.  Furrows. 

and  eighteenth  centuries  to  push  forward,  so  as  to  cover  roads  formerly 
open,  and  to  overwhelm  forests  of  ancient  growth. 

These  oscillations  enable  the  geologist  to  note  the  marks  which  a 
glacier  leaves  behind  it  as  it  retrogrades  ;  and  among  these  the  most 
prominent  is  the  terminal  moraine,  which  is  a  confused  heap  of  un- 
stratified  rubbish,  like  the  till  before  described ;  all  the  mud,  sand, 
and  pieces  of  rock,  with  which  the  glacier  was  loaded,  ^having  been 
slowly  deposited  in  the  same  spot  where  no  running  water  interfered 
to  sort  them,  by  carrying  the  smaller  and  lighter  particles  and  stones 
farther  than  the  bigger  and  heavier  ones.  These  terminal  moraines 
often  cross  the  valley  in  the  form  of  transverse  mounds,  more  or  less 
divided  into  separate  masses  or  hillocks  by  the  action  of  the  torrent 
which  flows  out  from  the  end  of  the  glacier.  Such  transverse  barriers 
were  formerly  pointed  out  by  Saussure,  below  the  glacier  of  the  Rhone, 
as  proving  how  far  it  had  once  transgressed  its  present  boundaries.  On 
these  moraines  we  see  many  large  angular  fragments,  which,  having 
been  carried  along  on  the  surface  of  the  ice,  have  not  had  their  edges 
worn  off  by  friction ;  there  are  also  many  boulders,  of  various  sizes, 
which  have  been  rounded ;  some,  as  before  stated,  by  the  power  of 
water  beneath  the  glacier,  others  by  the  mechanical  force  of  the  ice 
which  has  pushed  them  against  each  other,  or  against  the  rocks  flank- 
ing the  valley. 

As  the  terminal  moraines  are  the  most  prominent  of  all  the  monu- 


On.  XI.]  EXCAVATIONS  MADE  BY  CASCADES.  -^ 

merits  left  by  a  receding  glacier,  so  are  they  the  most  liable  to  oblit- 
eration ;  for  violent  floods  or  debacles  are  often  occasioned  in  the  Alps 
by  the  sudden  bursting  of  what  are  called  glacier-lakes.  These  tem- 
porary sheets  of  water  are  caused  by  the  damming  up  of  a  river  by  a 
glacier  which  has  increased  during  a  succession  of  cold  seasons,  and 
descending  from  a  tributary  into  the  main  valley,  has  crossed  it  from 
side  to  side.  On  the  failure  of  this  icy  barrier,  the  accumulated  waters 
are  let  loose,  which  sweep  away  and  level  many  a  transverse  mound  of 
gravel  and  loose  boulders  below,  and  spread  their  materials  in  confused 
and  irregular  beds  over  the  river-plain. 

In  addition  to  the  polished,  striated,,  and  grooved  surfaces  of  rock 
already  described,  another  mark  of  the  former  action  of  a  glacier  is, 
the  "  roche  moutonnee."  .  Projecting  eminences  of  rock  so  called  have 
been  smoothed  and  worn  into  the  shape  of  flattened  domes  by  the 
glacier  as  it  passed  over  them. 

Although  the  surface  of  almost  every  kind  of  rock,  when  exposed 
in  the  open  air,  wastes  away  by  decomposition,  yet  some  retain  for 
ages  their  polished  and  furrowed  exterior ;  and,  if  they  are  well  pro- 
tected by  a  covering  of  clay  or  turf,  these  marks  of  abrasion  seem 
capable  of  enduring  for  ever.  They  have  been  traced  in  the  Alps  to 
great  heights  above  the  present  glaciers,  and  to  great  horizontal  dis- 
tances beyond  them. 

There  are  also  found,  on  the  sides  of  the  Swiss  valleys,  round 
and  deep  holes  with  polished  sides,  such  holes  as  waterfalls  make  in 
the  solid  rock,  but  in  places  remote  from  running  waters,  and  where 
the  form  of  the  surface  makes  it  difficult  to  suppose  that  any  cascade 
could  ever  have  existed.  Similar  cavities  are  common  in  hard  rocks, 
such  as  gneiss  in  Sweden,  where  they  are  called  giant  caldrons,  and 
are  sometimes  ten  feet  and  more  in  depth ;  but  in  the  Alps  and  Jura 
they  often  pass  into  spoon-shaped  excavations  and  prolonged  gutters. 
We  learn  from  M.  Agassiz  that  hollows  of  this  form  are  now  cut  out 
by  streams  of  water  which,  after  flowing  along  the  surface  of  a  glacier, 
fall  into  open  fissures  in  the  ice  and  form  a  cascade.  Here  the  fallen 
water,  causing  the  gravel  and  sand  at  the  bottom  to  rotate,  cuts  out  a 
round  cavity  in  the  rock.  But  as  the  glacier  moves  on,  the  cascade 
becomes  locomotive,  and  what  would  otherwise  have  been  a  circular 
hole  is  prolonged  into  a  deep  groove.  The  form  of  the  rocky  bot- 
tom of  the  valley  down  which  the  glacier  is  moving  causes  the  rents  in 
the  ice  and  these  locomotive  cascades  to  be  formed  again  and  again, 
year  after  year,  in  exactly  the  same  spots. 

Another  effect  of  a  glacier  is  to  lodge  a  ring  of  stones  round  the 
summit  of  a  conical  peak,  or  a  single  block  on  a  sharp  ridge,  which 
may  happen  to  project  through  the  ice.  If  the  glacier  is  lowered 
greatly  by  melting,  these  blocks  or  circles  of  large  angular  fragments, 
which  are  called  "  perched  blocks,"  are  left  in  a  singular  situation  at  or 
near  the  top  of  a  sharp  pinnacle  or  ridge,  the  lower  parts  of  which 
may  be  destitute  of  boulders. 


142  COLOSSAL  SIZE  OF  ANCIENT  GLACIERS.  [Cn.  XL 

Alpine  blocks  on  the  Jura. — Some  or  all  the  marks  above  enumera- 
ted— the  moraines,  erratics,  polished  surfaces,  domes,  striae,  caldrons, 
and  perched  rocks — are  observed  in  the  Alps  at  great  heights  above 
the  present  glaciers,  and  far  below  their  actual  extremities  ;  also  in 
the  great  valley  of  Switzerland,  fifty  miles  broad ;  and  almost  every- 
where on  the  Jura,  a  chain  which  lies  to  the  north  of  this  valley. 
The  average  height  of  the  Jura  is  about  one-third  that  of  the  Alps, 
and  it  is  now  entirely  destitute  of  glaciers ;  yet  it  presents  almost 
everywhere  simular  moraines,  and  the  same  polished  and  grooved  sur- 
faces and  water-worn  cavities.  The  erratics,  moreover,  which  cover 
it,  presents  a  phenomenon  which  has  astonished  and  perplexed  the 
geologist  for  more  than  a  half  a  century.  No  conclusion  can  be 
more  incontestable  than  that  these  angular  blocks  of  granite,  gneiss, 
and  other  crystalline  formations,  came  from  the  Alps,  and  that  they 
have  been  brought  for  a  distance  of  fifty  miles  and  upward  across 
one  of  the  widest  and  deepest  valleys  in  the  world  ;  so  that  they  are 
now  lodged  on  the  hills  and  valleys  of  a  chain  composed  of  limestone 
and  other  formations,  altogether  distinct  from  those  of  the  Alps. 
Their  great  size  and  angularity,  after  a  journey  of  so  many  leagues, 
has  justly  excited  wonder ;  for  hundreds  of  them  are  as  large  as  cot- 
tages ;  and  one  in  particular,  composed  of  gneiss,  celebrated  under 
the  name  of  Pierre  a  Bot,  rests  on  the  side  of  a  hill  about  900 
feet  above  the  lake  of  Neufchatel,  and  is  no  less  than  40  feet  in  di- 
ameter. 

In  the  year  1821,  M.  Venetz  first  announced  his  opinion  that  the 
Alpine  glaciers  must  formerly  have  extended  far  beyond  their  present 
limits,  and  the  proofs  appealed  to  by  him  in  confirmation  of  this  doc- 
trine were  afterward  acknowledged  by  M.  Charpentier,  who  strength- 
ened them  by  new  observations  and  arguments,  and  declared,  in 
1836,  his  conviction  that  the  glaciers  of  the  Alps  must  once  have 
reached  as  far  as  the  Jura,  and  have  carried  thither  their  moraines 
across  the  great  valley  of  Switzerland.  M.  Agassiz,  after  several  ex- 
cursions in  the  Alps  with  M.  Charpentier,  and  after  devoting  himself 
for  some  years  to  the  study  of  glaciers,  published,  in  1 840,  an  admira- 
ble description  of  them  and  of  the  marks  which  attest  the  former  ac- 
tion of  great  masses  of  ice  over  the  entire  surface  of  the  Alps  and  the 
surrounding  country.* 

M.  Charpentier  conceived  that  the  Alps,  at  the  time  when  the  gla- 
ciers extended  continuously  from  them  to  the  Jura,  and  conveyed  to 
them  so  many  Alpine  erratics,  where  2000  or  3000  feet  higher  than 
now.  Professor  James  D.  Forbes,  in  his  excellent  work  on  the  Alps, 
published  in  1843,  came  in  like  manner  to  the  conclusion  that  the 
ancient  glaciers  were  of  colossal  size,  and  had  once  stretched  from  the 
principal  chain  to  the  Jura.  The  original  theory  of  Saussure,  that  the 
erratics  were  all  whirled,  along  to  great  distances  by  a  rapid  current  of 

*  Agassiz,  Etudes  sur  les  Glaciers,  and  SysteTne  Glaciere. 


CH.  XL]  CONTINENTAL  ICE  OF  GREENLAND.  143 

muddy  water  rushing  from  the  Alps,  has  long  been  exploded ;  and 
the  hypothesis  of  the  submergence  of  Switzerland  beneath  the  waters 
of  the  sea,  and  the  transportation  of  moraines  and  erratic  blocks  on 
ice-rafts  or  floating  icebergs  from  the  Alps  to  the  Jura,  then  an  island 
— a  view  to  which  I  myself  formerly  leaned — has  been  disproved  by 
a  careful  study  of  the  present  distribution  of  the  travelled  masses. 
Their  arrangement,  both  on  the  north  and  south  of  the  great  chain, 
whether  in  the  Pays  de  Vaud  and  Jura  or  in  the  plains  of  the  Po,  is 
such  as  to  imply  that  they  were  transported  to  their  present  sites  by 
glaciers  of  enormous  size  descending  by  the  existing  valleys  at  a  time 
when  all  the  great  lakes  were  filled  with  ice,  or,  in  other  words,  formed 
parts  of  these  same  glaciers.  The  entire  absence  of  marine  shells 
from  the  old  glacial  drift  of  Switzerland,  and  of  the  Alps  generally,  is 
confirmatory  of  this  theory,  and  against  the  doctrine  of  a  marine  sub- 
mergence. The  moraine-like  arrangement  of  the  boulders  has  also  led 
the  most  experienced  Swiss  and  Italian  geologists,  who  have  of  late 
years  devoted  much  time  and  talent  to  the  study  of  this  subject,  to 
adopt  the  same  hypothesis  of  land-glaciers.  Among  other  writers  I 
may  mention  MM.  Studer,  Guyot,  Escher  von  der  Linth,  Morlot,  Gas- 
taldi,  Gabriel  de  Mortillet,  Omboni,  and  others. 

It  has  been  stated  that  the  boulder  formation  and  all  the  attendant 
phenomena  of  striated  and  dome-shaped  rocks  and  far-transported 
erratics  become  more  and  more  conspicuous  in  proportion  as  we  ex- 
tend our  survey  to  higher  latitudes.  We  find,  for  example,  a  charac- 
teristic display  of  them  in  Norway,  Sweden,  and  Denmark,  the  south- 
ern borders  of  the  Baltic  or  Northern  Germany,  European  Russia, 
and  Finland.  They  are  also  observable  in  the  mountainous  regions 
of  Scotland,  Wales,  and  of  the  British  Isles  generally.  But,  besides 
the  appearances  already  noticed,  there  occur  here  and  there  in  the 
countries  just  alluded  to,  deposits  of  marine  fossil  shells,  strictly  be- 
longing to  the  glacial  period,  which  exhibit  so  arctic  a  character  that 
they  must  have  led  the  geologist  to  infer  the  former  prevalence  of  a 
much  colder  climate,  even  had  he  not  encountered  so  many  accompany- 
ing signs  of  ice-action.  The  same  marine  shells  demonstrate  the  sub- 
mergence of  large  areas  in  Scandinavia  and  the  British  Isles,  and 
other  regions,  during  parts  of  the  glacial  epoch. 

A  characteristic  feature  of  the  deposits  under  consideration  in  all 
these  countries  is  the  occurrence  of  large  erratic  blocks  and  sometimes 
of  moraine  matter,  in  situations  remote  from  lofty  mountains,  and  sep- 
arated from  the  nearest  points  where  the  parent  rocks  appear  at  the 
surface  by  great  intervening  valleys,  or  arms  of  the  sea.  Such  appear- 
ances require  us  to  suppose  important  geographical  changes  of  a  date 
subsequent  to  the  drift.  But  even  where  the  land  does  not  seem  to 
have  undergone  much  local  alteration,  such  as  would  result  from  up- 
heaval and  subsidence,  we  often  observe  striae  and  furrows,  as  in  Nor- 
way, Sweden,  and  Scotland,  which  are  not  in  strict  accordance  with 
the  direction  of  any  separate  glaciers,  which  can  be  supposed  to  have 


144  TRANSPORTATION  OF  DRIFT  BY  ICEBERGS.  [On.  XT. 

once  descended  through  existing  valleys.  Many  of  the  markings  re- 
ferred to  deviate  from  the  direction  which  they  ought  to  follow  if  they 
had  been  connected  with  the  present  line  of  drainage,  and  they,  there- 
fore, imply  the  prevalence  of  a  very  distinct  condition  of  things  at 
the  time  when  the  cold  was  most  intense.  The  actual  state  of  the 
Continent  of  North  Greenland  seems  to  afford  the  best  explanation  of 
such  abnormal  glacial  markings. 

Of  that  country  a  faithful  description  has  been  given  to  us  by  Rink, 
now  governor  of  the  Danish  Settlements  in  Baffin's  Bay,  who  has, 
more  than  any  other  scientific  traveller,  explored  both  the  coast  and 
the  interior.*  The  land,  he  says,  may  be  divided  into  two  regions — 
the  inland  and  the  outskirts.  The  inland  is  800  miles  from  west  to 
east,  and  of  much  greater  length  from  north  to  south.  It  is  a  vast 
unexplored  continent,  buried  under  one  continuous  and  colossal  mass 
of  ice  that  is  always  moving  seaward,  a  very  small  part  of  it  in  an 
easterly  direction,  and  all  the  rest  westward,  or  toward  Baffin's  Bay. 
All  the  minor  ridges  and  valleys  are  levelled  and  concealed  under  a 
general  covering  of  snow,  but  here  and  there  some  steep  mountains 
protrude  abruptly  from  the  icy  slope,  and  a  few  superficial  lines  of  stones 
or  moraines  are  visible  at  certain  seasons,  when  no  snow  has  fallen  for 
many  months,  and  when  evaporation,  promoted  by  the  wind  and  sun, 
has  caused  much  of  the  upper  snow  to  disappear.  After  penetrating 
a  great  distance  eastward  in  lat.  72°  N.,  Rink  still  saw  lines  of  these 
stones  in  the  extreme  distance,  indicating,  he  says,  the  existence  of 
precipitous  mountains,  piercing  through  the  snow  still  farther  east. 
The  height  of  this  continent  is  unknown,  but  it  must  be  very  great, 
as  the  most  elevated  lands  of  the  outskirts  which  are  described  as  com- 
paratively low,  attain  altitudes  of  4000  and  6000  feet.  The  icy  slope 
gradually  lowers  itself  toward  the  outskirts,  and  then  terminates 
abruptly  in  a  mass  about  2000  feet  in  thicknessj  the  great  discharge  of 
ice  taking  place  through  certain  large  friths  which,  at  their  upper  ends, 
are  usually  about  four  miles  across.  Down  these  friths  the  ice  is  pro- 
truded in  huge  masses,  several  miles  wide,  which  continue  their  course 
— grating  along  the  rocky  bottom  like  ordinary  glaciers  long  after 
they  have  reached  the  salt  water.  When  at  last  they  arrive  at  parts 
of  Baffin's  Bay  deep  enough  to  buoy  up  icebergs  from  1000  to  1500 
feet  in  vertical  thickness,  broken  masses  of  them  float  off,  carrying 
with  them  on  their  surface  not  only  fine  mud  and  sand  but  large 
stones.  These  fragments  of  rock,  as  I  am  informed  by  Dr.  Otto  Torell, 
who  has  examined  many  of  the  bergs  after  they  had  run  aground,  are 
often  polished  and  scored  on  one  or  more  sides,  and  as  the  ice  melts, 
they  drop  down  to  the  bottom  of  the  sea,  where  large  quantities  of 
mud  are  deposited,  and  this  muddy  bottom  is  inhabited  by  many 
mollusca. 


*  Rink,  Journal  of  Royal  Geograph.  Soc.,  vol.  xxiii.  p.  145,  and  Lyell,  Antiquity 
of  Man,  p.  236. 


CH.  XI.]  ICE   OF  GREENLAND. 

The  outskirts,  where  the  Danish  colonists  are  settled,  comprise  an 
area  of  30,000  square  miles  in  extent,  including  many  islands  and 
peninsulas,  and  some  fiords  from  50  to  100  miles  long,  down  which 
the  ice  passes,  either  floating  or  sometimes,  as  already  stated,  in  con- 
tact with  the  bottom.  Rink  counted  twenty-two  great  ice-streams 
along  the  coast,  which  indicate  the  position  of  as  many  concealed  val- 
leys or  straths,  by  which  relief  is  given  to  the  snow  and  ice  annually 
accumulating  in  the  interior.  From  the  same  points  the  principal 
glaciers  or  rivers  would  issue  if,  at  some  future  period,  there  should  be 
a  milder  climate.  But  although  the  direction  of  the  ice-streams  in 
Greenland  may  concide  in  the  main  with  that  which  separate  glaciers 
would  take  if  there  were  no  more  ice  than  there  is  now  in  the  Swiss 
Alps,  yet  the  striation  of  the  surface  of  the  rocks  on  an  ice-clad  con- 
tinent would,  on  the  whole,  vary  considerably  in  its  minor  details 
from  that  which  would  be  imprinted  on  rocks  constituting  a  region 
of  separate  glaciers.  For  where  there  is  a  universal  covering  of  ice 
there  will  be  a  general  outward  movement  from  the  higher  and 
more  central  regions  toward  the  circumference  and  lower  country, 
and  this  movement  will  be,  to  a  certain  extent,  independent  of  the 
minor  inequalities  of  hill  and  valley,  when  these  are  all  reduced  to 
one  level  by  the  snow.  The  moving  ice  may  sometimes  cross  even 
at  right  angles  deep  narrow  ravines,  or  the  crests  of  buried  ridges, 
on  which  last  it  may  afterward  seem  strange  to  detect  glacial  striae 
and  polishing  after  the  liquefaction  of  the  snow  and  ice  has  taken 
place. 

Rink  mentions  that,  in  North  Greenland,  powerful  springs  of 
clayey  water  escape  in  winter  from  under  the  ice,  where  it  descends 
to  "  the  outskirts,"  and  where,  as  already  stated,  it  is  often  2000  feet 
thick — a  fact  showing  how  much  grinding  action  is  going  on  upon  the 
surface  of  the  subjacent  rocks.  I  also  learn  from  Dr.  Torell  that 
there  are  large  areas  in  the  outskirts,  now  no  longer  covered  with 
permanent  snow  or  glaciers,  which  exhibit  on  their  surface  unmistak- 
able signs  of  ancient  ice-action,  so  that,  vast  as  is  the  power  now  ex- 
erted by  ice  in  Greenland,  it  must  once  have  operated  on  a  still  grand- 
er scale.  The  land,  though  now  very  elevated,  may  perhaps  have 
been  formerly  much  higher.  This,  indeed,  is  more  than  probable,  as, 
ever  since  the  country  has  been  known  to  the  Danes,  or  for  the 
last  four  centuries,  the  whole  coast,  from  latitude  60°  to  about  70° 
N.  has  been  sinking  at  the  rate  of  several  feet  in  a  century.  By 
this  means  a  surface  of  rock,  well  scored  and  polished  by  ice,  is  now 
slowly  subsiding  beneath  the  sea,  and  is  becoming  strewed  over,  as 
the  icebergs  melt,  with  impalpable  mud  and  smoothed  and  scratched 
stones. 

When  we  contemplate,  therefore,  the  effects  which  are  now  in  pro- 
gress in  North  Greenland  and  on  its  shores,  as  well  as  in  the  ^bed  of 
the  adjoining  sea,  under  the  influence  of  the  ice,  both  of  glaciers  and 
floating  bergs,  combined  with  a  vertical  movement  of  the  continent 
10 


146  DISPERSION  OF  ERRATICS.  [Cn.  XI. 

and  floor  of  the  ocean,  which  is  now  one  of  subsidence,  but  which 
may  at  some  future  time  be  converted  into  one  of  upheaval,  we  are 
presented  with  a  key  to  the  interpretation  of  many  distinct  classes  of 
glacial  phenomena  once  regarded  as  most  enigmatical. 

An  account  was  given  so  long  ago  as  the  year  1822,  by  Scoresby, 
of  icebergs  seen  by  him  in  the  Arctic  seas  drifting  along  in  latitudes 
69°  and  70°  N.,  which  rose  above  the  surface  from  100  to  200  feet, 
and  some  of  which  measured  a  mile  in  circumference.  Many  of 
them  were  loaded  with  beds  of  earth  and  rock,  of  such  thickness  that 
the  weight  was  conjectured  to  be  from  50,000  to  100,000  tons.  A 
similar  transportation  of  rocks  is  known  to  be  in  progress  in  the 
southern  hemisphere,  where  boulders  included  in  ice  are  far  more 
frequent  than  in  the  north.  One  of  these  icebergs  was  encountered 
in  1839,  in  mid-ocean,  in  the  antarctic  regions,  many  hundred  miles 
from  any  known  land,  sailing  northward,  with  a  large  erratic  block 
firmly  frozen  into  it.  In  order  to  understand  in  what  manner  long 
and  straight  grooves  may  be  cut  by  such  agency,  we  must  remember 
that  these  floating  islands  of  ice  have  a  singular  steadiness  of  motion, 
in  consequence  of  the  larger  portion  of  their  bulk  being  sunk  deep 
under  water,  so  that  they  are  not  perceptibly  moved  by  the  winds 
and  waves  even  in  the  strongest  gales.  Many  had  supposed  that  the 
magnitude  commonly  attributed  to  icebergs  by  unscientific  navigators 
was  exaggerated,  but  now  it  appears  that  the  popular  estimate  of 
their  dimensions  has  rather  fallen  within  than  beyond  the  truth. 
Many  of  them,  carefully  measured  by  the  officers  of  the  French  explor- 
ing expedition  of  the  Astrolabe,  were  between  100  and  225  feet  high 
above  water,  and  from  two  to  five  miles  in  length.  Captain  d'Urviile 
ascertained  one  of  them  which  he  saw  floating  in  the  Southern  Ocean 
to  be  13  miles  long  and  100  feet  high,  with  walls  perfectly  vertical. 
The  submerged  portions  of  such  islands  must,  according  to  the 
weight  of  ice  relatively  to  sea-water,  be  from  six  to  eight  times  more 
considerable  than  the  part  which  is  visible,  so  that  when  they  are 
once  fairly  set  in  motion,  the  mechanical  force  which  they  might  exert 
against  any  obstacle  standing  in  their  way  would  be  prodigious.* 
A  considerable  proportion  of  these  floating  masses  of  ice  is  supposed 
not  to  be  derived  from  terrestrial  glaciers,  but  to  be  formed  at  the  foot 
of  cliffs  by  the  drifting  of  snow  from  the  land  over  the  frozen  surface 
of  the  sea,  the  snow  by  repeated  melting  and  regelation  being  in 
time  converted  into  ice.  But  most  of  the  bergs  of  the  Southern 
Ocean  are  formed  in  the  same  way  as  the  principal  ones  in  Baffin's 
Bay ;  for  Dr.  Hooker  informs  me  that  the  ice  of  the  Antarctic  Con- 
tinent, or  Victoria  Land,  like  that  of  Greenland,  as  described  by  Rink, 
is  strewed  over  with  rocky  fragments,  there  being  always  some  bare 
precipices  and  mountain  peaks  protruding  from  the  great  wilderness 
of  snow  from  which  moraines  may  be  derived.  These  moraines  are 

*  T.  L.  Hayes,  Boston  Joura.  Nat.  Hist.,  1844. 


CH.  XL]  SEA-BEDS  FURROWED  AND  POLISHED. 

carried  down  to  the  coast  and  then  floated  northward  on  detached 
icebergs  to  great  distances. 

We  learn,  therefore,  from  a  study  both  of  the  arctic  and  antarctic 
regions,  that  a  great  extent  of  land  may  be  entirely  covered  throughout 
the  whole  year  by  snow  and  ice,  from  the  summits  of  the  loftiest 
mountains  to  the  sea  coast,  and  may  yet  send  down  angular  erratics 
to  the  ocean.  We  may  also  conclude  that  such  land  will  become  in 
the  course  of  ages  almost  everywhere  scored  and  polished  like  the 
rocks  which  underlie  a  glacier.  The  discharge  of  ice  into  the  sur- 
rounding sea  will  take  place  principally  through  the  main  valleys, 
although  these  are  hidden  from  our  sight.  Erratic  blocks  and  mo- 
raine matter  will  be  dispersed  somewhat  irregularly  after  reaching  the 
sea,  for  not  only  will  prevailing  winds  and  marine  currents  govern 
the  distribution  of  the  drift,  but  the  shape  of  the  submerged  area  will 
have  its  influence  ;  inasmuch  as  floating  ice,  laden  with  stones,  will  pass 
freely  through  deep  water  while  it  will  run  aground  where  there  are 
reefs  and  shallows.  Some  icebergs  in  Baffin's  Bay  have  been  seen 
stranded  on  a  bottom  1000  or  even  1500  feet  deep.  In  the  course  of 
ages  such  a  sea-bed  may  become  densely  covered  with  transported 
matter,  from  which  some  of  the  adjoining  greater  depths  may  be  free. 
If,  as  in  West  Greenland,  the  land  is  slowly  sinking,  a  large  extent  of 
the  bottom  of  the  ocean  will  consist  of  rock  polished  and  striated  by 
land-ice,  and  then  overspread  by  mud  and  boulders  detached  from 
melting  bergs.  But  other  large  areas  of  the  bed  of  the  sea  will  also 
be  marked  by  the  repeated  friction  of  masses  of  floating  ice,  some  of 
them  several  miles  in  diameter,  which,  when  they  strand  on  a  gently 
shelving  reef,  must  grate  along  the  bottom  for  some  distance  before 
their  course  is  arrested.  The  plasticity  of  ice,  or  its  capability,  by 
whatever  theory  explained,  of  moulding  itself  suddenly  into  new 
forms  under  great  pressure,  is  so  remarkable,  that  when  enormous 
masses  of  it  are  floating,  and  moving  at  the  rate  of  two  or  more  miles 
an  hour,  they  must,  on  arriving  at  a  shelving  floor  of  rock,  adapt  their 
forms  to  its  surface,  and  often  be  forced  with  violence  into  any  cavities 
which  the  uneven  bottom  may  present.  Before  the  momentum  of  so 
vast  a  volume  of  matter  can  be  overcome,  the  ice,  moving  with  what 
may  be  called  great  velocity,  when  contrasted  with  the  insensible  pro- 
gress of  a  glacier,  must  give  rise  to  no  small  trituration  of  rock. 
This  will  be  the  more  sure  to  happen,  because  the  largest  bergs,  by 
their  unequal  rate  of  melting  above  and  below  water,  are  continually 
capsizing,  the  centre  of  gravity  often  shifting ;  and  by  such  changes 
the  superficial  moraines,  often  firmly  frozen  into  the  ice,  are  carried 
down  to  form  the  base  of  the  iceberg,  and  supply  sand  and  stones  for 
polishing  and  scouring  the  ocean's  floor.  The  submarine  striae  and 
grooves  may  be  as  uniform  in  their  direction,  and  as  parallel  as  those 
scooped  out  by  glaciers  in  an  inland  valley  ;  for  in  the  same  tracts  the 
floating  ice-islands  will  annually  take  the  same  course  at  correspond- 
ing seasons  of  the  year,  being  carried  by  similar  winds  and  currents 


148  SUBMAKINE  AND  TERRESTRIAL  DRIFT.  [On.  XI. 

in  the  same  direction.  Their  vast  size  also  must  often  tend  to  give  an 
uniformity  to  their  scoring  action,  over  a  space  several  miles  in  width. 
Could  we  imagine  buildings  such  as  St.  Peter's  or  St.  Paul's  to  be 
submerged,  and  an  iceberg,  several  miles  in  diameter  and  two  thou- 
sand feet  in  height,  advancing  with  the  velocity  of  two  or  three  miles 
an  hour  to  strike  them,  it  is  evident  they  must  be  thrown  down  as 
readily  as  were  the  stone  walls  of  the  peasants'  chalets  in  the  early 
part  of  the  present  century  by  the  Gorner  glacier  above  Zermatt. 
We  may,  therefore,  fairly  presume  that  whenever  a  submerged  area 
which  had  once  been  traversed  by  floating  and  occasionally  strand- 
ing icebergs  is  converted  into  land  by  upheaval,  it  will  display  on  its 
surface  most  of  the  characteristics  which  mark  the  former  agency  of 
glaciers  on  dry  land.  No  sharp  pinnacles  of  rocks  can  be  left  stand- 
ing, since  they  will  all  have  been  worn  down  and  reduced  to  dome- 
shaped  masses,  while  scratches  and  long  grooves  will  everywhere  be 
left  on  rocky  surfaces.  Even  till,  or  unstratified  matter,  undistinguish- 
able  from  ordinary  moraines,. will  rarely  be  wanting. 

Those  who  have  had  opportunities  of  inspecting,  in  the  sea  off  the 
coast  of  Labrador,  packs  of  icebergs  which  have  run  aground  in 
water  having  sometimes  a  depth  of  many  hundred  feet,  describe 
lagoon-like  expanses  of  sea  perfectly  quiet,  and  free  from  all  agitation 
of  the  waves  of  the  Atlantic.  These  areas  of  still  water  are  sur- 
rounded on  all  sides  by  icebergs  from  100  to  300  feet  high,  frequently 
containing  moraine  matter  on  their  surface,  or  frozen  into  them. 
Such  icy  masses  may  remain  aground  for  weeks  or  months,  until  they 
are  reduced  by  melting  to  a  size  which  admits  of  their  floating  off 
and  resuming  their  wanderings.  The  mud,  sand,  and  boulders  which 
they  let  fall  in  still  water  must  be  exactly  like  the  moraines  of  terres- 
trial glaciers,  devoid  of  stratification  and  organic  remains.  But  occa- 
sionally, on  the  outer  side  of  such  packs  of  stranded  bergs,  the  waves 
and  currents  may  cause  the  detached  earthy  and  stony  materials  to  be 
sorted  according  to  size  and  weight  before  they  reach  the  bottom,  and 
to  acquire  a  stratified  arrangement. 

I  have  already  alluded  (p.  146)  to  the  large  quantity  of  ice,  con- 
taining great  blocks  of  stone,  which  are  sometimes  seen  floating  far 
from  land,  in  the  southern  or  Antarctic  seas.  It  is  evident  that  such 
glacial  drift,  wherever  it  may  happen  to  alight  on  the  floor  of  the 
ocean,  will  have  no  connection  with  the  external  shape,  or  internal 
composition,  of  the  rocks  on  which  it  may  chance  to  fall.  After  the 
emergence,  therefore,  of  such  a  submarine  area,  the  superficial  detritus 
will  have  no  necessary  relation  to  the  hills,  valleys,  and  river-plains 
over  which  it  will  be  scattered.  Many  a  water-shed  may  intervene 
between  the  starting-point  of  each  erratic  or  pebble  and  its  final 
resting-place,  and  the  only  means  of  discovering  the  country  from 
which  it  took  its  departure  will  consist  in  a  careful  comparison  of  its 
mineral  or  fossil  contents  with  those  of  the  parent  rocks. 

It  will  be  seen  in  the  next  chapter  that  throughout  large  parts  of 


CH.  XII.]  GLACIATION  OF  SCANDINAVIA. 


149 


Scotland,  Scandinavia,  and  other  countries,  the  till  and  boulders  are 
so  connected  in  mineral  and  lithological  character  with  the  structure 
of  the  hills  and  valleys  belonging  to  the  hydrographical  basins  over 
which  they  are  strown,  that  they  must  have  been  produced  by  land- 
glaciers,  although  in  the  same  regions  drift  of  submarine  origin  is 
occasionally  met  with. 


CHAPTER  XII. 

POST-PLIOCENE    PERIOD,    CONTINUED. GLACIAL    EPOCH,    CONCLUDED. 

Glaciation  of  Scandinavia  and  Kussia — Glaciation  of  Scotland — Marine  shells  in 
Scotch  glacial  drift — Their  Arctic  character — Rarity  of  organic  remains  in 
glacial  deposits — Contorted  strata  in  drift — Glaciation  of  Wales,  England,  and 
Ireland — Marine  shells  of  Moel  Tryfaen — Norfolk  drift — Glacial  formations  of 
North  America — How  far  of  submarine  origin — Many  species  of  testacea  and 
quadrupeds  survived  the  glacial  cold — Connection  of  the  predominance  of  lakes 
with  glacial  action — Morainic  lakes — Objections  to  the  hypothesis  of  the  erosion 
of  large  lake-basins  by  ice — Conversion  of  valleys  of  denudation  into  lakes  by 
upward  and  downward  movements — Action  of  ice  in  preventing  the  silting-up 
of  lake-basins — How  the  bed  of  a  sea  where  icebergs  have  abounded  may,  on 
emergence,  afford  lake-basins — General  causes  of  change  of  climate — Submer- 
gence of  the  Sahara  in  the  Post-pliocene  period  a  cause  of  Alpine  cold — Meteor- 
ites in  drift. 

HAVING  in  the  last  chapter  described  the  permanent  effects  which 
continental  ice,  glaciers,  and  icebergs  imprint  on  the  surface,  I  shall 
now  proceed  to  describe  some  of  the  geological  monuments  of  ice- 
action  of  more  ancient  date,  or  of  the  Post-pliocene  period,  observ- 
ble  in  Europe  and  North  America. 

Glaciation  of  Scandinavia  and  Russia. — In  large  tracts  of  Norway 
and  Sweden,  where  there  have  been  no  glaciers  in  historical  times, 
the  signs  of  ice-action  have  been  traced  as  high  as  6000  feet  above 
the  level  of  the  sea.  These  signs  consist  chiefly  of  polished  and  fur- 
rowed rock  surfaces,  of  moraines  and  erratic  blocks.  The  direction 
of  the  erratics,  like  that  of  the  furrows,  has  usually  been  conformable 
to  the  course  of  the  principal  valleys ;  but  the  lines  of  both  some- 
times radiate  outward  in  all  directions  from  the  highest  land,  in  a 
manner  which  is  only  explicable  by  the  hypothesis  of  a  general 
envelope  of  continental  ice,  like  that  of  Greenland,  noticed  in  the  last 
chapter.  Some  of  the  far-transported  blocks  have  been  carried  from 
the  central  parts  of  Scandinavia  toward  the  Polar  regions;  others 
southward  to  Denmark;  some  south  westward,  to  the  coast  of  Nor- 
folk in  England;  others  southeastward,  to  Germany,  Poland,  and 
Russia,  and  to  these  same  countries  small  stones  and  finer  matter 


150  GLACIATION  OF  EUSSIA.  [On.  XII. 

have  also  been  conveyed,  evidently  by  the  aid  of  floating  ice.  The 
southern  and  southeastern  limits  of  this  drift  have  been  well  marked 
out  by  Sir  Roderick  I.  Murchison  and  his  fellow-laborers,  M.  de  Ver- 
neuil  and  Count  Keyserling,  in  a  map  illustrating  their  great  work  on 
the  geology  of  Russia;  and  they  have  pointed  out  how  this  drift 
"  proceeded  eccentrically  from  a  common  central  region." 

It  appears  from  their  observations  that  the  blocks,  scattered  over 
large  districts  of  Russia  and  Poland,  agree  precisely  in  mineral  charac- 
ter with  rocks  of  the  mountains  of  Lapland  and  Finland ;  while  the 
masses  of  gneiss,  syenite,  porphyry,  and  trap,  strewed  over  the  low 
sandy  countries  of  Pomerania,  Holstein,  and  Denmark,  are  identical 
in  their  composition  with  the  mountains  of  Norway  and  Sweden. 

It  is  found  to  be  a  general  rule  in  Russia,  that  the  smaller  blocks 
are  carried  to  greater  distances  from  their  point  of  departure  than  the 
larger;  the  distance  being  sometimes  800,  and  even  1000,  miles  from 
the  nearest  rocks  from  which  they  were  broken  off;  the  direction 
having  been  from  N.W.  to  S.E.,  or  from  the  Scandinavian  mountains 
over  the  seas  and  low  lands  to  the  southeast.  That  its  accumulation 
throughout  this  area  took  place  in  part  during  the  Post-pliocene 
period,  is  proved  by  its  superposition  at  several  points  to  strata  con- 
taining recent  shells.  Thus,  for  example,  in  European  Russia,  Sir  R. 
Murchison  and  his  associates  found,  in  1840,  that  the  flat  country 
between  St.  Petersburg  and  Archangel,  for  a  distance  of  600  miles, 
consisted  of  horizontal  strata,  full  of  shells  similar  to  those  now  in- 
habiting the  Arctic  Sea,  and  on  these  rested  the  boulder  formation, 
containing  large  erratics. 

In  Sweden,  in  the  immediate  neighborhood  of  TJpsala,  I  had  ob- 
served, in  1834,  a  ridge  of  stratified  sand  and  gravel,  in  the.  midst  of 
which  occurs  a  layer  of  marl,  evidently  formed  originally  at  the  bot- 
tom of  the  Baltic;  by  the  slow  growth  of  the  mussel,  cockle,  and 
other  marine  shells  of  living  species,  intermixed  with  some  proper  to 
fresh  water.  The  marine  shells  are  all  of  dwarfish  size,  like  those 
now  inhabiting  the  brackish  waters  of  the  Baltic;  and  the  marl,  in 
which  myriads  of  them  are  imbedded,  is  now  raised  more  than  100 
feet  above  the  level  of  the  Gulf  of  Bothnia.  Upon  the  top  of  this 
ridge  repose  several  huge  erratics,  consisting  of  gneiss  for  the  most 
part  unrounded,  from  9  to  16  feet  in  diameter,  and  which  must  have 
been  brought  into  their  present  position  since  the  time  when  the 
neighboring  gulf  was  already  characterized  by  its  peculiar  fauna.* 
Here,  therefore,  we  have  proof  that  the  transport  of  erratics  con- 
tinued to  take  place,  not  merely  when  the  sea  was  inhabited  by  the 
existing  testacea,  but  when  the  north  of  Europe  had  already  assumed 
that  remarkable  feature  of  its  physical  geography,  which  separates 
the  Baltic  from  the  North  Sea,  and  causes  the  Gulf  of  Bothnia  to 
have  only  one-fourth  of  the  saltness  belonging  to  the  ocean.  In  Den- 

*  See  paper  by  the  Author,  Phil.  Trans.,  1835,  p.  15. 


CH.  XII.]  GLACIATION  OF  SCOTLAND. 

mark,  also,  recent  shells  have  been  found  in  stratified  beds,  closely 
associated  with  the  boulder  clay. 

It  was  stated  that  in  Russia  the  erratics  diminished  generally  in 
size  in  proportion  as  they  are  traced  farther  from  their  source.  The 
same  observation  holds  true  in  regard  to  the  average  bulk  of  the 
Scandinavian  boulders,  when  we  pursue  them  southward,  from  the 
south  of  Norway  and  Sweden  through  Denmark  and  Westphalia. 
This  phenomenon  is  in  perfect  harmony  with  the  theory  of  ice-islands 
floating  in  a  sea  of  variable  depth ;  for  the  heavier  erratics  require 
icebergs  of  a  larger  size  to  buoy  them  up  ;  and,  even  when  there  are 
no  stones  frozen  in,  more  than  seven-eighths,  and  often  nine-tenths, 
of  a  mass  of  drift-ice  is  under  water.  The  greater,  therefore,  the 
volume  of  the  iceberg,  the  sooner  would  it  impinge  on  some  shallower 
part  of  the  sea ;  while  the  smaller  and  lighter  floes,  laden  with  finer 
mud  and  gravel,  may  pass  freely  over  the  same  banks,  and  be  car- 
ried to  much  greater  distances.  In  those  places,  also,  where  in  the 
course  of  centuries  blocks  have  been  carried  southward  by  coast-ice, 
having  been  often  stranded  and  again  set  afloat  in  the  direction  of  a 
prevailing  current,  the  blocks  will  diminish  in  size  the  farther  they 
travel  from  their  point  of  departure,  for  two  reasons :  first,  because 
they  will  be  repeatedly  exposed  to  wear  and  tear  by  the  action  of  the 
waves  ;  secondly,  because  the  largest  blocks  are  seldom  without  divis- 
ional planes  or  "joints,"  which  cause  them  to  split  when  weathered. 
Hence,  as  often  as  they  start  on  a  fresh  voyage,  becoming  buoyant  by 
coast-ice  which  has  frozen  on  to  them,  one  portion  of  the  mass  is 
detached  from  the  rest.  An  examination  which  I  made  in  1852  of 
several  trains  of  huge  erratics  in  lat.  42°  50'  N.  in  the  United  States, 
in  Berkshire,  on  the  western  confines  of  Massachusetts,  has  convinced 
me  that  this  cause  has  been  very  influential  both  in  reducing  the  size 
of  erratics,  and  in  restoring  angularity  to  blocks  which  might  other- 
wise be  rounded  in  proportion  to  their  distance  from  their  original 
starting-point. 

Glaciation  of  Scotland. — Professor  Agassiz,  after  visiting  Scotland 
in  1 840,  came  to  the  opinion  that  the  Grampians  had  been  covered 
by  a  vast  thickness  of  ice,  and  had  once,  like  the  Alps,  been  an  inde- 
pendent centre,  whence  erratic  blocks  were  dispersed  in  all  directions. 
Mr.  Robert  Chambers,  in  1848,  maintained  in  like  manner  that  Scot- 
land had  once  been  "  moulded  in  ice,"  which  had  everywhere  smoothed 
and  scratched  the  rocks,  and  ground  them  down  so  as  to  enlarge  and 
widen  many  valleys.  Mr.  T.  F.  Jamieson,  following  up  the  same  line 
of  investigation  in  1858,  adduced  a  great  body  of  additional  facts  to 
prove  that  the  .Grampians  once  sent  down  glaciers  from  the  central 
regions  in  all  directions  toward  the  sea.  "  The  glacial  grooves,'^  he 
observed,  "  radiate  outward  from  the  central  heights  toward  all  points 
of  the  compass,  although  they  do  not  always  strictly  conform  to  the 
actual  shape  and  contour  of  the  minor  valleys  and  ridges." 

In  many  parts  of  Scotland,  and  conspicuously  in  the  basin  of  the 


152  GLACIATION  OF  SCOTLAND.  [On.  XII. 

Forth,  there  is  a  form  of  hill  to  which  Sir  James  Hall  gave  the 
name  of  "  Crag-and-Tail."  Isolated  ice-worn  hills,  or  knolls,  present 
polished  faces  to  the  west  and  northwest  in  the  district  alluded  to, 
with  rough  declivities  to  the  east  and  southeast,  or  where  the  tail 
occurs.  It  is  a  common  error,  says  Mr.  Geikie,  to  suppose  that  this 
"  tail "  consists  merely  of  detritus,  heaped  up  on  the  lee  side  of  each 
hill,  for  often  it  is  composed  in  great  part,  like  the  west  side  or 
"  crag,"  of  solid  rock,  but  usually  with  a  considerable  covering  of 
boulder  clay.* 

According  to  Mr.  T.  F.  Jamieson,  on  extending  our  survey  of 
Scotland  we  find  many  examples  of  such  "  crag,"  or  natural  escarp- 
ments, facing  the  inland  country,  or  that  from  which  we  may  suppose 
a  mass  of  continental  ice  to  have  descended,  whereas  the  "  tail "  or 
mound  of  sand,  and  boulders,  occupies  the  seaward  side.  It  has  also 
been  remarked  in  Scandinavia  that  abrupt  protuberances  and  out- 
standing ridges  of  rock  are  often  polished  and  furrowed  on  the  side 
facing  the  region  from  which  the  erratics  have  come  (usually  on  the 
north  side  in  Norway) ;  while  on  the  other,  or  "  lee  side,"  such  super- 
ficial markings  are  wanting.  There  is  usually  a  collection  on  this  lee 
side  of  boulders  and  gravel,  or  of  large  angular  fragments.  In  expla- 
nation, we  may  imagine  that  the  north  side  was  exposed,  when  still 
submerged,  to  the  action  of  icebergs,  and  afterwards,  when  the  land 
was  rising,  of  coast-ice,  which  ran  aground  upon  shoals,  so  that  there 
would  be  great  wear  and  tear  on  that  exposed  side,  whereas  on  the 
opposite  or  south  slope,  gravel  and  boulders  might  accumulate  in  a 
sheltered  position. 

The  facts  above  alluded  to,  and  other  characteristics  of  the  Scotch 
drift,  led  Mr.  Jamieson  to  infer,  first,  that  in  the  early  part  of  the 
glacial  period  Scotland  stood  much  higher  than  at  present,  so  that 
there  was  a  general  covering  of  snow  and  ice,  which,  as  it  slid  down 
to  lower  levels,  polished  the  subjacent  rocks,  and  swept  off  from  the 
surface  most  of  the  preexisting  alluvium,  leaving  in  its  place  till 
and  boulders  in  various  parts.  Secondly,  that  to  this  succeeded  a 
period  of  depression  and  partial  submergence,  when  the  sea  advanced 
and  gradually  covered  the  greater  part  of  the  country,  when  floating 
ice  abounded,  and  when  some  marine  drift  with  arctic  shells  was 
deposited.  Thirdly,  that  the  land  reemerged  from  the  water,  and, 
reaching  a  level  somewhat  above  its  present  heights,  became  con- 
nected with  the  Continent  of  Europe,  glaciers  being  formed  once 
more  in  the  higher  regions,  though  the  ice  probably  never  regained 
its  former  extension.f  After  all  these  changes,  there  were  some 
minor  oscillations  in  the  level  of  the  land,  on  which,  although  they 
have  had  important  geographical  consequences,  separating  Ireland 
from  England,  for  example,  and  England  from  the  continent,  we  need 
not  here  enlarge. 

*  Glacial  Drift  of  Scotland ;  Glasgow,  1863,  p.  30. 
f  Quart.  Geol.  Journ.,  1860,  vol.  xvi.  p.  370. 


CH.  XII.]    t  GLACIATION  OF  SCOTLAND. 

Mr.  Geikie  "has  arrived  at  the  same  general  conclusions  as  Mr. 
Jamieson,  with  respect  to  the  principal  movements  of  the  land  in 
Scotland.  The  great  mass  of  till,  of  which  in  some  of  the  lower 
valleys  the  thickness  exceeds  150  feet,  he  attributes  not  to  icebergs, 
but  to  ice  action  on  land,  for  it  consists  of  the  debris  of  rocks,  every- 
where found  in  situ  in  the  same  hydrographical  basin.  The  absence 
of  marine  shells  is  at  once  accounted  for  if  we  assume  it  to  be  of 
glacier  origin.  The  rarity  of  angular  stones,  those  in  the  till  being 
usually  rounded  or  sub-angular,  and  the  number  of  fragments  polished 
and  striated  on  one  or  several  sides,  may  also  be  explained  by  sup- 
posing the  till  to  have  been  shoved  along  under  a  heavy  mass  of  ice, 
like  that  of  Greenland,  instead  of  forming  parts  of  superficial  mo- 
raines, carried  down  without  trituration  on  the  top  of  the  ice.  If,  in 
accordance  with  the  views  above  set  forth,  we  admit  a  second  glacial 
period,  when  the  land  was  reelevated  after  the  great  submergence,  the 
action  of  ice  at  this  later  date  may  well  be  supposed  to  have  obliter- 
ated almost  all  signs  of  the  sojourn  of  the  sea  upon  the  land  in  the 
highest  regions,  where  the  cold  was  most  intense ;  but  in  the  lower 
country,  some  patches  of  marine  strata  with  arctic  shells  might  more 
easily  escape  destruction. 

The  greatest  height  to  which  marine  shells  have  yet  been  traced  in 
Scotch  drift  is  only  524  feet  above  the  level  of  the  sea,  at  which  ele- 
vation they  have  been  observed  at  Airdrie,  fourteen  miles  southeast 
of  Glasgow.  At  that  spot  they  were  found  imbedded  in  stratified 
clays  with  till  above  and  below  them.  There  appears  no  doubt  that 
the  overlying  deposit  was  true  glacial  till,  as  some  boulders  of  granite 
were  observed  in  it,  which  must  have  come  from  distances  of  sixty 
miles  at  the  least.* 

Fig.  129.  Fig.  130. 

Astarte  borealis.  Leda  oblonga. 


Fig.  181.  Fig.  182.  Fig.  183.  Fig.  134. 

Saxicava  rugosa.  Pecten  islandictis.        NaUca  clausa.  Trophon  clathratwn. 

Northern  shells  common  in  the  drift  of  the  Clyde,  in  Scotland. 

The  shells  here  figured  are  only  a  few  out  of  a  large  assemblage  of 
living  species,  which,  taken  as  a  whole,  bear  testimony  to  conditions 
far  more  arctic  than  those  now  prevailing  in  the  Scottish  seas. 

*  Smith,  of  Jordan  Hill,  Geol.  Quart.  Journ.,  vol.  vi.  p.  387.     1850. 


154:  ARCTIC  SHELLS  IN  SCOTCH  DRIFT.  [Cn.  XIT. 

• 

a  group  of  marine  shells,  indicating  a  still  greater  excess  of  cold,  lias 
been  brought  to  light  since  1860  by  the  Rev.  Thomas  Brown,  from 
glacial  drift  or  clay  on  the  borders  of  the  estuaries  of  the  Forth  and 
Tay.  This  clay  occurs  at  Elie  in  Fife,  and  at  Errol  in  Perthshire ; 
and  has  already  afforded  about  35  shells,  all  of  living  species,  and 
now  inhabitants  of  arctic  regions,  such  as  Leda  truncata,  Tellina 
proximo,  (see  figures  below),  Pecten  Groenlandicus,  Crenella  Icevigata, 
Gray,  Crenella  nigra,  Gray,  and  others,  some  of  them  first  brought  by 
Captain  Sir  E.  Parry  from  the  coast  of  Melville  Island,  latitude  76° 
N.  These  were  all  identified  in  1863  by  Dr.  Torell,  who  had  just 
returned  from  a  survey  of  the  seas  around  Spitzbergen,  where  he  had 
collected  no  less  than  150  species  of  mollusca,  living  chiefly  on  a  bot- 
tom of  fine  mud  derived  from  the  moraines  of  melting  glaciers  which 

Fig.  135.  Fig.  136. 


Leda  truncata.  Tellina  proxima. 

a.  Exterior  of  left  valve.  a.  Outside  of  left  valve. 

&.  Interior  of  same.  6.  Interior  of  same. 

there  protrude  into  the  sea.  He  informed  me  that  the  fossil  fauna 
of  this  Scotch  glacial  deposit  exhibits  not  only  the  species  but  also 
the  peculiar  varieties  of  mollusca  now  characteristic  of  very  high  lati- 
tudes. Their  large  size  implies  that  they  formerly  enjoyed  a  colder, 
or  what  was  to  them  a  more  genial  climate,  than  that  now  prevailing 
in  the  latitude  where  they  occur.  Marine  shells  have  also  been  found 
in  the  glacial  drift  of  Caithness  and  Aberdeenshire  at  heights  of  250 
feet,  and  in  Banff  of  350  feet,  and  stratified  drift  continuous  with  the 
above  ascends  to  heights  of  500  feet.  There  are,  likewise,  othei 
deposits  in  Scotland  very  similar  in  character  but  devoid  of  shells 
more  than  1000  feet  high,  resting  on  rocks  grooved  and  polished  by 
ice-action.  The  want  of  marine  shells  in  these  last  has  naturally 
inclined  some  geologists  to  suspect  that  they  may  have  been  de- 
posited in  glacier  lakes,  and  this  opinion  may  be  correct,  although  on 
this  subject  there  is  no  small  danger  of  drawing  false  conclusions 
from  negative  evidence,  so  partially  do  organic  remains  occur  in  gla- 
cial formations  even  in  those  of  indubitably  marine  origin.  When 
the  gravel  and  sand  are  of  a  porous  nature,  we  can  easily  account  for 
the  decomposition  of  the  shells  and  their  total  disappearance  in  the 
course  of  thousands  of  years,  but  a  large  part  of  the  Scotch  till  is  so 
impervious  to  water  that  the  absence  of  fossil  testacea  leads  us  rather 
to  suspect  that  it  was  originally  the  moraine  of  a  terrestrial  glacier, 
and,  therefore,  from  the  first  devoid  of  shells. 

I  formerly  suggested  that  the  absence  of  all  signs  of  organic  life  in 


CH.  XII.]  GLACIAL  SCORINGS  ON  SCOTTISH  ROCKS. 

a  great  portion  of  this  drift  might  be  connected  with  the  severity  of 
the  cold,  and  also  in  some  places  with  the  depth  of  the  sea  during 
the  period  of  extreme  submergence ;  but  my  faith  in  such  an  hypo- 
thesis has  been  shaken  by  modern  investigations,  an  exuberance  of 
life  having  been  observed  both  in  arctic  and  antarctic  seas  of  great 
depth,  and  where  floating  ice  abounds.  Thus,  Dr.  Hooker  enume- 
rates Crustacea,  mollusca,  serpulae,  and  other  invertebrata,  at  depths 
of  200  and  400  fathoms  off  Victoria  Land,  between  latitudes  71°  and 
78°  S.,  and  animal  life  was  traced  even  to  a  depth  of  550  fathoms ; 
whilst  MM.  Torell  and  Chydenius  in  1861  obtained  mollusca,  between 
Spitzbergen  and  Norway,  at  the  enormous  depths  of  1000  and  1500 
fathoms,  the  temperature  of  the  mud  being  between  32°  and  33° 
Fahrenheit. 

We  have  seen  that  the  scoring  and  polishing  of  the  rocks  in  Scot- 
land, as  in  Sweden  and  elsewhere,  is  not  confined  to  the  land,  but  is 
seen  to  pass  under  the  sea,  the  same  furrows  being  so  continuous  as 
to  imply  that  glaciers  or  continental  ice  once  acted  on  a  surface  now 
submerged.  Mr.  Geikie  observes  that,  on  the  west  coast  of  Scotland, 
these  glacial  markings  are  almost  always  fresher  at  and  below  the 
present  sea-level  than  at  higher  levels.  In  some  places,  even  where 
the  ice-moulded  rocks  are  washed  by  the  waves  of  the  sea,  they  retain 
their  finer  striae,  and  bosses  of  rock  their  rounded  and  smoothed  sur- 
faces. Yet,  at  an  elevation  of  20  feet  and  upward,  the  rounded  out- 
lines are  broken,  and  all  the  exposed  surfaces  disintegrated  by  the 
water.  In  explanation  of  these  peculiar  appearances,  he  supposes, 
first,  the  sinking  of  land  which  had  been  polished  and  striated  by 
continental  ice  in  the  manner  before  alluded  to,  p.  144 ;  secondly,  a 
very  recent  date  for  the  upheaval  of  the  lowest  25  feet  of  the  coast,  a 
suggestion  confirmed  by  the  occurrence  of  a  raised  beach  in  which 
the  recent  shells  agree  with  those  of  the  adjoining  sea,  and  indicate  a 
less  glacial  climate  than  those  of  an  older  beach  found  at  a  higher 
level,  or  about  40  feet  above  high-water  mark.  The  upper  of  the  two 
beaches  has  suffered  more  from  atmospheric  action  than  the  lower, 
and  has  evidently  been  exposed  for  a  much  longer  time. 

Besides  the  proofs  afforded  by  shells  at  the  height  of  about  500 
feet,  there  are  also  on  the  mountains  of  many  parts  of  Scotland,  as, 
for  example,  on  the  Grampians,  and  on  the  Sidlaw  and  Pentland 
Hills,  erratic  blocks,  at  heights  from' 1000  to  2000  feet  and  upward, 
so  wholly  unconnected  with  the  mineral  structure  of  the  region  where 
they  lie,  that  they  seem  to  point  to  a  former  period  of  submergence 
and  floating  ice.  There  is  also  another  curious  phenomenon  bearing 
on  this  subject  which  the  late  Hugh  Miller  styled  the  striated  "pave- 
ments "  of  the  boulder  clay.  Where  portions  of  the  till  have  been 
removed  by  the  sea  on  the  shores  of  the  Forth,  or  in  the  interior  by 
railway  cuttings,  the  boulders  imbedded  in  what  remains  of  the  drift 
are  seen  to  have  been  all  subjected  to  a  process  of  abrasion  and  stria- 
tion,  the  stria*  and  furrows  being  parallel  and  persistent  across  them 


156 


CONTORTED  STEATA  IN  DRIFT. 


[Cn.  XIL 


all,  exactly  as  if  a  glacier  or  iceberg  had  passed  over  them  and  scored 
them  in  a  manner  similar  to  that  which  the  solid  rocks  below  the 
glacial  drift  have  so  often  undergone.  It  is  possible,  as  Mr.  Geikie 
conjectures,  that  this  second  striation  of  the  boulders  may  be  refer- 
able to  the  second  era  of  drift  or  floating  ice.* 

Contorted  Strata  in  Drift. — In  Scotland  the  till  is  often  covered 
with  stratified  gravel,  sand,  and  clay,  the  beds  of  which  are  some- 
times horizontal  and  sometimes  contorted  for  a  thickness  of  several 
feet.  Such  contortions  are  not  uncommon  in  Forfarshire,  where  T 
observed  them,  among  other  places,  in  a  vertical  cutting  made  in 
1840  near  the  left  bank  of  the  South  Esk,  east  of  the  Bridge  of  Cor- 
tachie.  The  convolutions  of  the  beds  of  fine  and  coarse  sand,  gravel, 
and  loam,  extend  through  a  thickness  of  no  less  than  25  feet  perpen- 
dicular, or  from  b  to  c,  fig.  137,  the  horizontal  stratification  being 
resumed  very  abruptly  at  a  short  distance,  as  beyond  /,  g.  The  over- 
lying coarse  gravel  and  sand  a,  is  in  some  places  horizontal,  in  others 

Fig.  137. 


a  £3 


O      o 


0 

o 

•  —           o 

0      o 

^7^7 

77  7 

/   /    / 

Section  of  contorted  drift  overlying  till,  seen  on  left  bank  of  South  Esk,  near  Cortachie,  in 
1840.    Height  of  section  seen,  from  a  to  eZ,  about  50  feet. 

a.  Superficial  sand,  with  some  beds  of  coarse  gravel  with  cross  bedding  in  parts — 4  feet. 
&,  c.  Contorted  beds  25  feet  in  vertical  height,  by  the  side  of  which,  in  the  same  continuous 
section,  are  seen  horizontal  beds  of  stratified  drift,  some  of  them  with  coarse  gravel  and 
large  boulders. 
c,  d.  TJnstratified  red  till,  with  large  boulders  of  granite,  gneiss,  quartzite,  &c.,  20  feet  thick, 

the  red  loam  being  derived  from  triturated  old  red  sandstone. 
d,  d'.  Similar  till  continued,  thickness  unknown. 

e.  Inclined  strata  of  old  red  sandstone,  not  laid  open  in  this  place. 

it  exhibits  cross  bedding,  and  does  not  partake  of  the  disturbances 
which  the  strata  6,  c  have  undergone.  The  underlying  till  is  exposed 
for  a  depth  of  about  20  feet ;  and  we  may  infer  from  sections  in  the 
neighborhood  that  it  is  considerably  thicker,  and  that  it  rests  on  the 
edges  of  highly  inclined  strata  of  old  red  sandstone,  as  represented  in 
the  section. 

*  Geikie,  ibid.  p.  68. 


CH.  XII.]  HOW  ACCOUNTED  FOR. 

In  some  cases  I  have  seen  fragments  of  stratified  clays  and  sands, 
bent  in  like  manner,  in  the  middle  of  a  great  mass  of  till.  Mr.  Trim- 
mer has  suggested,  in  explanation  of  such  phenomena,  the  intercala- 
tion in  the  glacial  period  of  large  irregular  masses  of  snow  or  ice 
between  layers  of  sand  and  gravel.  Some  of  the  cliffs  near  Behring's 
Straits,  in  which  the  remains  of  elephants  occur,  consist  of  ice  mixed 
with  mud  and  stones ;  and  Middendorf  describes  the  occurrence  in 
Siberia  of  masses  of  ice,  found  at  various  depths  from  the  surface 
after  digging  through  drift.  We  are  as  yet  unacquainted  with  the 
mode  of  operation  by  which  such  intermixtures  of  earthy  matter  and 
ice  are  commonly  produced,  but  we  may  easily  conceive  their  occur- 
rence in  Siberia,  where  the  rivers  flow  from  south  to  north,  so  that 
the  thaw  begins  in  the  country  where  they  take  their  rise,  while  in 
the  lower  regions  which  they  overflow  their  channels  are  still  choked 
up  with  ice  and  snow.  In  the  arctic  and  antarctic  regions,  also,  the 
frozen  surface  of  the  sea  at  the  base  of  lofty  cliffs  is  sometimes  seen 
to  be  the  receptacle  first  of  mud  and  sand,  washed  down  from  the 
land  when  there  is  a  thaw,  and  then,  when  the  cold  returns,  of  dense 
masses  of  snow  drifted  by  the  wind  over  the  edge  of  the  cliff.  Ice- 
rafts,  supporting  such  alternations  of  snow  and  of  earthy 'and  stony 
matter,  have  been  seen  floating  from  place  to  place  in  polar  latitudes. 
Whenever  the  intercalation  of  snow  and  ice  with  drift,  whether  strati- 
fied or  unstratified,  has  taken  place,  the  melting  of  the  ice  will  cause 
such  a  failure  of  support  as  may  give  rise  to  flexures,  and  sometimes 
to  the  most  complicated  foldings. 

But  in  many  cases  the  strata  may  have  been  bent  and  deranged 
by  the  mechanical  pressure  of  an  advancing  glacier,  or  by  the  side- 
way  thrust  of  huge  islands  of  ice  running  aground  against  sand- 
banks ;  in  which  case,  the  position  of  the  beds  forming  the  founda- 
tion of  the  banks  may  not  be  at  all  disturbed  by  the  shock.  Mr. 
Geikie  has  described  examples,  in  the  basin  of  the  Clyde,  of  ex- 
tremely contorted  beds  of  sand  and  clay,  which  he  attributes  to 
powerful  pressure  experienced  under  a  glacier  or  mass  of  continental 
ice. 

It  should  also  be  borne  in  mind  that  lateral  pressure  may  be  exert- 
ed simply  by  the  weight  of  a  heavy  mass  of  materials  thrown  down 
on  some  adjoining  area,  to  which  pliant  beds  of  clay  and  sand  may  ex- 
tend. When  a  railway  embankment  is  thrown  across  a  marsh  or 
across  the  bed  of  a  drained  lake,  we  frequently  find  that  the  founda- 
tion, consisting  of  peat  and  shell-marl,  or  of  quicksand  and  mud,  gives 
way,  and  sinks  as  fast  as  the  embankment  is  raised  at  the  top.  At 
the  same  time,  there  is  often  seen  at  the  distance  of  many  yards,  in 
some  neighboring  part  of  the  morass,  a  squeezing  up  of  pliant  strata, 
the  amount  of  upheaval  -depending  on  the  volume  and  weight  of 
materials  heaped  upon  the  embankment.  In  1852  I  saw  a  remarka- 
ble  instance  of  such  a  downward  and  lateral  pressure,  in  the  surburbs 
of  Boston  (U.  S.),  near  the  South  Cove.  With  a  view  of  converting 


158  GLACIATION  OF  WALES.  [Cn.  XII. 

part  of  an  estuary  overflowed  at  high  tide  into  dry  land,  they  had 
thrown  into  it  a  vast  load  of  stones  and  sand,  upwards  of  900,000 
cubic  yards  in  volume.  Under  this  weight  the  mud  had  sunk  down 
many  yards  vertically.  Meanwhile  the  adjoining  bottom  of  the  estu- 
ary, supporting  a  dense  growth  of  salt-water  plants,  only  visible  at  low 
tide,  had  been  pushed  gradually  upward,  in  the  course  of  many 
months,  so  as  to  project  five  or  six  feet  above  high-water  mark.  The 
upraised  mass  was  bent  into  five  or  six  anticlinal  folds,  and  below  the 
upper  layer  of  turf,  consisting  of  salt-marsh  plants,  mud  was  seen 
above  the  level  of  high  tide,  full  of  sea-shells,  such  as  Mya  arenaria, 
Modiola  plicatula,  Sanguinolaria  fusca,  JVassa  obsoleta,  Natica  triseri- 
ata,  and  others.  In  some  of  these  curved  beds  the  layers  of  shells 
were  quite  vertical.  The  upraised  area  was  75  feet  wide,  and  several 
hundred  yards  long.  Were  an  equal  load,  melted  out  of  icebergs  or 
coast-ice,  thrown  down  on  the  floor  of  a  sea,  consisting  of  soft  mud 
and  sand,  similar  disturbances  and  contortions  might  result  in  some 
adjacent  pliant  strata,  yet  the  underlying  more  solid  rocks  might  re- 
main undisturbed,  and  newer  formations,  perfectly  horizontal,  might 
be  afterwards  superimposed. 

Cflaciation  of  Wales,  England,  and  Ireland. — The  mountains  of 
North  Wales  were  recognized,  in  1842,  by  Dr.  Buckland,  as  having 
been  an  independent  centre  of  the  dispersion  of  erratics, — great 
glaciers,  long  since  extinct,  having  radiated  from  the  Snowdonian 
heights  in  Carnarvonshire,  through  seven  principal  valleys  toward  as 
many  points  of  the  compass,  carrying  with  them  large  stony  fragments, 
and  grooving  the  subjacent  rocks  in  as  many  directions. 

Besides  this  evidence  of  land  glaciers,  Mr.  Trimmer  had  previously, 
in  1831,  detected  the  signs  of  a  great  submergence  in  Wales  in  the 
Post-pliocene  period.  He  had  observed  stratified  drift,  from  which 
he  obtained  about  a  dozen  species  of  marine  shells,  near  the  summit 
of  Moel  Tryfaen,  a  hill  1400  feet  high,  on  the  south  side  of  the 
Menai  Straits.  Although  his  observations  were  afterwards  confirmed 
by  the  late  E.  Forbes,  and  still  later  by  Mr.  Prestwich  and  Professor 
Ramsay,  doubts  as  to  the  nature  and  age  of  the  deposit  still  lingered 
in  many  minds.  But  on  these  subjects  all  doubt  has  at  length  been 
removed  by  aid  of  a  long  and  deep  cutting  made  through  the  drift  in 
1863  by  the  Alexandra  Mining  Company  in  search  of  slates.  In  this 
cutting  a  stratified  mass  of  incoherent  sand  and  gravel,  35  feet  thick, 
was  laid  open  near  the  summit  of  Moel  Tryfaen,  containing  shells, 
some  entire,  but  most  of  them  in  fragments.  In  the  summer  of  1863 
I  examined  the  newly-opened  section  in  company  with  the  Rev.  W.  S. 
Symonds,  and  we  obtained  20  species  of  shells  on  the  spot,  and  found 
in  the  lowest  beds  of  the  drift  large  heavy  boulders  of  far-transported 
rocks,  glacially  polished  and  scratched  on  more  than  one  side.  Un- 
derneath the  whole  we  saw  the  edges  of  vertical  slates  exposed  to 
view,  which  here,  like  the  rocks  in  other  parts  of  Wales,  some  at 
greater  and  some  at  less  elevations,  exhibit,  beneath  the  drift,  unequi- 


CH.  XII.]  MAKINE  SHELLS  OF  MOEL  TRYFAEN. 

vocal  marks  of  prolonged  glaciation.  Mr.  R.  D.  Darbishire,  after  a 
diligent  search  in  1863,  formed  a  collection  from  this  same  drift  of 
Moel  Tryfaen  of  no  less  than  54  species  of  mollusca,  besides  three 
characteristic  arctic  varieties — in  all  57  forms.  They  belong  without 
exception  to  species  still  living  in  British  or  more  northern  seas ;  eleven 
of  them  being  exclusively  arctic,  four  common  to  the  arctic  and  Brit- 
ish seas,  and  a  large  proportion  of  the  remainder  having  a  northward 
range,  or,  if  found  at  all  in  the  southern  seas  of  Britain,  being  com- 
paratively less  abundant. 

The  whole  deposit  has  much  the  appearance  of  an  accumulation  in 
shallow  water  or  on  a  beach,  and  it  probably  acquired  its  thickness 
during  the  gradual  subsidence  of  the  coast — an  hypothesis  which  would 
require  us  to  ascribe  to  it  a  high  antiquity,  since  we  must  allow  time, 
first  for  its  sinking,  and  then  for  its  re-elevation.  As  the  layers  of 
shell-bearing  sand  and  gravel  are  so  porous,  we  may  naturally  feel  sur- 
prise that  they  have  escaped  decomposition.  To  account  for  this,  Mr. 
Darbishire  suggests  that  a  bed  of  overlying  clay,  nearly  two  feet  thick, 
may,  by  its  impermeable  nature,  have  prevented  the  fossils  from  being 
dissolved  by  the  percolation  of  rain-water. 

The  elevation  reached  by  these  fossil  shells  on  Moel  Tryfaen  is  no 
less  than  1360  feet — a  most  important  fact  when  we  consider  that  we 
have  scarcely  a  well-authenticated  case  as  yet  on  record  beyond  the 
limits  of  Wales,  whether  in  Europe  or  North  America,  of  marine 
shells  having  been  found  in  glacial  drift  at  half  the  height  above  in- 
dicated. 

Mr.  Darwin,  after  studying  the  Welsh  glacial  drift  previously 
shown  by  Mr.  Trimmer  to  have  been  of  submarine  origin,  came  to 
the  opinion  that  the  land,  when  it  was  re-upheaved  to  its  present 
height,  was  covered  a  second  time,  at  least  in  the  higher  valleys,  by 
glaciers  which  swept  the  surface  clean  of  all  the  rubbish  left  by  the 
sea.* 

Professor  Eamsay,  also,  in  a  "  Memoir  on  the  Welsh  Glaciers,"  in 
1851,f  announced  his  conviction  that  there  had  been,  first,  an  intensely 
cold  period  when  the  land  was  more  elevated  than  now,  then  a  sub- 
mergence beneath  the  sea,  and  lastly,  a  re-elevation  attended  by  a  second 
period  of  glaciers.  Although  he  had  not  been  able  to  trace  marine 
shells  in  the  drift  to  a  level  exceeding  1300  feet  above  the  sea,  he  es- 
timated the  probable  amount  of  submergence  during  some  part  of  the 
glacial  period  at  about  2300  feet ;  for  he  was  unable  to  distinguish  the 
superficial  sands  and  gravel  which  reached  that  high  elevation  from  the 
drift  which,  at  Moel  Tryfaen  and  at  lower  points,  contains  shells  of 
living  species. 

The  evidence  of  the  marine  origin  of  the  highest  drift  is  no  doubt 
inconclusive  in  the  absence  of  shells,  so  great  is  the  resemblance  of  the 

*  Philosophical  Magazine,  ser.  3,  vol.  xxi.  p.  180. 
f  Quart.  Geol.  Journ.,  1852,  vol.  viii.  p.  372. 


160  NORFOLK  DRIFT.  [Cn.  XII. 

gravel  and  sand  of  a  sea  beach  and  of  a  river's  bed,  when  organic  re- 
mains are  wanting ;  but,  on  the  other  hand,  when  we  consider  the 
general  rarity  of  shells  in  drift  which  we  know  to  be  of  marine  origin, 
we  cannot  suppose  that,  in  the  shelly  sands  of  Moel  Tryfaen,  we  have 
hit  upon  the  exact  uppermost  limit  of  marine  deposition,  or,  in  other 
words,  a  precise  measure  of  the  submergence  of  the  land  beneath  the 
sea  during  the  glacial  period. 

We  are  gradually  obtaining  proofs  of  the  larger  part  of  England 
north  of  a  line  drawn  from  the  mouth  of  the  Thames  to  the  Bristol 
Channel,  having  been  under  the  sea  and  traversed  by  floating  ice  since 
the  commencement  of  the  glacial  epoch.  Among  recent  observations 
illustrative  of  this  point,  I  may  allude  to  the  discovery,  by  Mr.  J.  F. 
Bateman,  near  Blackpool,  fifty  miles  from  the  sea,  and  at  the  height 
of  568  feet  above  its  level,  of  till  containing  rounded  and  angular 
stones  and  marine  shells,  such  as  Turritella  communis,  Purpura 
lapillus,  Cardium  edule,  and  others,  among  which  Trophon  clathratum 
(=Fusus  Bamffius),  though  still  surviving  in  North  British  seas,  in- 
dicates a  cold  climate.  Drift  of  similar  character  covers  a  large  part 
of  Ireland,  although  marine  shells  have  not  been  detected  in  it  at 
greater  height  than  600  feet,  and  very  rarely  higher  than  500  ;  but 
there  can  be  no  doubt  that  that  island,  like  the  greater  part  of  Eng- 
land and  Scotland,  was  for  ages  an  archipelago  traversed  by  floating  ice. 
There  was  first  a  period  when  Ireland  formed  part  of  the  continent  of 
Europe,  from  whence  it  received  the  plants  and  animals  now  inhabit- 
ing it.  In  some  part  of  this  period  its  rocks  were  largely  smoothed 
and  striated  by  ice-action  in  the  more  mountainous  regions.  After  this 
there  was  great  subsidence,  and  the  conversion  of  the  island  into  an 
archipelago,  followed  by  a  re-elevation  of  land  and  a  second  continental 
period,  and,  after  all  these  changes,  a  final  separation  from  England  and 
Wales.* 

Norfolk  Drift. — In  England  the  monuments  of  the  period  of  sub- 
mergence can  nowhere  be  so  advantageously  studied  as  in  the  cliffs  of 
the  Norfolk  coast  between  Happisburgh  and  Cromer.  Vertical  sections, 
varying  in  height  from  30  to  300  feet,  are  there  exposed  to  view  for  a 
distance  of  about  fifty  miles,  where  the  series  of  formations,  beginning 
with  the  lowest,  is  as  follows  : — First,  chalk,  with  flints  in  nearly  hori- 
zontal strata ;  secondly,  Norwich  Crag,  or  a  marine  tertiary  formation 
of  the  Newer  Pliocene  era,  which  extends  from  Weybourne  seven  miles 
to  Cromer,  and  then  thins  out ;  thirdly,  the  forest  bed,  chiefly  com- 
posed of  vegetable  matter,  with  scattered  cones  of  the  Scotch  and 
spruce  firs,  and  many  other  recent  plants,  and  with  bones  of  the  ele- 
phant and  of  other  extinct  and  living  species  of  mammalia.  In  this 
forest  bed  the  stumps  of  many  trees  stand  erect  with  their  roots  in  an 
ancient  soil.  Fourthly,  a  fluvio-marine  series,  with  abundant  lignite 
beds,  and  with  alternations  of  freshwater  and  marine  strata  of  sand 

*  See  Antiquity  of  Man,  by  the  Author,  chap.  xiv. 


CH.  XII.]  NORFOLK  DRIFT. 


161 


and  clay,  the  shells  being  all  of  recent  species;  fifthly,  firmly  laminated 
blue  clay  without  fossils,  on  which  rests  the  boulder  clay  of  the  glacial 
period,  from  20  to  80  feet  thick,  with  far-transported  erratics,  some  of 
them  polished  and  scratched ;  sixthly,  contorted  drift ;  seventhly,  super- 
ficial gravel  and  sand. 

In  the  Norwich  Crag  above  mentioned,  which  will  be  described  in 
chap,  xiii.,  there  is  a  small  mixture  (about  12  per  cent.)  of  extinct 
species  of  shells,  but  in  the  overlying  formations,  beginning  with  the 
forest  bed,  the  species  are  identical  with  those  now  living,  and  it  is 
remarkable  that,  while  the  plants  in  the  forest  bed  and  lignite  are  such 
as  now  exist  in  Europe,  and  are  nearly  all  of  them  indigenous  in  Great 
Britain,  the  mammalian  fauna  contains  many  conspicuous  species 
which  no  longer  survive  in  any  part  of  the  globe.  Among  these  last, 
as  appears  from  the  rich  collections  of  Messrs.  Gunn  and  King,  are  no 
less  than  three  species  of  elephant,  namely,  first,  the  mammoth,  E. 
primigenius  ;  secondly,  the  elephant  first  observed  in  the  Val  d'Arno, 
E.  meridionalis,  Nesti ;  and,  thirdly,  E.  antiquus,  in  smaller  numbers 
than  the  two  former.  These  are  accompanied  by  ^Rhinoceros  etruscus 
(a  species  first  obtained  from  beds  of  the  same  age  near  Florence), 
Hippopotamus  major,  the  common  pig,  a  species  of  horse  and  of  bear, 
the  common  wolf,  a  bison,  the  large  Irish  deer,  the  reindeer,  and  other 
deer,  the  common  beaver,  besides  a  larger  extinct  species,  also  the 
walrus,  narwhal,  and  some  others.  They  amount  in  all  to  about  20 
species,  of  which  rather  more  than  half  are  extinct. 

It  will  be  seen  in  the  next  chapter  that  the  shells  of  some  of  the 
latest  deposits  of  Norwich  Crag  show  that  great  cold  prevailed  in 
the  British  seas  before  the  close  of  the  Newer  Pliocene  period ;  when 
we  speak,  therefore,  of  the  vegetation  and  quadrupeds  of  the  Cromer 
forest  being  pre-glacial,  we  merely  mean  that  they  preceded  the  era 
of  the  general  submergence  of  the  British  Isles  beneath  the  waters  of 
the  glacial  sea.  That  they  were  anterior  to  that  submergence  may 
be  inferred  from  the  superposition  on  the  forest  and  lignite  beds  of 
the  vast  load  of  boulder-clay  above  alluded  to,  which  contains  far- 
transported  blocks,  some  of  Scandinavian  origin,  and  probably  floated 
from  the  north  when  Norway  and  Sweden  were  as  much  covered  with 
ice  as  the  modern  continent  of  Greenland.  Other  portions  of  the  till 
may  have  come  from  the  northwest,  as  they  comprise  the  wreck  of 
the  Cretaceous,  Oolitic,  and  older  British  formations. 

The  fiuvio-marine  series  affords  distinct  evidence  of  several  alterna- 
tions of  fluviatile,  marine,  and  terrestrial  conditions.  Besides  the 
forest  bed,  for  example,  Professor  Philips  has  observed  at  one  point 
a  growth  of  land-plants  in  an  erect  position,  at  a  higher  level,  and 
Mr.  King  has  found  intercalated  beds  in  which  bivalve  shells,  such 
as  Mya  truncata,  are  so  placed  erect  in  the  loam  with  their  siphun- 
cular  ends  uppermost,  as  to  show,  as  unmistakably  as  does  the  erect 
position  of  the  trees  with  their  roots  still  fixed  in  their  original  soil, 
that  they  lived  on  the  spot  where  they  are  now  entombed.  It  was 
11 


162  NORFOLK  DRIFT.  [On.  XII. 

stated  that  upon  the  fluvio-marine  formation  repose  laminated  clays 
without  fossils,  and  these  are  followed  by  great  masses  of  till  or  un- 
stratified  clay  from  20  to  80  feet  thick.  Among  the  included  frag- 
ments of  rock  are  some  of  granite,  the  largest  of  which  are  from  6  to 
8  feet  in  diameter;  also  syenite,  of  Scandinavian  origin,  and  the 
wreck  of  the  Norwich  Grag,  London  Clay,  chalk,  oolite,  and  lias, 
with  boulders  of  more  ancient  fossiliferous  rocks. 

The  cliff-sections  above  described  show  that  in  various  parts  of 
Norfolk  and  Suffolk  several  of  the  extinct  as  well  as  the  living  species 
of  mammalia  lived  after  the  accumulation  of  the  glacial  till  and 
boulders,  as  well  as  before  it.  The  Elephas  primigenius  affords  an 
example  of  one  of  these  extinct  species,  and  in  many  British  locali- 
ties the  Elephas  antiquus  and  Hippopotamus  major  occur  in  the  allu- 
vium of  valleys  of  later  date  than  the  marine  boulder  clay.  Some  of 
the  valleys  in  question  have  been  excavated  through  the  glacial  drift 
after  the  latter  had  been  upraised  from  the  bed  of  the  sea. 

At  Mundesley,  in  the  Norfolk  cliffs,  and  at  Hoxne,  not  only  has 
such  denudation  taken  place,  but  the  hollows  near  Diss,  in  Suffolk, 
scooped  out  of  the  drift,  have  been  again  filled  up  with  freshwater 
strata,  in  some  of  which  the  remains  of  the  elephant  have  been  dis- 
covered.* 

One  of  the  formations  of  the  Norfolk  cliffs,  above  mentioned  as 
overlying  the  till,  has  been  called  contorted  drift,  so  frequently  are  its 
beds  of  gravel,  sand,  and  clay,  bent  and  folded  back  upon  themselves, 
in  the  same  manner  as  parts  of  the  Scotch  drift,  represented  in  fig. 
137,  p.  156.  In  some  cases  these  contortions  extend  for  a  height  of 
70  or  80  feet,  and  they  are  coiled  round  isolated  masses  of  chalk, 
such  as  may  have  fallen  in  landslips  from  a  perpendicular  cliff  on  the 
surface  of  a  frozen  sea,  or  of  an  ice-island  first  driven  by  the  winds 
and  currents  against  a  steep  coast,  and  then  carried  away  again  by  a 
change  of  the  wind  until  it  grounded  in  a  sea  of  sufficient  depth  to 
allow  of  the  deposition  of  its  earthy  and  stony  burthen  on  the  spot 
where  it  melted  on  the  bottom  of  the  sea.  The  bent  and  disturbed 
beds  often  rest  on  strata  of  sand  and  clay,  which  are  perfectly  hori- 
zontal. In  those  places  where  the  contortions  are  on  the  greatest 
scale,  as  at  Sherringham  for  example,  the  chalk  with  flints  at  the  base 
of  the  cliffs  retains  its  horizontality,  and  has  evidently  not  participated 
in  the  slightest  degree  in  the  violent  movements  to  which  the  strati- 
fied drift  and  the  huge  masses  of  chalk,  transported  bodily  from  their 
original  position,  bear  testimony.  The  probable  causes  of  such  par- 
tial derangement  in  the  strata  so  peculiarly  characteristic  of  the  gla- 
cial period  have  already  been  spoken  of  (p.  157).  The  successive 
deposits  seen  in  direct  superposition  on  the  Norfolk  coast  imply  at 
first  the  prevalence  over  a  wide  area  of  the  Newer  Pliocene  sea. 

*  For  a  fuller  account  of  these  Norfolk  deposits,  see  Lyell,  Antiquity  of  Man, 
chap.  xii. 


CH.  XII.]  AMERICAN  GLACIAL  FORMATIONS. 


163 


Afterward  the  bed  of  this  sea  was  converted  into  dry  land,  and 
underwent  several  oscillations  of  level,  so  as  to  be  first  land,  support- 
ing a  forest,  then  an  estuary,  then  again  land,  and  finally  a  sea  near 
the  mouth  of  a  river,  till  the  downward  movement  became  so  great 
as  to  convert  the  whole  area  into  a  sea  of  considerable  depth,  in 
which  much  floating  ice  carrying  mud,  sand,  and  boulders  melted  and 
let  fall  its  burthen  to  the  bottom.  Finally,  over  the  till,  with  boul- 
ders, stratified  drift  was  formed,  after  which,  but  not  until  the  total 
subsidence  had  amounted  to  more  than  400  feet,  an  upward  move- 
ment began,  which  reelevated  the  country,  so  that  the  lowest  of  the 
terrestrial  formations,  or  the  forest  bed,  was  brought  up  to  nearly  its 
pristine  level  in  such  a  manner  as  to  be  exposed  at  low  tide.  Both  the 
descending  and  ascending  movements  seem  to  have  been  very  gradual. 


GLACIAL    FORMATIONS    IN    NORTH    AMERICA. 

In  the  Western  Hemisphere,  both  in  Canada  and  as  far  south  as 
the  40th  and  even  38th  parallel  of  latitude  in  the  United  States,  we 
meet  with  a  repetition  of  all  the  peculiarities  which  distinguish  the 
European  boulder  formation.  Fragments  of  rock  have  travelled  for 
great  distances,  especially  from  north  to  south :  the  surface  of  the 
subjacent  rock  is  smoothed,  striated,  and  fluted ;  unstratified  mud  or 
till  containing  boulders  is  associated  with  strata  of  loam,  sand,  and 
clay,  usually  devoid  of  fossils.  Where  shells  are  present,  they  are 
of  species  still  living  in  northern  seas,  and  half  of  them  identical 
with  those  already  enumerated  as  belonging  to  European  drift.  The 
fauna  also  of  the  glacial  epoch  in  North  America  is  less  rich  in 
species  than  that  now  inhabiting  the  adjacent  sea,  whether  in  the 
Gulf  of  St.  Lawrence,  or  off"  the  shores  of  Maine,  or  in  the  Bay  of 
Massachusetts. 

The  extension  on  the  American  continent  of  the  range  of  erratics 
during  the  Post-pliocene  period  to  lower  latitudes  than  they  reached 
in  Europe,  agrees  well  with  the  present  southward  deflection  of  the 
isothermal  lines,  or  rather  the  lines  of  equal  winter  temperature. 
It  seems  that  formerly,  as  now,  a  more  extreme  climate  and  a  more 
abundant  supply  of  floating  ice  prevailed  on  the  western  side  of  the 
Atlantic. 

Another  resemblance  between  the  distribution  of  the  drift  fossils 
in  Europe  and  North  America  has  yet  to  be  pointed  out.  In  Canada 
and  the  United  States,  as  in  Norway,  Sweden,  Scotland,  and  Europe 
generally,  the  marine  shells  are  confined  to  very  moderate  elevations 
above  the  sea  (between  100  and  TOO  feet),  while  the  erratic  blocks 
and  the  grooved  and  polished  surfaces  of  rock  extend  to  elevations 
of  several  thousand  feet. 

I  described  in  1839  the  fossil  shells  collected  by  Captain  Bayfield, 
from  strata  of  drift  at  Beauport,  near  Quebec,  in  lat.  47°,  and  drew 


164 


CANADIAN  DRIFT. 


[Cn.  XII. 


from  them  the  inference  that  they  indicated  a  more  northern  climate, 
the  shells  agreeing  in  great  part  with  those  of  Uddevalla  in  Sweden.* 
The  shelly  beds  attain  at  Beauport  and  the  neighborhood  a  height  of 
200,  300,  and  sometimes  400  feet  above  the  sea,  and  dispersed  through 
some  of  them  are  large  boulders  of  granite,  which  could  not  have 
been  propelled  by  a  violent  current,  because  the  accompanying  fragile 
shells  are  almost  all  entire.  They  seem,  therefore,  said  Captain  Bay- 
field,  writing  in  1838,  to  have  been  dropped  down  from  melting  ice, 
like  similar  stones  which  are  now  annually  deposited  in  the  St.  Law- 
rence.f  I  visited  this  locality  in  1842,  and  made  the  annexed  sec- 
tion, fig.  138,  which  will  give  an  idea  of  the  general  position  of  the 
drift  in  Canada  and  the  United  States.  I  imagine  that  the  whole  of 


Fig.  138. 


K 


K.  Mr.  Kyland's  house. 

h.  Clay  and  sand  of  higher  grounds,  with 

Saxica/va,  &c. 
g.  Gravel  with  boulders. 
/    Mass  of  Saxfcava  rugosa,  12  feet  thick. 
c.  Sand  and  loam  with  Mya  truncata, 

Scalaria  Grcerilandica,  &c. 


d.  Drift,  with  boulders  of  syenite,  &c. 

c.  Yellow  sand. 

&.  Laminated  clay,  25  feet  thick. 

A.  Horizontal  lower  Silurian  strata. 

B.  Valley  re-excavated. 


the  valley,  B,  was  once  filled  up  with  the  beds  6,  c,  d,  e,  /,  which 
were  deposited  during  a  period  of  subsidence,  and  that  subsequently 
the  higher  country  (h)  was  submerged  and  overspread  with  drift. 
The  partial  reexcavation  of  B  took  place  when  this  region  was  again 
uplifted  above  the  sea  to  its  present  height.  Among  the  twenty-three 
species  of  fossil  shells  collected  by  me  from  these  beds  at  Beauport, 
all  were  of  recent  northern  species ;  the  only  supposed  exception, 
Astarte  Laurentiana,  being  now  considered  by  good  conchologists  as 
a  variety  of  the  British  A.  compressa  (see  fig.  139).  I  also  examined 

Fig.  139. 


Astarte  compressa,  Flem.  =  A.  Laurentiana. 
a.  Outside.  Z>.  Inside  of  right  valve.  c.  Left  valve. 

the  same  formation  farther  up  the  valley  of  the  St.  Lawrence,  in  the 
suburbs  of  Montreal,  where  some  of  the  beds  of  loam  are  filled  with 

*  Geol.  Trans.,  2d  series,  vol.  vi.  p.  135.     Mr.  Smith  of  Jordan  Hill  had  arrived 
at  similar  conclusions  as  to  climate  from  the  shells  of  the  Scotch  glacial  drift, 
f  Proceedings  of  Geol.  Soc.,  No.  63,  p.  119. 


CH.  XII.]  SUBMERGENCE  OF  NORTH  AMERICA.  105 

great  numbers  of  the  Mytilus  edulis,  or  our  common  European  mus- 
sel, retaining  both  its  valves  and  its  purple  color.  This  shelly 
deposit,  containing  among  other-  marine  shells  Saxicava  rugosa, 
characteristic  of  the  glacier  drift  of  Sweden,  also  occurs  at  an  elevated 
point  on  the  mountain  of  Montreal,  450  feet  above  the  level  of  the 
sea,* 

In  my  account  of  Canada  and  the  United  States,  published  in 
1845,  I  announced  the  conclusion  to  which  I  had  then  arrived,  that 
to  explain  the  position  of  erratics  and  the  polished  surfaces  of  rocks, 
and  their  striae  and  flutings,  we  must  assume  first  a  gradual  submer- 
gence of  the  land  in  North  America,  after  it  had  acquired  its  present 
outline  of  hill  and  valley,  cliff  and  ravine,  and  then  its  reemergence 
from  the  ocean.  In  order  to  account  for  the  universal  glaciation  of 
the  surface  of  the  solid  rocks,  on  which  the  drift  reposes  in  the  neigh- 
borhood of  the  great  lakes,  and  north  and  south  of  the  St.  Lawrence, 
it  seemed  necessary  to  assume  the  action  of  ice  previous  to  all  depo- 
sition of  drift  or  transportation  of  erratics.  The  general  direction  of 
the  furrows  from  north  to  south,  for  they  rarely  deviate  more  than 
10°  or  20°  to  the  east  or  west  of  the  meridian,  seemed  to  favor  the 
idea  of  their  being  for  the  most  part  due  to  the  running  aground  of 
icebergs  drifting  from  arctic  latitudes.  The  absence  in  many  regions, 
as  in  the  Niagara  district,  of  high  mountain  chains,  and  the  extension 
of  undiminished  ice  action  as  far  south  as  the  40th  parallel,  made  me 
unwilling  to  appeal,  save  in  some  exceptional  cases,  to  land  glaciers  as 
the  principal  agents  of  this  glaciation.  I  assumed,  therefore,  that 
while  the  land  was  slowly  sinking,  the  sea  which  bordered  it  was 
covered  with  islands  of  floating  ice  coming  from  the  north,  which,  as 
they  grounded  on  the  coast  and  on  shoals,  pushed  along  such  loose 
materials  of  sand  and  pebbles  as  lay  strewed  over  the  bottom.  By 
this  force  all  angular  and  projecting  points  were  broken  off,  and  frag- 
ments of  hard  stone,  frozen  into  the  lower  surface  of  the  ice,  scooped 
out  grooves  in  the  subjacent  solid  rock.  The  sloping  beach,  as  well 
as  the  floor  of  the  ocean,  might  be  polished  and  scored  by  this  ma- 
chinery, producing  such  long,  straight,  and  parallel  furrows,  as  are 
everywhere  visible  in  the  Niagara  district,  and  generally  in  the  region 
north  of  the  40th  parallel  of  latitude,  f 

This  hypothesis  of  a  slow  and  gradual  subsidence  of  the  land 
enables  us  to  imagine  that  the  polishing  and  grooving  action  may 
have  been  going  on  simultaneously  with  the  transportation  of  the 
erratics.  During  the  successive  depression  of  high  land,  varying 
originally  in  height  from  1000  to  3000  feet  above  the  sea-level,  every 
portion  of  the  surface  would  be  brought  down  by  turns  to  the  level  of 
the  ocean,  so  as  to  be  converted  first  into  a  coast-line,  and  then  into  a 
shoal ;  and  at  length,  after  being  well  scored  by  the  stranding  upon  it 

*  Travels  in  N.  America,  vol.  ii.  p.  141 
f  Ibid.,  vol.  ii.  chap.  xix.  p.  99. 


SUBMARINE  GLACIAL  DRIFT.  [On.  XII. 

year  after  year  of  large  masses  of  coast-ice  and  occasional  icebergs, 
might  be  sunk  to  a  depth  of  several  hundred  fathoms.  By  the  con- 
stant depression  of  land,  the  coast  would  recede  farther  and  farther 
from  the  successively  formed  zones  of  polished  and  striated  rock,  each 
outer  zone  becoming  in  its  turn  so  deep  under  water,  as  to  be  no 
longer  grated  upon  by  the  heaviest  icebergs.  Such  sunken  areas 
would  then  simply  serve  as  receptacles  of  mud,  sand,  and  boulders 
dropped  from  melting  ice,  perhaps  to  a  depth  scarcely,  if  at  all,  in- 
habited by  testacea  and  zoophytes.  Meanwhile,  during  the  forma- 
tion of  the  unstratified  and  unfossiliferous  mass  in  deep  water,  the 
smoothing  and  furrowing  of  shoals  and  beaches  would  still  go  on  else- 
where upon  and  near  the  coast  in  full  activity.  If  at  length  the  sub- 
sidence should  cease,  and  the  direction  of  the  movement  of  the  earth's 
crust  be  reversed,  the  sunken  area  covered  with  drift  would  be  slowly 
reconverted  into  land.  The  boulder  deposit,  before  emerging,  would 
then  for  a  time  be  brought  within  the  action  of  the  waves,  tides,  and 
currents,  so  that  its  upper  portion,  being  partially  denuded,  would 
have  its  materials  rearranged  and  stratified.  Streams  also  flowing 
from  the  land  would  in  some  places  throw  down  layers  of  sediment 
upon  the  till.  In  that  case,  the  order  of  superposition  will  be,  first 
and  uppermost,  sand,  loam,  and  gravel  occasionally  fossiliferous ;  sec- 
ondly, an  unstratified  and  unfossiliferous  mass  called  till,  for  the  most 
part  of  'much  older  date  than  the  preceding,  with  angular  erratics,  or 
with  boulders  interspersed  ;  and  thirdly,  beneath  the  whole,  a  surface 
of  polished  and  furrowed  rock. 

If  we  reflect  on  the  vast  area  over  which  the  dispersion  of  marine 
glacial  drift  is  now  in  progress,  we  shall  at  once  see  that  it  must 
equal,  if  it  does  not  greatly  exceed,  the  space  over  which  glaciers  and 
continental  ice  are  moving.  It  would,  therefore,  have  been  in  the 
highest  degree  perplexing  if  we  had  not  met  with  proofs  of  subma- 
rine glaciation  on  a  most  extensive  scale,  including  all  the  phenomena 
of  polishing,  scratching,  furrowing,  and  rounding  of  rocky  surfaces, 
and  the  transportation  of  erratics  and  finer  materials ;  seeing  that 
there  is  so  much  evidence  everywhere  in  Europe  and  North  America 
of  the  conversion  of  sea  into  land,  as  well  as  land  into  sea,  since  the 
commencement  of  the  glacial  epoch. 

But  although  a  large  portion  of  the  drift  of  North  America  has 
been  due,  like  that  of  Europe,  to  floating  ice  and  a  period  of  sub- 
mergence, that  continent  has  also  had  its  land-ice,  and  its  centres  of 
dispersion  of  erratic  blocks.  The  White  Mountains  of  New  Hamp- 
shire, lat.  44°  N.,  the  loftiest  of  which  is  more  than  6000  feet  high, 
may  be  cited  as  an  example ;  and  the  late  Professor  Hitchcock  in- 
ferred that  some  of  the  highest  hills  in  Massachusetts  once  sent  down 
their  glaciers  into  the  lower  country.  I  have  already  mentioned  that 
in  Europe  several  quadrupeds  of  living,  as  well  as  extinct,  species 
were  common  to  pre-glacial  and  post-glacial  times.  In  like  manner 
there  is  reason  to  suppose  that  in  North  America  much  of  the  ancient 


CH.  XII.]  MASTODON  GIGANTEUS. 

mammalian  fauna,  together  with  nearly  all  the  invertebrata,  lived 
through  the  ages  of  intense  cold. 

That  in  the  United  States,  the  Mastodon  giganteus  was  very  abundant 
after  the  drift  period  is  evident  from  the  fact  that  entire  skeletons  of  this 
animal  are  met  with  in  bogs  and  lacustrine  deposits  occupying  hollows 
in  the  drift.  They  sometimes  occur  in  the  bottom  even  of  small  ponds 
recently  drained  by  the  agriculturist  for  the  sake  of  the  shell  marl.  I  ex- 
amined one  of  these  spots  at  Geneseo  in  the  state  of  New  York,  from 
which  the  bones,  skull,  and  tusk  of  a  Mastodon  had  been  procured  in 
the  marl  below  a  layer  of  black  peaty  earth,  and  ascertained  that  all  the 
associated  freshwater  and  land  shells  were  of  a  species  now  common  in 
the  same  district.  They  consisted  of  several  species  of  Lymnea,  of  Pla- 
norbis  bicarinatus,  Physa  heterostropha,  &c. 

In  1845  no  less  than  six  skeletons  of  the  same  species  of  Mastodon 
were  found  in  Warren  county,  New  Jersey,  6  feet  below  the  surface,  by 
a  farmer  who  was  digging  out  the  rich  mud  from  a  small  pond  which 
he  had  drained.  Five  of  these  skeletons  were  lying  together,  and  a  large 
part  of  the  bones  crumbled  to  pieces  as  soon  as  they  were  exposed  to  the 
air.  But  nearly  the  whole  of  the  other  skeleton,  which  lay  about  10 
feet  apart  from  the  rest,  was  preserved  entire,  and  proved  the  correctness 
of  Cuvier's  conjecture  respecting  this  extinct  animal,  namely,  that  it 
had  twenty  ribs  like  the  living  elephant.  From  the  clay  in  the  interior 
within  the  ribs,  just  where  the  contents  of  the  stomach  might  naturally 
have  been  looked  for,  seven  bushels  of  vegetable  matter  were  extracted. 
I  submitted  some  of  this  matter  to  Mr.  A.  Henfrey,  of  London,  for 
microscopic  examination,  and  he  informs  me  that  it  consists  of  pieces  of 
small  twigs  of  a  coniferous  tree  of  the  Cypress  family,  probably  the  young 
shoots  of  the  white  cedar,  Thuja  occidentalis,  still  a  native  of  North 
America,  on  which  therefore  we  may  conclude  that  this  extinct  Mastodon 
once  fed. 

Another  specimen  of  the  same  quadruped,  the  most  complete  and 
probably  the  largest  ever  found,  was  exhumed  in  1845  in  the  town  of 
Newburg,  New  York,  the  length  of  the  skeleton  being  25  feet,  and  its 
height  12  feet.  The  anchylosing  of  the  last  two  ribs  on  the  right  side 
afforded  Dr.  John  C.  Warren  a  true  gauge  for  the  space  occupied  by  the 
intervertebrate  substance,  so  as  to  enable  him  to  form  a  correct  estimate 
of  the  entire  length.  The  tusks  when  discovered  were  10  feet  long,  but 
a  part  only  could  be  preserved.  The  large  proportion  of  animal  matter 
in  the  tusk,  teeth,  and  bones  of  some  of  these  fossil  mammalia  is  truly 
astonishing.  It  amounts  in  some  cases,  as  Dr.  C.  T.  Jackson  has  ascer- 
tained by  analysis,  to  27  per  cent.,  so  that  when  all  the  earthy  ingre- 
dients are  removed  by  acids,  the  form  of  the  bone  remains  as  perfect, 
and  the  mass  of  animal  matter  is  almost  as  firm,  as  in  a  recent  bone 
subjected  to  similar  treatment. 

It  would  be  rash,  however  to  infer  from  such  data  that  these  quadru- 
peds were  mired  in  modern  times,  unless  we  use  that  term  strictly  in  a 
geological  sense.  I  have  shown  that  there  is  a  fluviatile  deposit  in  the 


168  EXTINCT  MAMMALIA  ABOVE  DRIFT.  [Cn.  XII. 

valley  of  the  Niagara,  containing  shells  of  the  genera  Melania,  Lymnea, 
Planorbis,  Valvata,  Cyclas,  Uhio,  Helix,  &c.,  all  of  recent  species,  from 
which  the  bones  of  the  great  Mastodon  have  been  taken  in  a  very  perfect 
state.  Yet  the  whole  excavation  of  the  ravine,  for  many  miles  below 
the  Falls,  has  been  slowly  effected  since  that  fluviatile  deposit  was  thrown 
down. 

Whether  or  not,  in  assigning  a  period  of  more  than  30,000  years  for 
the  recession  of  the  Falls  from  Queenstown  to  their  present  site,  I  have 
over  or  under  estimated  the  time  required  for  that  operation,  no  one  can 
doubt  that  a  vast  number  of  centuries  must  have  elapsed  before  so  great 
a  series  of  geographical  changes  were  brought  about  as  have  occurred 
since  the  entombment  of  this  elephantine  quadruped.  The  freshwater 
gravel  which  incloses  it  is  decidedly  of  much  more  modern  origin  than 
the  drift  or  boulder  clay  of  the  same  region.* 

Other  extinct  animals  accompany  the  Mastodon  giganteus  in  the  post- 
glacial deposits  of  the  United  States,  among  which  the  Castoroides  ohi- 
oensis,  Foster  and  Wyman,  a  huge  rodent  allied  to  the  beaver,  and  the 
Capybara  may  be  mentioned.  But  whether  the  "loess,"  and  other 
freshwater  and  marine  strata  of  the  Southern  States,  in  which  skeletons 
of  the  same  Mastodon  are  mingled  with  the  bones  of  the  Megatherium, 
Mylodon,  and  Megalonyx,  were  contemporaneous  with  the  drift,  or  were 
of  subsequent  date,  is  a  chronological  question  still  open  to  discussion. 
It  appears  clear,  however,  from  what  we  know  of  the  tertiary  fossils  of 
Europe — and  I  believe  the  same  will  hold  true  in  North  America — that 
many  species  of  testacea  and  some  mammalia,  which  existed  prior  to  the 
glacial  epoch,  survived  that  era.  As  European  examples  among  the  warm- 
blooded quadrupeds,  the  Elephas  primigenius  and  Rhinoceros  tichorinus 
may  be  mentioned.  As  to  the  shells,  whether  freshwater,  terrestrial,  or 
marine,  they  need  not  be  enumerated  here,  as  allusion  will  be  made  to 
them  in  the  sequel,  when  the  pliocene  tertiary  fossils  of  Suffolk  are 
described.  The  fact  is  important,  as  refuting  the  hypothesis  that  the 
cold  of  the  glacial  period  was  so  intense  and  universal  as  to  annihilate 
all  living  creatures  throughout  the  globe. 

That  the  cold  was  greater  for  a  time  than  it  is  now  in  certain  parts  of 
Siberia,  Europe,  and  North  America,  will  not  be  disputed ;  but,  before 
we  can  infer  the  universality  of  a  colder  climate,  we  must  ascertain  what 
was  the  condition  of  other  parts  of  the  northern,  and  of  the  whole  south- 
ern, hemisphere  at  the  time  when  the  Scandinavian,  British,  and  Alpine 
erratics  were  transported  into  their  present  position.  It  must  not  be  for- 
gotten that  a  great  deposit  of  drift  and  erratic  blocks  is  now  in  full  pro- 
gress of  formation  in  the  southern  hemisphere,  in  a  zone  corresponding 
in  latitude  to  the  Baltic,  and  to  Northern  Italy,  Switzerland,  France,  and 
England.  Should  the  uneven  bed  of  the  southern  ocean  be  hereafter 
converted  by  upheaval  into  land,  the  hills  and  valleys  will  be  strewed 
over  with  transported  fragments,  some  derived  from  the  antarctic  conti- 

*  See  Travels  in  N.  America,  vol.  i.  chap,  ii.,  and  Principles  of  Geol.  chap  xiv. 


CH.  XII.]         RELATION  OF  LAKES  TO  GLACIAL  ACTION. 

nent,  others  from  islands  covered  with  glaciers,  like  South  Georgia, 
which  must  now  be  centres  of  the  dispersion  of  drift,  although  situ- 
ated in  a  latitude  agreeing  with  that  of  the  Cumberland  mountains  in 
England. 

Not  only  are  these  operations  going  on  between  the  45th  and  60th 
parallels  of  latitude  south  of  the  line,  while  the  corresponding  zone 
of  Europe  is  free  from  ice ;  but,  what  is  still  more  worthy  of  remark, 
we  find  in  the  southern  hemisphere  itself,  only  900  miles  distant  from 
South  Georgia,  where  the  perpetual  snow  reaches  to  the  sea-beach, 
lands  covered  with  forest,  as  in  Terra  del  Fuego.  There  is  here  no 
difference  of  latitude  to  account  for  the  luxuriance  of  vegetation  in 
one  spot,  and  the  absolute  want  of  it  in  the  other;  but  among 
other  refrigerating  causes  in  South  Georgia  may  be  enumerated  the 
countless  icebergs  which  float  from  the  antarctic  zone,  and  which 
chill,  as  they  melt,  the  waters  of  the  ocean,  and  the  surrounding  air, 
which  they  fill  with  dense  fogs.  The  contrast  of  climate  and  glacial 
conditions  in  corresponding  zones  of  the  northern  and  southern  hemi- 
spheres, and  even  in  corresponding  latitudes  on  the  same  side  of  the 
equator,  makes  it  highly  probable  that  the  extreme  of  cold  in  the 
glacial  period  was  not  experienced  simultaneously  in  North  America 
and  Europe. 

Connection  of  the  predominance  of  lakes  with  glacial  action. — It 
has  been  truly  remarked  that  lakes  are  very  common  in  those  coun- 
tries where  erratics,  striated  boulders,  and  rock  surfaces,  with  other 
signs  of  glaciation  abound ;  and  that  they  are  comparatively  rare  in 
tropical  and  subtropical  regions.  When  travelling  over  some  of  the 
lower  lands  in  Sweden,  far  -from  mountains,  as  well  as  over  the  coast 
region  of  Maine  in  the  United  States,  and  other  districts  in  North 
America,  I  was  much  struck  with  the  innumerable  ponds  and  small 
lakes,  of  which  counterparts  are  described  as  equally  characteristic  of 
Finland,  Canada,  and  the  Hudson's  Bay  Territories.  I  have  never 
seen  any  similar  form  of  the  surface  south  of  latitude  40°  N.  in  the 
western,  and  50°  N.  in  the  eastern  hemisphere.  The  relation  of  a 
certain  number  of  these  sheets  of  water  to  the  glacial  period  is  obvi- 
ous enough,  for  not  a  few  of  them  are  dammed  up  by  barriers  of 
unstratified  drift,  such  as  may  have  constituted  the  terminal  and  late- 
ral moraines  of  glaciers,  or  may  have  been  thrown  down  from  melting 
icebergs  when  the  country  was  still  under  water.  To  this  class  of 
lakes  and  ponds  the  term  "  morainic  "  has  been  applied.  But  I  agree 
with  Professor  Ramsay,  that  the  origin  of  many,  even  of  the  moder- 
ate-sized depressions  now  filled  with  water,  cannot  be  so  explained, 
because  many  of  them  have  their  barriers  formed  of  solid  rock. 

With  reference  to  cavities  of  large  dimensions  containing  water  in 
mountainous  regions,  they  have  been  truly  said  to  lie  almost  universally 
in  the  course  of  valleys  of  erosion,  being,  like  them,  narrow  in  propor- 
tion to  their  length.  If  many  of  them  run  in  the  lines  of  great  rents 
and  faults,  traversing  the  older  rocks,  this  is  no  more  than  may  be 


170  RELATION  OF  LAKES  TO  GLACIAL  ACTION.         [On.  XII. 

said  of  most  of  the  longitudinal  and  transverse  valleys  of  every  moun- 
tain chain.  Mr.  Jukes  has  well  observed  that  lake-basins  are  by  no 
means  caused  by  rents  gaping  or  widening  in  their  higher  extremities ; 
and  he  adds  that  where  fissures  have  been  examined  by  miners  in  the 
interior  of  the  earth,  whether  the  rocks  have  been  shifted  or  not,  they 
are  usually  only  a  few  feet  wide,  and  even  when  traced  for  more  than 
1000  feet  in  a  vertical  direction,  they  preserve  a  remarkable  uniformity 
in  width.  Nor  are  valleys  and  lake-basins  the  result  of  engulfment  or 
the  swallowing  up  in  subterranean  abysses  of  masses  once  at  or  near 
the  surface.  Had  this  been  the  case,  we  should  not  find,  as  we  now 
do,  the  same  strata  often  continuous  from  side  to  side,  at  the  upper  and 
lower  ends  of  the  lake.  It  is  evident  that  the  materials  which  once 
filled  the  basin  have  been  gradually  removed,  so  that  older  formations 
are  now  exposed  to  view  on  the  bottom.  It  may  be  said  of  the  par- 
ticular masses  of  rock  now  constituting  the  sides  of  such  cavities,  as 
we  may  affirm  of  valleys  in  general,  that  they  were  never  nearer  each 
other  than  they  are  at  present.  The  only  question,  then,  to  be  discussed 
is,  whether  the  denuding  cause  was  ice  or  running  water — a  glacier  or 
a  river. 

At  the  foot  of  every  cataract  we  see  that  the  water  has  formed  a 
deep  circular  pool.  In  like  manner  it  is  suggested  that  ice,  descend- 
ing a  precipice  or  steep  slope,  and  rubbing  off  sand  and  stones  from 
the  surface  of  the  same,  may,  when  it  reaches  the  bottom  and  presses 
on  it  with  its  whole  weight,  so  grind  down  and  wear  away  the  rock, 
as  to  scoop  out  one  of  those  cavities  called  tarns.  But  if  we  admit 
such  a  process  as  matter  of  speculation,  we  must  at  the  same  time 
suppose  that  after  it  has  worked  out  a  cavity  it  loses  all  power  to  ex- 
tend the  same,  being  wholly  unable  to  cut  a  gorge  through  the  barrier 
forming  the  lower  margin  of  the  tarn  at  the  point  where  the  discharge 
of  ice  formerly  took  place,  and  where  a  stream  now  issues.  This  di- 
minished force  of  erosion  wherever  the  ice  has  to  ascend  a  slope,  or  to 
move  horizontally,  seems  adverse  to  the  hypothesis  advanced  by 
Professor  Ramsay  of  the  formation  of  lakes  of  considerable  length 

«/  ^ 

and  depth  by  glaciers.  Yet  the  advocates  of  the  origin  of  lakes  by 
ice-action  do  not  hesitate  to  appeal  to  the  same  causation  to  account 
for  the  largest  Swiss  and  Italian  lakes  at  the  northern  and  southern 
foot  of  the  Alps,  such  as  those  of  Geneva,  Como,  and  Lago  Maggiore, 
which  vary  from  twenty  to  nearly  fifty  miles  in  length,  and  in  depth 
from  500  to  2000  feet,  and  more. 

In  speculating  on  such  a  mode  of  origin,  we  feel  greatly  the  want 
of  positive  data,  which  might  enable  us  to  test  the  actual  power  of  a 
glacier  to  scoop  cavities  out  of  a  floor  of  subjacent  rock.  It  may, 
however,  be  remarked,  that  where  opportunities  are  enjoyed  of  seeing 
part  of  a  valley  from  which  a  glacier  has  retreated  in  historical  times, 
no  basin-shaped  hollows  are  conspicuous.  Domeshaped  protuberances, 
the  "  roches  moutonnees"  before  described,  are  frequent ;  but  the  con- 
verse of  them,  or  cup  and  saucer-shaped  cavities,  are  wanting.  Every- 


CH.  XII.]  MORAINIC  LAKES. 

where  we  behold  proofs  that  the  glacier,  by  the  aid  of  sand  and  peb- 
bles, can  grind  down,  polish,  and  plane  the  bottom  ;  but  it  seems  in- 
capable of  doing  more,  although  the  fundamental  rocks  must  in  dif- 
ferent places,  be  of  very  unequal  hardness.  It  is  also  well  known  that 
at  certain  points  in  the  course  of  some  of  the  principal  glaciers  of  the 
Alps,  transverse  rents  in  the  ice,  or  crevices,  several  feet  wide  and  of 
great  number  and  depth,  occur,  which  are  referred  by  geologists  to 
inequalities  in  the  ground  below,  over  which  the  icy  mass  is  pushed. 
In  such  instances,  though  the  ice  moves  on  and  the  old  crevices  close 
up,  others  of  precisely  the  same  form  and  dimensions  are  renewed 
every  year,  century  after  century,  in  the  same  place,  implying  that 
even  where  the  declivity  is  very  great,  and  the  propelling  force  from 
behind  enormous,  the  ice  cannot  saw  through  and  get  rid  of  the  ob- 
stacles which  impede  the  freedom  of  its  onward  march. 

When  we  are  endeavoring  to  form  sound  opinions  as  to  the  rela- 
tion of  the  frequency  of  lake-basins  to  an  antecedent  glacial  period, 
we  must  not  forget  that  such  basins,  large  and  small,  are  met  with  in 
all  latitudes,  and  that  there  are  lacustrine  deposits  of  all  geological 
epochs,  attesting  the  existence  of  lakes  at  times  when  no  one  is  dis- 
posed to  attribute  them  to  the  agency  of  ice.  In  Central  France,  for 
example,  in  the  Miocene  and  Eocene  periods,  there  were  lakes  of  con- 
siderable dimensions  when  the  climate,  like  that  of  the  preceding 
Cretaceous  era,  was  sub-tropical.  It  would,  indeed,  be  the  most  per- 
plexing of  all  enigmas  if  we  did  not  find  that  lake-basins  were  now, 
and  had  been  at  all  times,  a  normal  feature  in  the  physiognomy  of  the 
earth's  surface,  since  we  know  that  unequal  movements  of  upheaval  and 
subsidence  are  now  in  progress,  and  were  going  on  at  all  former  geo- 
logical periods. 

It  needs  but  little  reflection  on  this  subject  to  discover  that,  when 
such  changes  of  level  are  in  progress,  some  of  the  principal  valleys  can 
hardly  fail  to  be  converted  in  some  parts  of  their  course  into  lakes  of 
considerable  magnitude.  To  escape  such  a  result  we  should  have  to 
assume  that  the  greatest  elevatory  movement  always  conforms  to  the 
central  axis  of  every  chain,  or,  what  would  be  still  more  singular, 
that  it  concides  in  direction  with  every  water-shed.  Occasionally,  no 
doubt,  there  would  be  such  a  coincidence,  and  if  so,  the  upheaval,  in- 
stead of  interfering  with  the  drainage  and  damming  back  the  rivers, 
would,  by  increasing  the  fall  of  water,  tend  even  to  obliterate  such 
lakes  as  preexisted.  But  sometimes  upheaval  will  be  in  excess  in  the 
lower  part  of  the  valley,  and  at  other  times  (which  would  equally  pro- 
duce lake-basins)  there  would  be  an  excess  of  subsidence  in  the  higher 
region,  the  alluvial  plains  below  sinking  at  a  less  rapid  rate,  or  being, 
perhaps,  stationary. 

When  controverting,  in  1863,  in  the  first  edition  of  my  "  Antiquity  of 
Man"  (p.  316),  Professor  Ramsay's  hypothesis  of  the  scooping  out  by 
ice  of  long  and  deep  cavities  like  those  containing  the  Swiss  and  Ital- 
ian lakes,  I  proposed  to  substitute  for  his  ice-agency  the  theory  of 


172  CONVERSION  OF  VALLEYS  INTO  LAKES.  [On.  XII. 

unequal  movements  of  upheaval  and  subsidence.  I  assumed  that  the 
Alpine  region  had  been  exposed  for  countless  ages  to  the  action  of  rain 
and  rivers  from  Older  Pliocene  if  not  from  Upper  Miocene  times,  and  I 
therefore  inferred  that  the  larger  valleys,  throughout  the  greater  part 
of  their  depth  and  width,  were  of  pre-glacial  origin.  If  they  were 
not  so,  it  seemed  to  me  that  we  should  be  called  upon  to  explain  a  more 
difficult  enigma  than  the  origin  of  the  lake-basins,  namely,  why  the 
rivers  had  been  idle  for  a  million  years  or  more,  leaving  to  glaciers  the 
task  of  doing  in  comparatively  modern  times  the  whole  work  of  ex- 
cavation. 

The  Alps  are  from  80  to  100  miles  across.  Let  us  suppose  a  cen- 
tral depression  in  this  chain  at  the  rate  of  5  feet  in  a  century,  while  the 
intensity  of  the  movement  gradually  diminishes  aa  it  approaches  the 
outskirts  of  the  chain,  till  at  length  it  dies  out  in  the  surrounding 
lower  region.  After  a  long  continuance  of  such  a  change  of  level, 
there  will  not  only  be  a  lessened  fall  of  all  the  rivers,  but  the  courses 
of  many  of  them  will,  at  various  points,  especially  near  the  foot  of  the 
mountains,  be  converted  into  lakes.  If,  in  the  case  of  Wales,  we  can 
demonstrate  an  upward  movement  of  1400  feet  during  a  part  of  the 
glacial  epoch,  we  may  well  suppose  still  greater  alterations  of  level  in 
the  Alps,  and  agree  with  Charpentier  that  those  mountains  which  from 
a  remote  geological  era  have  been  the  theatre  of  reiterated  upward 
and  downward  movements  may  have  been,  at  the  time  of  the  most  in- 
tense cold,  three  thousand  feet  higher  than  they  are  now.  They  may 
also  have  been  lowered  again,  as  I  have  elsewhere  suggested  ("  Anti- 
quity of  Man,"  p.  321,)  before  the  close  of  the  Glacial  epoch,  and 
oscillations  of  such  magnitude  may  well  have  been  accompanied  by 
such  inequalities  of  movement  as  would  inevitably  have  turned  some 
parts  of  the  preexisting  valleys  into  the  receptacles  of  vast  bodies  of 
ice,  destined  afterward  to  be  converted  into  water.  We  know  that 
in  the  earthquake  in  the  northern  island  of  New  Zealand,  in  January, 
1855,  there  was  a  permanent  rise  of  land  on  the  northern  shores  of 
Cook's  Strait  to  the  extent  of  9  feet  vertically.  On  one  side  of  Muko- 
muka  Point,  or  immediately  to  the  east,  there  was  no  movement, 
while  on  the  other  side,  or  to  the  westward,  there  was  a  gradual  dimi- 
nution of  the  upheaval  from  9  feet  to  a  few  inches,  until,  at  a  distance 
of  about  23  miles,  no  change  of  level  was  perceptible.  Simultaneous- 
ly with  this  elevation  of  land,  there  was  a  sinking  of  the  low  coast  to 
the  amount  of  5  feet  in  the  middle  island  south  of  Cook's  Strait. 
The  repetition  of  such  unequal  movements  may,  in  a  time  geologically 
brief,  turn  parts  of  any  valley  into  a  lake.  In  Finmark  an  ancient 
water-level  has  been  carefully  measured  along  the  borders  of  a  fiord, 
rising  gradually  at  the  rate  of  4  feet  in  a  mile  for  30  miles  from  south 
to  north,  until  at  one  extremity  it  attains  an  elevation  of  135  feet 
above  the  other  end,  and  this  movement  is  of  post-pliocene  date. 
Whenever  the  lower  part  of  a  fiord  or  valley  is  thus  raised,  or  when- 
ever in  the  upper  portion,  subsidence  is  in  like  manner  in  excess,  a 


CH.  XII.]  FORMATION  OF  LAKE-BASINS. 


1T3 


lake-basin  may  result  as  above  stated.  If  there  be  no  ice,  the  forma- 
tion of  a  lake  will  depend  on  the  relation  of  two  forces :  the  rate  at 
which  the  land  is  raised  or  sunk,  and  the  rate  at  which  the  river  can  de- 
posit sediment  in  the  new  depressions.  Should  the  movement  be  very 
slow,  the  river  may  fill  the  incipient  cavity  with  mud,  sand,  and  pebbles, 
as  fast  as  it  is  formed,  and  having  levelled  it  up  may  afterward  cut 
through  the  new  stony  barrier  at  the  lower  margin  of  the  depressed 
area ;  but  if  the  capacity  of  the  new  basin  increases  at  too  great  a 
rate,  the  river  will  only  be  able  to  encroach  partially  upon  it  by  form- 
ing a  delta  at  its  higher  extremity.  If  the  change  takes  place  in  a 
glacial  period,  the  thickness  of  the  ice  will  augment  from  century  to 
century,  not  in  consequence  of  erosion,  but  simply  because  the  con- 
tour of  the  valley  is  becoming  gradually  more  basin-shaped.  The 
mere  occupancy,  therefore,  of  cavities  by  ice,  by  preventing  fluviatile 
and  lacustrine  deposition,  is  one  cause  of  the  abundance  of  lakes 
which  will  come  into  existence  whenever  the  climate  changes  and  the 
ice  melts. 

In  Switzerland  there  are  lacustrine  formations  of  the  Post-pliocene 
period,  which  show  that  the  Lake  of  Zurich,  and  some  other  Swiss 
lakes,  were  formed  before  the  erosive  power  of  ice  had  been  exerted 
in  that  country  ("  Antiquity,"  p.  314).  In  Scotland,  also,  there  is 
evidence  that  some  of  the  main  valleys  by  which  the  drainage  now 
takes  place  were  in  existence  before  the  Glacial  epoch.  But  although 
most  of  the  valleys  of  the  Alps  and  some  of  the  lakes  were  pre-glacial, 
there  seems  ground  for  suspecting  that  not  a  few  of  the  valleys  were 
converted  into  lake-basins  during  the  long  series  of  ages  in  which  ice 
prevailed.  In  support  of  this  view,  many  good  observers  affirm  that 
below  the  present  outlet  of  the  great  lakes  in  Switzerland  and  Italy, 
an  ancient  fluviatile  alluvium  may  be  seen,  on  which  the  moraines  of 
the  great  glaciers  which  once  traversed  the  lakes  repose.  The  pebbles 
in  these  old  alluviums  comprise  all  those  varieties  of  rocks  which 
belong  to  the  upper  course  of  the  valley  above,  or  to  tributary  valleys 
in  the  same  higher  region.  The  phenomenon  here  alluded  to  would 
be  in  perfect  accordance  with  the  theory  that  the  rivers  were  once 
continuous,  or  not  intercepted  by  lake-basins  destined  to  be  filled  and 
traversed  by  glaciers.  It  is  unnecessary  to  resort  to  M.  de  Mortillet's 
hypothesis,  that  each  basin  was  first  filled  up  with  alluvium  sometimes 
above  2000  feet  thick,  and  that  this  was  afterward  cleared  out  by  a 
glacier,  for  such  removal  would  imply  a  capacity  of  erosion  which  we 
are  not  warranted  to  assume,  and  which,  if  granted,  might  have 
enabled  the  ancient  glacier  of  the  Rhone  to  excavate  the  basin  of  the 
Lake  of  Geneva  out  of  the  miocene  molasse.  Dr.  Falconer,  Mr.  Ball, 
and  other  writers,  have  pointed  out  that  the  form  of  several  of  the 
great  Italian  lakes,  such  as  Como,  Maggiore,  and  Garda,  is  by  no 
means  in  harmony  with  the  hypothesis  that  they  have  been  hollowed 
out  by  great  glaciers  which  once  passed  through  them. 

From  the  analogy  of  flowing  water,  we  have  reason  to  suspect  that 


174  FORMATION  OF  LAKE-BASINS.  [Cn.  XII. 

ice  would  move  slower  and  exert  less  friction  on  the  botton  in  propor- 
tion to  the  depth  of  the  cavity  which  it  fills,  for  the  motion  of  a  gla- 
cier resembles  that  of  a  river — the  upper  strata  moving  faster  than  the 
lower ;  and  if  there  be  a  depth  of  2600  feet,  as  in  Lago  Maggiore,  it 
is  difficult  to  conceive,  when  the  principal  discharge  of  ice  is  almost 
entirely  effected  in  the  upper  part  of  the  mass,  that  the  movement  at 
the  bottom  would  be  sufficiently  energetic  to  enable  the  ice  to  pene- 
trate deeply  into  the  rocks  below.  A  still  more  serious  objection  to 
the  ice-origin  of  lake-basins  is  deducible  from  absence  of  such  basins 
of  the  first  magnitude  in  the  plains  of  the  Po  at  certain  points  where 
the  greatest  of  the  extinct  glaciers  once  came  down  from  .the  Alps,  leav- 
ing their  gigantic  moraines  in  the  low  country.  Of  this  absence,  the 
finest  example  occurs  at  Ivrea  and  south  of  it,  where  we  observe  a 
moraine  more  than  1500  feet  high  in  its  northern  part,  consisting  of 
mud,  stones,  and  large  erratic  blocks,  evidently  brought  down  from  the 
two  highest  of  the  Alps,  Mont  Blanc  and  Monte  Rosa.  This  old  mor- 
aine, when  it  issues  from  the  mountains  and  spreads  over  the  plains  of 
the  Po,  reposes  on  marine  strata  of  the  Pliocene  age,  so  un consolidated 
that  the  glacier  might  have  scooped  out  of  it  a  deep  cavity  had  mov- 
ing ice  possessed  such  an  excavating  power. 

Another  example  of  the  absence  of  a  great  lake  where  we  ought  to 
have  found  one,  according  to  the  glacier-erosion  hypothesis,  occurs  in 
a  contiguous  region  on  the  other  side  of  Turin,  between  that  city  and 
Susa,  where  the  moraine  of  the  Dora  Riparia  extends  far  and  wide. 

If,  in  surveying  a  mountain-chain,  lengthwise  or  transversely,  we 
observe  a  capricious  distribution  of  lake-basins,  we  have  no  reason 
to  feel  surprise,  so  long  as  we  conceive  the  origin  of  the  basins  to  be 
due  to  subterranean  movements  in  the  earth's  crust,  for  these  may  be 
partial  in  their  extent,  or  may  vary  in  their  direction  in  a  manner 
which  has  no  relation  to  the  course  of  the  valleys.  But  if,  rejecting 
the  aid  of  changes  of  level,  we  invoke  a  superficial  agency,  like  that  of 
glaciers,  we  are  then  utterly  at  a  loss  to  explain  why  they  should  scoop 
out  a  hollow  in  one  valley  and  perform  no  similar  feat  in  an  adjoining 
one. 

We  have  shown  that  rivers  are  doubly  instrumental  in  preventing 
the  formation  of  lake-basins  ;  first,  by  labouring  incessantly  to  silt  up 
an  incipient  cavity,  and  secondly,  by  deepening  their  channels,  or  cut- 
ting out  new  ones  through  the  rocks,  which  may  have  been  slowly 
raised  up  so  as  to  interfere  with  the  regular  drainage.  There  is  no 
analogous  agency  at  work  at  the  bottom  of  the  sea  except  partially, 
where  marine  currents  deriving  sediment  from  wasting  shores,  or  from 
rivers,  deposit  it  at  the  bottom.  With  the  exceptions  of  such  areas 
of  submarine  deposition,  every  partial  subsidence  will  cause  a  perma- 
nent depression,  ready  to  become  the  receptacle  of  fresh  water  when- 
ever the  tract  emerges  or  is  turned  into  land.  As  to  the  extent  of  such 
lake-basins,  we  should  have  no  right  to  wonder  if  they  equal  in  size 
Lakes  Erie  and  Ontario,  or  even  Lake  Superior  itself,  provided  the 


CH.  XII.]  CAUSES  OF  CHANGE  OP  CLIMATE. 

lapse  of  geological  time  lias  been  sufficiently  protracted.     But  suppose 
the  submerged  area  to  have  been  continually  traversed  by  huge  ice- 
bergs like  Baffin's  Bay,  for  thousands  of  years  before  it  became  part 
of  the  continent.     In  that  case  we  should  not  only  find  on  it  a  multi 
tude  of  morainic  lakes  of  various  sizes,  but  probably  many  shallow 
saucer-like  cavities  worn  in  the  bed  of  the  sea,  out  of  rocks  in  situ,  by 
the  reiterated  impinging  upon  them  of  huge  masses  of  ice,  moving  (as 
before  described,  p.  148)  in  their  lowest  parts  with  a  velocity  of  as  many 
miles  as  even  the  uppermost  strata  of  a  glacier  move  inches.     The 
winds  and  currents  might  carry  hundreds  of  such  bergs  during  every 
century  toward  the  same  tracts,  and  these  might  exert  a  great  amount 
of  friction  on  the  floor  of  the  ocean.     The  mud  and  sand  formed  by 
the  abrasion  of  rock,  or  any  stones  which  might  be  frozen  into  the 
bottom  of  the  iceberg,  or  driven  into  it  when  the  mass  impinged  with 
great  force  on  the  bed  of  the  sea,  may  be  removed  as  soon  as  the  berg, 
by  melting  in  its  upper  part,  becomes  lighter,  and  rising  floats  away. 
In  this  instance  the  conditions  are  more  favorable,  both  for  triturating 
a  rocky  floor  and  clearing  out  earth  and  stones  from  the  new-formed 
cavity,  than  are  conceivable  in  the  case  of  a  glacier  descending  a  valley. 
Causes  of   Change  of   Climate. — Submergence  of  the  Sahara. — I 
endeavored  in  1830,  in  the  "  Principles  of  Geology,"  chapters  vii.  and 
viii.,  to  point  out  the  intimate  connection  of  climate  with  the  state  of 
the  physical  geography  of  the  globe  existing  at  any  given  period.     If, 
for  example,  at  certain  periods  of  the  past,  the  antarctic  land  was  less 
elevated  and  less  extensive  than  now,  while  that  at  the  north  pole  was 
higher  and  more  continuous,  the  conditions  of  the  northern  and  south- 
ern hemispheres  might  have  been  to  a  great  extent  the  reverse  of  what 
we  now  witness  in  regard  to  climate.     But  if  in  both  of  the  polar  re- 
gions a  considerable  area  of  elevated  dry  land  existed,  such  a  concur- 
rence of  refrigerating  conditions  in  both  hemispheres  might  have 
created  for  a  time  an  intensity  of  cold  never  experienced  since.    Some 
geologists  have  objected  that  the  cold  of  the  glacial  period  was  so 
general  throughout  the  polar  and  temperate  regions  on  both  sides  of 
the  equator,  that  mere  local  changes  in  the  external  configuration  of 
our  planet  cannot  be  imagined  to  afford  an  adequate  cause  for  a 
revolution  in  temperature  of  so  modern  a  date.     But  the  more  we 
compare  the  state  of  the  earth's  surface  in  pliocene,  post-pliocene,  and 
recent  times,  the  more  evidence  do  we  obtain  of  upward  and  down- 
ward movement  on  such  a  scale  as  to  convince  us  that  in  different  parts 
of  the  periods  in  question  a  map  of  the  world  would  no  more  resem- 
ble  our  present  maps   than    Europe    now  resembles    America    or 
Africa.     A  careful  study  of  the  distribution  of  the  living  species  of 
animals  and  plants  in  tertiary  and  recent  times  leads  to  similar  con- 
clusions as  to  the  vastness  of  the  changes  which  the  physical  geogra- 
phy of  the  globe  has  undergone,  so  that  the  theory  in  question  cannot 
be  impugned  on  the  score  of  a  want  of  universality  in  the  movements 
of  the  earth's  crust. 


176  SUBMERGENCE  OF  THE  SAHARA.        [Cn.  XII. 

The  changes  alluded  to  in  the  "  Principles  of  Geology  "  as  capable 
of  affecting  the  climates  of  the  globe  at  successive  geological  periods, 
consisted  chiefly  of  the  conversion  of  sea  into  land  and  land  into  sea, 
the  increased  or  diminished  height  of  mountain  chains  and  conti- 
nents, and  the  preponderance  of  land  and  water  in  high  and  low  lati- 
tudes, together  with  the  new  direction  given  to  the  principal  currents 
of  the  ocean,  such  as  the  Gulf-stream.  But  although  I  did  not  omit 
to  mention  the  vast  heat  which  is  carried  by  the  winds  from  the  great 
desert  of  Africa  to  those  parts  of  Europe  which  lie  immediately  north 
of  it,  I  was  not  able  to  avail  myself  of  a  geographical  fact  since  ascer- 
tained by  geologists  respecting  the  Sahara,  namely,  that  this  desert 
must  have  formed  part  of  the  sea  when  the  cold  of  the  glacial  epoch 
was  at  its  height.  Bitter  had  suggested  in  1817,  that  the  African 
desert  had  been  under  water  at  a  very  modern  period,  and  M.  Escher 
von  der  Linth  gave  it  as  his  opinion  in  1852,  that  if  this  submergence 
were  true,  it  would  explain  why  the  Alpine  glaciers  had  attained  in 
the  Post-pliocene  period  those  colossal  dimensions  which  Venetz  and 
Charpentier,  reasoning  on  geological  data,  first  assigned  to  them. 
Since  this  hint  was  thrown  out  by  the  distinguished  Swiss  geologists, 
Messrs.  Laurent  and  Tristram,  and  in  1863  M.  Escher  himself  to- 
gether with  MM.  Desor  and  Martins,  have  found  marine  shells,  espe- 
cially the  common  cockle,  Cardium  edule,  scattered  far  and  wide, 
from  west  to  east,  over  the  desert,  while  the  shells  of  these  and  other 
living  species  have  also  been  found  in  boring  Artesian  wells,  at  the 
depth  of  many  feet  below  the  surface. 

The  space  now  occupied  by  the  Sahara,  instead  of  forming  a  tract 
of  parched  and  burning  sand,  from  which  the  south  wind  or  sirocco 
now  derives  its  scorching  heat  and  dryness,  constituted  formerly  a 
wide  marine  area,  stretching  several  hundred  miles  north  and  south 
and  east  and  west.  From  this  area  the  south  wind  must  formerly 
have  absorbed  moisture,  and  must  have  been  still  farther  cooled  and 
saturated  with  aqueous  vapor  as  it  passed  over  the  Mediterranean. 
When  at  length  it  reached  the  Alps,  and,  striking  them,  was  driven 
into  the  higher  and  more  rarefied  regions  of  the  atmosphere,  it 
would  part  with  its  watery  burden  in  the  form  of  snow,  so  that  the 
same  aerial  current  which  under  the  name  of  the  Fohn  or  Sirocco 
now  plays  a  leading  part  with  its  hot  and  dry  breath,  sometimes  even 
in  the  depth  of  winter,  in  melting  the  snow  and  checking  the  growth 
of  glaciers,  must,  at  the  period  alluded  to,  have  been  the  principal 
feeder  of  Alpine  snow  and  ice. 

METEORITES    IN   DRIFT. 

As  my  account  of  the  glacial  period  has  led  me  to  speak  at  some 
length  of  post-pliocene  drift,  I  may  take  this  opportunity  of  referring 
to  the  discovery  of  a  meteoric  stone  at  a  great  depth  in  the  alluvium 
of  Northern  Asia. 


CH.  XII.]  METEORITES  IN  DRIFT. 

Erman,  in  his  Archives  of  Russia  for  1841  (p.  314),  cites  a  very  cir- 
cumstantial account  drawn  up  by  a  Russian  miner  of  the  finding  of  a 
mass  of  meteoric  iron  in  the  auriferous  alluvium  of  the  Altai.  Some 
small  fragments  of  native  iron  were  first  met  with  in  the  gold-washings 
of  Petropawlowsker  in  the  Mrassker  Circle ;  but  though  they  attracted 
attention,  it  was  supposed  that  they  must  have  been  broken  off  from  the 
tools  of  the  workmen.  At  length,  at  the  depth  of  31  feet  5  inches  from 
the  surface,  they  dug  out  a  piece  of  iron  weighing  17  J  pounds,  of  a 
steel-gray  color,  somewhat  harder  than  ordinary  iron,  and,  on  analyzing 
it,  found  it  to  consist  of  native  iron,  with  a  small  proportion  of  nickel,  as 
usual  in  meteoric  stones.  It  was  buried  in  the  bottom  of  the  deposit 
where  the  gravel  rested  on  a  flaggy  limestone.  Much  brown  iron  ore, 
as  well  as  gold,  occurs  in  the  same  gravel,  which  appears  to  be  part  of 
that  extensive  auriferous  formation  in  which  the  bones  of  the  mammoth, 
the  Rhinoceros  tichorhinus,  and  other  extinct  quadrupeds  abound.  No 
sufficient  data  are  supplied  to  enable  us  to  determine  whether  it  be  of 
Post-Pliocene  or  Newer  Pliocene  date. 

We  ought  not,  I  think,  to  feel  surprise  that  we  have  not  hitherto 
succeeded  in  detecting  the  signs  of  such  aerolites  in  older  rocks,  for, 
besides  their  rarity  in  our  own  days,  those  which  fell  into  the  sea  (and  it 
is  with  marine  strata  that  geologists  have  usually  to  deal),  being  chiefly 
composed  of  native  iron,  would  rapidly  enter  into  new  chemical  combi- 
nations, the  water  and  mud  being  charged  with  chloride  of  sodium  and 
other  salts.  We  find  that  anchors,  cannon,  and  other  cast-iron  imple- 
ments which  have  been  buried  for  a  few  hundred  years  off  our  English 
coast  have  decomposed  in  part  or  entirely,  turning  the  sand  and  gravel 
which  inclosed  them  into  a  conglomerate,  cemented  together  by  oxide  of 
iron.  In  like  manner  meteoric  ifon,  although  its  rusting  would  be  some- 
what checked  by  the  alloy  of  nickel,  could  scarcely  ever  fail  to  decompose 
in  the  course  of  thousands  of  years,  becoming  oxide,  sulphuret,  or  car- 
bonate of  iron,  and  its  origin  being  then  no  longer  distinguishable.  The 
greater  the  antiquity  of  rocks, — the  oftener  they  have  been  heated  and 
cooled,  permeated  by  gases  or  by  the  waters  of  the  sea,  the  atmosphere 
or  mineral  springs, — the  smaller  must  be  the  chance  of  meeting  with  a 
mass  of  native  iron  unaltered;  but  the  preservation  of  the  ancient 
meteorite  of  the  Altai,  and  the  presence  of  nickel  in  these  curious  bodies, 
renders  the  recognition  of  them  in  deposits  of  remote  periods  less  hope- 
less than  we  might  have  anticipated. 

12 


178  PRINCIPLES  OF  CLASSIFICATION.  [Cn.  XIII. 


CHAPTER  XIII. 


CLASSIFICATION    OF   TERTIARY   FORMATIONS. PLIOCENE    PERIOD. 

Order  of  succession  of  sedimentary  formations— Imperfection  of  the  record — Defec- 
tiveness  and  obscurity  of  the  monuments  greater  in  proportion  to  their  antiquity 
— Reasons  for  studying  the  newer  groups  first — General  principles  of  classifica- 
tion of  tertiary  strata — Detached  formations  scattered  over  Europe — Strata  of 
Paris  and  London — More  modern  groups — Peculiar  difficulties  in  determining  the 
chronology  of  tertiary  formations — Increasing  proportion  of  living  species  of 
shells  in  strata  of  newer  origin — Eocene,  Miocene,  and  Pliocene  terms  explained 
— Formations  of  the  Newer  Pliocene  period — Island  of  Ischia — Eastern  base  of 
Mount  Etna — Newer  Pliocene  strata  of  great  height  and  extent  in  Sicily — For- 
mations of  same  age  in  the  Upper  Val  d'Arno — Norwich  Crag — Chillesford 
beds — Bridlington  beds — Older  Pliocene  strata — Red  Crag  of  Suffolk — White 
or  coralline  Crag — Successive  refrigeration  of  climate  proved  by  the  pliocene 
shells  of  Suffolk  and  Norfolk — Antwerp  Crag — Subapennme  strata — Aralo-Cas- 
pian  formations. 

THE  post-tertiary  formations,  comprising  the  Post-pliocene  and 
Recent,  having  been  described  in  the  last  three  chapters,  I  have 
now  to  give  an  account  of  the  strata  called  tertiary  and  the  several 
groups  into  which  they  have  been  subdivided. 

The  annexed  diagram  will  -show  the  order  and  superposition  of  the 
principal  sets  of  fossiliferous  deposits  -enumerated  in  the  table,  page 

Fig.  140. 


.PRIMARY 

SECONDARY 

TERTIARY 

POST-TERTIARY 


101,  assuming  them  all  to  be  visible  in  one  continuous  section.  In 
nature,  as  before  hinted,  page  98,  we  have  never  an  opportunity  of 
seeing  the  whole  of  them  so  displayed  in  a  single  region ;  first,  be- 
cause sedimentary  deposition  is  confined,  during  any  one  geological 
period,  to  limited  areas ;  and  secondly,  because  strata,  after  they  have 
been  formed,  are  liable  to  be  utterly  annihilated  over  wide  areas  by 
denudation.  But  wherever  certain  members  of  the  series  are  pres- 
ent, they  overlie  one  another  in  the  order  indicated  in  the  diagram, 


CH.  XIII.]  PRINCIPLES  OF   CLASSIFICATION. 

though  not  always  in  the  exact  manner  there  represented,  because 
some  of  them  repose  occasionally  in  unconformable  stratification  on 
others.  This  mode  of  superposition  has  been  already  explained  at 
page  59.  Where  it  occurs  it  is  almost  invariably  accompanied  by  a 
great  dissimilarity  in  the  species  of  organic  remains  of  the  sets  of 
strata  next  in  succession,  the  discordance  implying  a  considerable 
lapse  of  time  which  intervened  between  the  two  formations  in  juxta- 
position. During  the  ages  which  elapsed,  and  of  which  no  records 
have  been  handed  down  to  us  in  the  area  in  question,  we  may  sup- 
pose a  gradual  change  to  have  been  going  on  in  the  state  of  the  ani- 
mal creation,  and  the  same  interval  allowed  time  for  a  great  amount 
of  movement  and  dislocation  to  have  been  brought  about  in  the 
earth's  crust,  so  that  the  strata  previously  existing  in  the  region 
alluded  to  had  been  much  disturbed  and  their  edges  exposed  to 
aqueous  denudation  before  the  more  modern  set  were  thrown  down 
upon  them. 

Where  the  widest  gaps  appear  in  the  sequence  of  organic  remains, 
as  between  the  Permian  and  Triassic  rocks,  or  between  the  Creta- 
ceous and  Eocene,  examples  of  such  unconformability  are  very  fre- 
quent. But  they  are  also  met  with  in  some  part  or  other  of  the 
world  at  the  junction  of  almost  all  the  other  principal  formations, 
and  sometimes  the  subordinate  divisions  of  any  one  of  the  leading 
groups  may  be  found  lying  unconformably  on  another  subordinate 
member  of  the  same — the  Upper,  for  example,  on  the  Lower  Silurian, 
or  the  superior  division  of  the  Old  Red  Sandstone  on  a  lower  mem- 
ber of  the  same,  and  so  forth.  Instances  of  such  irregularities  in  the 
mode  of  succession  of  the  strata  next  in  contact  are  the  more  intelli- 
gible the  more  we  extend  our  survey  of  the  fossiliferous  formations, 
for  we  are  continually  bringing  to  light  deposits  of  intermediate  date, 
which  have  to  be  intercalated  between  those  previously  known,  and 
which  reveal  to  us  a  long  series  of  events,  of  which  antecedently  to 
such  discoveries  we  had  no  knowledge. 

But  while  unconformability  invariably  bears  testimony  to  a  lapse 
of  unrepresented  time,  the  conformability  of  two  sets  of  strata  in 
contact  by  no  means  implies  that  the  newer  formation  immediately 
succeeded  the  older  one.  It  simply  implies  that  the  ancient  rocks 
were  subjected  to  no  movements  of  such  a  nature  as  to  tilt,  bend,  or 
break  them  before  the  more  modern  formation  was  superimposed. 
It  does  not  show  that  the  earth's  crust  was  motionless  in  the  region 
in  question,  for  there  may  have  been  a  gradual  sinking  or  rising, 
extending  uniformly  over  a  large  surface,  and  yet,  during  such  move- 
ment, the  stratified  rocks  may  have  retained  their  original  horizontal- 
ity  of  position.  There  may  have  been  a  conversion  of  a  wide  area 
from  sea  into  land  and  from  land  into  sea,  and  during  these  changes 
of  level  some  strata  may  have  been  slowly  removed  by  aqueous 
action,  and  after  this  new  strata  may  be  superimposed,  differing  per- 
haps in  date  by  thousands  of  years  or  centuries,  and  yet  resting  con- 


180  PRINCIPLES  OP  CLASSIFICATION  [Cu.  XIII. 

formably  on  the  older  set.  There  may  even  be  a  blending  of  the 
materials  constituting  the  older  deposit  with  those  of  the  newer,  so 
as  to  give  rise  to  a  passage  in  the  mineral  character  of  the  one  rock 
into  the  other  as  if  there  had  been  no  break  or  interruption  in  the 
depositing  process. 

Although  by  the  frequent  discovery  of  new  sets  of  intermediate 
strata  the  transition  from  one  type  of  organic  remains  to  another  is 
becoming  less  and  less  abrupt,  yet  the  entire  series  of  records  appears 
to  the  geologists  now  living  far  more  fragmentary  and  defective  than 
it  seemed  to  their  predecessors  half  a  century  ago.  The  earlier  en- 
quirers, as  often  as  they  encountered  a  break  in  the  regular  sequence 
of  formations,  connected  it  theoretically  with  a  sudden  and  violent 
catastrophe,  which  had  put  an  end  to  the  regular  course  of  events 
that  had  been  going  on  uninterruptedly  for  ages,  annihilating  at  the 
same  time  all  or  nearly  all  the  organic  beings  which  had  previously 
flourished,  after  which,  order  being  reestablished,  a  new  series  of  events 
was  initiated.  In  proportion  as  our  faith  in  these  views  grows  weaker, 
and  the  phenomena  of  the  organic  and  inorganic  world  presented  to 
us  by  geology  seem  explicable  on  the  hypothesis  of  gradual  and  in- 
sensible changes,  varied  only  by  minor  convulsions,  such  as  have  been 
witnessed  in  historical  times  ;  and  in  proportion  as  it  is  thought  possi- 
ble that  former  fluctuations  in  the  organic  world  may  be  due  to  the 
indefinite  modifiability  of  species  without  the  necessity  of  assuming 
new  and  independent  acts  of  creation,  the  number  and  magnitude  of 
the  gaps  which  still  remain,  or  the  extreme  imperfection  of  the  record, 
become  more  and  more  striking,  and  what  we  possess  of  the  ancient 
annals  of  the  earth's  history  appears  as  nothing  when  contrasted  with 
that  which  has  been  lost. 

When  we  examine  a  large  area  such  as  Europe,  the  average  as  well 
as  the  extreme  height  above  the  sea  attained  by  the  older  formations 
is  usually  found  to  exceed  that  reached  by  the  more  modern  ones,  the 
primary  or  paleozoic  rising  higher  than  the  secondary,  and  these  in 
their  turn  than  the  tertiary,  while  in  reference  to  the  three  divisions 
of  the  tertiary,  the  lowest  or  Eocene  group  attains  a  higher  summit 
level  than  the  Miocene,  and  these  again  a  greater  height  than  the 
Pliocene  formations.  Lastly,  the  post-tertiary  deposits,  such,  at 
least,  as  are  of  marine  origin,  are  most  commonly  restricted  to 
much  more  moderate  elevations  above  the  sea  level  than  the  tertiary 
strata. 

It  is  also  observed  that  strata,  in  proportion  as  they  are  of  newer 
date,  bear  the  nearest  resemblance  in  mineral  character  to  those  which 
are  now  in  the  progress  of  formation  in  seas  or  lakes,  the  newest 
of  all  consisting  principally  of  soft  mud  or  loose  sand,  in  some  places 
full  of  shells,  corals,  and  other  organic  bodies,  animal  or  vegetable,  in 
others  wholly  devoid  of  such  remains.  The  farther  we  recede  from 
the  present  time,  and  the  higher  the  antiquity  of  the  formations  which 
we  examine,  the  greater  are  the  changes  which  the  sedimentary  de- 


CH.  XIII.]  OF  TERTIARY  FORMATIONS. 


181 


posits  have  undergone.  Masses,  for  example,  which  were  originally 
soft  and  yielding  have  been  condensed  by  pressure,  others  which  were 
incoherent  have  been  solidified  by  the  infiltration  of  mineral  matter 
which  has  cemented  together  their  separate  parts  ;  others  have  been 
modified  by  heat,  traversed  by  shrinkage  cracks,  and  partially  crys- 
tallized, or  the  strata  have  been  fractured  during  earthquakes,  or  bent 
and  contorted  by  lateral  pressure,  or  thrown  into  a  vertical  position,  or 
even  overturned  so  that  the  original  order  of  superposition  has  been 
inverted,  and  the  beds  which  were  at  first  the  lowest  have  become  the 
uppermost. 

The  organic  remains  also  have  sometimes  been  obliterated  entirely, 
or  the  mineral  matter  of  which  they  were  composed  has  been  removed 
and  replaced  by  other  substances,  as  when  calcareous  fossils  have  been 
silicified. 

We  likewise  observe  that  the  older  the  rocks  the  more  widely  do 
their  organic  remains  depart  from  the  types  of  the  living  creation. 
First,  we  find  in  the  newer  tertiary  rocks  a  few  species  which  no  longer 
exist,  mixed  with  many  living  ones,  and  then,  as  we  go  farther  back, 
many  genera  and  families  at  present  unknown  make  their  appearance, 
until  we  come  to  strata  in  which  the  fossil  relics  of  existing  species  are 
nowhere  to  be  detected,  except  a  few  of  the  lowest  forms  of  inverte- 
brata,  while  some  orders  of  animals  and  plants  wholly  unrepresented 
in  the  living  world  begin  to  be  conspicuous. 

"When  we  study,  therefore,  the  geological  records  of  the  earth  and 
its  inhabitants,  we  find,  as  in  human  history,  the  defectiveness  and 
obscurity  of  the  monuments  always  increasing  the  remoter  the  era  to 
which  we  refer.  The  difficulty  of  determining  the  true  chronological 
relations  of  rocks  is  also  more  and  more  enhanced,  especially  when 
we  are  comparing  those  which  were  formed  simultaneously  in  very  dis- 
tant regions  of  the  globe.  Hence  we  advance  with  securer  steps  when 
we  begin  with  the  study  of  the  geological  records  of  later  times, 
proceeding  from  the  newer  to  the  older,  or  from  the  more  to  the  less 
known. 

In  thus  inverting  what  might  at  first  seem  to  be  the  more  natural 
order  of  historical  research,  we  must  bear  in  mind  that  each  of  the 
periods  above  enumerated,  even  the  shortest,  such  as  the  Post-tertiary, 
or  the  Pliocene,  Miocene,  or  Eocene,  embrace  a  succession  of  events 
of  vast  extent,  so  that  to  give  a  satisfactory  account  of  what  we  already 
know  of  any  one  of  them  would  require  many  volumes  of  the  size  of 
this  treatise.  When,  therefore,  we  approach  one  of  the  newer  groups 
before  endeavoring  to  decipher  the  monuments  of  an  older  one,  it  is 
like  endeavoring  to  master  the  history  of  our  own  country  and  that 
of  some  contemporary  nations,  before  we  enter  upon  Roman  History, 
or  like  investigating  the  annals  of  Ancient  Italy  and  Greece  before  we 
approach  those  of  Egypt  and  Assyria.  That  there  are  inconveniences 
in  thus  inverting  the  order  in  which  the  successive  events  are  spoken 
of  I  fully  admit,  but  there  are  also  unquestionable  advantages,  and 


182  PRINCIPLES  OF  CLASSIFICATION  [On.  XIII. 

practically  it  will  lead  to  no  misapprehension  as  to  the  chronological 
sequence  of  formations. 

The  origin  of  the  terms  Primary  and  Secondary  was  explained  in  the 
eighth  chapter,  p.  92. 

The  Tertiary  strata  were  so  called  because  they  were  all  posterior 
in  date  to  the  Secondary  series,  of  which  last  the  Chalk  or  Cretaceous, 
No.  9,  fig.  140,  constitutes  the  newest  group.  The  whole  of  them 
were  at  first  confounded,  as  before  stated,  p.  87,  with  the  superficial 
alluviums  of  Europe ;  and  it  was  long  before  their  real  extent  and 
thickness,  and  the  various  ages  to  which  they  belong,  were  fully  re- 
cognized. They  were  observed  to  occur  in  patches,  some  of  fresh- 
water, others  of  marine  origin,  their  geographical  area  being  usually 
small  as  compared  to  the  secondary  formations,  and  their  position 
often  suggesting  the  idea  of  their  having  been  deposited  in  differ- 
ent bays,  lakes,  estuaries,  or  inland  seas,  after  a  large  portion  of  the 
space  now  occupied  by  Europe  had  already  been  converted  into  dry 
land. 

The  first  deposits  of  this  class,  of  which  the  characters  were  accurately 
determined,  were  those  occurring  in  the  neighborhood  of  Paris,  described 
in  1810  by  MM.  Cuvier  and  Brongniart.  They  were  ascertained  to  con- 
sist of  successive  sets  of  strata,  some  of  marine,  others  of  freshwater 
origin,  lying  one  upon  the  other.  The  fossil  shells  and  corals  were  per- 
ceived to  be  almost  all  of  unknown  species,  and  to  have  in  general  a 
near  affinity  to  those  now  inhabiting  warmer  seas.  The  bones  and  skel- 
etons of  land  animals,  some  of  them  of  large  size,  and  belonging  to  more 
than  forty  distinct  species,  were  examined  by  Cuvier,  and  declared  by  him 
not  to  agree  specifically,  nor  even  for  the  most  part  generically,  with  any 
hitherto  observed  in  the  living  creation. 

Strata  were  soon  afterwards  brought  to  light  in  the  vicinity  of  London, 
and  in  Hampshire,  which  although  dissimilar  in  mineral  composition, 
were  justly  inferred  by  Mr.  T.  Webster  to  be  of  the  same  age  as  those  of 
Paris,  because  the  greater  number  of  the  fossil  shells  were  specifically 
identical.  For  the  same  reason  rocks  found  on  the  Gironde,  in  the  South 
of  France,  and  at  certain  points  in  the  North  of  Italy,  were  suspected  to 
be  of  contemporaneous  origin. 

A  variety  of  deposits  were  afterwards  found  in  other  parts  of  Europe, 
all  reposing  immediately  on  rocks  as  old  or  older  than  the  chalk, 
and  which  exhibited  certain  general  characters  of  resemblance  in  their 
organic  remains  to  those  previously  observed  near  Paris  and  London. 
An  attempt  was  therefore  made  at  first  to  refer  the  whole  to  one  pe- 
riod ;  and  when  at  length  this  seemed  impracticable,  it  was  contended 
that  as  in  the  Parisian  series  there  were  many  subordinate  formations 
of  considerable  thickness  which  must  have  accumulated  one  after  the 
other,  during  a  great  lapse  of  time,  so  the  various  patches  of  tertiary 
strata  scattered  over  Europe  might  correspond  in  age,  some  of  them 
to  the  older,  and  others  to  the  newer,  subdivisions  of  the  Parisian 
series. 


CH.  XIII.]  OF  TERTIARY  FORMATIONS. 


183 


This  error,  though  almost  unavoidable  on  the  part  of  those  who 
made  the  first  generalizations  in  this  branch  of  Geology,  retarded  se- 
riously for  some  years  the  progress  of  classification.  A  more  scrupu- 
lous attention  to  specific  distinctions,  aided  by  a  careful  regard  to  the 
relative  position  of  the  strata  containing  them,  led  at  length  to  the  con- 
viction that  there  were  formations  both  marine  and  freshwater  of  various 
ages,  and  all  newer  than  the  strata  of  the  neighborhood  of  Paris  and 
London. 

One  of  the  first  steps  in  this  chronological  reform  was  made  in  1811, 
by  an  English  naturalist,  Mr.  Parkinson,  who  pointed  out  the  fact  that 
certain  shelly  strata,  provincially  termed  "  Crag"  in  Suffolk,  lie  decidedly 
over  a  deposit  which  was  the  continuation  of  the  blue  clay  of  London. 
At  the  same  time*  he  remarked  that  the  fossil  testacea  in  these  newer 
beds  were  distinct  from  those  of  the  blue  clay,  and  that  while  some  ot 
them  were  of  unknown  species,  others  were  identical  with  species  now 
inhabiting  the  British  seas. 

Another  important  discovery  was  soon  afterwards  made  by  Brocchi  in 
Italy,  who  investigated  the  argillaceous  and  sandy  deposits  replete  with 
shells  which  form  a  low  range  of  hills,  flanking  the  Apennines  on  both 
sides,  from  the  plains  of  the  Po  to  Calabria.  These  lower  hills  were 
called  by  him  the  Subapennines,  and  were  formed  of  strata  chiefly  marine, 
and  newer  than  those  of  Paris  and  London. 

Another  tertiary  group  occurring  in  the  neighborhood  of  Bourdeaux 
and  Dax,  in  the  south  of  France,  was  examined  by  M.  de  Basterot  in 
1825,  who  described  and  figured  several  hundred  species  of  shells,  which 
differed  for  the  most  part  both  from  the  Parisian  series  and  those  of  the 
Subapennine  hills.  It  was  soon,  therefore,  suspected  that  this  fauna 
might  belong  to  a  period  intermediate  between  that  of  the  Parisian  and 
Subapennine  strata,  and  it  was  not  long  before  the  evidence  of  super- 
position was  brought  to  bear  in  support  of  this  opinion  ;  for  other  strata, 
contemporaneous  with  those  of  Bourdeaux,  were  observed  in  one  district 
(the  Valley  of  the  Loire),  to  overlie  ~the  Parisian  formation,  and  in  an- 
other (in  Piedmont)  to  underlie  the  Subapennine  beds.  The  first  exam- 
ple of  these  was  pointed  out  in  1829  by  M.  Desnoyers,  who  ascertained 
that  the  sand  and  marl  of  marine  origin  called  Faluns,  near  Tours,  in 
the  basin  of  the  Loire,  full  of  sea-shells  and  corals,  rested  upon  a  lacus- 
trine formation,  which  constitutes  the  uppermost  subdivision  of  the 
Parisian  group,  extending  continuously  throughout  a  great  table-land 
intervening  between  the  basin  of  the  Seine  and  that  of  the  Loire.  The 
other  example  occurs  in  Italy,  where  strata,  containing  many  fossils  sim- 
ilar to  those  of  Bourdeaux,  were  observed  by  Bonelli  and  others  in  the 
environs  of  Turin,  subjacent  to  strata  belonging  to  the  Subapennine 
group  of  Brocchi. 

Without  pretending  to  give  a  complete  sketch  of  the  progress  of  dis- 
covery, I  may  refer  to  the  facts  above  enumerated,  as  illustrating  the 
course  usually  pursued  by  geologists  when  they  attempt  to  found  new 
chronological  divisions.  The  method  bears  some  analogy  to  that  pur- 


184  PRINCIPLES  OF  CLASSIFICATION  [On.  XIH. 

sued  by  the  naturalist  in  the  construction  of  genera,  when  he  selects  a 
typical  species,  and  then  classes  as  congeners  all  other  species  of  animals 
and  plants  which  agree  with  this  standard  within  certain  limits.  The 
genera  A  and  C  having  been  founded  on  these  principles,  a  new  species 
is  afterwards  met  with,  departing  widely  both  from  A  and  C,  but  in 
many  respects  of  an  intermediate  character.  For  this  new  type  it  be- 
comes necessary  to  institute  the  new  genus  B,  in  which  are  included  all 
species  afterwards  brought  to  light,  which  agree  more  nearly  with  B  than 
with  the  types  of  A  or  C.  In  like  manner  a  new  formation  is  met  with 
in  geology,  and  the  characters  of  its  fossil  fauna  and  flora  investigated. 
From  that  moment  it  is  considered  as  a  record  of  a  certain  period  of  the 
earth's  history,  and  a  standard  to  which  other  deposits  may  be  com- 
pared. If  any  are  found  containing  the  same  or  nearly  the  same  organic 
remains,  and  occupying  the  same  relative  position,  they  are  regarded  in 
the  light  of  contemporary  annals.  All  such  monuments  are  said  to  re- 
late to  one  period,  during  which  certain  events  occurred,  such  as  the 
formation  of  particular  rocks  by  aqueous  or  volcanic  agency,  or  the  con- 
tinued existence  and  fossilization  of  certain  tribes  of  animals  and  plants. 
When  several  of  these  periods  have  had  their  true  places  assigned  to 
them  in  a  chronological  series,  others  are  discovered  which  it  becomes 
necessary  to  intercalate  between  those  first  known ;  and  the  difficulty  of 
assigning  clear  lines  of  separation  must  unavoidably  increase  in  propor- 
tion as  chasms  in  the  past  history  of  the  globe  are  filled  up. 

Every  zoologist  and  botanist  is  aware  that  it  is  a  comparatively  easy 
task  to  establish  genera  in  departments  which  have  been  enriched  with 
only  a  small  number  of  species,  and  where  there  is  as  yet  no  tendency 
in  one  set  of  characters  to  pass  almost  insensibly,  by  a  multitude  of  con- 
necting links,  into  another.  They  also  know  that  the  difficulty  of  classi- 
fication augments,  and  that  the  artificial  nature  of  their  divisions  becomes 
more  apparent,  in  proportion  to  the  increased  number  of  objects  brought 
to  light.  But  in  separating  families  and  genera,  they  have  no  other  al- 
ternative than  to  avail  themselves  of  such  breaks  as  still  remain,  or  of 
every  hiatus  in  the  chain  of  animated  beings  which  is  not  yet  filled  up. 
So  in  geology,  we  may  be  eventually  compelled  to  resort  to  sections  of 
time  as  arbitrary,  and  as  purely  conventional,  as  those  which  divide  the 
history  of  human  events  into  centuries.  But  in  the  present  state  of  our 
knowledge,  it  is  more  convenient  to  use  the  interruptions  which  still 
occur  in  the  regular  sequence  of  geological  monuments,  as  boundary 
lines  between  our  principal  groups  or  periods,  even  though  the  groups 
thus  established  are  of  very  unequal  value. 

The  isolated  position  of  distinct  tertiary  deposits  in  different  parts  of 
Europe  has  been  already  alluded  to.  In  addition  to  the  difficulty  pre- 
sented by  this  want  of  continuity  when  we  endeavor  to  settle  the  chrono- 
logical relations  of  these  deposits,  another  arises  from  the  frequent 
dissimilarity  in  mineral  character  of  strata  of  contemporaneous  date, 
such,  for  example,  as  those  of  London  and  Paris  before  mentioned.  The 
identity  or  non-identity  of  species  is  also  a  criterion  which  often  fails  us. 


CH.  XIII.1  OF  TERTIARY  FORMATIONS. 

For  this  we  might  have  been  prepared,  for  we  have  already  seen,  that 
the  Mediterranean  and  Red  Sea,  although  within  70  miles  of  each  other^ 
on  each  side  of  the  Isthmus  of  Suez,  have  each  their  peculiar  fauna ; 
and  a  marked  difference  is  found  in  the  four  groups  of  testacea  now 
living  in  the  Baltic,  English  Channel,  Black  Sea,  and  Mediterranean,  al- 
though all  these  seas  have  many  species  in  common.  In  like  manner  a 
considerable  diversity  in  the  fossils  of  different  tertiary  formations,  which 
have  been  thrown  down  in  distinct  seas,  estuaries,  bays,  and  lakes,  does 
not  always  imply  a  distinctness  in  the  times  when  they  were  pro- 
duced, but  may  have  arisen  from  climate  and  conditions  of  physical 
geography  wholly  independent  of  time.  On  the  other  hand,  it  is  now 
abundantly  clear,  as  the  result  of  geological  investigation,  that  different 
sets  of  tertiary  strata,  immediately  superimposed  upon  each  other,  con- 
tain distinct  imbedded  species  of  fossils,  in  consequence  of  fluctuations 
which  have  been  going  on  in  the  animate  creation,  and  by  which  in  the 
course  of  ages  one  state  of  things  in  the  organic  world  has  been  substi- 
tuted for  another  wholly  dissimilar.  It  has  also  been  shown  that  in 
proportion  as  the  age  of  a  tertiary  deposit  is  more  modern,  so  is  its 
fauna  more  analogous  to  that  now  in  being  in  the  neighboring  seas.  It 
is  this  law  of  a  nearer  agreement  of  the  fossil  testacea  with  the  species 
now  living,  which  may  often  furnish  us  with  a  clue  for  the  chronological 
arrangement  of  scattered  deposits,  where  we  cannot  avail  ourselves  of 
any  one  of  the  three  ordinary  chronological  tests ;  namely,  superposition, 
mineral  character,  and  the  specific  identity  of  the  fossils. 

Thus,  for  example,  on  the  African  border  of  the  Red  Sea,  at  the 
height  of  40  feet,  and  sometimes  more,  above  its  level,  a  white  calcare- 
ous formation  has  been  observed,  containing  several  hundred  species  of 
shells  differing  from  those  found  in  the  clay  and  volcanic  tuff  of  the 
country  round  Naples,  c.  g.  in  the  Bay  of  Baise.  Another  deposit 
has  been  found  at  Uddevalla,  in  Sweden,  in  which  the  shells  do  not 
agree  with  those  found  near  Naples.  But  although  in  these  three 
cases  there  may  be  scarcely  a  single  shell  common  to  the  three  different 
deposits,  we  do  not  hesitate  to  refer  them  all  to  one  period  (the  Post- 
Pliocene),  because  of  the  very  close  agreement  of  the  fossil  species  in 
every  instance  with  those  now  living  in  the  contiguous  seas. 

To  take  another  example,  where  the  fossil  fauna  recedes  a  few  steps 
farther  back  from  our  own  times.  We  may  compare,  first,  certain 
beds  at  the  eastern  base  of  Etna  near  Trezza,  hereafter  to  be  men- 
tioned ;  secondly,  others  of  nuvio-marine  origin  near  Norwich ;  and, 
lastly,  a  third  set  often  rising  to  considerable  heights  in  Sicily,  and  we 
discover  that  in  every  case  more  than  three-fourths  of  the  shells  agree 
with  species  still  living,  while  the  remainder  are  extinct.  Hence  we  may 
conclude  that  all  these,  greatly  diversified  as  are  their  organic  remains, 
belong  to  one  and  the  same  era,  or  to  a  period  immediately  antecedent 
to  the  Post-Pliocene,  because  there  has  been  time  in  each  of  the  areas 
alluded  to  for  an  equal  or  nearly  equal  amount  of  change  in  the  marine 
testaceous  fauna.  Contemporaneousness  of  origin  is  inferred  in  these 


186  FLUCTUATIONS  IN  FAUNA  AND  FLORA.  [On.  XIII. 

cases,  in  spite  of  the  most  marked  differences  of  mineral  character  or 
organic  contents,  from  a  similar  degree  of  divergence  in  the  shells  from 
those  now  living  in  the  adjoining  seas.  The  advantage  of  such  a  test 
consists  in  supplying  us  with  a  common  point  of  departure  in  all  coun- 
tries, however  remote. 

But  the  farther  we  recede  from  the  present  times,  and  the  smaller  the 
relative  number  of  recent  as  compared  with  extinct  species  in  the^  ter- 
tiary deposits,  the  less  confidence  can  we  place  in  the  exact  value  of  such 
a  test,  especially  when  comparing  the  strata  of  very  distant  regions ;  for 
we  cannot  presume  that  the  rate  of  former  alterations  in  the  animate 
world,  or  the  continual  going  out  and  coming  in  of  species,  has  been 
everywhere  exactly  equal  in  equal  quantities  of  time.  The  form  of  the 
land  and  sea,  and  the  climate,  may  have  changed  more  in  one  region 
than  in  another ;  and  consequently  there  may  have  been  a  more  rapid 
destruction  and  renovation  of  species  in  one  part  of  the  globe  than 
elsewhere.  Considerations  of  this  kind  should  undoubtedly  put  us  on 
our  guard  against  relying  too  implicitly  on  the  accuracy  of  this  test ; 
ye  it  can  never  fail  to  throw  great  light  on  the  chronological  re- 
lations of  tertiary  groups  with  each  other,  and  with  the  Post-Pliocene 
period. 

We  may  derive  a  conviction  of  this  truth  not  only  from  a  study  of 
geological  monuments  of  all  ages,  but  also  by  reflecting  on  the  tendency 
which  prevails  in  the  present  state  of  nature  to  a  uniform  rate  of  simul- 
taneous fluctuation  in  the  flora  and  fauna  of  the  whole  globe.  The 
grounds  of  such  a  doctrine  cannot  be  discussed  here,  and  I  have  ex- 
plained them  at  some  length  in  the  third  Book  of  the  Principles  of 
Geology,  where  the  causes  of  the  successive  extinction  of  species  are 
considered.  It  will  be  there  seen  that  each  local  change  in  climate  and 
physical  geography  is  attended  with  the  immediate  increase  of  certain 
species,  and  the  limitation  of  the  range  of  others.  A  revolution  thus 
effected  is  rarely,  if  ever,  confined  to  a  limited  space,  or  to  one  geograph- 
ical province  of  animals  or  plants,  but  affects  several  other  surrounding 
and  contiguous  provinces.  In  each  of  these,  moreover,  analogous  alter- 
ations of  the  stations  and  habitations  of  species  are  simultaneously  in 
progress,  reacting  in  the  manner  already  alluded  to  on  the  first  province 
Hence,  long  before  the  geography  of  any  particular  district  can  be  essen 
tially  altered,  the  flora  and  fauna  throughout  the  world  will  have  been 
materially  modified  by  countless  disturbances  in  the  mutual  relation  of 
the  various  members  of  the  organic  creation  to  each  other.  To  assume 
that  in  one  large  area  inhabited  exclusively  by  a  single  assemblage  of 
species  any  important  revolution  in  physical  geography  can  be  brought 
about,  while  other  areas  remain  stationary  in  regard  to  the  position  of 
land  and  sea,  the  height  of  mountains,  and  so  forth,  is  a  most  improba- 
ble hypothesis,  wholly  opposed  to  what  we  know  of  the  laws  now 
governing  the  aqueous  and  igneous  causes.  On  the  other  hand,  even 
were  this  conceivable,  the  communication  of  heat  and  cold  between  dif- 
ferent parts  of  the  atmosphere  and  ocean  is  so  free  and  rapid,  that  the 


CH.  XIII.]  IMPORTANCE  OF  FOSSIL  SHELLS. 

temperature  of  certain  zones  cannot  be  materially  raised  or  lowered 
without  others  being  immediately  affected ;  and  the  elevation  or  dimi- 
nution in  height  of  an  important  chain  of  mountains  or  the  submergence 
of  a  wide  tract  of  land  would  modify  the  climate  even  of  the  antipodes. 

It  will  be  observed  that  in  the  foregoing  allusions  to  organic  remains, 
the  testacea  or  the  shell-bearing  mollusca  are  selected  as  the  most  useful 
and  convenient  class  for  the  purposes  of  general  classification.  In  the 
first  place,  they  are  more  universally  distributed  through  strata  of  every 
age  than  any  other  organic  bodies.  Those  families  of  fossils  which  are 
of  rare  and  casual  occurrence  are  absolutely  of  no  avail  in  establishing 
a  chronological  arrangement.  If  we  have  plants  alone  in  one  group  of 
strata  and  the  bones  of  mammalia  in  another,  we  can  draw  no  conclusion 
respecting  the  affinity  or  discordance  of  the  organic  beings  of  the  two 
epochs  compared ;  and  the  same  may  be  said  if  we  have  plants  and 
vertebrated  animals  in  one  series  and  only  shells  in  another.  Although 
corals  are  more  abundant,  in  a  fossil  state,  than  plants,  reptiles,  or  fish, 
they  are  still  rare  when  contrasted  with  shells,  especially  in  the  European 
tertiary  formations.  The  utility  of  the  testacea  is,  moreover,  enhanced 
by  the  circumstance  that  some  forms  are  proper  to  the  sea,  others  to  the 
land,  and  others  to  freshwater.  Rivers  scarcely  ever  fail  to  carry  down 
into  their  deltas  some  land  shells,  together  with  species  which  are  at 
once  fluviatile  and  lacustrine.  By  this  means  we  learn  what  terrestrial, 
freshwater,  and  marine  species  coexisted  at  particular  eras  of  the  past ; 
and  having  thus  identified  strata  formed  in  seas  with  others  which  origi- 
nated contemporaneously  in  inland  lakes,  we  are  then  enabled  to  advance 
a  step  farther,  and  show  that  certain  quadrupeds  or  aquatic  plants,  found 
fossil  in  lacustrine  formations,  inhabited  the  globe  at  the  same  period 
when  certain  fish,  reptiles,  and  zoophytes  lived  in  the  ocean. 

Among  other  characters  of  the  molluscous  animals,  which  render 
them  extremely  valuable  in  settling  chronological  questions  in  geology, 
may  be  mentioned,  first,  the  wide  geographical  range  of  many  species ; 
and,  secondly,  what  is  probably  a  consequence  of  the  former,  the  great 
duration  of  species  in  this  class,  for  they  appear  to  have  surpassed  in 
longevity  the  greater  number  of  the  mammalia  and  fish.  Had  each 
species  inhabited  a  very  limited  space,  it  could  never,  when  imbedded  in 
strata,  have  enabled  the  geologist  to  identify  deposits  at  distant  points  ; 
or  had  they  each  lasted  but  for  a  .brief  period,  they  could  have  thrown 
no  light  on  the  connection  of  rocks  placed  far  from  each  other  in  the 
chronological,  or,  as  it  is  often  termed,  vertical  series. 

Many  authors  have  divided  the  European  tertiary  strata  into  three 
groups — lower,  middle,  and  upper ;  the  lower  comprising  the  oldest 
formations  of  Paris  and  London  before-mentioned  ;  the  middle  those  of 
Bourdeaux  and  Touraine  ;  and  the  upper  all  those  newer  than  the  mid- 
dle group. 

When  engaged  in  1828  in  preparing  my  work  on  the  Principles  of 
Geology,  I  conceived  the  idea  of  classing  the  whole  series  of  tertiary 
strata  in  four  groups,  and  endeavoring  to  find  characters  for  each,  ex- 


188  TERMS  EOCENE,  MIOCENE,  AND  PLIOCENE.          [Cn.  XIII. 

pressive  of  their  different  degrees  of  affinity  to  the  living  fauna.  "With 
this  view,  I  obtained  information  respecting  the  specific  identity  of  many 
tertiary  and  recent  shells  from  several  Italian  naturalists,  and  among 
others  from  Professors  Bonelli,  Guidotti,  and  Costa.  Having  in  1829 
become  acquainted  with  M.  Deshayes,  of  Paris,  already  well  known  by 
his  conchological  works,  I  learnt  from  him  that  he  had  arrived,  by  inde- 
pendent researches,  and  by  the  study  of  a  large  collection  of  fossil  and 
recent  shells,  at  very  similar  views  respecting  the  arrangement  of  tertiary 
formations.  At  my  request  he  drew  up,  in  a  tabular  form,  lists  of  all 
the  shells  known  to  him  to  occur  both  in  some  tertiary  formation  and  in 
a  living  state,  for  the  express  purpose  of  ascertaining  the  proportional 
number  of  fossil  species  identical  with  the  recent  which  characterized 
successive  groups ;  and  this  table,  planned  by  us  in  common,  was  pub- 
lished by  me  in  1833.*  The  number  of  tertiary  fossil  shells  examined 
by  M.  Deshayes  was  about  3000 ;  and  the  recent  species  with  which  they 
had  been  compared  about  5000.  The  result  then  arrived  at  was,  that 
in  the  lower  tertiary  strata,  or  those  of  London  and  Paris,  there  were 
about  3i  per  cent,  of  species  identical  with  recent ;  in  the  middle  ter- 
tiary of  the  Loire  and  Gironde  about  1 7  per  cent. ;  and  in  the  upper 
tertiary  or  Subapennine  beds,  from  35  to  50  per  cent.  In  formations 
still  more  modern,  some  of  which  I  had  particularly  studied  in  Sicily, 
where  they  attain  a  vast  thickness  and  elevation  above  the  sea,  the  num- 
ber of  species  identical  with  those  now  living  was  believed  to  be  from 
90  to  95  per  cent.  For  the  sake  of  clearness  and  brevity,  I  proposed 
to  give  short  technical  names  to  these  four  groups,  or  the  periods  to 
which  they  respectively  belonged.  I  called  the  first  or  oldest  of  them 
Eocene,  the  second  Miocene,  the  third  Older  Pliocene,  and  the  last  or 
fourth  Newer  Pliocene.  The  first  of  the  above  terms,  Eocene,  is  derived 
from  7jw£,  eos,  dawn,  and  xaivos,  cainos,  recent,  because  the  fossil  shells  of 
this  period  contain  an  extremely  small  proportion  of  living  species,  which 
may  be  looked  upon  as  indicating  the  dawn  of  the  existing  state  of  the 
testaceous  fauna,  no  recent  species  having  been  detected  in  the  older  or 
secondary  rocks. 

The  term  Miocene  (from  /XSJQV,  meion,  less,  and  xajvo?,  cainos,  recent) 
is  intended  to  express  a  minor  proportion  of  recent  species  (of  testacea), 
the  term  Pliocene  (from  -rXstov,  pleion,  more,  and  xouvocr,  cainos,  recent)  a 
comparative  plurality  of  the  same.  It  may  assist  the  memory  of  stu- 
dents to  remind  them,  that  the  Eocene  contain  a  minor  proportion,  and 
/Yiocene  a  comparative  £>Zurality  of  recent  species ;  and  that  the  greater 
number  of  recent  species  always  implies  the  more  modern  origin  of  the 
strata. 

It  has  sometimes  been  objected  to  this  nomenclature  that  certain  spe- 
cies of  infusoria  found  in  the  chalk  are  still  existing,  and,  on  the  other 
hand,  the  Miocene  and  Older  Pliocene  deposits  often  contain  the  remains 
of  mammalia,  reptiles,  and  fish,  exclusively  of  extinct  species.  But  the 

*  See  Princ.  of  Geol.  vol.  iii.  1st  ed. 


CH.  XIIL]  NEWER  PLIOCENE  BEDS  OF  ISCHIA. 


189 


reader  must  bear  in  mind  that  the  terms  Eocene,  Miocene,  and  Plio- 
cene were  originally  invented  with  reference  purely  to  conchological 
data,  and  in  that  sense  have  always  been  and  are  still  used  by  me. 

The  distribution  of  the  fossil  species  from  which  the  results  before 
mentioned  were  obtained  in  1830  by  M.  Deshayes  was  as  follow*: 

In  the  formations  of  the  Pliocene  periods,  older  and  newer,  -      777    ,— 

In  the  Miocene  (upper  or  Falunian),  -  .    1021 

In  the  Eocene  (including  the  Gres  de  Fontainebleau),         -  -    1238 

3036 

Since  the  year  1830,  the  number  of  new  living  species  obtained 
from  different  parts  of  the  globe  has  been  exceedingly  great,  supplying 
fresh  data  for  comparison,  and  enabling  the  paleontologist  to  correct 
many  erroneous  ^identifications  of  fossil  and  recent  forms.  New 
species  also  have  been  collected  in  abundance  from  tertiary  formations 
of  every  age,  while  newly  discovered  groups  of  strata  have  filled"  up 
gaps  in  the  previously  known  series.  Hence  modifications  and  reforms 
have  been  called  for  in  the  classification  first  proposed.  The  Eocen^f 
Miocene,  and  Pliocene  periods  have  been  made  to  comprehend  certain 
sets  of  strata  of  which  the  fossils  do  not  always  conform  strictly  in  the 
proportion  of  recent  to  extinct  species  with  the  definitions  first  given 
by  me,  or  which  are  implied  in  the  etymology  of  those  terms.  Of 
these  and  other  innovations  I  shall  treat  more  fully  in  the  fourteenth 
and  fifteenth  chapters. 

Newer  Pliocene — Ischia. — We  have  already  seen,  page  108,  that  in 
the  neighborhood  of  Naples  there  are  stratified  tuffs  containing  a  large 
number  of  fossil  shells  agreeing  specifically  with  those  now  living  in 
the  Mediterranean.  Of  an  age  immediately  antecedent  to  those 
Post-pliocene  formations  are  the  volcanic  tuffs  of  the  neighboring 
island  of  Ischia,  some  of  them  rising  in  the  summit  of  Santa  Nicola 
or  Monte  Epomeo  to  the  height  of  2605  feet  above  the  sea.  I  stated 
in  the  first  editions  of  the  "  Principles  of  Geology"  *  that  in  1828  I 
had  procured  many  fossil  shells  from  near  the  village  of  Moropano,  at 
an  elevation  of  2000  feet  above  the  Mediterranean.  I  have  since 
found,  on  revisiting  Ischia,  that  the  spot  is  not  more  than  1600  feet  , 
high ;  but  this  error  is  not  of  geological  importance,  as  the  beds  are 
admitted  to  form  a  part  of  the  same  greenish  and  bluish  marls  which 
reach  the  top  of  Epomeo.  The  whole  of  the  fossil  species,  28  in 
number,  which  I  first  collected  there,  were  examined  by  M.  Deshayes 
and  recognized  by  him  as  all  now  living.  I  called  them  Newer  Plio- 
cene, considering  .them  of  much  more  modern  date  than  the  Sub- 
apennine  strata,!  to  which  Signor  Spada  Lavini  proposed,  in  1853,  to 
refer  them.  He  seems  to  have  adopted  this  opinion,  because  among 

*  Principles  of  Geology,  vol.  iii.  p.  126,  1833.  ^ 

f  See  Principles,  Table,  vol.  iii.  pp.  16  and  126. 


190        NEWER  PLIOCENE  BEDS  OF  VESUVIUS  AND  ETNA.      [Cn.  XIII. 

a  larger  number  of  fossils  obtained  from  these  beds  in  Ischia,  Buccinum 
semistriatum  and  Murex  vaginatus  (see  fig.  141)  had  been  found. 
Both  of  these  shells  were  supposed  to  be  extinct ;  but  although  this 
is  true  of  the  first,  which  is  a  common  Subapennine  shell,  it  is  not  so 
of  the  other,  for  the  Murex  still  lives  in  the  Mediterranean,  though 
rare,*  and  recent  specimens  of  it  may  be  seen  in  Mr.  Cuming's  col- 
lection in  London,  from  which  the  annexed  figure  is  taken.  Several 
Italian  geologists,  who  had  not  examined  Ischia,  hastily  adopted 
the  classification  of  Signor  Spada ;  but  M.  Puggaard, 
who  was  well  acquainted  with  the  island,  immediately  ^  141« 

entered  his  protest  against  it ;  f  and  there  can  be 
no  doubt,  from  the  general  character  of  the  organic 
remains,  that  the  mass  of  Epomeo  was  formed  be- 
neath the  waters  of  the  sea  at  the  close  of  the 
Newer  Pliocene  period,  and  was  raised  to  a  height 
of  2600  feet  above  its  original  level  in  Post-pliocene 
times. 

Vesuvius. — The  old  cone  of  Vesuvius,  or  Monte 
Somma,  is,  geologically  speaking,  so  modern  that 
the  eruption  by  which  it  was  formed  burst  through 
marine  clays  and  tuffs  of  the  same  age  as  those  of  Phil- 

Ischia  above  mentioned.  Fragments  of  -tun7  and  conglomerate  found 
amongst  the  ancient  ejectamenta,  and  constituting  part  of  the  strata 
laid  open  in  the  ravine  called  Fosso  Grande  and  in  the  Kivo  di  Quag- 
lia,  the  latter  972  feet  high  above  the  sea,  have  supplied  Signor 
Guiscardi  with  100  shells,  among  which  one,  and  one  only,  namely, 
Buccinum  semistriatum,  before  alluded  to,  is  extinct.  The  oldest  erup- 
tions, therefore,  of  the  Campi  Phlegrsei,  or  volcanic  regions  of  Naples, 
took  place  precisely  at  the  close  of  the  Newer  Pliocene  period,  when 
about  one  shell  only  in  a  hundred  differed  from  those  now  living  in  the 
Mediterranean. 

Sicily,  ^Eastern  base  of  Mount  Etna. — At  several  points  north  of 
Catania,  on  the  eastern  seacoast  of  Sicily,  as  at  Aci-Castello,  for  ex- 
ample, Trezza,  and  Nizzeti,  marine  strata,  associated  with  volcanic  tuffs 
and  basaltic  lavas,  are  seen,  which  belong  to  a  period  when  the  first 
igneous  eruptions  of  Mount  Etna  were  taking  place  in  a  shallow  bay 
of  the  Mediterranean.  During  my  first  visit  to  Sicily  in  1828,  I  col- 
lected sixty-five  species  of  shells  from  these  clays  and  sands,  which  may 
be  said,  together  with  the  associated  igneous  products,  to  constitute 
the  foundations  of  the  great  volcano.  With  the  help  of  M.  Deshayes, 
I  was  enabled  to  publish  a  list  of  their  names,  J  showing  that  nearly 
all  of  them  agreed  with  species  now  inhabiting  -the  adjoining  sea. 


*  Lyell  on  Mount  Etna,  Phil.  Trans.,  p.  778,  1858. 

f  Bulletin  de  la  Soc.  Geol.  de  France,  torn.  xi.  2e  ser.,  p.  72,  and  torn.  xiii.  p. 
285,  and  xv.  p.  362. 

\  Principles  of  Geology,  vol.  iii.,  Appendix,  1833. 


CH.  XIII.]  EASTERN  BASE   OF  MOUNT  ETNA. 


191 


In  1857  and  1858,  Avhen  I  revisited  Sicily,  I  obtained,  through  the 
kindness  of  Dr.  Aradas,  of  Catania,  a  much  larger  number  of  species 
from  the  same  localities,  which  confirmed  the  conclusions  formerly  ar- 
rived at  as  to  the  age  of  these  deposits.  Out  of  142  shells,  all  but 
eleven  proved  to  be  identical  with  species  now  livijig.  Some  few  of 
these  eleven  shells  may  possibly  still  linger  in  the  depths  of  the  Med- 
iterranean, like  Murex  vaginatus,  fig.  141,  p.  190.  The  last-mentioned 
shell  had  already  become  rare,  when  the  sub-Etnean  deposits  were 
formed.  On  the  whole,  the  modern  character  of  the  testaceous  fauna 
under  consideration  is  expressed  not  only  by  the  small  proportion  of 
extinct  species,  but  by  the  relative  number  of  individuals  by  which 
most  of  the  other  species  are  represented,  for  the  proportion  agrees 
with  that  observed  in  the  present  fauna  of  the  Mediterranean.  The  only 
extinct  shell  which  can  be  said  to  be  common  is  Buccinum,  semistria- 
tum;  B.  musivum  comes  next  in  abundance.  The  rarity  of  the  other 
nine  is  such  as  to  imply  that  they  were  already  on  the  point  of  dying 
out,  having  flourished  chiefly  in  the  earlier  Pliocene  times  when  the 
Subapennine  strata  were  in  progress. 

Yet  since  the  accumulation  of  these  Newer  Pliocene  sands  and  clays, 
the  whole  cone  of  Etna,  11,000  feet  in  height  and  about  ninety 
miles  in  circumference  at  its  base,  has  been  slowly  built  up  ;  an  opera- 
tion requiring  many  tens  of  thousands  of  years  for  its  accomplish- 
ment, and  to  estimate  the  magnitude  of  which  it  is  necessary  to  study 
in  detail  the  internal  structure  of  the  mountain,  and  to  see  the  proofs 
of  its  double  axis,  or  the  evidence  of  the  lavas  of  the  present  great 
centre  of  eruption  having  gradually  overwhelmed  and  enveloped  a 
more  ancient  cone,  situated  3|-  miles  to  the  east  of  the  present  one. 
We  ought  also  to  satisfy  ourselves,  as  we  may  easily  do,  that  in  breadth 
and  thickness  each  of  the  older  lavas  did  not  exceed  in  their  average 
volume  the  products  of  single  outpourings  of  historical  times.  In  spec- 
ulating, moreover,  on  the  lapse  of  bygone  ages,  we  must  take  into  ac- 
count the  different  dates  and  varying  composition  of  the  dikes  up 
which  the  lavas  poured,  whether  belonging  to  the  eastern  or  western 
axis,  and  the  manner  in  which  one  set  of  dikes  cuts  through  an  older 
one ;  also,  the  vast  denudation  to  which  the  Yal  del  Bove,  or  deep 
valley,  on  the  eastern  flank  of  the  mountain,  bears  testimony ;  and, 
lastly,  the  gradual  upheaval  above  the  level  of  the  sea  of  some  of  the 
submarine  rocks  first  formed,  and  the  origin  of  many  hundred  minor 
cones,  the  result  of  lateral  outbreaks  during  the  most  modern  phase  of 
eruption.  These  and  other  observations  must  be  made,  before  the 
prodigious  antiquity  of  the  Newer  Pliocene  marine  strata  above  de- 
scribed can  be  fully  appreciated.* 

It  appears  that  while  Etna  was  increasing  in  bulk  by  a  series  of 
eruptions,  its  whole  mass,  comprising  the  foundations  of  subaqueous 

*  See  a  Memoir  on  the  Lavas  and  Mode  of  Origin  of  Mount  Etna,  by  the  Author, 
Phil.  Trans.,  1858. 


192  NEWER  PLIOCENE  STRATA  [On.  XIII. 

origin  above  alluded  to,  was  undergoing  a  slow  upheaval,  by  which 
those  marine  strata  were  raised  to  the  height  of  1200  feet  above  the 
sea,  as  seen  at  Catera,  and  perhaps  to  greater  heights,  for  we  cannot 
trace  their  extension  westward  owing  to  the  dense  and  continuous 
covering  of  modern  lava  under  which  they  are  buried.  During  the 
gradual  rise  of  these  Newer  Pliocene  formations  (consisting  of  clays, 
sands,  and  basalts),  other  strata  of  Post-pliocene  date,  marine  as  well 
as  fluviatile,  accumulated  round  the  base  of  the  mountain,  and  these, 
in  their  turn,  partook  of  the  upward  movement,  so  that  several  inland 
cliffs  and  terraces  at  low  levels,  due  partly  to  the  action  of  the  sea  and 
partly  to  the  river  Simeto,  originated  in  succession. 

Fossil  remains  of  the  elephant,  and  other  extinct  quadrupeds,  have 
been  found  in  these  Post-pliocene  strata,  associated  with  recent  shells. 

Newer  Pliocene  strata  of  Sicily. — There  is  probably  no  part  of  Europe 
where  the  Newer  Pliocene  formations  enter  so  largely  into  the  struc- 
ture of  the  earth's  crust,  or  rise  to  such  heights  above  the  level  of  the 
sea,  as  Sicily.  They  cover  nearly  half  the  island,  and  near  its  centre, 
at  Castrogiovanni,  reach  an  elevation  of  3000  feet.  They  consist  prin- 
cipally of  two  divisions,  the  upper  calcareous,  and  the  lower  argillaceous, 
both  of  which  may  be  seen  at  Syracuse,  Girgenti,  and  Castrogiovanni. 

According  to  Philippi,  to  whom  we  are  indebted  for  the  best  account 
of  the  tertiary  shells  of  this  island,  thirty-five  species  out  of  one  hundred 
and  twenty-four  obtained  from  the  beds  in  central  Sicily  are  extinct. 

A  geologist,  accustomed  to  see  nearly  all  the  Newer  Pliocene  forma- 
tions in  the  north  of  Europe  occupying  low  grounds  and  very  incoher- 
ent in  texture,  is  naturally  surprised  to  behold  formations  of  the  same 
age  so  solid  and  stony,  of  such  thickness,  and  attaining  so  great  an 
elevation  above  the  level  of  the  sea. 

The  upper  or  calcareous  member  of  this  group  in  Sicily  consists  in 
some  places  of  a  yellowish-white  stone,  like  the  Calcaire  Grossier  of 
Paris  ;  in  others,  of  a  rock  nearly  as  compact  as  marble.  Its  aggregate 
thickness  amounts  sometimes  to  TOO  or  800  feet.  It  usually  occurs  in 
regular  horizontal  beds,  and  is  occasionally  intersected  by  deep  valleys 
such  as  those  of  Sortino  and  Pentalica,  in  which  are  numerous  caverns. 
The  fossils  are  in  every  stage  of  preservation,  from  shells  retaining  por- 
tions of  their  animal  matter  and  color  to  others  which  are  mere  casts. 

The  limestone  passes  downward  into  a  sandstone  and  conglomer- 
ate, below  which  is  clay  and  blue  marl,  like  that  of  the  Subapen- 
nine  hills,  from  which  perfect  shells  and  corals  may  be  disengaged. 
The  clay  sometimes  alternates  with  yellow  sand. 

South  of  the  plain  of  Catania  is  a  region  in  which  the  tertiary  beds  are 
intermixed  with  volcanic  matter,  which  has  been  for  the  most  part  the 
product  of  submarine  eruptions.  It  appears  that,  while  the  clay,  sand, 
and  yellow  limestone  before  mentioned  were  in  course  of  deposition  at 
the  bottom  of  the  sea,  volcanoes  burst  out  beneath  the  waters,  like  that 
of  Graham  Island,  in  1831,  and  these  explosions  recurred  again  and 
again  at  distant  intervals  of  time.  Volcanic  ashes  and  sand  were  showered 


OH.  XIII.] 


OF   SICILY. 


193 


down  and  spread  by  the  waves  and  currents  so  as  to  form  strata  of  tuff, 
which  are  found  intercalated  between  beds  of  limestone  and  clay  contain- 
ing marine  shells,  the  thickness  of  the  whole  mass  exceeding  2000  feet. 
The  fissures  through  which  the  lava  rose  may  be  seen  in  many  places 
forming  what  are  called  dikes. 

In  part  of  the  region  above  alluded  to,  as,  for  example,  near  Lentini, 
a  conglomerate  occurs  in  which  I  observed  many  pebbles  of  volcanic 
rocks  covered  by  full  grown  serpulce.  We  may  explain  the  origin  of 
these  by  supposing  that  there  were  some  small  volcanic  islands  which 
may  have  been  destroyed  from  time  to  time  by  the  waves,  as  Graham 
Island  has  been  swept  away  since  183L  The  rounded  blocks  and 
pebbles  of  solid  volcanic  matter,  after  being  rolled  for  a  time  on  the 
beach  of  such  temporary  islands,  were  carried  at  length  into  some  tran- 
quil part  of  the  sea,  where  they  lay  for  years,  while  the  marine  serpulce 
adhered  to  them,  their  shells  growing  and  covering  their  surface,  as  they 
are  seen  adhering  to  the  shell  figured  in  p.  22.  Finally,  the  bed  of  peb- 
bles was  itself  covered  with  strata  of  shelly  limestone.  At  Vizzini,  a 
town  not  many  miles  distant  to  the  S.  W.,  I  remarked  another  striking 
proof  of  the  gradual  manner  in  which  these  modern  rocks  were  formed, 
and  the  long  intervals  of  time  which  elapsed  between  the  pouring  out  of 
distinct  sheets  of  lava.  A  bed  of  oysters  no  less  than  20  feet  in  thick- 
ness rests  upon  a  current  of  basaltic  lava.  The  oysters  are  perfectly  iden- 
tifiable with  our  common  eatable  species.  Upon  the  oyster  bed,  again, 
is  superimposed  a  second  mass  of  lava,  together  with  tuff  or  peperino. 
In  the  midst  of  the  same  alternating  igneous  and  aqueous  formations  is 
seen  near  Galieri,  not  far  from  Vizzini,  a  horizontal  bed,  about  a  foot  and 
a  half  in  thickness,  composed  entirely  of  a  common  Mediterranean  coral 
(Qaryophyllia  ccespitosa,  Lam.).  These  corals  stand  erect  as  they  grew; 

Fig.  142. 


Caryophyllia  ccespitosa,  Lam.         (Cladocora  stellaria,  Milne  Edw.  and  Hairae.) 

a.  Stem  with  young  stem  growing  from  its  side. 
a*.  Young  stem  of  same  twice  magnified. 

&.  Portion  of  branch,  twice  magnified,  with  the  base  of  a  lateral  branch ;  the  exterior 
ridges  of  the  main  branch  appearing  through  the  lamelhe  of  the  lateral  one. 

c.  Transverse  section  of  same,  proving  by  the  integrity  of  the  main  branch,  that  the 

lateral  one  did  not  originate  in  a  subdivision  of  the  animal. 

d.  A  branch,  having  at  its  base  another  laterally  united  to  it,  and  two  young  corals  at 

its  upper  part 

e.  A  main  branch,  with  a  fall  grown  lateral  one. 
/.   A  perfect  terminal  star. 

13 


194:  NEWER  PLIOCENE  STRATA  OF  SICILY.          [On.  XIU 

and,  after  being  traced  for  hundreds  of  yards,  are  again  found  at  a  cor- 
responding height  on  the  opposite  side  of  the  valley. 

The  corals  are  usually  branched,  but  not  by  the  division  of  the  animals 
as  some  have  supposed,  but  by  the  attachment  of  young  individuals  to 
the  sides  of  the  older  ones ;  and  we  must  understand  this  mode  of  in- 
crease, in  order  to  appreciate  the  time  which  was  required  for  the  building 
up  of  the  whole  bed  of  coral  during  the  growth  of  many  successive  gen- 
erations.* 

Among  the  other  fossil  shells  met  with  in  these  Sicilian  strata,  which 
still  continue  to  abound  in  the  Mediterranean,  no  shell  is  more  conspic- 
uous, from  its  size  and  frequent  occurrence,  than  the  great  scallop,  Pecten 
jacobceus  (see  fig.  143),  now  so  common  in  the  neighboring  seas.  We 
see  this  shell  in  the  calcareous  beds  at  Palermo  in  great  numbers,  in  the 
limestone  at  Girgenti,  and  in  that  which  alternates  with  volcanic  rocks  in 
the  country  between  Syracuse  and  Vizzini,  often  at  great  heights  above 
the  sea. 

Fig.  148. 


Pecten  jacobceus;  half  natural  size. 

The  more  we  reflect  on  the  preponderating  number  of  these  recent  shells, 
the  more  we  are  surprised  at  the  great  thickness,  solidity,  and  height 
above  the  sea  of  the  rocky  masses  in  which  they  are  entombed,  and  the 
vast  amount  of  geographical  change  which  has  taken  place  since  their 
origin.  It  must  be  remembered  that,  before  they  began  to  emerge,  the 
uppermost  strata  of  the  whole  must  have  been  deposited  under  water. 
In  order,  therefore,  to  form  a  just  conception  of  their  antiquity,  we  must 
first  examine  singly  the  innumerable  minute  parts  of  which  the  whole  is 
made  up,  the  successive  beds  of  shells,  corals,  volcanic  ashes,  conglomer- 
ates, and  sheets  of  lava ;  and  we  must  afterwards  contemplate  the  time 

*  I  am  indebted  to  Mr.  Lonsdale  for  the  details  above  given  respecting  the 
structure  of  this  coraL 


CH.  XIIL1  CAVE   BRECCIAS.  195 

required  for  the  gradual  upheaval  of  the  rocks,  and  the  excavation  of  the 
valleys.  The  historical  period  seems  scarcely  to  form  an  appreciable  unit 
in  this  computation,  for  we  find  ancient  Greek  temples,  like  those  of 
Girgenti  (Agrigentum),  built  of  the  modern  limestone  of  which  we  are 
speaking,  and  resting  on  a  hill  composed  of  the  same ;  the  site  having 
remained  to  all  appearance  unaltered  since  the  Greeks  first  colonized  the 
island. 

The  modern  geological  date  of  the  rocks  in  this  region  leads  to  another 
singular  and  unexpected  conclusion,  namely,  that  the  fauna  and  flora  of 
a  large  part  of  Sicily  are  of  higher  antiquity  than  the  country  itself, 
having  not  only  flourished  before  the  lands  were  raised  from  the  deep, 
but  even  before  their  materials  were  brought  together  beneath  the  waters. 
The  chain  of  reasoning  which  conducts  us  to  this  opinion  may  be  stated 
in  a  few  words.  The  larger  part  of  the  island  has  been  converted  from 
sea  into  land  since  the  Mediterranean  was  peopled  with  nearly  all  the 
living  species  of  testacea  and  zoophytes.  We  may  therefore  presume 
that,  before  this  region  emerged,  the  same  land  and  river  shells,  and 
almost  all  the  same  animals  and  plants,  were  in  existence  which  now 
people  Sicily ;  for  the  terrestrial  fauna  and  flora  of  this  island  are  pre- 
cisely the  same  as  that  of  other  lands  surrounding  the  Mediterranean. 
There  appear  to  be  no  peculiar  or  indigenous  species,  and  those  which 
are  now  established  there  must  be  supposed  to  have  migrated  from  pre- 
existing lands,  just  as  the  plants  and  animals  of  the  Neapolitan  territory 
have  colonized  Monte  Nuovo,  since  that  volcanic  cone  was  thrown  up  in 
the  sixteenth  century. 

Such  conclusions  throw  a  new  light  on  the  adaptation  of  the  attributes 
and  migratory  habits  of  animals  and  plants  to  the  changes  which  are  un- 
ceasingly in  progress  in  the  physical  geography  of  the  globe.  It  is  clear 
that  the  duration  of  species  is  so  great,  that  they  are  destined  to  outlive 
many  important  revolutions  in  the  configuration  of  the  earth's  surface ; 
and  hence  those  innumerable  contrivances  for  enabling  the  subjects  of  the 
animal  and  vegetable  creation  to  extend  their  range ;  the  inhabitants  of 
the  land  being  often  carried  across  the  ocean,  and  the  aquatic  tribes  over 
great  continental  spaces.  It  is  obviously  expedient  that  the  terrestrial  and 
fluviatile  species  should  not  only  be  fitted  for  the  rivers,  valleys,  plainsp- 
and  mountains  which  exist  at  the  era  of  their  creation,  but  for  others  that 
are  destined  to  be  formed  before  the  species  shall  become  extinct ;  and, 
in  like  manner,  the  marine  species  are  not  only  made  for  the  deep  and 
shallow  regions  of  the  ocean  existing  at  the  time  when  they  are  called 
into  being,  but  for  tracts  that  may  be  submerged  or  variously  altered  in 
depth  during  the  time  that  is  allotted  for  their  continuance  on  the 
globe.* 

*  The  three  last  pages,  on  "The  Newer  Pliocene  Strata  of  Sicily,"  are  given 
verbatim  as  they  appeared  thirty  years  ago  in  the  first  edition  of  the  Principles 
of  Geology  (vol.  iii.  p.  115,  1833).  The  last  sentence,  marked  with  inverted  com- 
mas, was  couched  in  language  implying  my  adherence  to  the  theory  that  each  spe- 
cies was  originally  created  such  as  it  now  exists,  and  was  incapable  of  varying  so  as 


196  NEWER  PLIOCENE  STRATA  OF  ENGLAND.  [Cn.  XIII. 

Newer  Pliocene  strata  of  the  Upper  Val  d'Arno. — When  we  ascend 
the  Arno  for  about  ten  miles  above  Florence,  we  arrive  at  a  deep  nar- 
row valley  called  the  Upper  Val  d'Arno,  which  appears  once  to  have 
been  a  lake  at  a  time  when  the  valley  below  Florence  was  an  arm  of 
the  sea.  The  horizontal  lacustrine  strata  of  this  upper  basin  are  12 
miles  long  and  2  broad.  The  depression  which  they  fill  has  been  ex- 
cavated out  of  Eocene  and  Cretaceous  rocks,  which  form  everywhere 
the  sides  of  the  valley  in  highly  inclined  stratification.  The  thick- 
ness of  the  more  modern  and  unconformable  beds  is  about  750  feet, 
of  which  the  upper  200  feet  consist  of  Newer  Pliocene  strata,  while 
the  lower  are  Older  Pliocene.  The  newer  series  are  made  up  of  sands 
and  a  conglomerate  called  "sansino."  Among  the  imbedded  fossil 
mammalia  are  Mastodon  arvernensis,  Elephas  meridionalis,  Rhinoceros 
etruscus,  Hippopotamus  major,  and  remains  of  the  genera  bear, 
hyaena,  and  felis. 

In  the  same  upper  strata  are  found,  according  to  M.  Gaudin,  the 
leaves  and  cones  of  Glyptostrobus  europceus,  a  plant  closely  allied  to 
@.  heterophyllus,  now  inhabiting  the  north  of  China  and  Japan. 
This  conifer  had  a  wide  range  in  time,  having  been  traced  back 
to  the  Lower  Miocene  strata  of  Switzerland — and  being  common 
at  QEningen  in  the  Upper  Miocene,  as  we  shall  see  in  the  sequel, 
Chapter  XV. 

Newer  Pliocene  strata  of  England. — It  is  in  the  counties  of  Nor- 
folk, Suffolk,  and  Essex,  that  we  obtain  our  most  valuable  information 
respecting  the  British  Pliocene  strata,  whether  newer  or  older.  They 
have  obtained  in  those  counties  the  provincial  name  of  "  Crag,"  ap- 
plied particularly  to  masses  of  shelly  sand  which  have  long  been  used 
in  agriculture  to  fertilize  soils  deficient  in  calcareous  matter. 

In  Suffolk  the  strata  so  named  are  divisible  into  the  Lower,  called 
the  White,  or  Coralline,  and  the  Upper,  or  the  Red  Crag ;  *  but  the 
inferior  division  occupies  a  very  limited  area,  and  the  Ked  Crag  usu- 
ally reposes  directly  and  without  the  intervention  of  the  Coralline  on 
older  strata,  as  in  Essex,  for  example,  where  the  relative  position  of 
the  Bed  Crag  to  the  London  Clay  (an  Eocene  deposit)  and  to  the 

to  pass  into  a  new  and  distinct  species.  In  my  recent  work  on  the  Geological  Evi- 
dences of  the  Antiquity  of  Man,  I  have  shown  (chaps,  xxi.  to  xxiv.)  that  Mr.  Dar- 
win's theory  of  natural  selection  removes  many  of  the  principal  difficulties  which 
stood  in  the  way  of  Lamarck's  doctrine  of  transmutation ;  and  had  I  inclined  as 
much  in  1833  toward  embracing  Mr.  Darwin's  views  as  I  do  now,  I  should  have 
expressed  myself  somewhat  differently.  But  I  have  thought  it  best  not  to  recast  a 
passage  which  has  been  so  often  cited,  both  by  writers  who  opposed  and  approved 
of  it.  The  main  proposition  which  seemed  so  startling  in  1833,  namely,  that  spe- 
cies in  general  may  be  older  than  the  lands  and  seas  they  inhabit,  is  now  the  creed 
of  almost  every  geologist,  whether  he  adopts  or  rejects  the  theory  that  species  may 
be  indefinitely  modified  in  their  organization  under  the  influence  of  new  conditions 
in  the  animate  and  inanimate  world. 

*  See  paper  by  E.  Charlesworth,  Esq. ;  London  and  Ed.  Phil.  Mag.,  No.  xxxviii. 
p.  81,  Aug.  1835. 


CH.  XIII.]  THE  NORWICH  CRAG. 

Fig.  144. 
Crag.  London  Clay. 


197 


Chalk. 


chalk  is  explained  in  the  foregoing  diagram.  Both  the  White  and 
the  Red  Crag,  as  we  shall  see  in  the  sequel,  belong  to  the  Older 
Pliocene  period,  whereas  a  more  modern  deposit,  occurring  in  the 
neighborhood  of  Norwich,  is  referable  to  the  Newer  Pliocene.  It 
consists  of  beds  of  incoherent  sand,  loam,  and  gravel,  which  are  ex- 
posed to  view  on  both  banks  of  the  Tare  near  Norwich.  As  they 
contain  a  mixture  of  marine,  land,  and  freshwater  shells,  with  ichthy- 
olites  and  bones  of  mammalia,  it  is  clear  that  these  beds  have  been 
accumulated  at  the  bottom  of  a  sea  near  the  mouth  of  a  river.  They 
form  patches  varying  from  2  to  20  feet  in  thickness,  resting  on  white 
chalk,  and  are  covered  by  a  dense  mass  of  stratified  flint-gravel.  The 
surface  of  the  chalk  is  often  perforated  to  the  depth  of  several  inches 
by  the  Pholas  crispata,  each  fossil  shell  still  remaining  at  the  bottom 
of  its  cylindrical  cavity,  now  filled  up  with  loose  sand  from  the  in- 
cumbent crag.  This  species  of  Pholas  still  exists,  and  drills  the  rocks 
between  high  and  low  water  on  the  British  coast.  The  most  common 
shells  of  these  strata,  such  as  Fusus  striatus,  F.  antiquus,  Turritella 
communis,  Cardium  edule,  and  Cyprina  islandica,  are  now  abundant 
in  the  British  seas ;  but  with  them  are  some  extinct  species,  such  as 
Nucula  Cobboldice  (fig.  145),  and  Tellina  obliqua  (fig.  146).  Natica 
helicoides  (fig.  147)  is  an  example  of  a  species  formerly  known  only 


Fig.  145. 


Fig.  146. 


Fig.  14T. 


Nucula,  Coliboldlw. 


Tellina  obliqua. 


Natica  heUcoidea, 
Johnston. 


as  fossil,  but  which  has  now  been  found  living  in  our  seas ;  and  I  have 
recently  seen,  in  the  British  Museum,  a  living  shell  from  Vancouver's 
Island,  so  closely  allied  to  N.  Cobboldice,  that  it  would  be  considered 
by  many  as  merely  a  marked  variety  of  the  same  form. 

The  Norwich  Crag  is  seen  resting  on  chalk  in  the  sea  cliff  between 
Weybourne  and  Cromer,  and  is  found  at  many  points  to  the  westward 
in  the  interior.  The  only  place  where  beds  containing  the  peculiar 
shells  of  this  formation  have  been  found  directly  overlying  the  Red 
Crag  is  at  Chillesford,  near  Orford  in  Suffolk;  but  we  do  not  require 
the  evidence  of  direct  superposition  to  prove  that  the  Norwich  is  a 
much  newer  deposit  than  the  Red  Crag,  since  the  proportion  of  recent 
to  extinct  species  is  so  much  greater  in  the  Norwich  beds,  amounting, 


198  MASTODON  AEVERNENSIS.  [Cn.  XIII. 

according  to  the  latest  investigations,  to  89  per  cent.,  whereas  in  the 
Red  Crag  it  does  not  exceed  60  per  cent. 

Among  the  accompanying  remains  of  mammalia  are  those  of  a 
Mastodon,  a  portion  of  the  upper  jawbone  with  a  tooth  having  been 
found  by  Mr.  Wigham  at  Postwick,  near  Norwich.  This  species  has 
also  been  found  in  the  Red  Crag,  both  at  Button  and  at  Felixstow, 
and  was  till  lately  regarded  as  an  Upper  Miocene  or  Falunian  species ; 
and  under  this  persuasion,  calling  it  M.  angustidens,  on  the  authority 
of  Professor  Owens,  I  suggested  that  its  remains  might  have  been 
washed  out  of  older  strata  into  the  Crag,  just  as  we  sometimes  ob- 
serve London  Clay  and  Chalk  fossils  introduced  into  the  same  de- 
posit. But  Dr.  Falconer,  who  has  devoted  many  years  to  the  study 
of  the  fossil  and  recent  Proboscideans,  has  shown  that  the  fossil  is  a 
Pliocene  species,  first  observed  in  Auvergne  by  MM*  Croizet  and 
Jobert,  and  named  by  them  Mastodon  arvernensis.  Cuvier  did  not 

Fig.  148. 


Mastodon  arvernensis  (Norwich  Crag,  Postwick,  also  found  in  Bed  Crag,  see  p.  202) ;  third 
milk  molar,  left  side,  upper  jaw ;  grinding  surface,  nat  size.    Newer  Pliocene. 

adopt  this  name,  for  he  had  seen  but  a  few  specimens  from  Auvergne, 
and  he  confounded  them  with  M.  angustidens.  The  entire  skeleton 
of  both  these  Mastodons  having  now  been  obtained,  they  are  found 
to  be  referable  to  two  distinct  sub-genera.  The  Crag  fossil  belongs 
to  the  Tetralophodon  of  Falconer,  a  sub-genus  of  which  five  species 
are  known,  so  called  because  there  are  four  ridges  in  the  penultimate 
true  molar  as  well  as  in  the  two  teeth  which  are  placed  immediately 
before  it  in  both  jaws.  The  Mastodon  angustidens,  on  the  other 
hand,  belongs,  with  six  other  species,  to  the  section  called  Trilopho- 
don,  in  which  the  corresponding  teeth  have  each  three  ridges ;  and  is, 
according  to  MM.  Lartet  and  Falconer,  characteristic  of  the  Faluns  of 
Touraine,  as  well  as  of  Sansan  at  the  foot  of  the  Pyrenees,  and  sev- 
eral other  Miocene  localities. 

The  Mastodon  arvernensis,  says  Dr.  Falconer,  is  the  only  one  yet 
found  in  England.     It  abounds  with  the  Hippopotamus  major  in  the 


CH.  XIII.]       THE  CHILLESFORD  AND  BRIDLINGTON   BEDS.  199 

Pliocene  strata  of  the  Val  d'Arno,  as  well  as  in  strata  of  the  same 
age  in  Piedmont  and  at  Montpelier.  It  may  be  considered,  there- 
fore, as  a  characteristic  Pliocene  species  in  Italy,  France,  and  Europe 
generally. 

This  Mastodon  has  never  been  found  in  the  Cromer  forest  bed 
above  mentioned,  p.  160,  but  several  of  the  mammalia  of  that  deposit, 
including  the  Elephas  meridionalis,  are  common  to  the  Norwich  beds, 
and  to  the  older  or  Red  Crag.  As  to  the  Norwich  Crag,  it  is  now 
ascertained  that  it  contains  a  larger  proportion  of  living  as  compared 
to  extinct  shells  than  was  formerly  supposed ;  for  many  of  the  lost 
species  once  referred  to  this  formation  are  worn  specimens,  few  in 
number,  and  evidently  washed  out  of  the  Red  Crag  into  the  newer 
strata.  Others,  which  are  really  of  contemporary  date,  and  which 
were  believexi  to  have  died  out,  have  been  found  living  in  the  British 
seas,  where  they  have  become  exceedingly  rare.  From  the  latest 
researches  of  Mr.  S.  P.  Woodward,  it  seems  probable  that  the  extinct 
species  do  not  exceed  1 1  in  a  hundred. 

Chillesford  beds. — It  was  stated  that  at  Chillesford,  near  Wood- 
bridge  in  Suffolk,  the  Norwich  Crag  has  been  found  overlying  the 
Red  Crag.  In  this  case  the  Newer  Pliocene  beds  are  argillaceous,  and 
about  20  feet  thick.  Messrs.  Prestwich  and  Searles  Wood  obtained 
from  them  23  species  of  shells,  of  which  2  only,  Nucula  Cobboldice 
and  Tcllina  obliqua,  are  extinct.  Among  the  other,  or  living  species, 
a  large  proportion,  such  as  Leda  lanceolata,  Cardium  grcenlandicum, 
Lucina  borealis,  Cyprina  islandica,  Panopcea  norvegica,  and  My  a 
truncata,  betray  a  northern  and  some  of  them  an  Arctic  character. 
There  is  good  reason  to  believe  that  the  Chillesford  beds  are  older 
than  the  forest  bed  of  Cromer,  before  alluded  to  ;  and  when  we  con- 
sider that  these  fossils  occur  within  eighty  miles  of  London,  in  the 
52 d  parallel  of  latitude,  we  see  in  them  a  proof  that  the  glacial  epoch 
began  before  the  end  of  the  Post-pliocene  period.* 

Bridlington  beds. — At  Bridliugton,  on  the  coast  of  Yorkshire,  near 
Flamborough  Head,  lat.  54°  N.,  another  deposit  occurs  of  about  the 
same  age  as  the  Chillesford  beds,  and  therefore  older  than  the  Cromer 
Forest,  though  somewhat  newer  than  the  Norwich  Crag  before  de- 
scribed, for  it  contains  a  still  larger  proportion  of  recent  shells.  The 
deposit  is  heterogeneous  in  composition,  consisting  of  sand  and  clay, 
with  pebbles  of  various  rocks,  chalk  and  flint  being  the  most  abun- 
dant. The  prevailing  color  resembles  that  of  London  Clay.  Mr.  S. 
P.  Woodward  has  lately  been  able  to  add  32  new  species  to  the  fos- 
sils of  this  formation  by  studying  the  collections  of  Messrs.  Bean  and 
Leckenley  at  Scarborough,  bringing  up  the  total  number  to  64,  of 
which  4  only  are  extinct,f  namely,  Natica  occlusa,  Cardita  analis, 
Nucula,  Cobboldice,  and  Tellina  obliqua,  giving  a  proportion  of  only  6 

*  Antiquity  of  Man,  by  the  Author,  p.  212. 
f  Geol.  Mag.,  Aug.  1864. 


200  OLDER  PLIOCENE  STRATA.  [Cn.  XIII. 

per  cent,  of  extinct  species  instead  of  11,  as  in  the  Norwich  beds  on 
the  Tare.  Of  the  whole  64  shells,  36  are  common  to  the  Norwich 
Crag  proper,  and  12  are  peculiar  to  Bridlington,  or  were  not  pre- 
viously known  in  any  pliocene  or  glacial  deposits  in  Great  Britain. 
What  is  most  remarkable  is  the  fact,  that  of  the  60  species  which 
remain  after  abstracting  the  extinct  forms,  no  less  than  30  are  inhabit- 
ants of  the  Arctic  regions,  none  of  them  extending  southward  to  the 
British  seas.  This  is  the  more  singular  when  we  consider  that  Brid- 
lington is  situated  in  lat.  54°  N.  It  will  be  seen  in  the  next  chapter 
that  the  cold  came  on  gradually,  beginning  when  the  White  Crag  was 
formed,  and  increasing  in  the  period  of  the  Red  Crag,  and  still  more 
in  that  of  the  Norwich  formation,  during  which  there  may  have  been 
several  oscillations  of  temperature.  The  refrigeration  seems  to  have 
reached  its  maximum,  and  to  have  been  developed  most  extensively 
in  Europe  in  Post-pliocene  times.  It  may,  no  doubt,  be  said  that  the 
shells  of  Moel  Tryfaen  above  mentioned,  found  at  a  height  of  nearly 
1400  feet  above  the  sea,  and  in  lat.  53°  N.,  or  nearly  the  same  as  that 
of  Bridlington,  do  not  imply  so  great  a  cold  as  the  latter,  as  they 
only  contain  11  shells  in  54  of  exclusively  Arctic  character,  or  only 
one-fifth  of  the  whole  number  of  species,  instead  of  nearly  half,  as  in 
the  case  of  Bridlington.  But  the  fauna  of  Moel  Tryfaen  does  not 
illustrate  the  extreme  cold  of  the  glacial  period  like  the  beds  of  Errol 
and  Elie,  on  the  borders  of  the  Tay  and  Forth.  (See  p.  153.) 

OLDER    PLIOCENE    STRATA. 

Red  Crag  of  Suffolk. — The  Crag  of  Suffolk,  as  already  mentioned, 
is  divisible  into  the  Upper  or  Red,  and  the  Lower  or  White  Crag.* 

These  deposits,  according  to  the  late  E.  Forbes,  appear  by  their 
imbedded  shells  to  have  been  formed  in  a  sea  of  moderate  depth, 
usually  from  15  to  25  fathoms,  but  in  some  few  spots  perhaps  deeper. 
Yet  they  cannot  be  called  littoral,  because  the  fauna  is  such  as  may 
have  extended  40  or  50  miles  from  land.  The  Upper  or  Red  Crag 
consists  chiefly  of  quartzose  sand,  with  an  occasional  intermixture  of 
shells,  for  the  most  part  rolled,  and  sometimes  comminuted.  It  is 
distinguished  by  the  deep  ferruginous  or  ochreous  color,  both  of  its 
sands  and  shells,  while  the  Older  Crag,  commonly  called  the  Coralline, 
is  white.  Both  formations  are  of  moderate  thickness  ;  the  Red  Crag 
rarely  exceeding  40,  and  the  Coralline  seldom  amounting  to  20  feet. 
But  their  importance  is  not  to  be  estimated  by  the  density  of  the 
mass  of  strata  or  its  geographical  extent,  but  by  the  extraordinary 
richness  of  its  organic  remains,  belonging  to  a  very  peculiar  type, 
which  seems  to  characterize  the  state  of  the  living  creation  in  the 
north  of  Europe  during  the  Older  Pliocene  era. 

*  See  paper  by  E.  Charlesworth,  Esq. ;  London  and  Ed.  Phil.  Mag.,  No.  xxxviii. 
p.  81,  Aug.  1835. 


CH.  XIII.]  FOSSILS  OF  THE  RED  CRAG.  201 

The  relative  position  of  the  Red  Crag  in  Essex  and  the  subjacent 
London  clay  and  chalk  has  been  already  pointed  out  (fig.  144). 
Whenever  the  two  divisions  are  met  with  in  the  same  district,  the 
Red  Crag  lies  uppermost ;  and  in  some  cases,  as  in  the  section  repre- 
sented in  fig.  149,  which  I  had  an  opportunity  of  seeing  exposed  to 

Fig.  149. 


Section  near  Ipswich,  in  Suffolk. 
a.  Eed  Crag.  &.  Coralline  Crag.  c.  London  Clay. 

view  in  1839,  it  is  clear  that  the  older  or  Coralline  mass  b  had  suffered 
denudation  before  the  newer  formation  a  was  thrown  down  upon  it. 
At  D  there  is  not  only  a  distinct  cliff,  8  or  10  feet  high,  of  Coralline 
Crag,  running  in  a  direction  N.E.  and  S.W.,  against  which  the  Red 
Crag  abuts  with  its  horizontal  layers  ;  but  this  cliff  occasionally  over- 
hangs. The  rock  composing  it  is  drilled  everywhere  by  Pholades, 
the  holes  which  they  perforated  having  been  afterwards  filled  with 
sand  and  covered  over  when  the  newer  beds  were  thrown  down.  As 
the  older  formation  is  shown  by  its  fossils  to  have  accumulated  in  a 
deeper  sea  (15,  and  sometimes  25,  fathoms  deep  or  more),  there  must 
no  doubt  have  been  an  upheaval  of  the  sea-bottom  before  the  cliff 
here  alluded  to  was  shaped  out.  We  may  also  conclude  that  so  great 
an  amount  of  denudation  could  scarcely  take  place,  in  such  incoherent 
materials,  without  many  of  the  fossils  of  the  inferior  beds  becoming 
mixed  up  with  the  overlying  crag,  so  that  considerable  difficulty  must 
be  occasionally  experienced  by  the  palaeontologists  in  deciding  which 
species  belong  severally  to  each  group. 

The  Red  Crag  being  formed  in  a  shallower  sea,  often  resembles  in 
structure  a  shifting  sandbank,  its  layers  being  inclined  diagonally,  and 
the  planes  of  stratification  being  sometimes  directed  in  the  same 
quarry  to  the  four  cardinal  points  of  the  compass,  as  at  Butley. 
That  in  this  and  many  other  localities,  such  a  structure  is  not  decep- 
tive or  due  to  any  subsequent  concretionary  rearrangement  of  parti- 
cles, or  to  mere  lines  of  color,  is  proved  by  each  bed  being  made  up 
of  flat  pieces  of  shell  which  lie  parallel  to  the  planes  of  the  smaller 
strata. 

Some  fossils  which  are  very  abundant  in  the  Red  Crag,  have  never 
been  found  in  the  white  or  coralline  division;  as,  for  example,  the 
Fusus  contrarius  (fig.  150),  and  several  species  of  Murex  and  Bucci- 
num  (or  Nassa)  (see  figs.  151,  152),  which  two  genera  seem  wanting 
in  the  Lower  Crag. 

Many  of  these  shells  are  found  in  a  good  state  of  preservation  in 
the  cliffs  of  Walton-on-Naze,  in  Essex ;  at  Felixstow  the  cliffs  afford 
fewer  shells,  and  most  of  them  are  fragmentary. 


202 


CORALLINE  CRAG. 


[CH.  xm. 


Fig.  150. 


Fossils  characteristic  of  the  Bed  Crag. 

Fig.  151.  Fig.  152. 


Naasa  granulata, 
Fig.  153. 


contrarius.  Purpura  tetragona.  Cyprcea  europcea. 

Fig.  150  half  nat.  size ;  the  others  nat.  size. 

Among  the  bones  and  teeth  of  fishes  are  those  of  large  sharks 
( Car  char  odon),  and  a  gigantic  skate  of  the  extinct  genus  Myliobates, 
and  many  other  forms,  some  common  to  our  seas,  and  many  foreign 
to  them.  It  is  questionable,  however,  whether  all  these  can  really  be 
ascribed  to  the  era  of  the  Red  Crag.  Not  a  few  of  them  may  possi- 
bly have  been  derived  from  older  strata,  especially  from  those  Lower 
Miocene  formations  to  be  described  in  the  next  chapter,  which  are 
largely  developed  in  Belgium,  and  of  which  a  fragment  only  (the 
Hempstead  beds  of  Forbes)  escaped  denudation  in  England. 

Many  of  the  fossils  found  in  the  Red  Crag  have  been  washed  out 
of  older  Tertiary  strata,  especially  out  of  the  London  Clay.  This  is 
particularly  the  case  in  one  of  the  lower  beds,  which  has  of  late  been 
much  used  in  agriculture  for  manure,  as  containing  nodules  of  phos- 
phate of  lime.  These  nodules  often  include  crabs  and  fishes  like 
those  of  the  London  Clay,  and  thus"  clearly  betray  the  date  of  their 
origin.  With  the  nodules  (in  which  there  is  nearly  60  per  cent,  of 
phosphate  of  lime),  occur  rolled  flint  pebbles,  and  others  of  sand- 
stone, containing  casts  of  crag-shells  and  many  ear-bones  of  whales. 

Some    teeth    of  the   Mastodon    arver- 
154-  nensis,  and  of  a  rhinoceros  and  tapir, 

have  also  been  found  in  the  same  bed, 
which  has  been  worked  near  Felixstow 
among  other  places.  As  to  the  ear- 
bones  of  cetacea,  Professor  Henslow 
found  those  of  two  or  three  distinct 

Tympanic  bone  of  Ealasna  emarginata,  .       .       -  .      ,..,,•,      ,      .   -^  -,. 

Owen ;  Bed  Crag,  Felixstow.        species  in  this  detrital  bed  at  Felixstow. 
They  belong,   according    to   Professor 

Owen,  to  true  whales  of  the  family  Balcenidce  (fig.  154).     Mr.  Wood 
is  of  opinion  that  they  are  of  the  age  of  the  Red  Crag,  or  if  not,  that 
they  may  be  derived  from  the  destruction  of  beds  of  Coralline  Crag. 
White  or  Coralline  Crag. — The  lower  or  Coralline  Crag  is  of  very 
limited  extent,  ranging  over  an  area  about  20  miles  in  length,  and  3 


On.  XIII.]  FOSSILS  OF  THE  SUFFOLK  CRAG. 

or  4  in  breadth,  between  the  rivers  Aide  and  Stour.  It  is  generally 
calcareous  and  marly — a  mass,  of  shells,  bryozoa,*  and  small  corals, 
passing  occasionally  into  a  soft  building  stone.  At  Sudbourn,  near 
Orford,  where  it  assumes  this  character,  are  large  quarries,  in  which 
the  bottom  of  it  has  not  been  reached  at  the  depth  of  50  feet.  At 
some  places  in  the  neighborhood,  the  softer  mass  is  divided  by  thin 
flags  of  hard  limestone,  and  bryozoa  placed  in  the  upright  position  in 
which  they  grew. 

From  the  abundance  of  these  bryozoa  or  coralloid  mollusca  the 
lowest  or  White  Crag  obtained  its  popular  name  ;  but  true  corals,  as 
now  defined,  or  zoantharia,  are  very  rare  in  this  formation. 

The  distinctness  of  the  fossils  of  the  Coralline  from  those  of  the 
Red  Crag,  arises  in  part  from  their  higher  antiquity,  and,  in  some 
degree,  from  a  difference  in  the  geographical  conditions  of  the  sub- 
marine bottom.  The  prolific  growth  of  echini,  bryozoa,  and  a  pro- 
digious variety  of  testacea,  implies  a  region  of  deeper  and  more  tran- 
quil water ;  whereas,  the  Red  Crag  may  have  been  formed  afterward 
on  the  same  spot,  when  the  water  was  shallower.  In  the  mean  time 
the  climate  became  decidedly  somewhat  cooler,  and  some  of  the 
zoophytes  which  flourished  in  the  first  period  disappeared,  so  that  the 
fauna  of  the  Red  Crag  acquired  a  character  more  nearly  resembling 
that  of  our  northern  seas,  as  is  implied  by  the  large  development  of 
certain  sections  of  the  genera  Fusus,  Huccinum,  Purpura,  and  Tro- 
chus,  proper  to  high  latitudes,  and  which  are  wanting  or  feebly  repre- 
sented in  the  inferior  crag. 

Some  of  the  corals  and  bryozoa  of  the  lower  Crag  of  Suffolk  belong 
to  genera  unknown  in  the  living  creation,  and  of  a  very  peculiar  struc- 
ture; as,  for  example,  that  represented  in  the  figure  (155)  on  the  fol- 
lowing page,  which  is  one  of  several  species  having  a  globular  form. 
The  great  number  and  variety  of  these  zoophytes  probably  indicate 
an  equable  climate,  free  from  intense  cold  in  winter.  On  the  other 
hand,  that  the  heat  was  never  excessive  is  confirmed  by  the  preva- 
lence of  northern  forms  among  the  testacea,  such  as  the  Glycimeris, 
Cyprina,  and  Astarte.  Of  the  genus  last  mentioned  (see  fig.  156) 
there  are  about  fourteen  species,  many  of  them  being  rich  in  indi- 
viduals ;  and  there  is  an  absence  of  genera  peculiar  to  hot  climates, 
such  as  Conus,  Oliva,  Mitra,  Fasciolaria,  Crassatella,  and  others. 
The  cowries  (Cyprcea,  fig.  153),  also,  are  small,  and  belong  to  a  sec- 
tion (Trivia)  now  inhabiting  the  colder  regions.  A  large  volute, 

*  Ehrenberg  proposed  in  1831  the  term  Bryozoum,  or  "Moss-animal,"  for  the 
molluscous  or  ascidian  form  of  polyp,  characterized  by  having  two  openings  to  the 
digestive  sack,  as  in  Eschara,  Flustra,  Retepora,  and  other  zoophytes  popularly 
included  in  the  corals,  but  now  classed  by  naturalists  as  mollusca.  The  term  Poly- 
zoum,  synonymous  with  Bryozoum,  was,  it  seems,  proposed  in  1830,  or  the  year 
before,  by  Mr.  J.  V.  Thompson,  but  is  less  generally  adopted.  The  animals  of  the 
Zoantharia  of  Milne  Edwards  and  Haime,  or  the  true  corals,  have  only  one  opening 
to  the  stomach. 


204 


OLDER  PLIOCENE  FORMATIONS. 


[Cn.  XIII 


called  Valuta  Lamberti  (fig.  157),  may  seem  an  exception;  but  it 
differs  in  form  from  the  volutes  of  the*  torrid  zone,  and  may,  like  the 
living  Valuta  Magellanica,  have  been  fitted  for  an  extra-tropical 
climate. 

The  occurrence  of  a  species  of  Lingula  at  Sutton  (see  fig.  160)  is 
worthy  of  remark,  as  these  Brachiopoda  seem  now  confined  to  more 
equatorial  latitudes ;  and  the  same  may  be  said  still  more  decidedly 

rig.  155. 


Fascicularia  aurantium,  Milne  Edwards.    Family,  Tubidiporidce,  of  same  author. 
Bryozoan  of  extinct  genus,  from  the  inferior  or  Coralline  Crag,  Suffolk. 

a.  Exterior.  6.  Vertical  section  of  interior.  o.  Portion  of  exterior  magnified. 

d.  Portion  of  interior  magnified,  showing  that  it  is  made  up  of  long,  thin,  straight  tubes, 
united  in  conical  bundles. 

Fig.  156. 


Astarte  (Orassina,  Lam.);  species  common  to  upper  and  lower  crag. 

Astarte  Omalit,  Lajonkaire;  Syn.  A.  lipartita,  Sow.  Min.  Con.  T.  521,  f.  3;  a  very  variable 
species,  most  characteristic  of  the  Coralline  Crag,  Suffolk. 


Pig.  15T. 


Fig.  153. 


Fig.  159. 


Voluta  Lambertt,  young 
individ.,  Cor.  and  Ked 
Crag. 


Pyrula  reticulata,  Lam. ; 
Coralline  Crag,  Kam- 
sholt. 


Temnechinus  excavatus, 
Forbes;  Temnopleurus 
eoccavatus,  Wood;  Cor. 
Crag,  Eamsholt. 


CH.  XIII.]         SUCCESSIVE  REFRIGERATION  OF  CLIMATE.  205 

of  a  species  of  Pyrula,  supposed  by  Mr.  Wood  to  be  identical  with 
P.  reticulata  (fig.  158),  now  living  in  the  Indian  Ocean.  A  genus 
also  of  echinoderms,  called  by  Professor  Forbes  Temnechinus  (fig. 
159),  is  peculiar  to  the  Red  and  Coralline  Crag  of  Suffolk.  The  only 
species  now  living  occur  in  the  Indian  Ocean. 

One  of  the  most  interesting  conclusions  deduced  from  a  careful 
comparison  of  the  shells  of  these  British  Older  Pliocene  strata  and 
the  fauna  of  our  present  seas,  has  been  pointed  out  by  Professor  E. 
Forbes.  It  appears  that,  during  the  glacial  period,  a  period  interme- 
diate, as  we  have  seen,  between  that  of  the  crag  and  our  own  time, 
many  shells,  previously  established  in  the  temperate  zone,  retreated 
southward  to  avoid  an  uncongenial  climate.  The  Professor  has  given 
a  list  of  fifty  shells  which  inhabited  the  British  seas  while  the  Coral- 
line and  Red  Crag  were  forming,  and  which,  though  now  living  in 
our  seas,  are  all  wanting  in  the  glacial  deposits.  They  must  there- 
fore, after  their  migration  to  the  south,  which  took  place  during  the 
glacial  period,  have  made  their  way  northward  again.  In  corrobora- 
tion  of  these  views,  it  is  stated  that  all  these  fifty  species  occur  fossil 
in  the  Newer  Pliocene  strata  of  Sicily,  Southern  Italy,  and  the  Gre- 
cian Archipelago,  where  they  may  have  enjoyed,  during  the  era  of 
floating  icebergs,  a  climate  resembling  that  now  prevailing  in  higher 
European  latitudes.* 

The  following  tables  have  been  drawn  up  for  me  by  Mr.  Samuel  P. 
Woodward,  showing  the  results  of  a  comparison  of  the  lists  of  Crag 
shells  described  by  Mr.  Searles  Wood  in  his  excellent  monograph  on 
the  fossil  testacea  of  the  British  Pliocene  formations.  The  list  of  the 
Norwich  Crag  shells  has  been  corrected  and  enlarged  by  Mr.  Wood- 
ward himself.  They  exhibit  clear  evidence  of  a  gradual  refrigeration 
of  climate,  which  went  on  in  the  area  of  England  from  the  time  of 
the  older  to  that  of  the  most  modern  Pliocene  strata,  a  refrigeration 
which  has  already  been  inferred  from  an  examination  of  the  Crag  shells 
in  1846  by  the  late  Edward  Forbes.f 


Number  of  known  Species  of  Marine  Testacea  in  the  three  English 
Pliocene  Deposits,  called  the  Norwich,  the  Bed,  and  the  Coralline 


Brachiopoda,  6 

Conchifera,   -                                     -  -  210 

Gasteropoda,  -  220 

Total,  -            -  436 


*  E.  Forbes,  Mem.  Geol.  Survey  Gt.  Brit.,  vol.  i.  p.  386. 
\  Mem.  of  Geol.  Survey,  London,  1846,  p.  391. 

i  The  25  shells  peculiar  to  Bridlington  (p.  199)  are  not  included  in  the  Norwict 
Crag  shells  of  these  tables. 


206  SUCCESSIVE  REFRIGERATION  OF  CLIMATE.         [Cn.  XIII. 

Distribution  of  the  above  Marine  Testacea. 

Norwich  Crag,  -  -     110  —  of  which    34  are  peculiar. 

Red  Crag,          -  -    219—         "        43 

Coralline  Crag,  -  -    317—         "       188 

Species  common  to  the 

Norwich  and  Red  Crag,  and  not  in  Coralline,  -  42 

Norwich  and  Coralline,  and  not  in  Red,        -  3 

Red  and  Coralline,  and  not  in  Norwich,        -  -  103 

Norwich,  Red,  and  Coralline,  -  31* 

Proportion  of  Recent  to  Extinct  Species. 

Eecent.  Extinct.  Per-centage  of  Eecent.     ] 

Norwich  Crag,                         98  12                      89 

Red  Crag,                          -     132  87                      60 

Coralline  Crag,     -            -     165  152                      52 

Recent  Species  not  living  now  in  British  Seas. 

Northern.  Southern. 

Norwich  Crag,       -  15  0 

Red  Crag,  -  11  19 

Coralline  Crag,       -  1  28 

In  the  above  list  the  shells  of  the  Glacial  beds,  those,  for  example, 
of  the  Clyde,  Enrol,  and  Elie,  and  Moel  Tryfaen  (pp.  154  and  158), 
and  other  British  deposits  newer  than  the  Norwich  Crag,  have  not  been 
included.  The  land  and  freshwater  shells  have  also  been  purposely 
omitted,  as  well  as  some  London  Clay  shells,  and  others  suspected  to 
be  spurious. 

By  far  the  greater  number  of  the  recent  marine  species  included 
in  these  tables  are  still  inhabitants  of  the  British  seas  ;  but  even  these 
differ  considerably  in  their  relative  abundance,  some  of  the  com- 
monest of  the  Crag  shells  being  now  extremely  scarce ;  as,  for  ex- 
ample, Buccinum  Dalei,  and  others  rarely  met  with  in  a  fossil  state, 
being  now  very  common,  as  Murex  erinaceus  and  Cardium  echina- 
tum. 

The  last  table  throws  light  on  a  marked  alteration  in  the  climate  of 
the  three  successive  periods.  It  will  be  seen  that  in  the  Coralline 
Crag  there  are  28  Southern  shells,  including  26  Mediterranean  and  1 
West  Indian  species  (Erato  Maugerice).  Of  these  only  13  occur  in 
the  Red  Crag,  associated  with  3  new  Southern  species,  while  the  whole 
of  them  disappear  from  the  Norwich  beds.  On  the  other  hand,  the 
Coralline  Crag  contains  only  2  shells  closely  related  to  living  Northern 
forms,  namely,  Admete  and  Limopsis  ;  whereas,  in  the  Red  Crag,  as 

*  These  31  species  must  be  added  to  the  numbers  42,  3,  and  103,  respectively, 
in  order  to  obtain  the  full  amount  of  common  species  in  each  of  those  cases. 


CH.  XIII.]  ANTWERP  CRAG.  207 

stated  in  the  table,  there  are  11  Northern  species  all  common  to  the 
Norwich  Crag,  in  which  last  we  have  also  4  additional  inhabitants  of 
the  Arctic  regions  ;  so  that  there  is  good  evidence  of  a  continual  re- 
frigeration of  climate  during  the  Pliocene  period  in  Britain.  The 
presence  of  these  Northern  shells  cannot  be  explained  away  by  suppos- 
ing that  they  were  inhabitants  of  the  deep  parts  of  the  sea ;  for  some 
of  them,  such  as  Tellina  calcarea  (=T.  obliqua)  and  Astarte  borealis, 
occur  plentifully,  and  sometimes  with  the  valves  united  by  their  liga- 
ment, in  company  with  other  littoral  shells,  such  as  My  a  arenaria  and 
Littorina  rudis,  and  evidently  not  thrown  up  from  deep  water.  Yet 
the  Northern  character  of  the  Norwich  Crag  is  not  fully  shown  by 
simply  saying  that  it  contains  12  Northern  species.  It  is  the  pre- 
dominance of  certain  genera  and  species,  such  as  Rhynchonella  psittacea, 
Tellina  calcarea,  Astarte  borealis,  Scalaria  grcenlandica  and  Fusus 
carinatus  which  satisfies  the  mind  of  a  conchologist  as  to  the  Arctic 
character  of  the  Norwich  Crag.  In  like  manner,  it  is  the  presence  of 
such  genera  as  Pyrula,  Columbella,  Terebra,  Cassidaria,  Pholadoniya, 
Lingula,  Discina,  and  others,  which  give  a  southern  aspect  to  the 
Coralline  Crag  shells. 

The  cold,  which  had  gone  on  increasing  from  the  time  of  the  Cor- 
alline to  that  of  the  Norwich  Crag,  continued,  though  not  perhaps 
without  some  oscillations  of  temperature,  to  become  more  and  more 
severe  after  the  accumulation  of  the  latter,  until  it  reached  its  maxi- 
mum in  what  has  been  called  the  glacial  epoch.  The  marine  fauna  of 
this  last  period  contains,  both  in  Ireland  and  Scotland,  recent  species 
of  mollusca  now  living  in  Greenland  and  other  seas  far  north  of  the 
areas  where  we  find  their  remains  in  a  fossil  state. 

Antwerp  Crag. — Strata  of  the  same  age  as  the  Red  and  Coralline 
Crag  of  Suffolk  have  been  long  known  in  the  country  round  Antwerp 
and  on  the  banks  of  the  Scheldt,  below  that  city.  More  than  200  spe- 
cies of  testacea  had  been  collected  by  MM.  De  Wael,  Nyst,  and  others, 
when  I  visited  Antwerp  in  1851,  of  which  two-thirds  were  indentified 
with  Suffolk  fossils  by  Mr.  Wood.  Among  these  he  recognized  Lin- 
gula  Dumortieri  of  Nyst  (fig.  160),  which  I  found  in  abundance  in 
what  was  called  by  M.  de  Wael  the  Middle  Crag.  More  than  half  of 
the  shells  of  this  Antwerp  deposit  agree  with 
living  species,  and  these  belong  in  great  part  to 
the  fauna  of  our  Northern  seas,  though  some 
Mediterranean  species  appear  among  them.  I 
also  met  with  numerous  cetacean  bones  of  the 
genera  Balcenoptera  and  Ziphius  in  the  Upper 
Antwerp  Crag.  They  are  not  rolled,  as  if 
washed  out  of  older  beds,  and  I  infer  that  the 
animals  to  which  they  belong  once  coexisted  in 
the  same  sea  with  the  associated  fossil  mollusca.* 

*  Lyell  on  Belgian  Tertiaries,  Quart.  Journ.  Geol.  Soc.,  1852,  p.  282. 


208  SUBAPENNINE  STRATA  [Cn.  XIII. 

Three  divisions  of  the  Antwerp  Crag  have  been  recognized  by  the 
Belgian  geologists  :  first,  the  Uppermost  or  Yellow  Crag,  in  which  81 
species  of  shells  were  known  when  I  gave  a  list  of  them  in  1852  ;  sec- 
ondly, the  Middle  Crag,  from  which  94  species  were  known ;  and 
thirdly,  the  lowest  or  Black  Crag,  from  which  65  shells  had  been  ob- 
tained. This  bed  derives  its  name  from  the  dark  color  of  most  of  the 
sand,  which  consists  of  green  grains  of  glaucouite. 

There  can  be  no  doubt  that  the  two  first  formations  are  referable  to 
the  Older  Pliocene  period,  the  Yellow  Crag  containing  about  60  per 
cent,  of  recent  species,  while  the  Middle  or  Grey  Crag  contains  about 
50  per  cent.  Their  close  connection  with  the  Red  and  Coralline  Crag 
of  Suffolk  is  equally  clear,  for  in  a  list  of  52  shells  from  the  Upper  or 
Yellow  Crag,  and  of  94  from  the  Middle  Crag,  there  are  only  7  species 
which  are  not  found  in  the  British  formations  of  corresponding  age. 
As  we  might  have  expected,  the  Upper  Antwerp  Crag  agrees  more 
with  the  Red  Crag  of  England,  while  the  shells  of  the  Middle  Ant- 
werp Crag  correspond  more  with  the  Older  or  Coralline  group  of 
Suffolk. 

But  when  we  come  to  the  Lowest  or  Black  Crag  we  are  beginning 
to  pass  beyond  the  limits  of  the  Older  Pliocene  formations,  and  ap- 
proaching the  Miocene.  Only  two-thirds  of  the  shells  agree  with  those 
of  the  Coralline  Crag,  and  somewhat  less  than  half  of  the  fossil  species 
are  identifiable  with  species  still  living.  They  seem  to  form  the  first 
links  of  a  chain  of  passage  by  which  we  shall  in  time  be  conducted 
without  a  break  to  those  older  formations,  the  Upper  Miocene  of  Bel- 
gium, to  be  treated  of  in  the  next  chapter. 

Normandy. — I  observed  in  1840  a  small  patch  of  shells  correspond- 
ing to  those  of  the  Suffolk  Crag,  near  Yalognes,  in  Normandy ;  and 
there  is  a  deposit  containing  similar  fossils  at  St.  George  Bohon,  and 
several  places  a  few  leagues  to  the  south  of  Carentan,  in  Normandy ; 
but  they  have  never  been  traced  farther  southward. 

OLDER   PLIOCENE    FORMATIONS    IN    ITALY. 

Subapennine  Strata. — The  Apennines,  it  is  well  known,  are  com- 
posed chiefly  of  secondary  rocks,  forming  a  chain  which  branches  off 
from  the  Ligurian  Alps  and  passes  down  the  middle  of  the  Italian  pen- 
iDsula.  At  the  foot  of  these  mountains,  on  the  side  both  of  the  Adri- 
atic and  the  Mediterranean,  are  found  a  series  of  tertiary  strata,  which 
form,  for  the  most  part,  a  line  of  low  hills  occupying  the  space  be- 
tween the  older  chain  and  the  sea.  Brocchi,  as  we  have  seen  (p.  183), 
was  the  first  Italian  geologist  who  described  this  newer  group  in  detail, 
giving  it  the  name  of  the  Subapennine  ;  and  he  classed  all  the  tertiary 
strata  of  Italy,  from  Piedmont  to  Calabria,  as  parts  of  the  same  sys- 
tem. Certain  mineral  characters,  he  observed,  were  common  to  the 
whole  ;  for  the  strata  consists  generally  of  light  brown  or  blue  marl, 
covered  by  yellow  calcareous  sand  and  gravel.  There  are  also,  he 


CH.  XIII.]  SUBAPENNINE  STRATA.  209 

added,  some  species  of  fossil  shells  which  are  found  in  these  deposits 
throughout  the  whole  of  Italy. 

We  have  now,  however,  satisfactory  evidence  that  the  Subapennine 
beds  of  Brocchi,  although  chiefly  composed  of  Older  Pliocene  strata, 
belong  nevertheless,  in  part,  both  to  older  and  newer  members  of  the 
tertiary  series.  The  strata,  for  example,  of  the  Superga,  near  Turin, 
are  Miocene  ;  those  of  Asti  and  Parma  Older  Pliocene,  as  is  the  blue 
marl  of  Sienna ;  while  the  shells  of  the  incumbent  yellow  sand  of  the 
same  territory  approach  more  nearly  to  the  recent  fauna  of  the  Medi- 
terranean, and  may  be  Newer  Pliocene. 

We  have  seen  that  most  of  the  fossil  shells  of  the  Older  Pliocene 
strata  of  Suffolk  which  are  of  recent  species  are  identical  with  testa- 
cea  now  living  in  British  seas,  yet  some  of  them  belong  to  Mediterra- 
nean species,  and  a  few  even  of  the  genera  are  those  of  warmer  cli- 
mates. We  might  therefore  expect,  in  studying  the  fossils  of  corre- 
sponding age  in  countries  bordering  the  Mediterranean,  to  find  among 
them  some  species  and  genera  of  warmer  latitudes.  Accordingly,  in 
the  marls  belonging  to  this  period  at  Asti,  Parma,  Sienna,  and  parts 
of  the  Tuscan  and  Roman  territories,  we  observe  the  genera  Conus, 
Cyprcea,  Strombus,  Pyrula,  Mitra,  Fasciolaria,  Sigaretus,  Delphi- 
nula,  Ancillaria,  Oliva,  Terebellum,  Terebra,  Perna,  Plicatula,  and 
Corbis,  some  characteristic  of  tropical  seas,  others  represented  by 
species  more  numerous  or  of  larger  size  than  those  now  proper  to  the 
Mediterranean. 

The  proportion  borne  by  the  recent  to  the  extinct  species  varies  in 
the  same  district,  as  Professor  Ponzi  pointed  out  to  me,  in  1857,  in 
the  neighborhood  of  Rome,  according  to  the  place  in  the  series  occu- 
pied by  different  sets  of  superimposed  marls  and  sands. 

The  classification  of  these  several  members  of  the  Pliocene  period, 
and  the  separation  of  them  from  the  Miocene,  is  a  task  the  accom- 
plishment of  which  will  task  the  skill  and  industry  of  the  Italian 
geologists  for  many  years  to  come. 

I  have  already  alluded  to  the  Newer  Pliocene  deposits  of  the 
Upper  Yal  d'Arno  above  Florence,  and  stated  that  below  those  sands 
and  conglomerates,  containing  the  remains  of  the  filephas  meridionalis 
and  other  associated  quadrupeds,  lie  an  older  horizontal  and  conform- 
able series  of  beds,  which  may  be  classed  as  Older  Pliocene.  They 
consist  of  blue  clays  with  some  subordinate  layers  of  lignite,  and 
exhibit  a  richer  flora  than  the  overlying  Newer  Pliocene  beds,  and 
one  receding  farther  from  the  existing  vegetation  of  Europe.  They 
also  comprise  more  species  common  to  the  antecedent  Miocene  period. 
Among  the  genera  of  flowering  plants  M.  Gaudin  enumerates  Pinus, 
Glyptostrobus,  Taxodium,  Sequoia,  Ilex,  Quercus,  Prunus,  Platanus, 
Alnus,  Ulmus,  Ficus,  Laurus,  Per  sea,  Oreodaphne  (fig.  161),  Cinna- 
momum,  Cassia,  Acer,  Juglans,  Betula,  Bhamnus,  Carya,  Rhas,  Smi- 
lax,  Sassafras,  Psoralea,  and  some  others. 

This  assemblage  of  plants  indicates  a  warm  climate,  but  not  so 
14 


210 


SUBAPENNINE  STRATA. 


[CH.  XIII. 


subtropical  a  one  as  that  of  the  Upper  Miocene  period,  which  will 
presently  be  considered.. 

M.  Gaudin,  jointly  with  the  Marquis  Strozzi,  has  thrown  much 
light  on  the  botany  of  beds  of  the  same  age  in  another  part  of  Tus- 
cany at  a  place  called  Montajone,  between  the  rivers  Elsa  and  Evola, 
where,  among  other  plants,  is  found  the  Oreodaphne  Heerii,  Gaud, 
(see  fig.  161),  which  is  probably  only  a  variety  of  Oreodaphne  foetens, 


Fig.  161. 


Fig.  162. 


Oreodaphne  Heerii.  Liquidambar  europceum  var.  trilobatum,  A.  Br. ;  (some- 

Leaf  half  nat.  size.*  times  4-lobed  and  more  commonly  5-lobed). 

a.  Leaf,  half  nat. size.  c.  Fruit,  nat.  size. 

&.  Part  of  same,  nat.  size.        d.  Seed,  do.    (Eningen. 

or  the  laurel  called  the  Til  in  Madeira,  where,  as  in  the  Canaries,  it 
constitutes  a  large  portion  of  the  native  woods,  but  cannot  now 
endure  the  climate  of  Europe.  In  the  fossil  specimens  the  same 
glands  or  protuberances  as  those  which  are  observed  in  the  axils  of 
the  primary  veins  of  the  leaves  in  the  recent  Til  are  preserved.f 

Another  plant  also  indicating  a  warmer  climate  is  the  Liquidambar 
europceum,  Brong.  (see  fig.  162),  a  species  nearly  allied  to  L.  styra- 
cifluum,  L.,  which  flourishes  in  most  places  in  the  Southern  States  of 
North  America,  on  the  borders  of  the  Gulf  of  Mexico. 

As  the  leaves  come  nearer  to  this  American  form,  while  the  fruit, 
according  to  Heer,  is  smaller  and  nearer  to  the  Syrian  Liquidambar 
orientale,  the  fossil  may,  according  to  the  doctrine  of  transmutation, 
have  been  the  original  stock  from  which  both  have  diverged.  The 
Javanese  Liquidambar  is  very  distinct ;  the  fossil,  according  to  Heer, 
ranges  from  the  Older  Pliocene  to  the  Newer  Miocene,  but  the  genus 
has  now  disappeared  from  Europe. 


*  Feuilles  fossiles  de  la  Toscane. 
Gaudin  and  Strozzi.    Plate  11,  fig.  3. 
f  Gaudin,  p.  22. 


Contributions  a  la  More  fossile  Italienne. 


CH.  XIII.]  ARALO-CASPIAN  FORMATIONS.  211 

The  Tuscan  blue  marls  of  various  localities,  from  which  the  above- 
mentioned  flora  was  obtained,  have  yielded  36  species  of  marine  mol- 
lusca,  in  which  1 6,  according  to  M.  Karl  Mayer,  are  recent. 

Aralo- Caspian  formations. — This  name  has  been  given  by  Sir  R. 
Murchison  and  M.  de  Verneuil  to  the  limestone  and  associated  sandy 
beds  of  brackish-water  origin,  which  have  been  traced  over  a  very 
extensive  area,  surrounding  the  Caspian,  Azof,  and  Aral  Seas,  and 
parts  of  the  northern  and  western  coasts  of  the  Black  Sea.  The 
fossil  shells  are  partly,  freshwater,  as  Paludina,  Neritina,  &c.,  and 
partly  marine,  of  the  family  Cardiacice  and  Mytili.  The  species  are 
identical,  in  great  part,  with  those  now  inhabiting  the  Caspian ;  and 
when  not  living,  they  are  analogous  to  forms  now  found  in  the  inland 
seas  of  Asia,  rather  than  to  oceanic  types.  The  limestone  rises  occa- 
sionally to  the  height  of  several  hundred  feet  above  the  sea,  and  is 
supposed  to  indicate  the  former  existence  of  a  vast  inland  sheet  of 
brackish  water  as  large  as  the  Mediterranean,  or  larger. 

The  proportion  of  recent  species  agreeing  with  the  fauna  of  the 
Caspian  is  so  considerable,  as  to  leave  no  doubt  in  the  minds  of  the 
geologists  above  cited  that  this  rock,  also  called  by  them  the  "  Steppe 
Limestone,"  belongs  to  the  Pliocene  period.* 

*  Geol.  of  Russia,  p.  279. 


212  MIOCENE  STRATA  OF  FRANCE.  [On.  XIV. 


CHAPTER    XIV. 

MIOCENE    PERIOD. 

Upper  Miocene  strata  of  France — Faluns  of  Touraine — Depth  of  sea  and  littoral 
character  of  fauna — Tropical  climate  implied  by  the  testacea — Proportion  of 
recent  species  of  shells — Faluns  more  ancient  than  the  Suffolk  Crag — Varieties 
of  Voluta  Lamberti  peculiar  to  Faluns  and  to  Suffolk  Crag — The  same  spe- 
cies are  common  to  more  than  one  geological  Period — Lower  Miocene  strata 
of  France — Remarks  on  classification,  and  where  to  draw  the  line  of  separation 
between  Miocene  and  Eocene  strata — Relations  of  the  Ores  de  Fontainebleau  to 
the  Faluns  and  to  the  Calcaire  Grossier — Lower  Miocene  strata  of  Central 
France — Lacustrine  strata  of  Auvergne — Indusial  limestone — Fossil  mammalia 
of  the  Limagne  d' Auvergne — Freshwater  strata  of  the  Cantal — Its  resemblance 
in  some  places  to  white  chalk  with  flints — Proofs  of  gradual  deposition — Miocene 
strata  of  Bordeaux  and  South  of  France — Upper  Miocene  strata  of  Gers — 
Dryopitheeus — Belgian  and  British  Miocene  formations — Edeghem  beds  near 
Antwerp — Diest  sands  of  Belgium  and  contemporaneous  iron-sands  of  North 
Downs — Upper  Miocene  beds  of  Belgium— Bolderberg — Lower  Miocene  strata 
of  Kleyn  Spawen — Hempstead  beds,  Isle  of  Wight — Bovey  Tracey  Lignites 
in  Devonshire — Isle  of  Mull  Leaf-beds — Miocene  formations  of  Germany — 
Mayence  basin — Upper  Miocene  beds  of  Vienna  basin — Lower  Miocene  of 
Croatia — Fossil  Lepidoptera — Oligocone  strata  of  Professor  Beyrich — Miocene 
strata  of  Italy. 

MIOCENE    STRATA    OF   FRANCE. UPPER   MIOCENE    FALUNS    OF 

TOURAINE. MIOCENE    FORMATIONS. 

THE  strata  which  we  meet  with  next  in  the  descending  order  are 
those  called  by  many  geologists  "Middle  Tertiary,"  for  which  in  1833 
I  proposed  the  name  of  Miocene,  selecting  the  "  faluns "  of  the  valley 
of  the  Loire  in  France  as  my  example  or  type. 

I  shall  now  call  these  Falunian  deposits  Upper  Miocene,. to  distin- 
guish them  from  others  to  which  the  name  of  Lower  Miocene  will  be 
given.  The  latter  were  classed  by  me  in  former  editions  of  this  work 
as  Upper  Eocene,  and  the  reasons  which  have  induced  me  to  alter  this 
classification  will  be  fully  explained  to  the  reader  in  this  and  the  fol- 
lowing chapter.  The  term  "  faluns  "  is  given  provincially  by  French 
agriculturists  to  shelly  sand  and  marl  spread  over  the  land  in  Touraine, 
just  as  the  "  crag  "  was  formerly  much  used  to  fertilize  the  soil  in  Suffolk. 
Isolated  masses  of  such  faluns  occur  from  near  the  mouth  of  the  Loire,  in 
the  neighborhood  of  Nantes,  to  as  far  inland  as  a  district  south  of  Tours. 
They  are  also  found  at  Pontlevoy,  on  the  Cher,  about  70  miles  above  the 
junction  of  that  river  with  the  Loire,  and  30  miles  S.E.  of  Tours.  De- 
posits of  the  same  age  also  appear  under  new  mineral  conditions  near  the 


CH.  XIV.]  FALUNS  OF  TOURAINE.  213 

towns  of  Dinan  and  Rennes,  in  Brittany.  I  have  visited  all  the  locali- 
ties above  enumerated,  and  found  the  beds  on  the  Loire  to  consist  princi- 
pally of  sand  and  marl,  in  which  are  shells  and  corals,  some  entire,  some 
rolled,  and  others  in  minute  fragments.  In  certain  districts,  as  at  Doue, 
in  the  department  of  Maine  and  Loire,  10  miles  S.  W.  of  Saumur,  they 
form  a  soft  building-stone,  chiefly  composed  of  an  aggregate  of  broken 
shells,  bryozoa,  corals,  and  echinodettns,  united  by  a  calcareous  cement ; 
the  whole  mass  being  very  like  the  Coralline  Crag  near  Aldborough  and 
Sudbourn  in  Suffolk.  The  scattered  patches  of  faluns  are  of  slight 
thickness,  rarely  exceeding  50  feet ;  and  between  the  district  called 
Sologne  and  the  sea  they  repose  on  a  great  variety  of  older  rocks ;  being 
seen  to  rest  successively  upon  gneiss,  clayslate,  various  secondary  for- 
mations, including  the  chalk ;  and,  lastly,  upon  the  upper  freshwater 
limestone  of  the  Parisian  tertiary  series,  which,  as  before  mentioned 
(p.  183),  stretches  continuously  from  the  basin  of  the  Seine  to  that  of 
the  Loire. 

At  some  points,  as  at  Louans,  south  of  Tours,  the  shells  are  stained  of 
a  ferruginous  color,  not  unlike  that  of  the  Red  Crag  of  Suffolk.  The 
species  are,  for  the  most  part,  marine,  but  Fig.  162  a. 

a  few  of  them  belong  to  land  and  fluviatile 
genera.  Among  the  former,  Helix  turo- 
nensis  (fig.  45,  p.  30)  is  the  most  abun- 
dant. Remains  of  terrestrial  quadrupeds 
are  here  and  there  intermixed,  belonging 
to  the  genera  Deinotherium  (fig.  162  a), 
Mastodon,  Rhinoceros,  Hippopotamus, 
Chaeropotamus,  Dichobune,  Deer,  and 
others,  and  these  are  accompanied  by 
cetacea,  such  as  the  Lamantine,  Morse, 
Sea-Calf,  and  Dolphin,  all  of  extinct 

species.  Deinotherium  giganteum,  Kaup. 

Professor  E.  Forbes,  after  studying  the  fossil  testacea  which  I  obtained 
from  these  beds,  informs  me  that  he  has  no  doubt  they  were  formed 
partly  on  the  shore  itself  at  the  level  of  low  water,  and  partly  at  very 
moderate  depths,  not  exceeding  ten  fathoms  below  that  level.  The  mol- 
luscous fauna  of  the  "  faluns"  is  on  the  whole  much  more  littoral  than 
that  of  the  Red  and  Coralline  Crag  of  Suffolk,  and  implies  a  shallower 
sea.  It  is,  moreover,  contrasted  with  the  Suffolk  Crag  by  the  indications 
it  affords  of  an  extra-European  climate.  Thus  it  contains  seven  species  of 
Cyprcea,  some  larger  than  any  existing  cowry  of  the  Mediterranean,  sev- 
eral species  of  Olivet,  Ancillaria,  Mitra,  Terebra,  Pyrula,  Fasciolaria, 
and  Conus.  Of  the  cones  there  are  no  less  than  eight  species,  some  very 
large,  whereas  the  only  European  cone  is  of  diminutive  size.  The  genus 
Nerita,  and  many  others,  are  also  represented  by  individuals  of  a  type  now 
characteristic  of  equatorial  seas,  and  wholly  unlike  any  Mediterranean 
forms.  These  proofs  of  a  more  elevated  temperature  seem  to  imply  the 
higher  antiquity  of  the  faluns  as  compared  with  the  Suffolk  Crag,  and 


214       COMPARISONS  OF  THE  CRAG  AND  FALUNS.   [Cn.  XIV. 

are  in  perfect  accordance  with  the  fact  of  the  smaller  proportion  of  testacea 
of  recent  species  found  in  the  faluns. 

Out  of  290  species  of  shells,  collected  by  myself  in  1840  at  Pontlevoy, 
Louans,  Bossee,  and  other  villages  twenty  miles  south  of  Tours  ;  and  at 
Savigne,  about  fifteen  miles  northwest  of  that  place,  seventy-two  only 
could  be  identified  with  recent  species,  which  is  in  the  proportion  of 
twenty-five  per  cent.  A  large  number  of  the  290  species  are  common  to 
all  the  localities,  those  peculiar  to  each  not  being  more  numerous  than  we 
might  expect  to  find  in  different  bays  of  the  same  sea. 

The  total  number  of  testaceous  mollusca  from  the  faluns,  in  my  pos- 
session, is  302  ;  of  which  forty-five  only  were  found  by  Mr.  Wood  to  be 
common  to  the  Suffolk  Crag.  The  number  of  corals,  including  bryozoa 
and  zoantharia,  obtained  by  me  at  Doue,  and  other  localities  before  ad- 
verted to,  amounts  to  forty-three,  as  determined  by  Mr.  Lonsdale,  of  which 
seven  (one  of  them  a  zoantharian)  agree  specifically  with  those  of  the  Suf- 
folk Crag.  Only  one  has,  as  yet,  been  identified  with  a  living  species. 
But  it  is  difficult,  notwithstanding  the  advances  recently  made  by  MM. 
Dana,  Milne  Edwards,  Haime,  and  Lonsdale,  to  institute  a  satisfactory 
comparison  between  recent  and  fossil  zoantharia  and  bryozoa.  Some  of  the 
genera  occurring  fossil  in  Touraine,  as  the  Astrea,  Dmdrophyllia,  Lunu- 
lites,  have  not  been  found  in  European  seas  north  of  the  Mediterranean  ; 
nevertheless  the  zoantharia  of  the  faluns  do  not  seem  to  indicate  on  the 
whole  so  warm  a  climate  as  would  be  inferred  from  the  shells. 

It  was  stated  that,  on  comparing  about  300  species  of  Touraine  shells 
with  about  450  from  the  Suffolk  Crag,  forty-five  only  were  found  to  be 
common  to  both,  which  is  in  the  proportion  of  only  fifteen  per  cent. 
The  same  small  amount  of  agreement  is  found  in  the  corals  also.  I  for- 
merly endeavored  to  reconcile  this  marked  difference  in  species  with  the 
supposed  coexistence  of  the  two  faunas,  by  imagining  them  to  have  sever- 
ally belonged  to  distinct  zoological  provinces  or  two  seas,  the  one  opening 
to  the  north,  and  the  other  to  the  south,  with  a  barrier  of  land  between 
them,  like  the  Isthmus  of  Suez,  separating  the  Red  Sea  and  the  Medi- 
terranean. But  I  now  abandon  that  idea  for  several  reasons ;  among 
others,  because  I  succeeded  in  1841  in  tracing  the  Crag  fauna  southwards 
in  Normandy  to  within  seventy  miles  of  the  Falunian  type,  near  Dinan, 
yet  found  that  both  assemblages  of  fossils  retained  their  distinctive  char- 
acters, showing  no  signs  of  any  blending  of  species  or  transition  of  cli- 
mate. 

On  a  comparison  of  280  Mediterranean  shells  with  600  British  species, 
made  for  me  by  an  experienced  conchologist  in  1841,  160  were  found  to 
be  common  to  both  collections,  which  is  in  the  proportion  of  fifty-seven 
per  cent.,  a  fourfold  greater  specific  resemblance  than  between  the  seas  of 
the  crag  and  the  faluns,  notwithstanding  the  greater  geographical  dis- 
tance between  England  and  the  Mediterranean  than  between  Suffolk  and 
the  Loire.  The  principal  grounds,  however,  for  referring  the  English  crag 
to  the  Older  Pliocene  and  the  French  faluns  to  the  Miocene  epochs,  con- 
sist in  the  predominance  of  fossil  shells  in  the  British  strata  identifiable 


CH.  XIV.]  VARIATION  OF  SPECIES.  215 

with  species  not  only  still  living,  but  which  are  now  inhabitants  of 
neighboring  seas,  while  the  accompanying  extinct  species  are  of 
genera  such  as  characterize  Europe.  In  the  faluns,  on  the  contrary, 
the  recent  species  are  in  a  decided  minority ;  and  most  of  them  are 
now  inhabitants  of  the  Mediterranean,  the  coast  of  Africa,  and  the 
Indian  Ocean ;  in  a  word,  less  northern  in  character  and  pointing  to 
the  prevalence  of  a  warmer  climate.  They  indicate  a  state  of  things 
receding  farther  from  the  present  condition  of  central  Europe  in 
physical  geography  and  climate,  and  doubtless,  therefore,  receding 
farther  from  our  era  in  time. 

Among  the  conspicuous  shells  which  are  common  to  the  faluns  of 
the  Loire  and  the  Suffolk  Crag  is  the  Voluta  Lamberti,  before  men- 
tioned, page  204.  All  the  specimens  of  this  shell  which  I  have  my- 
self collected  in  Touraine  or  have  seen  in  museums  are  thicker  and 
heavier  than  British  individuals  of  the  same  species,  and  shorter  in 
proportion  to  their  width,  and  have  the  folds  on  the  columella  less 
oblique,  as  represented  in  the  annexed  figures. 

Fig.  162  &.  Fig.  163. 


Voluta  Lamberti.  V.  Laniberti. 

Variety  characteristic  of  Faluns          Variety  characteristic  of  Suffolk  Crag, 
of  Touraine.    Miocene.  Pliocene. 

Mr.  Searles  "Wood  has  fully  appreciated  these  constant  differences, 
but  has,  I  think,  with  propriety  regarded  the  two  forms  as  mere 
varieties,  or  races  of  one  and  the  same  species.  It  is  remarkable, 
however,  that  the  late  Alcide  d'Orbigny,*  who  so  often  founded 
species  on  very  fine  distinctions,  should  have  coincided  in  this  view. 
It  may,  I  think,  be  fairly  assumed  that  he  would  not  have  done  so 
had  he  not  imagined  the  Suffolk  Crag  to  be  identical  in  age  with  the 

*  A.  d'Orbigny,  Cours  Elementaire  de  Paleontologie,  vol.  ii.  pp.  793,  797,  1852. 


216  VARIATION  OF  SPECIES.  [On.  XIV. 

faluns  of  the  Loire,  not  being  aware  that  it  differed  in  so  many 
important  respects,  especially  in  its  approach  to  the  living  fauna  of 
the  neighboring  sea,  from  the  French  deposit.  He  was  one  of  those 
naturalists  who  advocated  the  doctrine  that  there  was  a  complete  dis- 
tinction between  the  fossil  species  of  periods  standing  next  to  each 
other  in  chronological  succession.  Had  he  ranked  the  faluns  as 
Miocene  and  the  Crag  of  Suffolk  as  Pliocene,  he  would  not  have  as- 
similated two  forms  so  easily  distinguishable.  This  we  are  entitled  to 
infer  from  his  refusal  to  admit  the  specific  agreement  of  any  falunian 
and  living  shells,  and,  what  is  still  more  remarkable,  his  refusing  to 
allow  the  existence  of  more  than  44  recent  species  out  of  437  in  his 
newer  or  Subapennine  group.  He  divided  the  whole  tertiary  series 
into  five  stages,  each  supposed  to  mark  an  era  of  repose  on  the  earth's 
surface,  at  the  end  of  which  all  the  living  inhabitants  were  annihilated 
by  a  great  catastrophe,  the  earth  being  afterward  repeopled  with  a 
new  set  of  forms.  Even  when  he  was  forced  to  admit  that  one  or  two 
in  a  hundred  of  the  fossils  passed  from  one  formation  to  another,  he 
was  inclined  to  attribute  that  small  amount  of  agreement  to  the  wash- 
ing of  dead  shells  from  older  into  newer  strata.  This  doctrine  of  the 
absolute  distinction  of  species  in  formations  next  in  the  order  of  suc- 
cession would  scarcely  be  worth  referring  to  now  that  it  is  so  generally 
rejected  by  the  most  experienced  geologists,  were  it  not  for  the  great 
ingenuity  with  which  some  of  its  advocates  have  defended  their  views. 
When  the  shells  are  confessedly  undistinguishable,  it  has  sometimes 
been  suggested,  that  if  the  soft  parts  of  the  animals  had  been  preserved, 
they  would  probably  have  been  found  to  differ.  '/  On  the  other  hand, 
it  is  not  uninstructive  to  note  how  easily  palaeontologists  of  unques- 
tionable merit  can,  if  they  are  under  the  influence  of  a  theory,  such 
as  thai*  above  alluded  to,  find  specific  distinctions  wherever  they  are 
wanted,  or,  on  the  other  hand,  pronounce  the  same  to  have  merely  the 
value  of  a  variety.  '' 

The  points  of  difference  expressed  in  the  two  figs.  162  b.  and  163 
may  be  regarded  by  the  same  zoologist  as  mere  races  or  geographical 
varieties  so  long  as  both  are  believed  to  belong  to  the  same  precise  era, 
but  they  will  take  the  rank  of  species  if  one  be  regarded  as  Miocene 
and  the  other  as  Pliocene.' '  Specimens  have  occasionally  been  found 
of  this  volute  in  the  Coralline  Crag  which  help  to  connect  the  Tour- 
aine  form  with  that  of  the  Red  Crag ;  but  it  often  happens  in  analo- 
gous cases  that  no  formation  of  intermediate  age  is  extant,  and  then  all 
intermediate  gradations,  all  evidence  of  there  having  been  a  passage 
from  one  form  to  the  other,  and  of  both  having  had  a  common  descent, 
may  be  lost.  Zoologists,  whether  they  adopt  or  reject  the  theory  of 
the  origin  of  species  by  natural  selection,  are  still  bound  to  be  consist- 
ent with  themselves  in  regard  to  the  amount  of  deviation  from  certain 
types  which  shall  be  deemed  sufficient  to  constitute  a  specific  difference. 
It  is  sufficiently  difficult  to  arrive  at  philosophical  conclusions  when 
the  characters  relied  on  are  strictly  those  of  the  external  forms  and  inter- 


CH.  XIV.]  LOWER  MIOCENE  STRATA  OF  FRANCE. 

nal  peculiarities  of  individuals  ;  but  when  once  our  specific  determina- 
tions are  biassed  by  geological  or  geographical  considerations,  there  is 
an  end  of  all  reasonable  hope  of  coming  to  consistent  results. 


LOWER   MIOCENE    STRATA    OF   FRANCE. 

Remarks  on  classification,  and  where  to  draw  the  line  of  separation 
between  Miocene  and  Eocene  strata. — The  marine  faluns  of  the  valley 
of  the  Loire  have  been  already  described  as  resting  in  some  places  on 
a  freshwater  tertiary  limestone,  fragments  of  which  have  been  broken 
off  and  rolled  on  the  shores  and  in  the  bed  of  the  Miocene  sea.  Such 
pebbles  are  frequent  at  Pontlevoy  on  the  Cher,  with  hollows  drilled 
in  them  in  which  the  perforating  marine  shells  of  the  Falunian  period 
still  remain.  Such  a  mode  of  superposition  implies  an  interval  of 
time  between  the  origin  of  the  freshwater  limestone  and  its  submerg- 
ence beneath  the  waters  of  the  Upper  Miocene  sea.  The  limestone 
in  question  forms  a  part  of  the  formation  called  the  Calcaire  de  la 
Beauce,  which  constitutes  a  large  tableland  between  the  basins  of  the 
Loire  and  the  Seine.  It  is  associated  with  marls  and  other  deposits, 
such  as  may  have  been  formed  in  marshes  and  shallow  lakes  in  the 
newest  part  of  a  great  delta.  Beds  of  flint,  continuous  or  in  nodules, 
accumulated  in  these  lakes,  and  aquatic  plants  called  Charce,  left  their 
stems  and  seed-vessels  embedded  both  in  the  marl  and  flint,  together 
with  freshwater  and  land  shells.  Some  of  the  siliceous  rocks  of  this 
formation  are  used  extensively  for  millstones.  The  flat  summits  or 
platforms  of  the  hills  round  Paris,  and  large  areas  in  the  forest  of 
Fontainebleau,  as  well  as  the  Plateau  de  la  Beauce,  already  alluded  to, 
are  chiefly  composed  of  these  freshwater  strata.  Next  to  these  in  the 
descending  order  are  marine  sands  and  sandstone,  commonly  called  the 
Gres  de  Fontainebleau,  from  which  a  considerable  number  of  shells, 
very  distinct  from  those  of  the  faluns,  have  been  obtained  at  fitampes, 
south  of  Paris,  and  at  Montmartre  and  other  hills  in  Paris  itself,  or  in 
its  suburbs.  At  the  bottom  of  these  sands  a  green  clay  occurs,  con- 
taining a  small  oyster,  Ostrea  cyathida,  Lam.,  wThich,  although  ol 
slight  thickness,  is  spread  over  a  wide  area.  This  clay  rests  im- 
mediately on  the  Paris  gypsum,  or  that  series  of  beds  of  gypsum  and 
gypseous  marl  from  which  Cuvier  first  obtained  several  species  of 
Paleotherium  and  other  extinct  mammalia.*  At  this  point  the  ma- 
jority of  French  geologists  have  always  drawn  the  line  between  the 
Middle  and  Lower  Tertiary,  or  between  the  Miocene  and  Eocene 
formations,  regarding  the  Fontainebleau  sands  and  the  Ostrea  cyathula 
clay  as  the  base  of  the  Miocene,  and  the  gypsum  with  its  mammalia 
as  the  top  of  the  Eocene  group.  From  that  method  of  classification 
I  formerly  dissented,  agreeing  with  M.  Deshayes  that  the  fossils  of 

*  See  below,  Chapter  XVI. 


218  LINE  BETWEEN  MIOCENE  AND  EOCENE.  [Cn.  XIV. 

the  marine  sands  showed  a  much  greater  affinity  to  the  subjacent 
Eocene  formations  than  to  the  more  modern  faluns  of  Touraine. 
In  his  classical  work  on  the  fossil  shells  of  the  environs  of  Paris 
(1824-'37r)  he  had  described  twenty-nine, species  from  the  Fontaine- 
bleau  sands,  of  which  some  few  could  be  identified  with  fossils  be- 
longing to  the  older  Calcaire  Grossier,  whereas  no  one  of  them  was 
common  to  the  faluns  of  Touraine.  He  also  insisted  on  the  general 
aspect  or  fades  of  the  fauna  bearing  a  far  greater  resemblance  to  the 
testacea  of  the  older  or  Eocene  group  than  to  that  of  the  faluns. 

A  few  years  after  the  publication  of  my  "  Principles  of  Geology  " 
(vol.  iii.)  in  1833,  the  directors  of  the  Government  Survey  of  France, 
MM.  Dufrenoy  and  E.  de  Beaumont,  referred  the  Paris  gypsum  in  their 
geological  map  of  the  Eocene,  and  the  overlying  marine  sands  and 
Calcaire  de  la  Beauce  to  the  Miocene,  the  faluns  of  Touraine  being  re- 
garded by  them  as  constituting  an  upper  division  of  the  same  Miocene 
series.  M.  d'Archiac,  in  1839,  adopted  the  same  method;  and  M. 
Alcide  d'Orbigny,  in  his  Paleontology,  in  1852,  classed  the  Gres  de 
Fontainebleau,  or  "  Sables  Superieurs,"  as  "  Falunien  A,"  and  the  faluns 
of  the  Loire  as  "  Falunien  B,"  thus  giving  in  his  adhesion  to  the  same 
system  of  classification.  That  there  should  have  been  much  differ- 
ence of  opinion  on  this  subject  was  very  natural,  for,  at  the  time  when 
I  first  took  part  in  the  controversy,  there  seemed  very  little  prospect 
of  bridging  over  the  wide  gap  between  the  two  formations  which  it 
was  thus  proposed  to  link  together  in  one  group.  In  1857,  by  aid  of 
a  railway  cutting  at  fitampes,  the  number  of  marine  shells  derived 
from  the  Fontainebleau  sands  was  suddenly  raised  from  29  to  90  spe- 
cies. The  newly-discovered  fossils  furnished  arguments  both  for  and 
against  the  views  of  those  who  desired  to  refer  the  strata  containing 
them  to  the  Miocene  rather  than  to  the  Eocene  series.  As  bearing 
against  those  views,  may  be  mentioned  the  fact  that  none  of  the  90 
shells  agreed  with  species  proper  to  the  faluns  of ^ the  Loire,  while 
some  of  them  were  identical  with  Calcaire  Grossier  species.  This 
was  the  more  worthy  of  note  because  £tampes  is  within  seventy  miles 
of  Pontlevoy,  near  Blois,  and  not  more  than  100  miles  from  Savigne, 
near  Tours,  two  localities  where  the  falunian  shells  are  very  abundant. 
So  striking  a  difference  between  the  species  of  the  valley  of  the  Loire 
and  those  of  the  basin  of  the  Seine,  when  we  consider  the  contiguity 
of  the  spots  above  alluded  to,  could  not  be  the  result  of  geographical 
distribution  at  one  and  the  same  era,  but  must  evidently  have  depended 
on  a  great  difference  in  the  age  of  the  deposits.  It  marked  the  influ- 
ence of  Time,  and  not  of  Space. 

On  the  other  hand,  in  favor  of  grouping  the  fitampes  or  Fontaine- 
bleau sands  with  the  newer  Falunian  rather  than  with  the  older  Eocene 
formations,  M.  Hebert  pointed  out  that  a  majority  of  the  90  ifitampes 
and  Gres  de  Fontainebleau  fossils  agreed  specifically  with  shells  which, 
in  Belgium,  Mayence,  and  other  localities,  had  been  shown  by  the 
labors  of  MM.  Dumont,  Nyst,  De  Koninck,  and  Bosquet  to  occupy  a 


CH.  XIV.]  LINE  BETWEEN  MIOCENE  AND  EOCENE.  219 

very  distinct  geological  position  above  the  typical  Eocene  series  of  the 
Paris  basin,  and  of  which  the  equivalents  at  Mayence  had  long  been 
recognized  as  Miocene.  M.  Hebert  also  published,  in  1855,  a  map 
descriptive  of  the  areas  of  two  tertiary  seas,  which  succeeded  each 
other  in  the  Paris  basin, — the  first  that  of  the  Calcaire  Grossier,  and 
the  second  that  of  the  Fontainebleau  Sands, — showing  how  marked  is 
the  want  of  coincidence  between  them ;  a  fact  which  implies  the 
occurrence  of  great  geographical  changes  in  the  interval  of  time  be- 
tween the  two  eras  compared.  In  the  explanation  of  his  map  he 
gives  his  reasons  for  regarding  the  zone  of  Cerithium  plicatum,  or 
that  of  the  Fontainebleau  Sands,  as  the  most  convenient  line  of  de- 
marcation between  Lower  and  Middle  Tertiary,  or  between  Eocene  and 
Miocene.* 

When  I  was  hesitating  as  to  the  course  which  it  would  be  most  ex- 
pedient to  take  in  drawing  the  line  between  Eocene  and  Miocene,  M. 
Lartet,  the  distinguished  French  zoologist,  whose  writings  on  fossil 
mammalia  are  of  such  acknowledged  value,  remarked  to  me  that  although 
the  fossil  testacea  of  the  Fontainebleau  Sands  show  a  preponderance 
of  affinities  toward  an  Eocene  fauna,  and  small  connection  with  the 
faluns  of  Touraine,  yet,  on  the  other  hand,  the  freshwater  "  Calcaire 
de  la  Beauce,"  immediately  overlying  the  Fontainebleau  Sands,  and 
other  lacustrine  formations  in  Auvergne  and  Central  France,  as  well  as 
the  fossiliferous  strata  of  the  Mayence  basin,  cannot  be  included  in  the 
same  Eocene  system  without  doing  violence  to  paleontological  princi- 
ples. \The  grouping  of  the  fossil  mammalia,  he  observed,  becomes  less 
natural  by  such  an  arrangement ;  for  not  only  many  genera,  but  even 
some  species,  are  found  on  both  sides  of  the  arbitrary  line  of  demarca- 
tion thus  drawn  between  Eocene  and  Miocene.  The  genera  Dorca- 
therium,  Cainotherium,  Anchitherium,  and  Titanomys,  for  example, 
and  Rhinoceros  incisivus  and  others,  would  thereby  be  made  common 
to  Eocene  and  Miocene. 

Other  arguments  drawn  from  fossil  botany  in  favor  of  uniting  the 
Gres  de  Fontainebleau  and  faluns  in  one  group  will  be  more  fully  set 
forth  in  the  next  chapter,  when  I  treat  of  the  tertiary  strata  called 
"  Molasse  "  in  Switzerland,  and  of  the  German  Brown  Coal. 

My  unwillingness  to  include  the  Fontainebleau  sands  and  other 
strata  of  the  same  age  in  the  Miocene  Epoch  arose  partly  from  the 
necessity  thereby  incurred  of  abandoning  for  such  deposits  the  defini- 
tion which  I  had  already  given  of  the  term  Miocene  as  implying  that 
a  marked  proportion,  though  a  minority,  of  the  fossil  shells  belong 
to  living  species.  I  had  felt  myself  obliged,  even  in  1833,  to  disre- 
gard this  difficulty,  when,  in  the  first  edition  of  the  "  Principles  of 
Geology,"  I  classed  the  strata  of  the  Mayence  basin  as  Miocene,  con- 
ceiving that,  although  almost  every  species  of  shell  was  extinct,  they 
had  more  aflSnity  with  the  Falunian  than  with  the  Eocene  formations. 

*  Bulletin,  1856,  torn.  xii.  p.  760. 


220  LOWER  MIOCENE  STRATA  OF  FRANCE.  [Cn.  XIV. 

From  the  first  I  had  advocated  the  doctrine  that  there  has  been  a  con- 
tinual coming  in  of  new  species,  and  dying  out  of  old  ones,  and  a 
gradual  change  in  the  physical  geography  and  climate  of  the  earth, 
and  not  such  a  recurrence  of  sudden  revolutions  in  the  animate  and 
inanimate  worlds,  as  was,  in  1833,  insisted  upon  by  many  English  ge- 
ologists of  note,  and  is  still  maintained  by  some  eminent  continental 
writers.  I  therefore  foretold  that  from  time  to  time  new  sets  of  strata 
would  come  to  light,  and  require  to  be  intercalated  between  those  al- 
ready described,  in  which  case  the  fossils  of  some  of  the  newly-found 
beds  would  "  deviate  from  the  normal  types  first  selected,  and  approxi- 
mate more  and  more  to  the  types  of  the  antecedent  or  subsequent 
epochs."  According  to  this  view,  it  was  obvious  from  the  first  that 
the  oldest  Miocene  records,  whenever  they  were  detected,  would  not  be 
easily  distinguishable  from  the  youngest  members  of  the  Eocene  series, 
especially  in  the  proportion  of  the  living  to  the  extinct  species  of 
fossil  shells.  The  importance,  indeed,  of  the  latter  test  must  diminish 
rapidly  the  more  we  recede  from  the  Pliocene  and  approach  the 
Miocene,  and  still  more  the  Eocene  formations,  although  it  is  never 
without  its  value,  and  often  furnishes  the  only  common  standard  of 
comparison  between  strata  of  very  distant  countries.  To  this  subject 
of  classification,  or  the  line  of  demarcation  between  the  Eocene  and 
Miocene  strata,  I  shall  again  refer  in  this  and  the  sixteenth  chapter. 

Lower  Miocene  strata  of  Central  France. — Lacustrine  strata,  belong- 
ing, for  the  most  part,  to  the  same  Miocene  system  as  the  Calcaire  de 
la  Beauce,  are  again  met  with  in  Auvergne,  Cantal,  and  Velay,  the  sites 
of  which  may  be  seen  in  the  annexed  map.  They  appear  to  be  the 
monuments  of  ancient  lakes,  which,  like  some  of  those  now  existing  in 
Switzerland,  once  occupied  the  depressions  in  a  mountainous  region, 
and  have  been  each  fed  by  one  or  more  rivers  and  torrents.  The 
country  were  they  occur  is  almost  entirely  composed  of  granite  and 
different  varieties  of  granitic  schist,  with  here  and  there  a  few  patches 
of  secondary  strata,  much  dislocated,  and  which  have  probably  suf- 
fered great  denudation.  There  are  also  some  vast  piles  of  volcanic 
matter  (see  the  map),  the  greater  part  of  which  is  newer  than  the 
freshwater  strata,  and  is  sometimes  seen  to  rest  upon  them,  while  a 
small  part  has  evidently  been  of  contemporaneous  origin.  Of  these 
igneous  rocks  I  shall  treat  more  particularly  in  another  part  of  this 
work. 

Before  entering  into  any  details,  I  may  observe  that  the  study  of 
these  regions  possesses  a  peculiar  interest,  very  distinct  in  kind  from  that 
derivable  from  the  investigation  either  of  the  Parisian  or  English  ter- 
tiary areas.  For  we  are  presented  in  Auvergne  with  the  evidence  of  a 
series  of  events  of  astonishing  magnitude  and  grandeur,  by  which  the 
original  form  and  features  of  the  country  have  been  greatly  changed, 
yet  never  so  far  obliterated  but  that  they  may  still,  in  part  at  least,  be 
restored  in  imagination.  Great  lakes  have  disappeared — lofty  moun- 
tains have  been  formed,  by  the  reiterated  emission  of  lava,  preceded  and 


CH.  XIV.]  LOWER  MIOCENE  OF  CENTRAL  FRANCE. 


221 


Fig.  164. 


222  SUCCESSION  OF  CHANGES  IN  AUVERGNE.          [Cn.  XIV. 

followed  by  showers  of  sand  and  scoriae, — deep  valleys  have  been  sub- 
sequently furrowed  out  through  masses  of  lacustrine  and  volcanic  origin, 
— at  a  still  later  date,  new  cones  have  been  thrown  up  in  these  valleys, — 
new  lakes  have  been  formed  by  the  damming  up  of  rivers, — and  more 
than  one  creation  of  quadrupeds,  birds,  and  plants,  Eocene,  Miocene,  and 
Pliocene,  have  followed  in  succession  ;  yet  the  region  has  preserved  from 
first  to  last  its  geographical  identity ;  and  we  can  still  recall  to  our 
thoughts   its   external   condition  and  physical   structure   before   these 
wonderful  vicissitudes  began,  or  while  a  part  only  of  the  whole  had 
been  completed.     There  was  first  a  period  when  the  spacious  lakes,  of 
which  we  still  may  trace  the  boundaries,  lay  at  the  foot  of  mountains  of 
moderate  elevation,  unbroken  by  the  bold  peaks  and  precipices  of  Mont 
Dor,  and  unadorned  by  the  picturesque  outline  of  the  Puy  de  Dome,  or 
of  the  volcanic  cones  and  craters  now  covering  the  granitic  platform. 
During  this  earlier  scene  of  repose  deltas  were  slowly  formed ;  beds  of 
marl  and  sand,  several  hundred  feet  thick,  deposited  ;  siliceous  and  cal- 
careous rocks  precipitated  from  the  waters  of  mineral  springs  ;  shells  and 
insects  imbedded,  together  with  the  remains  of  the  crocodile  and  tor- 
toise, the  eggs  and  bones  of  water  birds,  and  the  skeletons  of  quadru- 
peds, some  of  them  belonging  to  the  same  genera  as  those  entombed  in 
the  Eocene  gypsum  of  Paris.     To  this  tranquil  condition  of  the  surface 
succeeded  the  era  of  volcanic  eruptions,  when  the  lakes  were  drained, 
and  when  the  fertility  of  the  mountainous  district  was  probably  enhanced 
by  the  igneous  matter  ejected  from  below,  and  poured  down  upon  the 
more  sterile  granite.     During  these   eruptions,  which  appear  to  have 
taken  place  after  the  disappearance  of  the  upper  Eocene  fauna,  and  partly 
in  the  Miocene  epoch,  the  mastodon,  rhinoceros,  elephant,  tapir,  hippo- 
potamus, together  with  the  ox,  various  kinds  of  deer,  the  bear,  hyaena, 
and  many  beasts  of  prey,  ranged  the  forest,  or  pastured  on  the  plain,  and 
were  occasionally  overtaken  by  a  fall  of  burning  cinders,  or  buried  in 
flows  of  mud,  such  as  accompany  volcanic  eruptions.     Lastly,  tttese 
quadrupeds  became  extinct,  and  gave  place  in  their  turn  to  the  species 
now  existing.     There  are  no  signs,  during  the  whole  time  required  for 
this  series  of  events,  of  the  sea  having  intervened,  nor  of  any  denuda- 
tion which  may  not  have  been  accomplished  by  currents  in  the  differ- 
ent lakes,  or  by  rivers  and  floods  accompanying  repeated  earthquakes, 
or  subterranean  movements,  during  which  the  levels  of  the  district 
have  in  some  places  been  materially  modified,  and  perhaps  the  whole 
upraised  relatively  to  the  surrounding  parts  of  France. 

Auvergne. — The  most  northern  of  the  freshwater  groups  is  situated 
in  the  valley-plain  of  the  Allier,  lying  in  the  department  of  the  Puy  de 
Dome,  being  the  tract  which  went  by  the  name  of  the  Lirnagne  d' Au- 
vergne. It  is  enclosed  by  two  parallel  mountain  ranges, — that  of 
the  Forez,  which  divides  the  waters  of  the  Loire  and  Allier  on  the 
east ;  and  that  of  the  Monts  Domes,  which  separates  the  Allier  from  the 
Sioule  on  the  west.*  The  average  breadth  of  this  tract  is  about  twenty 

*  Scrope,  Geology  of  Central  France,  p.  15. 


On.  XIV.]  LOWER  MIOCENE  OF  CENTRAL  FRANCE.  223 

miles  ;  and  it  is  for  tlie  most  part  composed  of  nearly  horizontal  strata  of 
sand,  sandstone,  calcareous  marl,  clay,  and  limestone,  none  of  which  ob- 
serve a  fixed  and  invariable  order  of  superposition.  The  ancient  borders 
of  the  lake,  wherein  the  freshwater  strata  were  accumulated,  may  gen- 
erally be  traced  with  precision,  the  granite  and  other  ancient  rocks  rising 
up  boldly  from  the  level  country.  The  actual  junction,  however,  of  the 
lacustrine  and  granitic  beds  is  rarely  seen,  as  a  small  valley  usually  in- 
tervenes between  them.  The  freshwater  strata  may  sometimes  be  seen 
to  retain  their  horizontality  within  a  very  slight  distance  of  the  border- 
rocks,  while  in  some  places  they  are  inclined,  and  in  few  instances  vertical. 
The  principal  divisions  into  which  the  lacustrine  series  may  be  separated 
are  the  following : — 1st,  Sandstone,  grit,  and  conglomerate,  including  red 
marl  and  red  sandstone.  2dly,  Green  and  white  foliated  marls.  3dly, 
Limestone  or  travertin,  often  oolitic.  4thly,  Gypseous  marls. 

1.  a.  Sandstone  and  conglomerate. — Strata  of  sand  and  gravel,  some- 
times bound  together  into  a  solid  rock,  are  found  in  great  abundance 
around  the  confines  of  the  lacustrine  basin,  containing,  in  different  places, 
pebbles  of  all  the  ancient  rocks  of  the  adjoining  elevated  country ;  namely, 
granite,  gneiss,  mica-schist,  clay-slate,  porphyry,  and  others,  but  without 
any  intermixture  of  basaltic  or  other  tertiary  volcanic  rocks.  These  strata 
do  not  form  one  continuous  band  around  the  margin  of  the  basin,  being 
rather  disposed  like  the  independent  deltas  which  grow  at  the  mouths  of 
torrents  along  the  borders  of  existing  lakes. 

At  Chamalieres,  near  Clermont,  we  have  an  example  of  one  of  these 
deltas,  or  littoral  deposits,  of  local  extent,  where  the  pebbly  beds  slope 
away  from  the  granite,  as  if  they  had  formed  a  talus  beneath  the  waters 
of  the  lake  near  the  steep  shore.  A  section  of  about  50  feet  in  vertical 
height  has  been  laid  open  by  a  torrent,  and  the  pebbles  are  seen  to  con- 
sist throughout  of  rounded  and  angular  fragments  of  granite,  quartz, 
primary  slate,  and  red  sandstone.  Partial  layers  of  lignite  and  pieces  of 
wood  are  found  in  these  beds. 

At  some  localities  on  the  margin  of  the  basin  quartzose  grits  are  found ; 
and,  where  these  rest  on  granite,  they  are  sometimes  formed  of  separate 
crystals  of  quartz,  mica,  and  felspar,  derived  from  the  disintegrated  granite, 
the  crystals  having  been  subsequently  bound  together  by  a  siliceous  ce- 
ment. In  these  cases  the  granite  seems  regenerated  in  a  new  and  more 
solid  form ;  and  so  gradual  a  passage  takes  place  between  the  rock  of 
crystalline  and  that  of -mechanical  origin,  that  we  can  scarcely  distinguish 
where  one  ends  and  the  other  begins. 

In  the  hills  called  the  Puy  de  Jussat  and  La  Roche,  we  have  the  advan- 
tage of  seeing  a  section  continuously  exposed  for  about  700  feet  in  thick- 
ness. At  the  bottom  are  foliated  marls,  white  and  green,  about  400  feet 
thick ;  and  above,  resting  on  the  marls,  are  the  quartzose  grits,  cemented 
by  calcareous  matter,  which  is  sometimes  so  abundant  as  to  form  imbed- 
ded nodules.  These  sometimes  constitute  spheroidal  concretions  6  feet  in 
diameter,  and  pass  into  beds  of  solid  limestone,  resembling  the  Italian 
travertins,  or  the  deposits  of  mineral  springs. 


224:  LACUSTRINE  STRATA,  AUVERGNE.  [On.  XIV. 

1.  5.  Red  marl  and  sandstone. — But  the   most  remarkable   of  the 
arenaceous  groups  is  one  of  red  sandstone  and  red  marl,  which  are  iden- 
tical in  all  their  mineral  characters  with  the  secondary  New  Red  sand- 
stone and  marl  of  England.     In  these  secondary  rocks  the  red  ground  is 
sometimes  variegated  with  light  greenish  spots,  and  the  same  may  be 
seen  in  the  tertiary  formation  of  freshwater  origin  at  Coudes,  on  the  Al- 
lier.     The  marls  are  sometimes  of  a  purplish-red  color,  as  at  Champheix, 
and  are  accompanied  by  a  reddish  limestone,  like  the  well-known  "  corn- 
stone,"  which  is  associated  with  the  Old  Red  sandstone  of  English  geol- 
ogists.    The  red  sandstone  and  marl  of  Auvergne  have  evidently  been 
derived  from  the  degradation  of  gneiss  and  mica-schist,  which  are  seen 
in  situ  on  the  adjoining  hills,  decomposing  into  a  soil  very  similar  to  the 
tertiary  red  sand  and  marl.     We  also  find  pebbles  of  gneiss,  mica-schist, 
and  quartz  in  the  coarser  sandstones  of  this  group,  clearly  pointing  to 
the  parent  rocks  from  which  the  sand  and  marl  are  derived.     The  red 
beds,  although  destitute  themselves  of  organic  remains,  pass  upwards 
into  strata  containing  tertiary  fossils,  and  are  certainly  an  integral  part  of 
the  lacustrine  formation.     From  this  example  the  student  will  learn  how 
small  is  the  value  of  mineral  character  alone,  as  a  test  of  the  relative  age 
of  rocks. 

2.  Green  and  white  foliated  marls. — The  same  primary  rocks  of  Au- 
vergne,  which,  by  the  partial  degradation  of  their  harder  parts,  gave  rise 
to  the  quartzose  grits  and  conglomerates  before  mentioned,  would,  by  the 
reduction  of  the  same  materials  into  powder,  and  by  the  decomposition 
of  their  felspar,  mica,  and  hornblende,  produce  aluminous  clay,  and,  if  a 
sufficient  quantity  of  carbonate  of  lime  was  present,  calcareous  marl. 
This  fine  sediment  would  naturally  be  carried  out  to  a  greater  distance 
from  the  shore,  as  are  the  various  finer  marls  now  deposited  in  Lake 
Superior.    And  as,  in  the  American  lake,  shingle  and  sand  are  annually 
amassed  near  the  northern  shores,  so  in  Auvergne  the  grits  and  con- 
glomerates before  mentioned  were  evidently  formed  near  the  borders. 

The  entire  thickness  of  these  marls  is  unknown ;  but  it  certainly  ex- 
ceeds, in  some  places,  700  feet.  They  are,  for  the  most  part,  either  light- 
green  or  white,  and  usually  calcareous.  They  are  thinly  foliated, — a 
character  which  frequently  arises  from  the  innumerable  thin  shells,  or 
carapace-valves,  of  that  small  crustacean  called  Cypris,  which  is  pro- 
vided with-  two  small  valves,  not  unlike  those  of  a  bivalve  shell,  and 
moults  its  integuments  periodically,  which  the  conchiferous  mollusks  do 
not.  This  circumstance  may  partly  explain  the  countless  myriads  of  the 
shells  of  Cypris  which  were  shed  in  the  ancient  lakes  of  Auvergne,  so  as 
to  give  rise  to  divisions  in  the  marl  as  thin  as  paper,  and  that,  too,  in 
stratified  masses  several  hundred  feet  thick.  A  more  convincing  proof  of 
the  tranquillity  and  clearness  of  the  waters,  and  of  the  slow  and  gradual 
process  by  which  the  lake  was  filled  up  with  fine  mud,  cannot  be  desired. 
But  we  may  easily  suppose  that,  while  this  fine  sediment  was  thrown 
down  in  the  deep  and  central  pans  of  the  basin,  gravel,  sand,  and  rocky 
fragments  were  hurried  into  the  lake,  and  deposited  near  the  shore,  form- 
ing the  group  described  in  the  preceding  section. 


CH.  XIV.]  INDUSIAL  LIMESTONE,   AUVERGNE.  225 

Not  far  from  Clermont,  the  green  marls,  containing  the  Cypns  m 
abundance,  approach  to  within  a  few  yards  of  the  granite  which  forms 
the  borders  of  the  basin.  The  occurrence  of  these  marls  so  near  the 
ancient  margin  may  be  explained  by  considering  that,  at  the  bottom  of 
the  ancient  lake,  no  coarse  ingredients  were  deposited  in  spaces  inter- 
mediate between  the  points  where  rivers  and  torrents  entered,  but  finer 

Fig.  165. 


Vertical  strata  of  marl,  at  Champradelle,  near  Clermont 

A.  Granite.  B.  Space  of  60  feet,  in  which  no  section  is  seen. 

O.  Green  marl,  vertical  and  inclined.       D.  White  marl. 

mud  only  was  drifted  there  by  currents.  The  vertically  of  some  of  the 
beds  in  the  above  section  bears  testimony  to  considerable  local  disturb- 
ance subsequent  to  the  deposition  of  the  marls  ;  but  such  inclined  and 
vertical  strata  are  very  rare. 

3.  Limestone,  travertin,  oolite. — Both  the  preceding  members  of  the 
lacustrine  deposit,  the  marls  and  grits,  pass  occasionally  into  limestone. 
Sometimes  only  concretionary  nodules  abound  in  them ;  but  these,  where 
there  is  an  increase  in  the  quantity  of  calcareous  matter,  unite  into  reg- 
ular beds. 

On  each  side  of  the  basin  of  the  Limagne,  both  on  the  west  at  Gan- 
nat,  and  on  the  east  at  Vichy,  a  white  oolitic  limestone  is  quarried.  At 
Vichy,  the  oolite  resembles  our  Bath  stone  in  appearance  and  beauty  ; 
and,  like  it,  is  soft  when  first  taken  from  the  quarry,  but  soon  hardens 
on  exposure  to  the  air.  At  Gannat,  the  stone  contains  land-shells  and 
bones  of  quadrupeds.  At  Chadrat,  in  the  hill  of  La  Serre,  the  limestone 
is  pisolitic,  the  small  spheroids  combining  both  the  radiated  and  concen- 
tric structure. 

Indusial  limestone. — There  is  another  remarkable  form  of  freshwater 
limestone  in  Auvergne,  called  "  indusial,"  from  the  cases,  or  indusice,  ol 
caddis-worms  (the  larvae  of  PJiryganea)\  great  heaps  of  which  have 
been  incrusted,  as  they  lay,  by  carbonate  of  lime,  and  formed  into  a  hard 
travertin.  The  rock  is  sometimes  purely  calcareous,  but  there  is  occa- 
sionally an  intermixture  of  siliceous  matter.  Several  beds  of  it  are  fre- 
quently seen,  either  in  continuous  masses,  or  in  concretionary  nodules, 
one  upon  another,  with  layers  of  marl  interposed.  The  annexed  drawing 
(fig.  166)  will  show  the  manner  in  which  one  of  these  indusial  beds  (a) 
is  laid  open  at  the  surface,  between  the  marls  (b  6),  near  the  base  of  the 
hill  of  Gergovia ;  and  affords,  at  the  same  time,  an  example  of  the  extent 
to  which  the  lacustrine  strata,  which  must  once  have  filled  a  hollow,  have 
been  denuded,  and  shaped  out  into  hills  and  valleys,  on  the  site  of  the 
ancient  lakes. 

15 


226 


INDUSIAL  LIMESTONE,  AUVERGNE. 
Fig.  166. 


[Ca  XIV. 


Fig.  167. 


Bed  of  indusial  limestone,  interstratified  with  freshwater  marl,  near  Clermont  (Kleinschrod). 

We  may  often  observe  in  our  ponds  the  Phryganea  (or  Caddis-fly), 
in  its  caterpillar  state,  covered  with  small  freshwater  shells,  which  they 
have  the  power  o£  fixing  to  the  outside  of  their  tubular  cases,  in  order, 
probably,  to  give  them  weight  and  strength.  The  individual  figured  in 
the  annexed  cut,  which  belongs  to  a  species  very  abundant  in  England, 
has  covered  its  case  with  shells  of  a  small 
Planorbis.  In  the  same  manner  a  large 
species  of  caddis-worm  which  swarmed  in  the 
Eocene  lakes  of  Auvergne  was  accustomed 
to  attach  to  its  dwelling  the  shells  of  a  small 
spiral  univalve  of  the  genus  Paludina.  A 
Larva  of  recent  Phryganea*  hundred  of  these  minute  shells  are  some- 
times seen  arranged  around  one  tube,  part  of  the  central  cavity  of  which 
is  often  empty,  the  rest  being  filled  up  with  thin  concentric  layers  of 
travertin.  The  cases  have  been  thrown  together  confusedly,  and  often 
lie,  as  in  fig.  168,  at  right  angles  one  to  the  other.  When  we  consider 

Fig.  168. 


a.  Indusial  limestone  of  Auvergne.         &.  Fossil  Paludina  magnified. 
I  believe  that  the  British  specimen  here  figured  is  P.  rhombica,  Linn. 


CH.  XIV.]        FEESH WATER  FORMATIONS  OF  AUVERGNE. 


227 


that  ten  or  twelve  tubes  are  packed  within  the  compass  of  a  cubic  inch, 
and  that  some  single  strata  of  this  limestone  are  6  feet  thick,  and  may- 
be traced  over  a  considerable  area,  we  may  form  some  idea  of  the  count- 
less number  of  insects  and  mollusca  which  contributed  their  integuments 
and  shells  to  compose  this  singularly  constructed  rock.  It  is  unnecessa- 
ry to  suppose  that  the  Phryganece  lived  on  the  spots  where  their  cases 
are  now  found ;  they  may  have  multiplied  in  the  shallows  near  the 
margin  of  the  lake,  or  in  the  streams  by  which  it  was  fed,  and  their 
cases  may  have  been  drifted  by  a  current  far  into  the  deep  water. 

In  the  summer  of  1837,  when  examining,  in  company  with  Dr.  Beck, 
a  small  lake  near  Copenhagen,  I  had  an  opportunity  of  witnessing  a 
beautiful  exemplification  of  the  manner  in  which  the  tubular  cases  of 
Auvergne  were  probably  accumulated.  This  lake,  called  the  Fuure-Soe, 
occurring  in  the  interior  of  Seeland,  is  about  twenty  English  miles  in 
circumference,  and  in  some  parts  200  feet  in  depth.  Round  the  shallow 
borders  an  abundant  crop  of  reeds  and  rushes  may  be  observed,  covered 
with  the  indusiaB  of  the  Phryganea  grandis  and  other  species,  to  which 
shells  are  attached.  The  plants  which  support  them  are  the  bullrush, 
Scirpus  lacustris,  and  common  reed,  Arundo  phragmites,  but  chiefly  the 
former.  In  summer,  especially  in  the  month  of  June,  a  violent  gust  of 
wind  sometimes  causes  a  current  by  which  these  plants  are  torn  up  by 
the  roots,  washed  away,  and  floated  off  in  long  bands,  more  than  a  mile 
in  length,  into  deep  water.  The  Cypris  swarms  in  the  same  lake ;  and 
calcareous  springs  alone  are  wanting  to  form  extensive  beds  of  indusial 
limestone,  like  those  of  Auvergne. 

4.  Gypseous  marls. — More  than  50  feet  of  thinly  laminated  gypseous 
marls,  exactly  resembling  those  in  the  hill  of  Montmartre,  at  Paris,  are 
worked  for  gypsum  at  St.  Romain,  on  the  right  bank  of  the  Allier.  They 
rest  on  a  series  of  green  cypridiferous  marls  which  alternate  with  grit,  the 
united  thickness  of  this  inferior  group  being  seen,  in  a  vertical  section  on 
the  banks  of  the  river,  to  exceed  250  feet. 

General  arrangement,  origin,  and  age  of  the  freshwater  formations 
of  Auvergne. — The  relations  of  the  different  groups  above  described  can- 
not be  learnt  by  the  study  of  any  one  section  ;  and  the  geologist  who 
sets  out  with  the  expectation  of  finding  a  fixed  order  of  succession  may 
perhaps  complain  that  the  different  parts  of  the  basin  give  contradictory 
results.  The  arenaceous  division,  the  marls,  and  the  limestone,  may  all 
be  seen  in  some  places  to  alternate  with  each  other  ;  yet  it  can  by  no 
means  be  affirmed  that  there  is  no  order  of  arrangement.  The  sands, 
sandstone,  and  conglomerate  constitute  in  general  a  littoral  group  ;  the 
foliated  white  and  green  marls,  a  contemporaneous  central  deposit ;  and 
the  limestone  is  for  the  most  part  subordinate  to  the  newer  portions  of 
both.  The  uppermost  marls  and  sands  are  more  calcareous  than  the 
lower  ;  and  we  never  meet  with  calcareous  rocks  covered  by  a  consider- 
able thickness  of  quartzose  sand  or  green  marl.  From  the  resemblance 
of  the  limestones  to  the  Italian  travertins,  we  may  conclude  that  they 
were  derived  from  the  waters  of  mineral  springs,— such  springs  as  even 


228  LACUSTRINE  STRATA,  AUYERGNE.  [Cn.  XIV. 

now  exist  in  Auvergne,  and  which  may  be  seen  rising  up  through  the 
granite,  and  precipitating  travertin.  They  are  sometimes  thermal,  but 
this  character  is  by  no  means  constant. 

It  seems  that,  when  the  ancient  lake  of  the  Limagne  first  began  to  be 
filled  with  sediment,  no  volcanic  action  had  yet  produced  lava  and  scoriae 
on  any  part  of  the  surface  of  Auvergne.  No  pebbles,  therefore,  of  lava 
were  transported  into  the  lake, — no  fragments  of  volcanic  rocks  im- 
bedded in  the  conglomerate.  But  at  a  later  period,  when  a  considerable 
thickness  of  sandstone  and  marl  had  accumulated,  eruptions  broke  out, 
and  lava  and  tuff  were  deposited,  at  some  spots,  alternately  with  the 
lacustrine  strata.  It  is  not  improbable  that  cold  and  thermal  springs, 
holding  different  mineral  ingredients  in  solution,  became  more  numerous 
during  the  successive  convulsions  attending  this  development  of  volcanic 
agency,  and  thus  deposits  of  carbonate  and  sulphate  of  lime,  silex,  and 
other  minerals  were  produced.  Hence  these  minerals  predominate  in 
the  uppermost  strata.  The  subterranean  movements  may  then  have 
continued,  until  they  altered  the  relative  levels  of  the  country,  and  caused 
the  waters  of  the  lakes  to  be  drained  off,  and  the  farther  accumulation 
of  regular  freshwater  strata  to  cease. 

We  may  easily  conceive  a  similar  series  of  events  to  give  rise  to  anal- 
ogous results  in  any  modern  basin,  such  as  that  of  Lake  Superior,  for 
example,  where  numerous  rivers  and  torrents  are  carrying  down  the 
detritus  of  a  chain  of  mountains  into  the  lake.  The  transported  mate- 
rials must  be  arranged  according  to  their  size  and  weight,  the  coarser 
near  the  shore,  the  finer  at  a  greater  distance  from  land ;  but  in  the 
gravelly  and  sandy  beds  of  Lake  Superior  no  pebbles  of  modern  volcanic 
rocks  can  be  included,  since  there  are  none  of  these  at  present  in  the 
district.  If  igneous  action  should  break  out  in  that  country,  and  pro- 
duce lava,  scoriae,  and  thermal  springs,  the  deposition  of  gravel,  sand, 
and  marl  might  still  continue  as  before ;  but,  in  addition,  there  would 
then  be  an  intermixture  of  volcanic  gravel  and  tuff,  and  of  rocks  precip- 
itated from  the  waters  of  mineral  springs. 

Although  the  freshwater  strata  of  the  Limagne  approach  generally  to 
a  horizontal  position,  the  proofs  of  local  disturbance  are  sufficiently 
numerous  and  violent  to  allow  us  to  suppose  great  changes  of  level  since 
the  lacustrine  period.  We  are  unable  to  assign  a  northern  barrier  to  the 
ancient  lake,  although  we  can  still  trace  its  limits  to  the  east,  west,  and 
south,  where  they  were  formed  of  bold  granite  eminences.  Nor  need 
we  be  surprised  at  our  inability  to  restore  entirely  the  physical  geography 
of  the  country  after  so  great  a  series  of  volcanic  eruptions ;  for  it  is  by 
no  means  improbable  that  one  part  of  it,  the  southern,  for  example,  may 
have  been  moved  upwards  bodily,  while  others  remained  at  rest,  or  even 
suffered  a  movement  of  depression. 

It  is  scarcely  possible  to  determine  the  age  of  the  oldest  part  of  the 
freshwater  series  of  the  Limagne,  large  masses  both  of  the  sandy  and 
marly  strata  being  devoid  of  fossils.  Some  of  the  lowest  beds  may  be 
of  upper  Eocene  date,  although,  according  to  M.  Pomel,  only  one  bone 


CH.  XIV.j  LOWER  MIOCENE   STRATA— AUVERGNE.  229 

of  a  Paleotherium  has  been  discovered  in  Auvergne.  But  in  Velay, 
in  strata  containing  some  species  of  fossil  mammalia  common  to  the 
Limagne,  no  less  than  four  species  of  Paleothere  have  been  found  by 
M.  Aymard,  and  one  of  these  is  generally  supposed  to  be  identical 
with  Paleotherium  magnum,  an  undoubted  Upper  Eocene  fossil,  of  the 
Paris  gypsum,  the  other  three  being  peculiar. 

Not  a  few  of  the  other  mammalia  of  the  Limagne  made  known  to 
us  by  the  labours  of  MM.  Bouillet,  Bravard,  Croizet,  Jobert,  Laizer, 
Robert,  Aymard,  and  Pomel,  belong  undoubtedly  to  genera  and 
species  elsewhere  proper  to  the  Lower  Miocene.  Thus,  for  example, 
the  Gainotherium  of  Brevard,  a  genus  not  far  removed  from  the 
Anoplotherium,  is  represented  by  several  species,  one  of  which,  as  I 
learn  from  Mr.  Waterhouse,  agrees  with  Microtherium  Renggeri  of 
the  Mayence  basin.  In  like  manner  the  Amphitragulus  elegans  of 
Pomel,  an  Auvergne  fossil,  is  identified  by  Waterhouse  with  Dorca- 
therium  nanum  of  Kaup,  a  Rhenish  species  from  Weissenau,  near 
Mayence.  A  small  species  also  of  rodent,  of  the  genus  Titanomys  of 
H.  von  Meyer,  is  common  to  the  Lower  Miocene  of  Mayence  and  the 
Limagne  d' Auvergne,  and  there  are  many  other  points  of  agreement 
which  the  discordance  of  nomenclature  tends  to  conceal.  A  remarka- 
ble carnivorous  genus,  the  Hyrenodon  of  Laizer,  is  represented  by 
more  than  one  species.  The  same  genus  has  also  been  found  in  the 
Upper  Eocene  marls  of  Hordwell  Cliff,  Hampshire,  just  below  the  level 
of  the  Bembridge  Limestone,  and  therefore  a  formation  older  than  the 
Gypsum  of  Paris.  Several  species  of  opossum  (Didelphis)  are  met 
with  in  the  same  strata  of  the  Limagne.  The  association  of  such 
genera  as  Dinotherium,  Tapir,  Anthracotherium,  and  Rhinoceros  with 
those  above  mentioned,  helps  to  connect  the  Auvergne  fauna  with  the 
Upper  Miocene,  but  the  species  are  different  from  those  of  the 
neighboring  faluns  of  the  Loire,  or  those  of  Sansan,  in  the  South  of 
France.  Nor  do  the  Upper  Miocene  species  appear,  so  far  as  we  yet 
know,  in  the  overlying  volcanic  formations  of  Auvergne,  where  the 
quadrupeds  hitherto  discovered  belong  either  to  the  older  or  newer 
Pliocene  periods. 

The  total  number  of  mammalia  enumerated  by  M.  Pomel  as  apper- 
taining to  the  Lower  Miocene  fauna  of  the  Limagne  and  Velay,  falls 
little  short  of  a  hundred,  and  with  them  are  associated  some  large 
crocodiles  and  tortoises,  and  some  Ophidian  and  Batrachian  reptiles. 

Cantal. — A  freshwater  formation  already  alluded  to,  of  about  the 
same  age  and  very  analogous  to  that  of  Auvergne,  is  situated  in  the 
Department  of  Haute  Loire,  near  the  town  of  Le  Puy,  in  Velay  ;  and 
another  occurs  near  Aurillac,  in  Cantal.  The  leading  feature  of  the 
formation  last  mentioned,  as  distinguished  from  those  of  Auvergne 
and  Velay,  is  the  immense  abundance  of  silex  associated  with  calcare- 
ous marls  and  limestone. 

The  whole  series  may  be  separated  into  two  divisions ;  the  lower,  com- 
posed of  gravel,  sand,  and  clay,  such  as  might  have  been  derived  from 


230  LOWER  MIOCENE  STRATA— CANTAL.  [Cn.  XIV. 

the  wearing  down  and  decomposition  of  the  granitic  schists  of  the 
surrounding  country  ;  the  upper  system,  consisting  of  siliceous  and  calca- 
reous marls,  contains  subordinately  gypsum,  silex,  and  limestone. 

The  resemblance  of  the  freshwater  limestone  of  the  Cantal,  and  its 
accompanying  flint,  to  the  upper  chalk  of  England,  is  very  instructive, 
and  well  calculated  to  put  the  student  upon  his  guard  against  rely- 
ing too  implicitly  on  mineral  character  alone  as  a  safe  criterion  of  rela- 
tive age. 

When  we  approach  Aurillac  from  the  west,  we  pass  over  great  heathy 
plains,  where  the  sterile  mica-schist  is  barely  covered  with  vegetation. 
Near  Ytrac,  and  between  La-Capelle  and  Viscamp,  the  surface  is  strewed 
over  with  loose  broken  flints,  some  of  them  black  in  the  interior,  but 
with  a  white  external  coating ;  others  stained  with  tints  of  yellow  and 
red,  and  in  appearance  precisely  like  the  flint  gravel  of  our  chalk  districts. 
When  heaps  of  this  gravel  have  thus  announced  our  approach  to  a  new 
formation,  we  arrive  at  length  at  the  escarpment  of  the  lacustrine  beds. 
At  the  bottom  of  the  hill  which  rises  before  us,  we  see  strata  of  clay 
and  sand,  resting  on  mica-schist ;  and  above,  in  the  quarries  of  Belbet, 
Leybros,  and  Bruel,  a  white  limestone,  in  horizontal  strata,  the  surface  ol 
which  has  been  hollowed  out  into  irregular  furrows,  since  filled  up  with 
broken  flint,  marl,  and  dark  vegetable  mould.  In  these  cavities  we  recog- 
nize an  exact  counterpart  to  those  which  are  so  numerous  on  the  fur- 
rowed surface  of  our  own  white  chalk.  Advancing  from  these  quarries 
along  a  road  made  of  the  white  limestone,  which  reflects  as  glaring  a  light 
in  the  sun  as  do  our  roads  composed  of  chalk,  we  reach,  at  length,  in 
the  neighborhood  of  Aurillac,  hills  of  limestone  and  calcareous  marl,  in 
horizontal  strata,  separated  in  some  places  by  regular  layers  of  flint  in 
nodules,  the  coating  of  each  nodule  being  of  an  opaque  white  color,  like 
the  exterior  of  the  flinty  nodules  of  our  chalk. 

.  The  abundant  supply  both  of  siliceous,  calcareous,  and  gypseous  mat- 
ter, which  the  ancient  lakes  of  France  received,  may  have  been  connected 
with  the  subterranean  volcanic  agency  of  which  those  regions  were  so 
long  the  theatre,  and  which  may  have  impregnated  the  springs  with  min- 
eral matter,  even  before  the  great  outbreak  of  lava.  It  is  well  known  that 
the  hot  springs  of  Iceland,  and  many  other  countries,  contain  silex  in  solu- 
tion ;  and  it  has  been  lately  affirmed,  that  steam  at  a  high  temperature  is 
capable  of  dissolving  quartzose  rocks  without  the  aid  of  any  alkaline  or 
other  flux.*  Warm  water  charged  with  siliceous  matter  would  immedi- 
ately part  with  a  portion  of  its  silex,  if  its  temperature  was  lowered  by 
mixing  with  the  cooler  waters  of  a  lake. 

A  hasty  observation  of  the  white  limestone  and  flint  of  Aurillac  might 
convey  the  idea  that  the  rock  was  of  the  same  age  as  the  white  chalk  of 
Europe ;  but  when  we  turn  from  the  mineral  aspect  and  composition  to 
the  organic  remains,  we  find  in  the  flints  of  the  Cantal  seed-vessels  of  the 
freshwater  Chara,  instead  of  the  marine  zoophytes  so  abundant  in  chalk 

*  See  Proceedings  of  Royal  Soc.,  No.  44,  p.  288. 


CH.  XIV.]  SLOWNESS  OF  DEPOSITION.  231 

flints  ;  and  in  the  limestone  we  meet  with  shells  of  Limnea,  PlanorUx, 
and  other  lacustrine  genera. 

Proofs  of  gradual  deposition. — Some  sections  of  the  foliated  marls  in 
the  valley  of  the  Cer,  near  Aurillac,  attest,  in  the  most  unequivocal  man- 
ner, the  extreme  slowness  with  which  the  materials  of  the  lacustrine  series 
were  amassed.  In  the  hill  of  Barrat,  for  example,  we  find  an  assemblage 
of  calcareous  and  siliceous  marls ;  in  which,  for  a  depth  of  at  least  60 
feet,  the  layers  are  so  thin,  that  thirty  are  sometimes  contained  in  the 
thickness  of  an  inch  ;  and  when  they  are  separated,  we  see  preserved  in 
every  one  of  them  the  flattened  stems  of  Charce,  or  other  plants,  or  some- 
times myriads  of  small  Paludince  and  other  freshwater  shells.  These 
minute  foliations  of  the  marl  resemble  precisely  some  of  the  recent  lamina- 
ted beds  of  the  Scotch  marl  lakes,  and  may  be  compared  to  the  pages  of 
a  book,  each  containing  a  history  of  a  certain  period  of  the  past.  The 
different  layers  may  be  grouped  together  in  beds  from  a  foot  to  a  foot 
and  a  half  in  thickness,  which  are  distinguished  by  differences  of  composi- 
tion and  color,  the  tints  being  white,  green,  and  brown.  Occasionally 
there  is  a  parting  layer  of  pure  flint,  or  of  black  carbonaceous  vegetable 
matter,  about  an  inch  thick,  or  of  white  pulverulent  marl.  We  find  sev- 
eral hills  in  the  neighborhood  of  Aurillac  composed  of  such  materials,  for 
the  height  of  more  than  200  feet  from  their  base,  the  whole  sometimes 
covered  by  rocky  currents  of  trachytic  or  basaltic  lava.* 

Thus  wonderfully  minute  are  the  separate  parts  of  which  some  of  the 
most  massive  geological  monuments  are  made  up  !  When  we  desire  to 
classify,  it  is  necessary  to  contemplate  entire  groups  of  strata  in  the  aggre- 
gate ;  but  if  we  wish  to  understand  the  mode  of  their  formation,  and  to 
explain  their  origin,  we  must  think  only  of  the  minute  subdivisions  of 
which  each  mass  is  composed.  We  must  bear  in  mind  how  many  thin 
leaf-like  seams  of  matter,  each  containing  the  remains  of  myriads  of  tes- 
tacea  and  plants,  frequently  enter  into  the  composition  of  a  single  stratum, 
and  how  vast  a  succession  of  these  strata  unite  to  form  a  single  group ! 
We  must  remember,  also,  that  piles  of  volcanic  matter,  like  the  Plomb 
du  Cantal,  which  rises  in  the  immediate  neighborhood  of  Aurillac,  are 
themselves  equally  the  result  of  successive  accumulation,  consisting  of 
reiterated  sheets  of  lava,  showers  of  scoriae,  and  ejected  fragments  of 
rock. — Lastly,  we  must  not  forget  that  continents  and  mountain-chains, 
colossal  as  are  their  dimensions,  are  nothing  more  than  an  assemblage  of 
many  such  igneous  and  aqueous  groups,  formed  in  succession  during  an 
indefinite  lapse  of  ages,  and  superimposed  upon  each  other. 

Miocene  strata  of  Bordeaux  and  South  of  France. — A  great  extent 
of  country  between  the  Pyrenees  and  the  Gironde  is  overspread  by 
tertiary  deposits  of  various  ages  and  chiefly  of  Miocene  date.  M. 
Tournouer,  in  an  able  memoir  on  these  formations,!  has  shown  that 

*  Lyell  and  Murchison,  Sur  les  Depots  Lacustres  Tertiaires  du  Cantal,  &c.  Ann. 
des  Sci.  Nat.,  Oct.  1829. 

f  Bulletin  Soc.  Geol.  de  France,  tome  xviii.,  1861-'2,  p.  1035. 


232  MIOCENE  OF  BORDEAUX.  [Cn.  XIV. 

there  is  a  remarkable  continuity  in  the  succession  of  strata,  the  upper- 
most being  somewhat  newer  than  the  faluns  of  Touraine  and  the  low- 
est somewhat  older  than  the  Fontainebleau  sandstone  already  alluded 
to.  In  the  highest  group,  that  of  Salles,  in  which  Valuta  Lamberti 
and  Cardita  Jouanneti  occur,  there  are  many  fossils  common  to  the 
Pliocene  or  Subapennine  strata.  Next  below  these  are  the  faluns 
proper  of  Bordeaux,  which  include  the  faluns  of  Saucata,  and  Leognan 
and  those  of  Dax  in  the  adjoining  basin  of  the  Adour.  These  forma- 
tions, which  contain  among  other  shells  Pecten  Burdigalensis  and 
Ancillaria  glandiformis,  coincide  in  age  with  the  faluns  of  Touraine  ; 
but  so  many  of  the  species  are  peculiar  to  the  south  as  to  imply  that 
there  was  a  separation  by  a  considerable  tract  of  land  between  the 
basins  of  the  Loire  and  Gironde. 

Strata  which  may  be  referred  to  the  Lower  Miocene  come  next  in 
the  descending  order,  comprising  those  of  Merignac  and  Bazas,  the 
first  blackish  and  the  latter  of  marine  origin.  In  this  fluvio-marine 
series,  Cerithium  plicatum  (fig.  173,  p.  240),  C.  margaritaceum,  C. 
Brongniarti,  &c.,  and  in  the  marine  beds  Pyrula  Lainei  occur.  The 
greater  part  of  this  series  is  considered  by  M.  Tournouer  to  correspond 
in  age  with  the  freshwater  limestone  of  La  Beauce  in  the  basins  of  the 
Loire  and  Seine. 

Still  lower  is  the  Asterias  limestone,  which  with  its  overlying  marls 
is  about  300  feet  in  thickness,  in  which  Cerithium  plicatum  and  C. 
margaritaceum  are  again  met  with,  together  with  Natica  crassatina 
and  other  shells  characteristic  of  the  Etampes  and  Fontainebleau  sands 
before  mentioned.  In  these  lower  strata  are  many  species  common  to 
the  Parisian  Eocene  system,  to  the  Calcaire  Grossier  for  example,  and 
even  beds  still  lower.  There  are  also  several  species  of  nummulites  in 
the  Asterias  limestone,  and  their  presence  marks  a  difference  in  the 
character  of  the  Lower  Miocene  of  the  South  of  Europe,  as  con- 
trasted with  that  of  the  North.  These  and  other  indications  of  a 
passage  from  an  older  to  a  newer  group,  is  just  what  we  might  expect 
in  proportion  as  our  series  of  monuments  begins  to  be  more  and 
more  complete.  According  to  M.  Tournouer,  the  Lower  Miocene 
shells  identifiable  with  Eocene  species  are  always  varieties  of  the 
same — an  important  fact  as  bearing  on  theories  of  the  origin  of 
species.  Below  the  whole  of  these  formations  lies  a  true  Eocene  lime- 
stone called  the  Calcaire  de  Blaye,  of  the  age  of  the  Calcaire  Grossier 
of  the  Paris  basin.  In  order  to  explain  the  succession  of  beds  in  the 
basin  of  the  Gironde,  several  oscillations  of  level  are  necessary. 
The  same  wide  area  was  alternately  converted  into  sea  and  land  and 
into  brackish-water  lagoons,  and  finally  into  freshwater  ponds  and 
lakes. 

Upper  Miocene  strata  'of  Gers. — Among  the  freshwater  strata  last 
alluded  to  near  the  base  of  the  Pyrenees,  are  many  of  Upper  Miocene 
age,  from  which  bones  of  the  Dinotherium  giganteum  and  entire  skel- 
etons of  the  Mastodon  angustidens  have  been  obtained  by  M.  Lartet. 


CH.  XIV.]  UPPER  MIOCENE  STRATA  OF  GERS.  233 

In  one  of  these  deposits  that  eminent  comparative  anatomist  discov- 
ered, in  1837,  the  first  remains  of  quadrumana  which  had  been  de- 
tected in  Europe.  They  were  associated  with  the  quadrupeds  above 
mentioned  in  beds  of  freshwater  marl,  limestone,  and  sand  near  Auch, 
in  the  Department  of  Gers,  about  forty  miles  west  of  Toulouse.  They 
were  referred  by  MM.  Lartet  and  Blainville  to  a  genus  closely  allied  to 
the  Gibbon,  to  which  they  gave  the  name  of  Pliopithecus.  More  recently 
(1856)  M.  Lartet  described  another  species  of  the  same  family  of  long- 
armed  apes  (Hylobates),  which  he  obtained  from  strata  of  the  same 
age  at  Saint-Gauclens,  in  the  Haute  Garonne.  The  fossil  remains  of 
this  animal  consists  of  a  portion  of  a  lower  jaw  with  teeth  and  the 
shaft  of  a  humerus.  It  is  supposed  to  have  been  a  tree-climbing  fru- 
givorous  ape,  equalling  Man  in  stature.  As  the  trunks  of  oaks  are 
common  in  the  lignite  beds  in  which  it  lay,  it  has  received  the  generic 
name  of  Dryopiihecus.  The  angle  formed  by  the  ascending  ramus 
of  the  jaw  and  the  alveolar  border  is  less  open,  and  therefore  more  like 
the  human  subject  than  in  the  Chimpanzee,  and,  what  is  still  more 
remarkable,  the  fossil,  a  young  but  adult  individual,  had  all  its  milk 
teeth  replaced  by  the  second  set,  while  its  last  true  molar  (or  wisdom 
tooth)  was  still  undeveloped,  or  only  existed  as  a  germ  in  the  jaw-bone. 
In  the  mode,  therefore,  of  the  succession  of  its  teeth  (which,  as  in  all 
the  Old  World  apes,  exactly  agree  in  number  with  those  in  Man)  it 
differed  from  the  Gorilla  and  Chimpanzee  and  corresponded  with  the 
human  species. 

This  peculiarity  in  its  dentition,  however,  it  shared,  as  M.  Lartet 
reminds  us,  with  one  of  the  living  Gibbons  called  the  Siamang.  It  is 
only  one  of  several  characters,  such  as  the  more  globular  form  of  the 
cranium  and  the  smaller  size  of  the  canine  teeth  of  the  lower  jaw,  in 
which  the  Gibbons  approach  Man  in  their  structure  more  nearly  than 
do  any  other  of  the  tailless  apes.  There  is  an  analogy  between  such 
points  of  agreement  and  the  fact  that  man  and  the  Orang  (Pithecus) 
have  each  twelve  pair  of  ribs,  whereas  the  Gorilla  and  Chimpanzee 
(Troglodytes),  notwithstanding  that  in  the  aggregate  of  their  charac- 
ters they  approach  nearer  to  the  human  type  than  the  Orang,  have 
each  thirteen  pair.  A  still  more  curious  analogy  is  afforded  by  some 
of  the  platyrrhine  monkeys  of  South  America,  which,  although  they 
differ  from  all  the  Old  World  quadrumana  and  from  Man  in  having 
four  supernumerary  molars,  yet  are  not  only  less  prognathous  than  the 
catarrhine  monkeys,  but  have  the  cerebellum  more  decidedly  overlapped 
by  the  posterior  lobe  of  the  cerebrum  than  the  Old  World  apes.  Yet 
the  brains  of  the  latter  are,  on  the  whole,  much  more  akin  to  the 
human  in  their  anatomical  structure. 

BELGIAN    AND    BRITISH    MIOCENE    FORMATIONS. 

Upper  Miocene  near  Antwerp. — Edeghem  beds. — The  black  or  Glau- 
coniferous  Crag  of  Antwerp  was  mentioned  at  page  208  as  bearing  a 


234  BELGIAN  AND  BRITISH  MIOCENE.  [On.  XIV. 

considerable  affinity  to  that  of  Suffolk,  about  two-thirds  of  the  65 
shells  obtained  from  it  being  common  to  the  Suffolk  Coralline  Crag, 
and  somewhat  less  than  half  of  the  whole  being  of  living  species. 

About  the  year  1862,  an  important  discovery  was  made  at  Edeghem, 
in  the  environs  of  Antwerp,  of  another  deposit  somewhat  older  than 
the  Black  Crag.  In  excavating  for  brick  earth,  they  came  upon  a  bed 
of  argillaceous  sand,  in  which  no  less  than  152  fossils  were  found,  com- 
prising 145  mollusca  and  echinoderms,  and  some  zoophytes,  especially 
a  large  species  of  Flabellum.  All  these  have  been  examined  and  tabu- 
lated by  M.  Nyst,  and  carefully  compared  with  the  fossils  of  other  Miocene 
and  Pliocene  deposits  of  Europe.*  These  Edeghem  beds,  which  re- 
pose on  Lower  Miocene  clay,  the  "  Rupelian  "  of  Dumont,  are  most 
nearly  related  by  their  fossils  to  the  Black  Crag  above  alluded  to,  but 
they  betray  many  indications  of  greater  antiquity.  Fifty-eight  of  the 
species  are  new  to  the  Belgian  tertiaries,  and  of  these  14  only,  or 
about  25  per  cent.,  are  recent.  Of  the  whole  145  Edeghem  shells,  52 
are  considered  by  Nyst  as  living  species,  besides  5  others,  which  are 
probably  identical  with  the  living,  making,  if  all  are  accepted,  a  pro- 
portion of  39  per  cent.,  which  is  decidedly  smaller  than  that  observed 
in  the  Antwerp  Black  Crag  (see  above,  p.  208).  A  still  more  signifi- 
cant indication  of  the  connection  of  the  Edeghem  sands  with  an  older 
or  Miocene  period  is  afforded,  first,  by  the  fact  that  no  less  than  83  of 
the  145  mollusca  are  falunian,  as  shown  by  M.  Nyst's  tables,  or,  in 
other  words,  a  proportion  of  J56j:)er  cent,  are  specifically  identical  with 
shells  occuring  in  the  Upper  Miocene  beds  of  North  Germany,  Tour- 
aine,  the  Vienna  basin,  the  Bordeaux  faluns,  and  other  localities  un- 
questionably of  Upper  Miocene  date  ;  secondly,  what  is  perhaps  even 
more  in  favor  of  their  antiquity,  there  occur  in  them  shells  of  the 
genera  Conus,  Ancillaria,  and  Olivet,  all  of  which  are  not  only  want- 
ing in  the  Red  and  Coralline  Crag  of  Suffolk,  and  in  the  Upper  and 
Middle  Crags  of  Antwerp,  but  are  also  absent  from  the  lowest  or  Black 
Crag  of  Antwerp.  These  same  genera  are  also  met  with  in  the  strata 
of  the  Bolderberg  in  Belgium,  a  true  Upper  Miocene  formation,  the 
fauna  of  which  recedes  still  farther  from  that  now  existing  in  the  pro- 
portion of  its  shells  of  living  species. 

Upper  Miocene  (?)  of  Belgium  and  England. — Diest  Sands. — M. 
Nyst  is  of  opinion  that  the  formation  called  by  Dumont  the  Diestian 
is  of  the  same  age  as  the  sands  of  Edeghem — a  conclusion  which  is 
probably  well  founded.  These  ferruginous  sands  and  sandstones  of 
Diest  are  well  seen  near  the  town  of  that  name,  about  thirty  miles 
north-east  of  Brussels.  They  abound  in  green  grains,  resembling  in 
mineral  character  the  ferruginous  beds  of  the  Lower  Greensand  in  the 
south-east  of  England.  The  strata  contain  but  a  small  number  of 
fossils,  the  Terebratula  grandis  being  one  of  the  few  which  are  well 
preserved.  The  Diest  sands  are  conspicuous  as  forming  the  cappings 

*  Nyst,  Bulletin  Acad.  Roy.,  Bruselles,  1862. 


CH.  XIV.]  UPPER  MIOCENE   OF  BELGIUM.  235 

of  hills  stretching  from  Diest  by  Louvain  and  westward  by  Oudenarde 
to  Cassel  in  French  Flanders,  where  they  are  seen  at  the  summit  of  a 
hill  515  feet  high.  After  having  been  thus  traced  for  a  hundred 
miles  from  east  to  west,  they  are  again  seen  retaining  the  same  mineral 
character  for  another  hundred  miles  in  a  similar  westward  direction, 
first  capping  the  Downs  near  Folkestone,  and  then  appearing  at  vari- 
ous points,  such  as  Paddlesworth,  Lenham  near  Maidstone,  and  Vigo 
Hill  near  Otford  in  Kent. 

The  geological  position  of  these  iron  sands  in  England  was  first 
made  out  by  Mr.  Prestwich,  who,  in  a  paper  read  to  the  Geological 
Society  of  London  in  1857,  described  them  as  being  possibly  older 
than  the  Coralline  Crag,  and  as  occurring  on  the  summit  of  the  North 
Downs  at  various  points  between  Folkestone  and  Dorking.  He  men- 
tioned their  resemblance  to  the  sands  at  Diest  in  Belgium,  and  that 
they  contained  the  Terebratula  grandis,  and  casts  of  Astarte  pyrula, 
Emarginula,  and  other  fossils,  all  common  to  the  British  Crag.  After 
the  publication  of  Mr.  Prestwich's  paper,  I  visited  with  him  the  prin- 
cipal localities  in  Kent  to  which  he  had  called  attention,  and  saw  the 
ferruginous  sands,  twenty  feet  thick,  resting  on  the  chalk  near  the  edge 
of  the  escarpment,  about  a  mile  N.E.  of  Folkestone,  and  again  at  Pad- 
dlesworth, on  the  summit  of  the  Downs,  four  miles  W.N.W.  of  Folke- 
stone, where  the  sands  are  about  forty  feet  thick,  and  where  they  occur 
at  an  elevation  of  about  500  feet  above  the  sea.  At  Lenham,  ten  miles 
east  of  Maidstone,  fragments  of  the  more  consolidated  ferruginous 
layers,  full  of  casts  of  marine  shells  and  other  fossils,  are  preserved  in 
vertical  sandpipes,  which  penetrate  the  white  chalk.  Here  I  saw  or- 
ganic remains,  reminding  me  of  those  which  I  had  seen  in  1850  at 
Kesseloo,  near  Louvain,  in  the  "  Diest  Sands,"  which  there  overlie  the 
Limburg  or  Lower  Miocene  beds.*  The  evidence,  both  in  Belgium 
and  in  Kent,  being  derived  from  casts,  consists  mainly  in  the  corre- 
spondence of  genera ;  but  some  of  the  species,  such  as  the  large  Tere- 
bratula and  a  Turbinolia,  seem  identical. 

We  cannot  determine  at  present,  in  consequence  of  the  dearth  of 
fossils  in  the  Diest  sands,  their  exact  relation  to  the  Edeghem  beds, 
or  whether  they  may  be  intermediate  between  the  Edeghem  and  Bol- 
derberg  strata,  but  we  may  at  least  affirm  that  the  only  British  strata 
at  present  known  which  can  have  any  claim  to  be  regarded  as  Upper 
Miocene  are  the  ferruginous  sands  of  the  North  Downs  here  alluded 
to. 

Upper  Miocene  of  the  Bolderberg  in  Belgium. — In  a  small  hill  or 
ridge  called  the  Bolderberg,  which  I  visited  in  1851,  situated  near 
Hasselt,  about  forty  miles  E.N.E.  of  Brussels,  strata  of  sand  and  gravel 
occur,  to  which  M.  Dumont  first  called  attention  as  appearing  to  con- 
stitute a  northern  representative  of  the  faluns  of  Touraine.  On  the 
whole  they  are  very  distinct  in  their  fossils  from  the  two  upper  divis- 

*  See  a  Memoir  by  V.  Raulin,  1848  :  Bordeaux. 


236  MIOCENE  STRATA  OF  BELGIUM.  [Cn.  XIV. 

ions  of  the  Antwerp  Crag  before  mentioned,  and  contain  shells  of 
the  genera  Oliva,  Conus,  Ancillaria,  Pleuro- 
toma,  and  Cancellaria  in  abundance.  The  most 
common  shell  is  an  Olive  (see  fig.  169),  called 
by  Nyst  Oliva  Dufresnii,  Bast. ;  and  consti- 
tuting, as  M.  Bosquet  observes,  a  smaller  and 
shorter  variety  of  the  Bordeaux  species.* 

The   Upper  Miocene  strata  in   the   Bolder- 
berg   occur  at   the  height  of  about  200   feet 
Dufresnu,  Bast    above  the  level  of  the  sea.     They  are  covered 
Boiderberg,    Belgium,    by   the    Diestian    sands   and    iron    sandstone 

nat.   size.        a.    Front        ~        .        .          MI  in 

view;  &,  back  view.      already  described,  and  they  repose  on  Lower 

Miocene  beds  called  Rupelian  by  Dumont.     So 

far  as  the  shells  are  known,  the  proportion  of  recent  species  agrees 

with  that  in  the  faluns  of  Touraine,  and  the  climate  must  have  been 

warmer  than  that  of  the  Coralline  Crag  of  England. 

In  none  of  the  Belgium  Lower  Miocene  strata  could  I  find  any 
nummulites ;  and  M.  d'Archiac  had  previously  observed  that  these 
foraminifera  characterize  his  "  Lower  Tertiary  Series,"  as  contrasted 
with  the  Middle,  and  may  therefore  serve  as  a  good  test  of  age  in  the 
North  of  Europe  at  least,  between  Eocene  and  Miocene.  The  same 
naturalist  informs  us  that  one  nummulite  only  has  ever  yet  been  seen 
to  penetrate  upwards  into  the  middle  tertiary,  viz.,  Nummulites  inter- 
media, an  Eocene  species.  It  has  been  found  in  the  hill  of  the  Su- 
perga,  near  Turin,  in  Miocene  beds,  somewhat  older  than  the  falunian 
type  (see  above  p.  107). 

North  Germany. — We  learn  from  the  able  treatise  published  by  M. 
Beyrich,  in  1853,  that  the  same  fossil  fauna,  which  is  so  meagrely  ex- 
hibited in  the  Boiderberg,  is  rich  in  species  in  other  localities  in  North 
Germany,  as  in  Mecklenburg,  Luneburg,  the  Island  Sylt,  and  at  Bersen- 
briick,  north  of  Osnabruck,  in  Westphalia,  where  it  was  first  observed 
by  F.  Romer.f 

Lower  Miocene,  Belgium. — It  was  stated  that  the^jgolderberg  beds 
rests  on  the  Rupelian  of  Dumont,  a  Lower  Miocene  formation  best 
seen  at" the  villages  of  Rupelmonde  and  Boom,  ten  miles  south  of  Ant- 
werp, on  the  banks  of  the  Scheldt  and  near  the  junction  with  it  of  a 
small  stream  called  the  Rupel.  A  stiff  clay  abounding  in  fossils  is  ex- 
tensively worked  at  the  above  localities  for  making  tiles.  It  attains  a 
thickness  of  about  100  feet,  and,  though  very  different  in  age,  much 
resembles  in  mineral  character  the  "  London  Clay,"  containing,  like  it, 
septaria  or  concretions  of  argillaceous  limestone  traversed  by  cracks 
in  the  interior,  which  are  filled  with  calc-spar.  The  shells,  referable 
to  about  forty  species,  have  been  described  by  MM.  Nyst  and  De 

*  Lyell  on  Belgian  Tertiaries,  Quart%  Geol.  Journ.,  1852,  p.  295.  Nyst's  figure 
seems  to  be  copied  from  that  given  by  Basterot  of  the  Bordeaux  fossil. 

f  Beyrich,  Die  Conchylien  der  Norddeutschen  Tertiargebirge  :  Berlin,  1853. 


CH.  XIV.]  MIOCENE  STRATA  OF  BELGIUM.  237 

Koninck.      Among  them  Leda  (or  Nucula)  Deshayesiana  (see  fig. 
170)  is  by  far  the  most  abundant;    a  fossil  unknown  as  yet  in  the 

Fig.  170. 


Leda  Deshayesiana.    Nyst    Syn.  Nucula  Deshayesiana. 

English  tertiary  strata,  but  when  young  resembling  Leda  amygdaloides 
of  the  London  clay  proper  (see  fig.  256  p.  294).  Among  other  char- 
acteristic shells  are  Pecten  Hoeninghausii,  and  a  species  of  Cassidaria, 
and  several  of  the  genus  Pleurotoma.  Not  a  few  of  these  testacea 
agree  with  English  Eocene  species,  such  as  Actceon  simulatus,  Sow., 
Cancellaria  evulsa,  Brander,  Cprbula,  pisum  (fig.  lYl),  and  Nautilus 
(Aturia)  ziczac.  They  are  accompanied  by  many  teeth  of  sharks,  as 
Lamna  contortidens,  Ag.,  Oxyrhina  xiphodon,  Ag.,  Charcharodon  hetero- 
don  (see  fig.  240),  Ag.,  and  other  fish,  some  of  them  common  to  the 
Middle  Eocene  strata. 

Rupelian  Clay  of  Hermsdorf  near  Berlin. — Professor  Beyrich  has 
described  a  mass  of  clay,  used  for  making  tiles,  within  seven  miles  of  „ 
the  gates  of  Berlin,  near  the  village  of  Herrasdorf,  rising  up  from 
beneath  the  sands  with  which  that  country  is  chiefly  overspread.  This 
clay  is  more  than  forty  feet  thick,  of  a  dark  bluish-grey  color,  and, 
like  that  of  Rupelmonde,  contains  septaria.  Among  other  shells,  the 
Leda  Deshayesiana  before  mentioned  (fig.  170)  abounds,  together 
with  many  species  of  Pleurotoma,  Voluta,  &c.,  a  certain  proportion 
of  the  fossils  being  identical  in  species  with  those  of  Rupelmonde. 
The  succession  of  the  Lower  Miocene  strata  of  Belgium  can  be  best 
studied  in  the  environs  of  Kleyn  Spawen,  a  village  situated  about 
seven  miles  west  of  Maestricht,  in  the  old  province  of  Limburg  in 
Belgium.  In  that  region,  about  200  species  of  testacea,  marine  and 
freshwater,  have  been  obtained,  with  many  foraminifera  and  remains 
of  fish. 

The  following  table  will  show  the  position  of  these  Belgian  or  Lim- 
burg beds : — 

UPPER  MIOCENE. 
A.   Bolderberg  beds,  see  p.  235,  seen  near  Hasselt. 

LOWER  MTOCENE. 

B.  1.   Nucula  Loam  of  Kleyn  Spawen,  same  J  Li  beds._Rupelian  of 

age    as   the    clay  of   Rupelmonde  V     p^^ 

and  Boom. 
B.  2.   Fluvio-marine  beds  of  Bergh,  Lethen,  )  Middle  Limburg  beds.— Upper  T 

and  other  places  near  Kleyn  Spawen.  J      grian  of  Dumont. 


238  LOWER   MIOCENE  OF  BELGIUM.  [Cn.  XIV. 

B.  3.   Marine  green  sand  of  Bergb,  Neere-  )  T 

,  m  '      ,         /  Lower  Limburg  beds.  —  Lower  Ton- 

pen,  &c.,  and  Tongres,  near  Kleyn  >•         .        f        ' 
Spawen.  )      gnan  of  Dumont. 


UPPER  EOCENE. 

C.  Calcareous  sandy  beds  of  Laeken,  near  Brussels,  with  nummulites,  &c.,  of 
same  age  as  the  "  Sables  Moyens  "  of  the  Paris  basin  and  the  Barton  clay 
of  Hampshire. 

The  uppermost  of  the  three  subdivisions  (B.  1)  into  which  the 
Lower  Miocene  or  Limburg  series  is  separated  in  the  above  table,  con- 
tains at  Kleyn  Spawen  many  of  the  same  fossils  as  the  clay,  above 
mentioned,  of  Rupelmonde  and  Boom,  places  sixty  miles  N.W.  of 
Kleyn  Spawen. 

The  lower,  or  Tongrian  divisions,  B.  2  and  B.  3,  are  much  better 
developed  at  Kleyn  Spawen  than  B.  1.  The  first  of  these,  B.  2,  con- 
sists of  several  alternations  of  sand  and  marls,  in  which  a  greater  or 
less  intermixture  of  fluviatile  and  marine  shells  occurs,  implying  the 
occasional  entrance  of  a  river  near  the  spot,  and  possibly  oscillations 
in  the  level  of  the  bottom  of  the  sea.  Among  the  shells  are  found 
Cyrena  semistriata  (fig.  172),  Cerithium  plicatum,  Lam.,  (fig.  173) 
Rissoa  Chastelii,  Bosq.  (fig.  175),  and  Corbula  pisum  (fig.  171),  four 
shells  all  common  to  the  Hempstead  or  British  Lower  Miocene  beds 
of  the  Isle  of  Wight,  to  be  mentioned  in  the  sequel.  With  the  above, 
Lucina  Thierensii,  and  other  marine  forms  of  the  genera  Venus, 
Limopsis,  Trochus,  &c.,  are  met  with. 

In  B.  3,  or  the  Lower  Tongrian,  more  than  100  marine,  shells  have 
been  collected,  among  which  the  Ostrea  vcntilabrum  is  very  conspi- 
cuous. Species  common  to  the  underlying  Brussels  sands,  or  the 
Upper  Eocene,  are  numerous,  constituting  a  third  of  the  whole  ;  but 
most  of  these  are  feebly  represented  in  comparison  with  the  more 
peculiar  and  characteristic  shells,  such  as  Ostrea  ventilabrum  Mytilus 
Nystii,  Valuta  suturalis,  &c. 

Whether  this  Lower  Tongrian  should  be  classed  as  the  lowest 
member  of  the  Miocene  series,  or  as  the  uppermost  of  the  Eocene, 
or,  in  other  words,  as  the  marine  equivalent  of  the  freshwater  gypsum 
of  Paris,  is  a  question  not  yet  decided.  I  incline  at  present  to  the 
belief  that  it  is  somewhat  newer  than  the  Paris  gypsum,  but  certainly 
near  the  boundary  line  which  separates  the  two  systems.  Its  relation 
to  the  Upper  Eocene  deposits  of  England  or  the  Isle  of  Wight  will  be 
more  fully  discussed  in  the  sixteenth  chapter,  p.  281. 

In  none  of  the  Belgian  Lower  Miocene  strata  could  I  find  any 
nummulites  ;  and  M.  d'Archiac  had  previously  observed  that  these 
foraminifera  characterized  his  "  Lower  Tertiary  Series,"  as  contrasted 
with  the  Middle,  and  they  therefore  served  as  a  good  test  of  age  be- 
tween Eocene  and  Miocene,  at  least  in  Belgium  and  the  North  of 
France.* 

*  D'Archiac,  Monogr.,  pp.  79,  100. 


CH.  XIV]  LOWER  MIOCENE,   ISLE  OF  WIGHT.  239 

Between  the  Bolderberg  beds  and  the  Rupelian  clay  there  is  a  great 
chasm  in  Belgium,  which  seems,  according  to  M.  Beyrich,  to  be  filled 
up  in  the  North  of  Germany  by  what  he  calls  the  Sternberg  beds,  and 
which,  had  Dumont  found  them  in  Belgium,  he  might  probably  have 
termed  Upper  Eupelian. 


LOWER    MIOCENE    STRATA    OF    ENGLAND. 

Hempstead  beds,  Isle  of  Wight. — We  have  already  seen  that  the 
Upper  Miocene  period  is  meagrely  and  somewhat  questionably  repre- 
sented in  England  by  certain  ferruginous  sands  on  the  North  Downs, 
of  the  age  of  the  Diestian  beds  of  Belgium.  The  Lower  Miocene 
period  is  more  decidedly  represented  by  certain  strata  in  the  Isle  of 
Wight,  the  true  age  of  which  was  not  recognized  until  the  year  1852, 
when  the  late  Edward  Forbes  observed  *  that  there  was  a  series  of  ter- 
tiary strata  near  Yarmouth  newer  than  those  of  Binstead  and  Bern- 
bridge.  These  last  are  the  undoubted  equivalants  of  the  Paris  gypsum, 

being  characterized  by  the  same  species  of  Paleotherium  Anoplo-  . 
therium,  &c.,  as  those  described  by  Cuvier  from  Montmartre.  The 
Lower  Miocene  deposits  alluded  to  are  170  feet  in  thickness  and  rich 
in  fossils,  and  have  been  called  the  Hempstead  series,  from  a  hill  of 
that  name  on  the  coast  near  Yarmouth.-)-  The  following  is  the  succes- 
sion of  the  strata : — 

SUBDIVISIONS   OP   THE   HEMPSTEAD    SERIES. 

1.  The  uppermost  or  Corbula  beds,  consisting  of  marine  sands  and  clays,  contain 
Voluta  JRatkieri,  a  characteristic  Lower  Miocene  shell,  Corbula,  pisum,  fig.  171, 
a  species  common  to  the  Upper  Eocene  clay  of  Barton ;  Cyrena  semistriata,  fig. 
172,  several  Cerithia,  and  other  shells  peculiar  to  this  series. 

Fig.  171.  Tig.  172. 


Corbula  pisum.    Hempstead  Beds,  Cyrena  semistriata. 

Isle  of  Wight.  .Hempstead  Beds. 

2.  Next  below  are  freshwater  and  estuary  marls  and  carbonaceous  clays,  in  the 
brackish-water  portion  of  which  are  found  abundantly  Cerithium  plicatum, 
fig.  173,  C.  elegans,  fig.  174,  and  O.  tricinctum  ;  also  Rissoa  Chastelii,  fig. 
a  very  common  Kleyn  Spawen  shell,  and  which  occurs  in  each  of  the  four  sub- 
divisions of  the  Hempstead  series  down  to  its  base,  where  it  passes  into  the 
Bembridge  beds.  In  the  freshwater  portion  of  the  same  beds  Paludina  lento, 

*  E.  Forbes,  Geol.  Quart.  Journ.,  1853. 

f  This  hill  must  not  be  confounded  with  Hampstead  Hill,  near  London,  where 
the  Lower  Eocene  or  London  Clay  is  capped  by  Middle  Eocene  sands. 


240  LOWER  MIOCENE,  ISLE  OF  WIGHT.  [On.  XIV. 

fig.  176,  occurs  a  shell  identified  by  some  conchologists  with  a  species  now  liv- 
ing, P.  unicolor  ;  also  several  species  of  Lymneus,  Planorbis,  and  Unio. 

3.  The  next  series,  or  middle  freshwater  and  estuary  marls,  are  distinguished  by 
the  presence  of  Melania  fasciata,  Paludina  lenta,  and  clays  with  Cypris  ;  the  I/ 
lowest  bed  contains  Cyrena  semistriata,  fig.  172,  mingled  with  Cerithia  and  a 
Ponopcea. 

4.  The  lower  freshwater  and  estuary  marls  contain  Melania  costata,  Sow.,  Melanop- 
sis,  &c.    The  bottom  bed  is  carbonaceous,  and  called  the  "  Black  band,"  in  which 
Rissoa  Chastelii,  fig.  175,  before  alluded  to,  is  common.     This  bed  contains  a 

Fig.  173.  Fig.  174.  Fig.  175.  Fig.  176. 


Cerithium  plicatum,      CeritMum  elegans,      liissoa  Chastelii,  Nyst,          Paludina  lenta. 
Lam.  Hempstead.  Hempstead.  Sp.  Hempstead,  Isle          Hempstead  Bede. 

of  Wight. 

mixture  of  Hempstead  shells  with  those  of  the  underlying  Upper  Eocene  or  Bern- 
bridge  series.  The  mammalia,  among  which  is  Hyopolamus  bovinus,  differ,  so  far 
as  they  are  known,  from  those  of  the  Bembridge  beds.  Among  the  plants,  Pro- 
fessor Heer  has  recognized  four  species  common  to  the  lignite  of  Bovey  Tracey,  a 
Lower  Miocene  formation  presently  to  be  described :  namely,  Sequoia  Couttsice, 
Heer ;  Andromeda  reticulata,  Etting ;  Nymphcea  Doris,  Heer ;  and  Carpolithes 
Websteri,  Brong.*  The  seed-vessels  of  Ohara  medicaginula,  Brong.,  and  C. 
helecteres  are  characteristic  of  the  Hempstead  beds  generally. 

The  Hyopotamus  belongs  to  the  hog  tribe,  or  the  same  family  as 
the  Anthracotherium,  of  which  seven  species,  varying  in  size  from  the 
hippopotamus  to  the  wild  boar,  have  been  found  in  Italy  and  other 
parts  of  Europe  associated  with  the  lignites  of  the  Lower  Miocene 
period. 

Lignites  and  Clays  of  Bovey  Tracey,  Devonshire. — Surrounded  by  the 
granite  and  other  rocks  of  the  Dartmoor  hills  in  Devonshire,  is  a  for- 
mation of  clay,  sand,  and  lignite,  long  known  to  geologists  as  the 
Bovey  Coal  formation,  respecting  the  age  of  which,  until  the  year 
1861,  opinions  were  very  unsettled.  This  deposit  is  situated  at  Bovey 
Tracey,  a  village  distant  eleven  miles  from  Exeter  in  a  south-west,  and 
about  as  far  from  Torquay  in  a  north-west  direction.  The  strata  extend 
over  a  plain  nine  miles  long,  and  they  consist  of  the  materials  of  decom- 
posed and  worn-down  granite  and  vegetable  matter,  and  have  evident- 
ly filled  up  an  ancient  hollow  or  lake-like  expansion  of  the  valleys  of 
the  Bovey  and  Teign. 

*  Pengelly,  preface  to  The  Lignite  Formation  of  Bovey  Tracey,  p.  xvii. :  Lon- 
don, 1863. 


CH.  XIV.]  LIGNITES  OF  BOVEY  TRACEY.  241 

The  lignite  is  of  bad  quality  for  economical  purposes,  as  there  is 
a  great  admixture  in  it  of  iron  pyrites,  and  it  emits  a  sulphurous 
odour,  but  it  has  been  successfully  applied  to  the  baking  of  pottery, 
for  which  some  of  the  fine  clays  are  well  adapted.  Mr.  Pengelly  has 
confirmed  Sir  H.  De  la  Beche's  opinion  that  much  of  the  upper  por- 
tion of  this  old  lacustrine  formation  has  been  removed  by  denu- 
dation.* 

At  the  surface  is  a  dense  covering  of  clay  and  gravel  with  angular 
stones  probably  of  the  Post-pliocene  period,  for  in  the  clay  are  three 
species  of  willow  and  the  dwarf  birch,  Betula  nana,  indicating  a  cli- 
mate colder  than  that  of  Devonshire  at  the  present  day. 

Below  this  are  Lower  Miocene  strata  about  300  feet  in  thickness,  in 
the  upper  part  of  which  are  twenty-six  beds  of  lignite,  clay,  and  sand, 
at  their  base  a  ferruginous  quartzose  sand,  varying  in  thickness  from 
two  to  twenty-seven  feet.  Below  this  sand  are  forty-five  beds  of 
alternating  lignite  and  clay.  No  shells  or  bones  of  mammalia,  and 
no  insect  with  the  exception  of  one  fragment  of  a  beetle  (Buprestis) ; 
in  a  word,  no  organic  remains  except  plants  have  as  yet  been  found. 
These  plants  occur  in  fourteen  of  the  beds,  namely,  in  two  of  the 
clays,  and  the  rest  in  the  lignites.  One  of  the  beds  is  a  perfect  mat 
of  the  debris  of  a  coniferous  tree,  called  by  Heer  Sequoia  Couttsice, 
intermixed  with  leaves  of  ferns.  The  same  Sequoia  is  spread  through 
all  parts  of  the  formation,  its  cones,  and  seeds,  and  branches  of  every 
age  being  preserved.  It  is  a  species  supplying  a  link  between 
S.  Langsdorfii  (see  figs.  201,  202  p.  263)  and  8.  Sternbergi,  the 
widely-spread  fossil  representatives  of  the  two  living  trees  S.  sempervi- 
rens  and  S.  gigantea  (or  Wellingtonia),  both  confined  in  the  living 
creation  to  California.  Another  bed  is  full  of  the  large  rhizomes  of 
ferns,  while  two  others  are  rich  in  dicotyledonous  leaves.  In  all  Pro- 
fessor Heer  enumerates  forty-nine  species  of  plants,  twenty  of  which 
are  common  to  the  Miocene  bed  of  the  Continent,  a  majority  of  them 
being  characteristic  of  the  Lower  Miocene.  The  new  species,  also  of 
Bovey,  are  allied  to  plants  of  the  older  Miocene  deposits  of  Switzer- 
land, Germany,  and  other  continental  countries.  The  grape-stones  of 
two  species  of  vine  occur  in  the  clays,  and  the  leaves  of  three  species 
of  fig,  seeds  also  supposed  to  belong  to  three  new  species  of  Nyssa,  or 
Tupelo  tree,  a  genus  now  common  in  the  swamps  of  South  Carolina 
and  Florida,  two  species  of  Annona,  and  a  new  water-lily.  The  oak 
and  laurel  have  supplied  many  leaves.  Of  the  triple-nerved  laurel.' 
three  or  four  are  referred  to  Cinnamomum.  There  is  a  palm  also,  of 
which  the  genus  is  not  determined.  Among  the  ProteaceaB  are  men- 
tioned Dryandroides  HaJcecefolia  (fig.  198),  D.  Banlcsicefolia,  and 
another.  Among  the  ferns  is  the  well-known  continental  fossil  Las- 
trcea  stiriaca  (fig.  203,  p.  264),  displaying  at  Bovey  as  in  Switzerland 
its  fructification. 

*  Phil.  Trans.,  1863.     Paper  by  W.  Pengelly,  F.R.S.,  and  Dr.  Oswald  Heer. 
16 


242  LEAF-BEDS  OF  MULL  IN  SCOTLAND.  [On.  XIV. 

The  croziers  of  some  of  the  young  ferns  are  very  perfect,  and  were 
at  first  mistaken  by  collectors  for  shells  of  the  genus  Planorbis.  On 
the  whole,  the  vegetation  of  Bovey  implies  the  existence  in  Devonshire, 
in  the  Lower  Miocene  period,  of  a  sub-tropical  climate. 

Scotland. — Isle  of  Mull. — In  the  sea-cliffs  forming  the  headland  of 
Ardtun  on  the  west  coast  of  Mull,  in  the  Hebrides,  several  bands  of 
tertiary  strata  containing  leaves  of  dicotyledonous  plants  were  discov- 
ered in  1851  by  the  Duke  of  Argyle.*  From  his  description  it  ap- 
pears that  there  are  three  leaf-beds,  varying  in  thickness  from  1-J  to 
2  J  feet,  which  are  interstratified  with  volcanic  tuff  and  trap,  the  whole 
mass  being  about  130  feet  in  thickness.  A  sheet  of  basalt  40  feet 
thick  covers  the  whole  ;  and  another  columnar  bed  of  the  same  rock, 
10  feet  thick,  is  exposed  at  the  bottom  of  the  cliff.  One  of  the  leaf- 
beds  consists  of  a  compressed  mass  of  leaves  unaccompanied  by  any 
stems,  as  if  they  had  been  blown  into  a  marsh  where  a  species  of 
Equisetum  grew,  of  which  the  remains  are  plentifully  embedded  in 
clay. 

It  is  supposed  by  the  Duke  of  Argyle  that  this  formation  was  ac- 
cumulated in  a  shallow  lake  or  marsh  in  the  neighborhood  of  a  vol- 
cano, which  emitted  showers  of  ashes  and  streams  of  lava.  The 
tufaceous  envelope  of  the  fossils  may  have  fallen  into  the  lake  from  the 
air  as  volcanic  dust,  or  have  been  washed  down  into  it  as  mud  from 
the  adjoining  land.  Even  without  the  aid  of  organic  remains  we 
might  have  decided  that  the  deposit  was  newer  than  the  chalk,  for 
chalk  flints  containing  cretaceous  fossils  were  detected  by  the  Duke  in 
the  principal  mass  of  volcanic  ashes  or  tuff.f 

The  late  Edward  Forbes  observed  that  some  of  the  plants  of  this 
formation  resembled  those  of  Croatia,  described  by  linger,  and  his 
opinion  has  been  confirmed  by  Professor  Heer,  who  found  that  the 
conifer  most  prevalent  was  the  Sequoia  Langsdorfii  (figs.  201,  202), 
also  Corylus  grosse-dentata,  a  Lower  Miocene  species  of  Switzerland 
and  of  Menat  in  Auvergne.  There  is  likewise  a  plane  tree,  the  leaves 
of  which  seem  to  agree  with  those  of  Platanus  aceroides  (fig.  187,  p. 
254),  and  a  fern  which  is  as  yet  peculiar  to  Mull,  Filicites  hebridica, 
Forbes. 

These  interesting  discoveries  in  Mull  naturally  raise  the  question, 
whether  the  basalt  of  Antrim  in  Ireland,  and  of  the  celebrated  Giant's 
Causeway,  may  not  be  of  the  same  age.  For  in  Antrim  the  basalt 
overlies  the  chalk,  and  the  upper  mass  of  it  covers  everywhere  a  bed 
of  lignite  and  charcoal,  in  which  wood,  with  the  fibre  well  preserved, 
and  evidently  dicotyledonous,  is  enclosed.  The  general  dearth  of 
strata  in  the  British  Isles,  intermediate  in  age  between  the  formation 
of  the  Eocene  and  Pliocene  periods,  may  arise,  says  Professor  Forbes, 
from  the  extent  of  dry  land  which  prevailed  in  that  vast  interval  of 
time.  If  land  predominated,  the  only  monuments  we  are  likely  ever 

*  Quart,  Geol.  Joura.,  1851,  p.  89.  f  Ibid.,  p.  90. 


CH.  XIV.]  MAYENCE  BASIN.  243 

to  find  of  Miocene  date  are  those  of  lacustrine  and  volcanic  origin, 
such  as  the  Bovey  Coal  in  Devonshire,  the  Ardtun  beds  in  Mull,  or 
the  lignites  and  associated  basalts  in  Antrim. 


MIOCENE    FORMATIONS    OF    GERMANY. 

Mayence  basin. — An  elaborate  description  has  been  published  by 
Dr.  F.  Sandberger  of  the  Mayence  tertiary  area,  which  occupies  a 
tract  from  five  to  twelve  miles  in  breadth,  extending  for  a  great  dis- 
tance along  the  left  bank  of  the  Rhine  from  Mayence  to  the  neighbor- 
hood of  Manheim,  and  which  is  also  found  to  the  east,  north,  and 
south-west  of  Frankfort.  .  M.  de  Koninck,  of  Liege,  first  pointed  out 
to  me  that  the  purely  marine  portion  of  the  deposit  contained  many 
species  of  shells  common  to  the  Kleyn  Spawen  beds,  and  to  the  clay 
of  Rupelmonde,  near  Antwerp.  Among  these  he  mentioned  Cassi- 
daria  depressa,  Tritonium  argutum,  Brander  (T.  flandricum,  De  Kon- 
inck), Tornatella  simulata,  Aporrhais  Sowerbyi,  Leda  Deshayesiana 
(fig.  170,  p.  237),  Corbula  pisum  (fig.  lYl),  and  Pectunculus  terebra- 
tularis. 

First,  in  the  neighborhood  of  the  above-mentioned  strata  of  the 
Mayence  basin  are  the  sands  of  Eppelsheim,  containing  Dinotherium 
giganteum,  and  other  Falunian  or  Upper  Miocene  quadrupeds.  Next, 
the  uppermost  part  of  the  Mayence  series  consists  of  what  is  called 
the  Littorinella  Limestone,  which  contains  among  other  mammalia 
Hippotherium  gracile,  Acerotherium  (or  Rhinoceros)  incisivum  Paleo- 
meryx,  and  Chalicomys,  all  indicating  a  Lower  Miocene  fauna. 

The  shell  (fig.  177)  from  which  the  above-mentioned  limestone  is 
named  much  resembles  the  recent  Littorinella  (or  Hissoa)  ulva.    Each 
shell  is  like  a  grain  of  rice  in  size,  and  they  are  often  in       Fig.  177. 
such  quantity  as  to  form  entire  beds  of  marl  and  lime- 
stone, in  stratified  masses  from  fifteen  to  thirty  feet  in 
thickness,  just  as  in  the  Baltic  modern  accumulations 
several  feet  thick  of  the  Littorinella  ulva  are  spread  far 
and  wide  over  the  bottom  of  the  sea.     In  the  same  beds, 
several  species  of  Dreissena  abound,  a  form  common  to  the      Mayence. 
Headon  or  Upper  Eocene  beds  of  the  Isle  of  Wight,  as  well  as  to  the 
existing  seas. 

Among  the  plants  obtained  by  M.  Ludwig  from  argillaceous  strata 
of  the  Littorinella  limestone  series,  are  many  which  have  a  wide  range 
in  the  Miocene  period,  but  two  of  them,  says  Heer,  viz.,  Dryandroides 
Banksicefolia  and  D.  arguta,  are  characteristic  of  the  Lower  Miocene, 
or  of  beds  below  the  faluns  or  Marine  Molasse  of  Switzerland. 

Next  below  the  marls  containing  Cyrena  semistriata,  Cerithium 
plicatum,  C.  margaritaceum,  and  C.  Lamarckii*  These  marls,  with 

*  Sandberger  Bulletin,  torn.  xvii.  p.  153.     1860. 


UPPER  MIOCENE  BEDS  OF  VIENNA  BASIN.        [On.  XIV. 

the  underlying  clays  containing  Leda  Deshayesiana,  are  regarded  as 
the  Rupelian  of  Dumont,  while  the  shell-bearing  sands  of  Weinheim, 
near  Alzey,  are  supposed  to  be  somewhat  older,  and  the  equivalents 
of  the  Gres  de  Fontainebleau. 

Upper  Miocene  beds  of  the  Vienna  basin. — In  South  Germany  the 
general  resemblance  of  the  shells  of  the  Vienna  tertiary  basin  with 
those  of  the  faluns  of  Touraine  has  long  been  acknowledged.  In  Dr. 
Homes'  excellent  work  on  the  fossil  mollusca  of  that  formation  we  see 
accurate  figures  of  many  shells,  clearly  of  the  same  species  as  those 
found  in  the  falunian  sands  of  Touraine. 

According  to  Professor  Suess,  the  most  ancient  and  purely  marine 
of 'the  Miocene  strata  in  this  basin  consist  of  sands,  conglomerates, 
limestones,  and  clays,  and  they  are  inclined  inwards  or  from  the 
borders  of  the  trough  toward  the  centre,  their  outcropping  edges 
rising  much  higher  than  the  newer  beds,  whether  Miocene  or  Pliocene, 
which  overlie  them,  and  which  occupy  a  small  area  at  an  inferior 
elevation  above  the  sea.  M.  Homes  has  described  500  species  of 
gasteropods,  of  which  he  identifies  one-fifth  with  living  species  of  the 
Mediterranean,  Indian,  or  African  seas,  but  the  proportion  of  existing 
species  among  the  lamelli-branchiate  bivalves  exceeds  this  average. 
Among  many  univalves  agreeing  with  those  of  Africa  on  the  eastern 
side  of  the  Atlantic  are  Cyprecea  sanguinolenta,  Buccinum  lyratum 
and  Oliva  flammulata.  In  the  lowest  marine  beds  of  the  Vienna 
basin  the  remains  of  several  mammalia  have  been  found,  and  among 
them  a  species  of  Dinotherium,  a  Mastodon  of  the  Trilophodon  family, 
a  Rhinoceros  (allied  to  R.  megarhinus,  Christol),  also  Listriodon, 
Meyer  (of  the  hog  tribe),  and  a  carnivorous  animal  of  the  canine 
family. 

The  Helix  turonensis  (fig.  45,  p.  30),  the  most  common  land-shell 
of  the  French  faluns,  accompanies  the  above.  In  a  higher  member 
of  the  Vienna  Miocene  series  are  found  Dinotherium  giganteum,  Mas- 
todon longirostris,  Rhinoceros  Schleiermacheri,  Acerotherium  incisivum 
and  Hippotherium  gracile,  all  of  them  equally  characteristic  of  an 
Upper  Miocene  deposit  occurring  at  Eppelsheim  in  Hesse  Darmstadt, 
above  alluded  to.  M.  Alcide  d'Orbigny  has  shown  that  the  foraminifera 
of  the  Vienna  basin  differ  alike  from  the  Eocene  and  Pliocene  species, 
and  agree  with  those  of  the  faluns,  so  far  as  the  latter  are  known. 
Among  the  Vienna  foraminifera,  the  genus  Amphistegina  (fig.  178)  is 

Kg.  ITS. 


AmpMstegina  Hauerina,  D'Orb.    Upper  Miocene  strata,  Vienna. 


CH.  XIV.]  LOWER  MIOCENE  BEDS  OF  CROATIA.  245 

very  characteristic,  and  is  supposed  by  D'Archiac  to  take  the  same 
place  among  the  Rhizopods  of  the  Upper  Miocene  era  which  the 
Nummulities  occupy  in  the  Eocene  period. 

The  flora  of  the  Vienna  basin  exhibits  some  species  which  have  a 
general  range  through  the  whole  Miocene  period,  such  as  Cinnamomum 
polymorphum  (fig.  188),  and  another  species,  C.  Scheuchzeri  also 
Planera  Richardi,  Mich.,  (fig.  205),  Liquidambar  europcsum  (fig.  160), 
Juglans  bilinica,  Cassia  ambigua,  and  C.  lignitum.  With  these  are 
also  found  one  or  two  Older  Miocene  forms,  together  with  some  of 
the  Upper  Miocene  plants  of  (Eningen  in  Switzerland,  such  as  Plat- 
anus  aceroides  (fig.  187),  Myrica  vindobonensis,  Heer,  &c. 

Lower  Miocene  beds  of  Croatia. — The  Brown  Coal  of  Radaboj,  near 
Angram  in  Croatia,  not  far  from  the  borders  of  Styria,  is  covered, 
says  Yon  Buch,  by  beds  containing  the  marine  shells  of  the  Vienna 
basin,  or,  in  other  words,  by  Upper  Miocene  or  Falunian  strata. 
They  appear  to  correspond  in  age  to  the  Mayence  basin,  or  to  the 
Rupelian  strata  of  Belgium.  They  have  yielded  more  than  200  spe- 
cies of  fossil  plants,  of  which  Professor  Unger  has  given  an  admirable 
description.  They  are  well  preserved  in  a  hard  marlstone,  and  con- 
tain several  palms ;  among  them  the  Sabal,  fig.  197,  p.  259,  and  an- 
other genus  allied  to  the  date-palm  Phoenicites  spectabilis.  Among  the 
fossils  of  the  same  marls  we  also  find  a  fern,  which  will  be  mentioned 
in  the  next  chapter  (fig.  195,  p.  258),  called  Woodwardia  Rossneriana. 
The  only  abundant  plant  among  the  Radaboj  fossils  which  is  charac- 
teristic of  the  Upper  Miocene  period  is  the  Populus  mutabilis,  whereas 
no  less  than  fifty  of  the  Radaboj  species  are  common  to  the  more 
ancient  flora  of  the  Lower  Molasse  of  Switzerland. 

The  insect  fauna  is  very  rich,  and,  like  the  plants,  indicates  a  more 
tropical  climate  than  do  the  fossils  of  (Eningen  presently  to  be  men- 
tioned. There  are  ten  species  of  Termites,  or  white  ants,  some  of 
gigantic  size,  and  large  dragon-flies  with  speckled  wings,  like  those  of 
the  Southern  States  in  North  America ;  there  are  also  grasshoppers 
of  considerable  size,  and  even  the  Lepidoptera  are  not  unrepresented. 

Fig.  179. 


Vanessa  Pluto  ;  nat.  size.    Lower  Miocene,  Eadaboj,  Croatia. 


246  MIOCENE  STRATA  OF  ITALY.         [Cn.  XIV. 

In  one  instance,  the  pattern  of  a  butterfly's  wing  has  escaped  oblitera- 
tion in  the  marlstone  of  Kadaboj ;  and  when  we  reflect  on  the  remote- 
ness of  the  time  from  which  it  has  been  faithfully  transmitted  to  us, 
this  fact  may  inspire  the  reader  with  some  confidence  as  to  the  reli- 
able nature  of  the  characters  which  other  insects  of  a  more  durable 
texture,  such  as  the  beetles,  may  aiford  for  specific  determination. 
The  Vanessa  above  figured  retains,  says  Heer,  some  of  its  colors,  and 
corresponds  with  V.  Hadena  of  India. 

The  lignites  called  Brown  Coal  in  Germany  belong,  for  the  most 
part,  to  the  Lower  Miocene  epoch.  Among  these  may  be  mentioned 
those  of  the  Siebengebirge,  near  Bonn,  which  are  associated  with 
volcanic  rocks. 

Professor  Beyrich,  in  his  important  "  Memoirs  on  the  Tertiary 
Strata  of  the  North  of  Germany,"  *  has  made  known  to  us  the  exist- 
ence of  a  long  succession  of  marine  strata  which  lead,  by  an  almost 
gradual  transition,  from  the  Sternberg  beds  (see  above,  p.  239), 
approaching  in  age  to  the  faluns  of  the  Loire,  to  others  agreeing  in 
date  with  the  Lower  Tongrian  of  Dumont,  already  mentioned,  p.  238, 
as  the  base  of  the  Miocene.  In  conformity  with  the  method  which  I 
formerly  adopted,  he  has  appropriated  the  term  Miocene  exclusively 
to  the  faluns  of  Touraine  and  strata  of  that  age ;  but  for  all  the  for- 
mations below  that  level,  as  far  down  as  the  Uppermost  Eocene,  he 
has  proposed  the  new  term  of  Oligocene.  The  Sternberg  beds  are 
called  Upper  Oligocene ;  the  next  five  groups,  to  which  those  of  the 
Mayence  basin,  amongst  others,  belong,  as  well  as  the  Calcaire  de  la 
Beauce  and  Fontainebleau  Sandstone,  are  named  Middle  Oligocene ; 
while  the  Egeln  beds  and  some  North  German  Brown  Coals  of  the 
age  of  the  Lower  Tongrian  of  Dumont  are  called  Lower  Oligocene. 
The  difficulty  of  drawing  a  boundary  line  between  these  last  forma- 
tions and  the  Eocene  is  precisely  the  same  as  that  of  separating  the 
Lower  Miocene  and  Eocene  (as  defined  in  the  preceding  chapters)  in 
France  and  Belgium.  After  full  consideration,  it  seems  to  me  most 
convenient  to  accept  the  classification  so  long  adopted  by  many  wri- 
ters, which  places  the  gypsum  of  Montmartre  as  the  uppermost  of  the 
Eocene  subdivisions  ;  and  if  it  can  be  demonstrated  that  any  part  of 
the  Tongrian  of  Dumont,  or  of  the  German  strata  classed  by  Beyrich 
as  Lower  Oligocene,  is  strictly  contemporaneous  with  the  Paris  gyp- 
sum or  the  Bembridge  strata  of  the  Isle  of  Wight,  I  should  then  sepa- 
rate them  from  the  Lower  Miocene,  and  consider  them  as  Upper 
Eocene.  We  are  now  arriving  at  that  stage  of  progress  when  the 
line,  wherever  it  be  drawn,  will  be  an  arbitrary  one,  or  one  of  mere 
convenience,  as  I  shall  have  an  opportunity  of  showing  when  the 
Upper  Eocene  formations  in  the  Isle  of  Wight  are  described  in  the 
sixteenth  chapter. 

*  Abhandlungen  der  Konigl.  Acad.  der  Wissen.  zu  Berlin,  1855,  and  ibid.  1858, 
p.  59. 


CH.  XIV.]         UPPER  MIOCENE  FORMATIONS  OF  GREECE. 

Miocene  strata  of  Italy. — We  are  indebted  to  Signer  Michelotti 
for  a  valuable  work  on  the  Miocene  shells  of  Northern  Italy.  Those 
found  in  the  hill  called  the  Superga,  near  Turin,  have  long  been 
known  to  correspond  in  age  with  the  faluns  of  Touraine,  and  they 
contain  so  many  species  common  to  the  Upper  Miocene  strata  of 
Bordeaux  as  to  induce  M.  Tournouer  to  conclude  that  there  was  a 
free  communication  between  the  northern  part  of  the  Mediterranean 
and  the  Bay  of  Biscay  in  the  Upper  Miocene  period.  In  the  hills 
of  which  the  Superga  forms  a  part  there  is  a  great  series  of  Tertiary 
strata  which  pass  downward  into  the  Lower  Miocene.  Even  in  the 
Superga  itself  there  are  some  fossil  plants  which,  according  to  Heer, 
have  never  been  found  in  Switzerland  so  high  as  the  Marine  Molasse, 
such  as  BanJcsia  longifolia,  and  Carpinus  grandis*  In  several  parts 
of  the  Ligurian  Apennines,  as  at  Dego  and  Carcare,  the  Lower  Mio- 
cene appears,  containing  some  nummulites,  and  at  Cadibona,  north 
of  Savona,  freshwater  strata  of  the  same  age  occur,  with  dense  beds 
of  lignite  enclosing  remains  of  the  Anthracotherium  magnum  and 
A.  minimum,  besides  other  mammalia  enumerated  by  GaStaldi.  Jiln 
these  beds  a  great  number  of  the  Lower  Miocene  plants  of  Switzer- 
land have  been  discovered. 

Upper  Miocene  formations  of  Greece. — At  Pikerme,  near  Athens, 
MM.  Wagner  and  Roth  have  described  a  deposit  in  which  they  found 
the  remains  of  the  genera  Mastodon,  Dinotherium,  Hipparion,  Ante- 
lope, two  Giraffes,  and  others,  some  living  and  others  extinct.  With 
them  were  also  associated  fossil  bones  of  the  Semnopithecus,  showing 
that  here,  as  in  the  South  of  France,  the  quadrumana  were  character- 
istic of  this  period.  The  whole  fauna  attests  the  former  extension  of 
a  vast  expanse  of  grassy  plains  where  we  have  now  the  broken  and 
mountainous  country  of  Greece — plains  which  were  probably  united 
with  Asia  Minor,  spreading  over  the  area  where  the  deep  Egean  Sea 
and  its  numerous  islands  are  now  situated. 

*  Recherches  sur  le  Climat  et  la  Vegetation  du  Pays  Tertiaire,  par  Oswald 
Heer.  1851. 


248  MIOCENE  STRATA  OF  SWITZERLAND.  [On.  XV. 


CHAPTER    XV. 

MIOCENE  FORMATIONS — continued. 

Miocene  Strata  of  Switzerland — Upper  Miocene  beds  of  (Eningen — Importance  of 
Fossil  Plants — Heer's  work  on  the  Swiss  Miocene  flora — Plants  and  insects  of 
(Eningen  imbedded  in  different  seasons — Fossil  fruits  and  flowers,  as  well  as 
leaves — Middle  or  Marine  Molasse  of  Switzerland — Lower  Molasse,  or  Lower 
Miocene — Dense  conglomerates  and  proofs  of  subsidence — Fossil  plants  of 
Lower  Miocene  period  more  tropical — Preponderance  of  arborescent  species — 
Supposed  discordance  in  relative  numbers  of  living  species  of  plants  and  shells 
in  Upper  Miocene  formations — Theory  of  a  Miocene  Atlantis — Whether  the 
American  plants  abounding  in  the  Miocene  of  Europe  migrated  by  a  westerly 
or  an  easterly  route — Objections  derived  from  depth  and  width  of  the  Atlantic — 
Arguments  in  favor  of  a  Trans-Asiatic  migration — Miocene  fossils  of  Oregon — 
Agreement  of  Miocene  corals  of  the  West  Indies  and  Europe  opposed  to  the 
theory  of  an  Atlantic  Continent — Upper  Miocene  formations  of  India — Sub- 
Himalayan  or  Siwalik  Hills — Older  Pliocene  and  Miocene  formations  in  the 
United  States  of  America. 

MIOCENE    STRATA    OF    SWITZERLAND. 

Upper  Miocene  beds  of  (Eningen. — The  faluns  of  the  Loire  first 
served,  as  already  stated  (p.  212),  as  the  type  of  the  Miocene  forma- 
tions in  Europe.  They  yielded  a  plentiful  harvest  of  fossil  shells  and 
zoophytes,  but  were  entirely  barren  of  plants  and  insects.  In  Swit- 
zerland, on  the  other  hand,  deposits  of  the  same  age  have  been  dis- 
covered, remarkable  for  their  botanical  and  entomological  treasures. 

We  are  indebted  to  Professor  Heer  of  Zurich  for  the  description, 
restoration,  and  classification  of  more  than  900  species  of  these  fossil 
plants,  the  whole  of  which  he  has  illustrated  by  excellent  figures  in 
his  "  Flora  Tertiaria  Helvetise."  *  In  this  great  work  he  has  achieved 
for  the  botany  of  the  Tertiary  formations  what  his  distinguished  pre- 
decessor, Adolphe  Brongniart,  had  done  for  the  fossil  plants  of  the 
Primary  and  Secondary  rocks.  MM.  linger  and  Goppert,  by  their 
able  descriptions  of  the  plants  of  the  Brown  Coal  of  Germany,  had 
already  prepared  the  minds  of  geologists  to  expect  that  botany 
would  one  day  play  almost  as  important  a  part  as  conchology  in  ena- 
bling us  to  identify  and  classify  the  middle  tertiary  strata.  But  no 

*  This  work,  in  three  vols.,  containing  155  folio  plates  of  fossil  plants,  was  pub- 
lished at  Winterthur  in  1855-'9,  and  a  French  translation  of  those  chapters  which 
relate  to  the  geology,  botany,  and  climate  of  the  Swiss  Miocene  strata  appeared  in 
1862,  edited  by  Prof.  Heer  and  M.  Charles-Th.  Gaudin,  entitled  "  Recherch.es  sur  le 
Climat  et  la  Vegetation  du  Pays  Tertiaire." 


CH.  XV.]  MIOCENE  STRATA  OF  SWITZERLAND.  249 

small  skepticism  had  always  prevailed  among  botanists  of  the  highest 
attainments  as  to  whether  fossil  remains  of  the  vegetable  kingdom 
could  ever  afford  sufficient  data  for  determining  the  species,  or  even 
the  genera  or  families,  of  plants  of  which  nothing  but  the  leaves  are 
imbedded  in  the  rocks.  In  truth,  before  such  remains  could  be  ren- 
dered available,  a  new  science  had  to  be  created.  It  was  necessary  to 
study  the  outlines,  nervation,  and  microscopic  structure  of  the  leaves 
with  a  degree  of  care  which  had  never  been  called  for  in  the  classifi- 
cation of  living  plants,  where  the  flower  and  fruit  afforded  characters 
so  much  more  definite  and  satisfactory.  As -geologists,  we  cannot  be 
too  grateful  to  those  who,  instead  of  despairing  when  a  task  of  such 
difficulty  was  presented  to  them,  entered  with  full  faith  and  enthusi- 
asm into  the  new  and  unexplored  field.  That  they  should  frequently 
have  fallen  into  errors  was  unavoidable,  but  it  is  remarkable,  espe- 
cially if  we  inquire  into  the  history  of  Professor  Heer's  researches, 
how  often  early  conjectures  as  to  the  genus  and  family  founded  on 
leaves  alone  were  afterwards  confirmed  when  fuller  information  was 
obtained  ;  as,  for  example,  when  the  fruit,  and  in  some  instances  both 
fruit  and  flower,  were  found  attached  to  the  same  stem  as  the  leaves 
which  had  been  first  described.  Nor  should  we  forget  that  when  a 
skilful  botanist  has  devoted  his  powers  of  discrimination  to  the 
classification  of  the  leaves  according  to  their  forms,  veining,  and 
minute  or  microscopic  structure,  he  may  afford  the  most  important 
palseontological  assistance  to  the  geologist,  even  if  he  happen  to  make 
some  erroneous  guesses  as  to  the  generic  or  even  ordinal  affinities  of 
the  plants  in  question.  His  power  of  recognizing  the  same  identical 
fossil  in  two  distinct  places  or  two  distinct  formations  may  settle  a 
disputed  point  in  chronology,  where  there  is  no  other  evidence  at 
hand,  and  the  conclusions  drawn  from  such  data  as  to  the  relative  age 
of  the  beds  have  often  held  good,  even  when  it  was  afterwards  proved 
that  several  species,  or  even  genera,  had  been  constructed  out  of  the 
leaves  of  the  same  plant,  or  that  the  fruit  and  leaves  of  one  and  the 
same  tree  had  been  referred  to  genera  of  distinct  families. 

The  Miocene  formations  of  Switzerland  have  been  called  Molasse, 
a  term  derived  from  the  French  mol,  and  applied  to  a  soft,  incoherent, 
greenish  sandstone,  occupying  the  country  between  the  Alps  and  the 
Jura.  This  molasse  comprises  three  divisions,  of  which  the  middle 
one  is  marine,  and  being  closely  related  by  its  shells  to  the  faluns  of 
Touraine,  may  be  classed  as  Upper  Miocene.  The  two  others  are 
freshwater,  the  upper  of  which  may  be  also  grouped  with  the  faluns, 
while  the  lower  must  be  referred  to  the  Lower  Miocene,  as  defined  in 
the  last  chapter. 

The  upper  freshwater  Molasse  may  first  be  considered.  It  is  best 
seen  at  (Eningen,  in  the  valley  of  the  Rhine,  between  Constance  and 
Schaffhausen,  a  locality  celebrated  for  having  produced  in  the  year 
1700  the  supposed  human  skeleton  called  by  Scheuchzer  "homo 
diluvii  testis,"  a  fossil  afterwards  demonstrated  by  Cuvier  to  be  a 


250  UPPER  MIOCENE  OF  SWITZERLAND.  [Cn.  XV. 

reptile,  or  aquatic  salamander,  of  larger  dimensions  than  even  its 
great  living  representative  the  salamander  of  Japan. 

The  QEningen  strata  consist  of  a  series  of  marls  and  limestones, 
many  of  them  thinly  laminated,  and  which  appear  to  have  slowly 
accumulated  in  a  lake  probably  fed  by  springs  holding  carbonate  of 
lime  in  solution. 

The  elliptical  area  over  which  this  freshwater  formation  has  been 
traced  extends,  according  to  Sir  Roderick  Murchison,  for  a  distance 
of  ten  miles  east  and  west  from  Berlingen,  on  the  right  bank  of  the 
river  to  Wangen,  and  to  JCEningen,  near  Stein,  on  the  left  bank.  The 
organic  remains  have  been  chiefly  derived  from  two  quarries,  the 
lower  of  which  is  about  550  feet  above  the  level  of  the  Lake  of 
Constance,  while  the  upper  quarry  is  150  feet  higher.  In  this  last, 
a  section  thirty  feet  deep  displays  a  great  succession  of  beds,  most  of 
them  splitting  into  slabs  and  some  into  very  thin  laminae.  Twenty- 
one  beds  are  enumerated  by  Professor  Heer,  the  uppermost  a  bluish- 
gray  marl  seven  feet  thick,  without  organic  remains,  resting  on  a  lime- 
stone with  fossil  plants,  including  leaves  of  poplar,  cinnamon,  and 
pond-weed  (Potamogeton),  together  with  some  insects ;  while  in  the 
bed  No.  4,  below,  is  a  bituminous  rock,  in  which  the  Mastodon  an- 
gustidens,  a  characteristic  Upper  Miocene  quadruped,  has  been  met 
with.  The  5th  bed,  two  or  three  inches  thick,  contains  fossil  fish,  e.  g. 
Leuciscus  (roach),  and  the  larvae  of  dragon-flies,  with  plants  such  as 
the  elm  ( Ulmus),  and  the  aquatic  Chara.  Below  this  are  other  plant- 
beds  ;  and  then,  in  No.  9,  the  stone  in  which  the  great  salamander 
(Andrias  Scheuchzeri)  and  some  fish  were  found.  Below  this,  other 
strata  occur  with  fish,  tortoises,  the  great  salamander  before  alluded 
to,  freshwater  mussels,  and  plants.  In  No.  16  the  fossil  fox  of 
(Eningen,  Galecynus  (Eningensis,  Owen,  was  obtained  by  Sir  R. 
Murchison.  To  this  succeed  other  beds  with  mammalia  (Lagomys), 
reptiles  (Emys),  fish,  and  plants,  such  as  walnut,  maple,  and  poplar. 
In  the  19th  bed  are  numerous  fish,  insects,  and  plants,  below  which 
are  marls,  of  a  blue  indigo  color. 

In  the  lower  quarry  eleven  beds  are  mentioned,  in  which,  as  in 
the  upper,  both  land  and  freshwater  plants  and  many  insects  occur. 
In  the  6th,  reckoning  from  the  top,  many  plants  have  been  obtained, 
such  as  Liquidambar,  Daphnogene,  Podogonium,  and  JElm,  together 
with  tortoises,  besides  the  bones  and  teeth  of  a  ruminant  quadruped, 
named  by  H.  V.  Meyer  Paleomeryce  eminens.  No.  9  is  called  the  in- 
sect bed,  a  layer  only  a  few  inches  thick,  which,  when  exposed  to  the 
frost,  splits  into  leaves  as  thin  as  paper.  In  these  thin  laminae  plants 
such  as  Liquidambar,  Daphnogene,  and  Glyptostrobus  occur,  with  in- 
numerable insects  in  a  wonderful  state  of  preservation,  usually  found 
singly.  Below  this  is  an  indigo-blue  marl,  like  that  at  the  bottom  of 
the  higher  quarry,  resting  on  yellow  marl  ascertained  to  be  at  least 
thirty  feet  thick. 

All  the   above  fossil-bearing   strata  were   evidently  formed  with 


CH.  XV.]  UPPER  MIOCENE  STRATA,   SWITZERLAND.  251 

extreme  slowness.  Although  the  fossiliferous  beds  are,  in  the  aggre- 
gate, not  more  than  a  few  yards  in  thickness,  and  have  only  been 
examined  in  the  small  area  comprised  in  the  two  quarries  just  alluded 
to,  they  give  us  an  insight  into  the  state  of  animal  and  vegetable  life 
in  part  of  the  Upper  Miocene  period,  such  as  no  other  region  in  the 
world  has  elsewhere  supplied.  In  the  year  1859,  Professor  Heer  had 
already  determined  no  less  than  475  species  of  plants  and  900  insects 
from  these  (Eningen  beds.  He  supposes  that  a  river  entering  a  lake 
floated  into  it  some  of  the  leaves  and  land-insects,  together  with  the 
carcasses  of  quadrupeds,  such  as  the  great  Mastodon.  Occasionally, 
during  tempests,  twigs  and  even  boughs  of  trees  with  their  leaves 
were  torn  off  and  carried  for  some  distance  so  as  to  reach  the  lake. 
Springs,  containing  carbonate  of  lime,  seem  at  some  points  to  have 
supplied  calcareous  matter  in  solution,  giving  origin  locally  to  a  kind 
of  travertin,  in  which  organic  bodies  sinking  to  the  bottom  became 
hermetically  sealed  up.  The  laminae,  says  Heer,  which  immediately 
succeed  each  other,  were  not  all  formed  at  the  same  season,  for  it  can 
be  shown  that,  when  some  of  them  originated,  certain  plants  were  in 
flower,  whereas,  when  the  next  of  these  layers  was  produced,  the 
same  plants  had  ripened  their  fruit.  This  inference  is  confirmed  by 
independent  proofs  derived  from  insects.  The  principal  insect-bed  is 
rarely  two  inches  thick,  and  is  composed,  says  Heer,  of  about  250 
leaflike  laminae,  some  of  which  were  deposited  in  the  spring,  when 
the  Cinnamomum  polymorphum  (p.  254)  was  in  flower ;  others  in 
summer,  when  winged  ants  were  numerous,  and  when  the  poplar  and 
willow  had  matured  their  seed ;  others,  again,  in  autumn,  when  the 

Fig.  180.  Fig.  181. 


Podogomium  Knorii.    Upper  Miocene  of  GEningen  and  many  parts  of  Germany. 

Fig.  180.    Eestoration  of  the  plant  by  Prof.  Heer.    Frontispiece,  Flora  Tert.  Hel.    £  nat.  size. 

a.  Branch  bearing  flowers  before  the  leaves  appear.     &.  Branch  with  leaves  and  ripe  fruit 

Fig.  181.    a.  Pod  of  P.  Knorii.    (Eningen.    £  nat.  size.       c.  Formica  lignittwrn. 

5.  Leaf  of  gramineous  plant.  d.  ffist&r  coprolithorum. 

Heer,  pi.  184,  fig.  26. 

same  Cinnamomum  polymorphum  (fig.  188)  was  in  fruit,  as  well  as 
the  liquidambar,  oak,  clematis,  and  many  other  plants. 

The  ancient  lake  seems  to  have  had  round  its  borders  a  belt  of 


252 


UPPER  MIOCENE  FLORA  OF  GSNINGEN. 


[On.  XV. 


poplars  and  willows,  countless  leaves  of  which  became  imbedded  in 
the  mud.  Together  with  them,  at  some  points,  a  species  of  reed, 
ArundOj  was  very  common. 

One  of  the  most  characteristic  shrubs  is  a  papilionaceous  and  legu- 
minous plant  of  an  extinct  genus,  called  by  Heer  Podogonium,  of 
which  two  species  are  known.  Entire  twigs  have  been  found  (a,  fig. 
180),  with  flowers,  and  always  without  leaves,  the  flowers  having  evi- 
dently come  out,  as  in  the  poplar  and  willow  tribe,  before  any  leaves 
made  their  appearance.  Other  specimens  have  been  obtained  with 
ripe  fruit  accompanied  by  leaves,  as  shown  in  the  branch  b,  fig.  180. 
In  some  specimens  are  seen  the  embryo  and  cotyledons,  in  others  the 
calyx  and  young  fruit.  The  leaves  resemble  those  of  the  tamarind, 
but  each  pod  contains  only  a  single  seed,  whereas  the  pod  of  the 
tamarind,  an  allied  genus,  contains  many  seeds. 

In  fig.  181  we  see  a  ripe  seed-vessel  of  this  plant,  and  on  the  same 
thin  slab  a  winged  ant,  c,  formica  lignitum,  Heer.  Another  species 
of  ant,  also  with  wings,  has  been  found  associated  with  the  same 
Podogonium  in  fructification,  from  which  fact  Professor  Heer  con- 
cludes that  it  ripened  its  seed  in  summer,  at  which  season  alone 
swarms  of  perfect  male  and  female  ants,  having  their  wings  fully 
developed,  make  their  flights.  Such,  for  example,  is  the  habit  of  the 
living  Formica  herculeana,  which  comes  very  near  to  F.  lignitum. 
In  the  same  slab,  at  d,  is  a  portion  of  a  beetle  of  the  genus  Hister. 

The  Upper  Miocene  flora  of  (Eningen  is  peculiarly  important,  in 
consequence  of  the  number  of  genera  of  which  not  merely  the  leaves, 

Fig.  182. 


Acer  trilobatwm,  normal  form.    Heer,  Flora  Tert.  Helv.,  pi.  114,  fig.  2.    Size  $  (Ham. 

(Part  only  of  the  long  stalk  of  the  original  fossil  specimen  is  here  given.) 

Upper  Miocene,  (Eningen ;  also  found  in  Lower  Miocene  of  Switzerland. 

but,  as  in  the  case  of  the  Podogonium  just  mentioned,  the  fruit  also 
and  even  the  flower  are  known.     Thus  there  are  nineteen  species  of 


CH.  XV.] 


UPPER  MIOCENE  STRATA,  SWITZERLAND. 


253 


maple,  ten  of  which  have  already  been  found  with  fruit.  Although 
in  no  one  region  of  the  globe  do  so  many  maples  now  nourish,  we 
need  not  suspect  Professor  Heer  of  having  made  too  many  species  in 
this  genus  when  we  consider  the  manner  in  which  he  has  dealt  with 
one  of  them,  Acer  trilobatum,  figs.  182,  183,  185.  Of  this  plant  the 
number  of  marked  varieties  figured  and  named  is  very  great,  and  no 
less  than  three  of  them  had  been  considered  as  distinct  species  by 

Fig.  188. 


Acer  trilobatvm. 

a.  Abnormal  variety  of  leaf.    Heer,  pi.  110,  fig.  16. 
&.  Flower  and  bracts,  normal  form.    Heer,  pi.  Ill,  fig.  21. 
c.  Half  a  seed-vessel.    Heen  pi.  Ill,  fig.  5. 


Fig.  184. 


Fig.  185. 


Fig.  184.  Acer  rubrum,  L.  Fig.  185.  Acer  trilobatwm. 

Living  in  N.  America.  Fossil,  (Eningen. 

Heer,  pi.  Ill,  fig.  22;  natural  size.  Heer,  pi.  155,  fig.  9 ;  natural  size. 

a.  The  carpels.  c.  Three  petals  of  the  corolla.  d.  Calyx. 

Fig.  186.   Acer  trilobatwm. 
5.  The  two  carpels.    Heer,  pi.  Ill,  fig.  18. 

other  botanists,  while  six  of  the  others  might  have  laid  claim,  with 
nearly  equal  propriety,  to  a  like  distinction.      The  common  form, 


254 


UPPER  MIOCENE  FLORA  OF  (ENINGEN. 


[Cn.  XV. 


Fig.  187. 


called  Acer  trilobatum,  fig.  182,  may  be  taken  as  a  normal  representa- 
tive of  the  (Eningen  fossil,  and  fig.  183  as  one  of  the  most  divergent 
varieties,  having  almost  four  lobes  in  the  leaf  instead  of  three. 

We  have  a  remarkable  example  in  fig.  185  of  the  preservation  of 
the  female  flower,  enabling  the  botanist  to  recognize  the  resemblance 
between  the  petals  of  the  Miocene  species  and  those  of  the  living 
Acer  rubrum,  fig.  184.* 

In  like  manner  the  fossil  specimen,  fig.  186  6,  shows  how  much 
more  pointed  were  the  winged  appendages  of  the  seed-vessels  than 
are  those  of  the  most  nearly  allied  living  species,  fig.  184  a. 

Among  the  genera  which  abounded  in  the  Miocene  period  in  Eu- 
rope is  the  plane-tree,  Platanus,  the  fos- 
sil species  being  considered  by  Heer  to 
come  nearer  to  the  American  P.  occiden- 
talis  than  to  P.  orientalis  of  Greece  and 
Asia  Minor.  In  some  of  the  fossil  speci- 
mens the  male  flowers  are  preserved. 
Among  other  points  of  resemblance 
with  the  living  plane-trees,  as  we  see 
them  in  the  parks  and  squares  of  Lon- 
don, fossil  fragments  of  the  trunk  are 
met  with,  having  pieces  of  their  bark 
peeling  off. 

No  leaves  of  the  beech-tree  or  of  the 
chestnut  have  yet  been  found  in  any  Mio- 
cene  strata  of  Switzerland,  Although  in 
formations  of  the  same  age  in  Germany, 
leaves  of  one  of  them,  namely,  the  beech,  have  been  detected.  Many 
species  of  the  laurel  tribe  characterize  the  flora  both  of  the  Upper 


Plata/nuB  aceroides,  Gopp 

Heer,  pi.  88,  figs.  5-8. 
Size  f  diam.    Upper  Miocene, 

(Eningen. 
a.  Leaf. 
&. 
c. 


Fig.  188. 


Fig.  189. 


Cinnamomum  polymorphism,  Ad.  Brong. 
a.  Leaf. 

&.  Flower,  nat.  size.    Heer,  pi.  93,  fig.  28. 
Upper  and  Lower  Miocene. 


a.  Eipe  fruit  of  Cinnamomum  polymorphum, 
from  (Eningen.  Heer,  pi.  94,  fig.  14. 

&.  Fruit  of  recent  Cinnamomum  camphora  of 
Japan.  Heer,  pi.  152,  fig.  18. 


*  Heer,  vol.  iii.  p.  197. 


CH.  XV.]  UPPER  MIOCENE  STRATA,   SWITZERLAND. 


255 


and  Lower  Miocene  strata  in  Switzerland  and  Germany,  especially  the 
cinnamon  (see  fig.  188).  The  leaves -of  this  genus  are  easily  recog, 
nizable,  and  often  serve  as  useful  guides  to  the  geologist.  The  fruit 
also  and  the  flower  are  found  at  (Eningen. 

Professor  Heer  observes  that  the  fruit  in  the  fossil,  fig.  189  a,  is 
more  oval  in  shape  than  that  of  the  recent  Japanese  plant,  C.  cam- 
phora,  b,  fig.  189,  which  conies  nearest  to  it,  and  that  the  peduncle  is 
not  thickened  at  its  upper  end  as  in  the  living  one. 

The  vine  of  (Eningen,  Vitis  teutonica,  Ad.  Brong.,  is  of  a  North 
American  type,  approaching  nearest  to  Vitis  vulpina,  L. ;  both  the 
leaves  and  seeds  have  been  found  at  (Eningen,  and  bunches  of  com- 
pressed grapes  of  the  same  species  have  been  met  with  in  the  Brown 
Coal  of  Wetteravia  in  Germany. 

No  less  than  eight  species  of  smilax,  a  monocotyledonous  genus, 
occur  at  (Eningen  and  in  other  Upper  Miocene  localities,  the  flowers 
of  some  of  them,  as  well  as  the  leaves,  being  preserved,  as  in  the  case 
of  the  very  common  fossil  S.  sagittifera,  fig.  190  a. 

Fig.  190. 


Smilax  sagittifera.    Heer,  pi.  30,  fig.  7.    Size  i  diameeer. 

a.  Leaf.     5.  Flower  magnified,  one  of  the  six  petals  wanting  at  d.    Upper  Miocene,  (Eningen. 
c.  Leaf  of  Smilax  obtusifoUa.    Heer,  pi.  80,  fig.  9 ;  nat.  size.    Upper  Miocene,  (Eningen. 

Plants  referable  to  no  less  than  five  genera  of  the  order  Proteacea3 
have  been  obtained  partly  from  (Eningen  and  partly  from  the  lacus- 

Fig.  191. 


Fruit  of  the  fossil  and  recent  species  of  Hakea,  a  genus  of  Proteaceae. 
a.  Leaf  of  fossil  species,  Hakea  salicina.    Upper  Miocene,  (Eningen;  called  Embothrium 

l>y  Heer,  pi.  97,  fig.  29.    \  diam. 
&.  Fruit  of  same.    }  diam.   •  c.  Seed  of  same.    Natural  size. 

d.  Fruit  of  living  Australian  species,  Hakea  saligna,  E.  Brown.    J  diam. 

e.  Seed  of  same.    Natural  size. 


256  UPPER  MIOCENE  INSECTS,   (ENINGEN.  [On.  XV. 

trine  formation  of  the  same  age  at  Locle  in  the  Jura.  These  five 
.genera  all  of  them,  except  the  last,  now  living  in  Australia,  are  the 
following :  Banksia,  Grevillea,  ITakea,  Persoonia,  and  Dryandroides. 
Of  Hakea  both  the  seed-vessel  and  the  seeds  have  been  obtained,  so 
that  they  can  be  compared  with  the  recent ;  and  the  dimensions  of 
the  fossil  fruit  are  similar  in  size,  the  difference  in  d  and  6,  fig.  191, 
arising  from  the  different  scale  of  reduction  (see  description  of  figure). 
More  will  be  said  of  the  Proteacese  when  I  treat  of  the  plants  of 
the  Lower  Miocene  period,  at  which  era  that  family  was  still  more 
prevalent  in  Europe.  In  the  same  beds  at  Locle  with  the  Proteacese 
there  occurs  a  fan  palm  of  the  American  type  Sabal,  a  genus  which 
ranges  throughout  the  low  country  near  the  sea  from  the  Carolinas  to 
Florida  and  Louisiana. 

Among  the  Conifers  of  Upper  Miocene  age  is  found  a  deciduous 
cypress  nearly  allied  to  the  Taxodium  dis- 
tichum  of  N.  America,  and  a  Glyptostrobus, 
fig.  192,  very  like  the  Japanese  G.  heterophyl- 
lus,  now  common  in  our  shrubberies. 

It  was  stated  that  in  the  upper  quarry  at 
(Eningen  the  remains  of  the  Mastodon  angusti- 
dens  occur.  The  association  of  so  characteristic 
a  falunian  fossil  with  the  flora  above  described 
is  important,  as  helping  to  settle  the  true  Upper 
Miocene  date  of  these  beds.  M.  Ziegler  showed 
me  in  the  museum  at  Winterthur  in  Switzer- 
land>  in  185^»  two  fine  specimens  of  the  skulls 
and  jaws  of  the  same  species,  one  young  and 
the  other  adult,  determined  by  Dr.  Falconer,  which  had  been  found 
at  Veltheim  in  that  neighborhood,  in  strata  belonging,  like  the  OEnin- 
gen  beds,  to  the  upper  freshwater  molasse.  This  formation  is  there 
seen  to  overlie  the  marine  falunian  beds  of  Rorbas.  In  that  same 
molasse  the  Podogonium  Knorii,  above  described,  and  Populus  latior, 
with  other  characteristic  (Eningen  plants,  have  been  met  with. 

Before  the  appearance  of  Heer's  work  on  the  Miocene  flora  of 
Switzerland,  Unger  and  Goppert  had  already  pointed  out  the  large 
proportion  of  living  North  American  genera  which  distinguished  the 
vegetation  of  the  Miocene  period  in  Central  Europe.  Next  in  num- 
ber, says  Heer,  to  these  American  forms  at  (Eningen  the  European 
genera  preponderate,  the  Asiatic  ranking  in  the  third,  the  African  in 
the  fourth,  and  the  Australian  in  the  fifth  degree.  The  American 
forms  are  more  numerous  than  in  the  Italian  Pliocene  flora,  and  the 
whole  vegetation  indicates  a  warmer  climate,  though  not  so  high  a 
temperature,  as  that  of  the  older  or  Lower  Miocene  period. 

The  conclusions  drawn  from  the  insects  are  for  the  most  part  in 
perfect  harmony  with  those  derived  from  the  plants,  but  they  have 
a  somewhat  less  tropical  and  less  American  aspect,  the  South  Euro- 
pean types  being  more  numerous.  On  the  whole,  the  insect  fauna  is 


CH.  XV.]  MIOCENE   STRATA  OF  SWITZERLAND.  257 

richer  than  that  now  inhabiting  any  part  of  Europe.  No  less  than 
844  species  are  reckoned  by  Heer  from  the  (Eningen  beds  alone,  the 
number  of  specimens  which  he  has  examined  being  5080.  The  entire 
list  of  Swiss  species  from  the  Upper  and  Lower  Miocene  together 
amount  to  1322.  Almost  all  the  living  families  of  Coleoptera  are 
represented,  but,  as  we  might  have  anticipated  from  the  preponder- 
ance of  arborescent  and  ligneous  plants,  the  wood-eating  beetles  play 
the  most  conspicuous  part,  the  Buprestidse  and  other  long-horned 
beetles  being  particularly  abundant.  There  are  also  no  less  than 
thirty  species  of  those  beetles,  of  which  the  larvae  feed  on  the  dung 
of  mammalia,  implying,  says  Heer,  the  existence  of  a  great  many 
more  ruminants  in  the  days  of  the  (Eningen  Lake  than  the  single  one 
of  that  class  known  to  us,  namely,  the  Palceomeryx  eminens  of  Meyer. 
There  were  also  species  of  the  carrion-feeding  Silpha  ;  also  twenty- 
four  species  of  water-beetles  of  the  genera  Dytiscus,  Hydrophilus,  &c. 

The  patterns  and  some  remains  of  the  colors  both  of  Coleoptera 
and  Hemiptera  are  preserved  at  CEningen,  as,  for  example,  in  the  an- 
nexed figure  of  Harpactor,  in  which  the  antennae,  one  of  the  eyes, 
and  the   legs  and  wings  are  retained. 
The  characters,  indeed,  of  many  of  the  Fte-  m 

insects  are  so  well  denned  as  to  incline 
us  to  believe  that  if  this  class  of  the  in- 
vertebrata  were  not  so  rare  and  local, 
they  might  be  more  useful  than  even 
the  plants  and  shells  in  settling  chrono- 
logical points  in  geology.* 

Few  of  the  genera  of  insects  are  ex- 
tinct, but  many  of  them  imply  a  geo- 
graphical distribution  widely  different 
from  that  now  obtaining  in  the  same 
part  of  the  world.  Thus,  for  example, 
in  this  Swiss  fauna,  there  were  many 
white  ants  or  Termites,  and  dragon-flies 
of  a  South  African  type  called  Agrion, 

besides   several    Indian   and  American  Harpactor  macuUp^  Heer.    Upper 
forms  referable  to  various  orders.  Miocene, 


To  account  for  the  perfect  state  of  the 

specimens,  Heer  supposes  that  the  insects  which  sank  to  the  bottom 
of  the  water  may  have  been  killed  by  mephitic  gases  which  rose  from 
the  lake,  and  which  were  connected  with  the  volcanic  eruptions  of 
which  some  of  the  products  are  seen  at  Hochgau,  and  which  are 
believed  by  Swiss  geologists  to  have  taken  place  in  the  Upper  Mio- 
cene period. 

*  See  Heer's  beautiful  figures  and  descriptions  of  ffiningen  beetles,  &c.,  in  the 
Haarlem  Transactions.  Naturkundige  Verhandelingen  van  der  Hollandsche  Maat- 
scliappij  der  Wetensch,  &c.  Haarlem,  1862. 


258 


LOWER  MIOCENE  STEATA,   SWITZERLAND.  [On.  XV. 


Middle  or  Marine  Molasse  (Upper  Miocene)  of  Switzerland. — It 
was  before  stated  that  the  Miocene  formation  of  Switzerland  con- 
sisted of,  1st,  the  upper  freshwater  molasse,  comprising  the  lacustrine 
marls  of  (Eningen ;  2dly,  the  marine  molasse,  corresponding  in  age  to 
the  faluns  of  Touraine ;  and  3dly,  the  lower  freshwater  molasse. 
Some  of  the  beds  of  the  marine  or  middle  series  reach  a  height  of 
2470  feet  above  the  sea.  A  large  number  of  the  shells  are  common 
to  the  faluns  of  Touraine,  the  Vienna  basin,  and  other  Upper  Miocene 
localities.  The  terrestrial  plants  play  a  subordinate  part  in  the  fossil- 
iferous  beds,  yet  more  than  90  of  them  are  enumerated  by  Heer  as 
belonging  to  this  falunian  division,  and  of  these  more  than  half  are 
common  to  subjacent  Lower  Miocene  beds,  while  a  proportion  of 
about  45  in  a  hundred  are  common  to  the  overlying  (Eningen  flora. 
Twenty-six  of  the  92  species  are  peculiar. 

Lower  Molasse  (Lower  Miocene)  of  Switzerland. — Next  in  descend- 
ing order  comes  the  Lower  Molasse,  almost  entirely  of  freshwater  ori- 
gin, of  which  the  Upper  division  contains  211  species  of  plants  and 
the  Lower  no  less  than  336  species.  The  first  of  these  two  is  called 
in  Heer's  work  the  "  Mayencien,"  it  being  supposed  to  agree  in  age 
with  the  strata  of  the  Mayence  basin  already  described,  while  the 
lower  division  is  called  the  "  Aquitanien,"  as  corresponding  with  some 
of  the  older  Miocene  beds  of  the  South  of  France.  But  the  fossil 
shells  by  which  these  comparisons  have  been  made  appear  to  me  to 
be  at  present  too  few  in  number  to  enable  us  to  place  much  reliance 
on  such  identifications.  The  superposition,  however,  of  the  Molasse 
called  "Mayencien"  to  the  lower  beds  called  "Aquitanien,"  which 
last  are  well  seen  on  the  borders  of  the  Lake  of  Geneva,  is  perfectly 
clear. 

To  the  upper  group  belong  the  sandy  marls  of  Eriz,  in  the  Canton 
of  Berne,  in  which  there  are  68  species  of  plants,  half  of  them  com- 
mon to  the  (Eningen  strata.  Among  the  North  American  forms  in 
this  locality  the  tulip  tree  may  be  mentioned,  a  species  very  closely 
allied  to  the  Liriodendron  tulipifera,  L. 


Fig.  194. 


Fig.  195. 


Liriodendron  Procawinii,  linger. 
Ilcer,  pi.  108,  fig.  6.    Eriz.    Lower  Miocene. 


Woodwardia  Rossneriana,  Unger. 
Heer,  pi.  5.    Eriz.    Lower  Miocene. 
a.  Part  of  a  branch.      &.  Part  of  a  leaf  mag- 
nified, showing  the  position  of  the  son. 


CH.  XV.]  LOWER  MIOCENE  STRATA,   SWITZERLAND.  259 

The  most  abundant  of  the  associated  plants  are  two  species  of  cin- 
namon, one  of  them  already  mentioned  as  frequent  at  (Eningen,  C. 
polymorphum^  fig.  188.  Next  to  these  in  number  come  species  of 
the  dogwood,  or  Cornus,  of  the  hornbeam,  Carpinus,  and  of  the  buck- 
thorn, JRhamnus.  Among  the  fir-tribe  or  coniferse  is  a  Taxodium 
nearly  allied  to  the  deciduous  cypress,  T.  distichum,  of  N.  America. 
Professor  Goppert  considers  it  the  same,  but  linger  and  Heer  have 
pointed  out  differences,  showing  that  it  is  at  least  a  marked  variety. 
Among  the  ferns  is  found  a  Woodwardia  (see  fig.  195),  so  like  the 
living  W.  radicans,  that  in  spite  of  the  large  size  and  some  slight  dif- 
ferences in  the  shape  of  the  leaf  (a  part  so  often  variable  in  ferns),  it 
may,  says  Heer,  be  a  question  with  some  botanists  whether  the  fossil 
does  not  agree  specifically  with  the  recent  plant.  Yet  this  fern  ranges 
still  lower,  being  also  found  at  Monod,  a  locality  to  which  I  shall 
presently  allude. 

Before  quitting  the  plants  of  this  lower  division  of  the  molasse,  I 
may  mention  that  a  fan-palm,  Chamcerops  Helvetica  (fig.  196),  occurs 
at  IJtznach,  in  the  Canton  of  St.  Gall,  in  Lower  Miocene  strata  some- 
what higher  in  the  series  than  those  of  Eritz.  This  genus  is  now 
South  European,  Asiatic,  and  American. 

Fig.  196.  Tig.  19T. 


Chamerops  Helvetica,  Heer.  Sdbal  major,  Unger  sp.    Vevay,  Lower 

Utznach,  St.  Gall,  Lower  Miocene.    (Heer,  Flora  Miocene.     (Heer,  pL  41.)     Genus  now 

FOES.  Helvet,  pi.  41.)  proper  to  America. 

The  inferior  subdivision  of  the  Lower  Molasse,  called  Aquitanian 
in  Heer's  work,  is  best  seen  on  the  northern  coast  of  the  Lake  of 
Geneva.  The  beds  consist  of  sandstone  and  conglomerate,  and  are 
nearly  2000  feet  thick.  The  conglomerates  are  often  very  unequal  in 
thickness,  in  closely  adjoining  districts,  as  might  be  expected,  since 
in  a  littoral  formation  accumulations  of  pebbles  would  swell  out  in 
certain  places  where  rivers  entered  the  sea,  and  would  thin  out  to 
comparatively  small  dimensions  where  no  streams  or  only  small  ones 
came  down  to  the  coast.  These  old  shingle-beds  attain  in  the  Bigi, 
and  in  the  mountain  called  Speer,  near  Lucerne,  a  thickness  of  500< 
and  7000  feet. 


260  FOSSIL  PLANTS  OF  [Cn.  XV, 

Nearly  the  whole  of  this  Lower  Molasse  is  freshwater,  yet  some  of 
the  lowest  beds  contain  a  mixture  of  marine  and  fluviatile  shells,  the 
Cerithium  margaritaceum,  a  well-known  Lower  Miocene  fossil,  being 
one  of  the  marine  species.  Notwithstanding,  therefore,  that  some  of 
these  Lower  Miocene  strata  reach  an  elevation  of  6000  or  even  7000 
feet  above  the  sea,  the  deposition  of  the  whole  series  must  have  be- 
gun at  or  below  that  level.  For  ages,  in  spite  of  a  gradual  sinking  of 
the  coast  and  adjacent  sea-bottom,  the  rivers  continued  to  cover  the 
sinking  area  with  their  deltas ;  but  finally,  the  subsidence  being  in 
excess,  the  sea  of  the  Middle  Molasse  gained  upon  the  land,  and  ma- 
rine beds  were  thrown  down  over  the  dense  mass  of  freshwater  and 
brackish-water  deposit,  called  the  Lower  Molasse,  which  had  pre- 
viously accumulated. 

The  great  change  of  level  above  alluded  to  must  be  borne  in  mind 
if  we  would  account  for  a  phenomenon  by  which  geologists  have  been 
much  puzzled ;  namely,  the  fact  that  in  the  "  nagelflue,"  as  the  con- 
glomerates are  called  by  the  Swiss,  pebbles  of  gneiss,  granite,  and 
porphyry  are  common,  and  yet  no  such  rocks  now  enter  into  the 
structure  of  the  Alps.  Along  the  original  coast-line,  when  the  peb- 
ble-beds of  the  Lower  Miocene  were  forming,  there  may  have  been 
hills  of  granite  and  gneiss  more  than  a  thousand  feet  high,  but  when 
the  subsidence  had  continued  for  a  long  series  of  years,  these  would 
all  be  gradually  submerged  and  covered  over  by  fluviatile  sediment ; 
for  the  effect  of  a  general  depression  going  on  at  a  faster  rate  than 
the  accumulation  of  sediment  is  to  cause  the  shore-line  to  retreat 
inland,  the  sea  occupying  successively  old  zones  of  coast.  In  the 
present  period  we  see  at  the  southern  base  of  the  Alps  in  Italy,  hills 
of  gneiss  and  porphyry  of  moderate  height,  although  rocks  of  this 
class  form  at  present  no  part  of  the  chain  itself,  and  these  crystalline 
formations  might  be  submerged  and  buried  under  deltas  derived  from 
the  detritus  of  the  higher  Alps,  if  the  level  of  the  whole  region  were 
to  be  lowered  by  another  great  downward  movement. 

As  I  have  already  stated,  the  inferior  portion  of  the  Swiss  Lower 
Miocene,  called  Aquitanian  by  Heer,  may  best  be  studied  on  the 
northern  borders  of  the  Lake  of  Geneva  between  Lausanne  and  Ve- 
vay,  where  the  contiguous  villages  of  Monod  and  Rivaz  are  situated. 
The  strata  there,  which  I  have  myself  examined,  consist  of  alterna- 
tions of  conglomerate  sandstone  and  finely  laminated  marls  with  fossil 
plants.  A  small  stream  falls  in  a  succession  of  cascades  over  the 
harder  beds  of  puddingstone,  which  resist,  while  the  sandstone  and 
plant-bearing  shales  and  marls  give  way.  From  the  latter  no  less 
than  193  species  of  plants  have  been  obtained  by  the  exertions  of 
MM.  Heer  and  Gaudin,  and  they  are  considered  to  afford  a  true  type 
of  the  vegetation  of  the  inferior  subdivision  of  the  Lower  Miocene 
formations  of  Switzerland — a  vegetation  departing  farther  in  its 
character  from  that  now  flourishing  in  Europe  than  any  of  the  higher 
members  of  the  series  before  alluded  to,  and  yet  displaying  so  much 


CH.  XV.]  LOWER  MIOCENE  STRATA,   SWITZERLAND.  261 

affinity  to  the  flora  of  (Eningen  as  to  make  it  natural  for  the  botanist 
to  refer  the  whole  to  one  and  the  same  Miocene  period.  There  are, 
indeed,  no  less  than  81  species  of  these  Older  Miocene  plants  which 
pass  up  into  the  flora  of  (Eningen,  and  in  this  number,  says  Heer,  are 
many  of  those  which,  by  an  abundance  of  individuals  and  by  their 
arborescence,  must  have  constituted  a  leading  feature  in  the  forests 
of  that  era. 

Nearly  all  the  plants  at  Monod  are  contained  in  three  layers  of 
marl  separated  by  two  of  soft  sandstone.  The  thickness  of  the  marls 
is  ten  feet,  and  vegetable  matter  predominates  so  much  in  some  layers 
as  to  form  an  imperfect  lignite.  One  bed  is  filled  with  large  leaves 
of  a  species  of  fig  (Ficus  populina\  and  of  a  hornbeam  (Carpinus 
grrandis),  the  strength  of  the  wind  having  probably  been  great  when 
they  were  blown  into  the  lake ;  whereas  another  contiguous  layer 
contains  almost  exclusively  smaller  leaves,  indicating,  apparently,  a 
diminished  strength  in  the  wind.  Some  of  the  upper  beds  at  Monod 
abound  in  leaves  of  Proteacese,  Cypercaceae,  and  ferns,  while  some 
of  the  lower  ones,  Sequoia,  Cinnamomum,  and  Sparganium,  are  com- 
mon. In  one  bed  of  sandstone  the  trunk  of  a  large  palm  tree  was 
found  unaccompanied  by  other  fossils,  and  near  Vevay,  in  the  same 
series  of  Lower  Miocene  strata,  the  leaves  of  a  palm  of  the  genus 
Sabal  were  obtained  (see  fig.  197,  p.  259). 

Among  other  genera  of  the  same  class  is  a  Flabellaria  occurring 
near  Lausanne,  and  a  magnificent  Phoenicites  allied  to  the  date  palm. 
When  these  plants  flourished  the  climate  must  have  been  much  hot- 
ter than  now.  The  Alps  were  no  doubt  lower,  and  the  palms  now 
found  fossil  in  strata  elevated  2000  feet  above  the  sea  grew  nearly  at 
the  sea-level,  as  is  demonstrated  by  the  brackish-water  character  of 
some  of  the  beds  into  which  they  were  carried  by  winds  or  rivers 
from  the  adjoining  coast. 

In  the  same  plant-bearing  deposits  of  the  Lower  Molasse  in  Switz- 
erland have  been  found  no  less  than  20  species  of  Proteaceae,  an 
order  already  spoken  of  as  being  well  represented  in  the  (Eningen 
beds,  though  by  no  means  so  plentifully  as  in  these  Lower  Miocene 
strata,  and  which  were  still  more  strikingly  predominant  in  the  ante- 
cedent Eocene  and  in  the  still  more  ancient  Cretaceous  formations. 

One  of  the  following  named  plants,  Dryandra  Schrankii,  comes 
very  near  to  D.  formosa,  R.  Brown,  a  living  New  Holland  species, 
and  is  considered  by  Heer  as  "  homologous,"  but  the  leaf  only  of  the 
fossil  is  known.  This  is  one  of  the  species  which  characterizes  all 
stages  of  the  Lower  Miocene,  and  is  not  found  in  the  Upper.  It  also 
occurs  in  Great  Britain  in  the  Miocene  beds  of  the  Island  of  Mull,  in 
the  Hebrides,  and  in  the  lignite  of  Bovey  Tracey,  in  Devonshire. 

The  Proteas  and  other  plants  of  this  family  now  flourish  at  the 
Cape  of  Good  Hope  ;  while  the  Banksias,  and  a  set  of  genera  distinct 
from  those  of  Africa  grow  most  luxuriantly  in  the  southern  and 
temperate  parts  of  Australia,  They  were  probably  inhabitants,  says 


262 


FOSSIL  PLANTS  OF 
Fig.  198. 


[On.  XV. 


Fig.  199. 


Fig.  200. 


Fig.  198.    a.  Leaf  of  Dryandroides  ffakecefolia.    Lower  Miocene.    £  nat.  size.    Monod,  near 

Lausanne.    (Heer,  pi.  98,  fig.  6.) 
6.  Small  portion  of  the  same  magnified.    (Heer,  pi.  98,  fig.  13.) 

Fig.  199.    Hakea  exulata.    Hohen  Ehonen,  Switzerland.    Lower  Miocene.   Nat.  size.    (Heer, 
pi.  98,  fig.  19.) 

Fig.  200.    Dryandra  SchranMi.  Monod.  Lower  Miocene.  J  nat  size.  (Heer,  pi.  98,  fig.  20  5.) 

Heer,  of  dry  hilly  ground,  and  the  stiff  leathery  character  of  their 
leaves  must  have  been  favorable  to  their  preservation,  allowing  them 
to  float  on  a  river  for  great  distances  without  being  injured  and  then 
to  sink,  when  water-logged,  to  the  bottom.  It  has  been  objected  by 
some  botanists  that  the  fruit  of  the  Proteaceae  is  of  so  tough  and  en- 
during a  texture  that  it  ought  to  have  been  more  commonly  met 
with,  instead  of  being  restricted  to  a  single  example  like  that  of  the 
Hakea  saligna  before  mentioned  (fig.  191,  p.  255) ;  but  the  season  of 
fructification  in  these  plants  may  not  have  coincided  with  that  of  the 
most  active  sedimentary  deposition,  and  there  may  be  other  reasons 
for  the  absence  of  the  fruit  of  which  we  are  at  present  ignorant. 
Some  mistakes  have  certainly  been  made,  and  Count  Saporta  has 
shown  that  one  plant  formerly  referred  to  Dryandroides,  and  of  which 
he  discovered  the  fruit,  really  belongs  to  the  bog-myrtle,  or  sweet-gale 
tribe  (Myricd).  But  there  is  no  reason  to  question  the  general  accu- 
racy of  the  determination  of  the  fossil  Proteacese.  Those  of  the  cre- 
taceous marls  of  Aix-la-Chapelle  were  formerly  disputed,  but  fortu- 
nately the  leaves  in  that  case,  notwithstanding  their  antiquity,  are  so 
much  better  preserved  than  any  known  Miocene  plants,  that  their  epi- 
dermis can  be  examined  microscopically.  A  leaf  from  Aix  which, 
from  its  form  and  nervation,  had  been  referred  to  the  genus  Grevillea, 
was  found,  when  submitted  to  this  test,  to  have  regular  and  polygonal 
cellules  resembling  in  shape  and  thickness  those  of  the  living  G. 
oleoides  of  Australia. 

The  eight  or  nine  species  of  fig  (Ficus)  which  are  met  with  at  Mo- 
nod and  Rivaz,  have  their  nearest  living  analogues  in  the  hotter  parts 
of  India,  Africa,  and  America.  Among  the  Coniferse  the  Sequoia 


CH.  XV.] 


LOWER  MIOCENE  STRATA,   SWITZERLAND. 


263 


§S£'£3'L«££ 


21> 
and 


here  figured  is  common  at  Rivaz,  and  Fis-  201. 

is  one  of  the  most  universal  plants  in 
the  Lowest  Miocene  of  Switzerland, 
while  it  also  characterizes  the  Mio- 
cene Brown  Coals  of  Germany  and 
certain  beds  of  the  Val  d'Arno,  which 
I  have  called  Older  Pliocene,  p.  196. 

It  is  an  interesting  fact  that  this 
tree  should  also  have  been  discovered 
in  the  surturbrand  or  lignite  of  Ice- 
land, and  by  Dr.  Walker  in  Disco 
Island,  in  Greenland,  in  lat.  70°  N. 
It  comes  so  near  to  the  living  S.  sem- 
pervirens  (Taxodium)  of  California, 
that  some  botanists  entertain  doubts 

whether  they  may  not  be  varieties  of  the  same  species.  As  a  fossil, 
its  geographical  range  extends  from  Greenland,  lat  70°  N.,  to  Sini- 
gaglia  in  Italy,  lat.  44°  N.,  and  in  an  east  and  west  direction  from  the 
Hebrides  (Isle  of  Mull)  to  the  Steppe  of  the  Kirghis. 

Sir  John  Richardson  found  this  same  fossil  tree  on  the  Mackenzie 
River,  two  miles  north  of  its  junction  with  Bear  River,  lat.  65°  N., 
or  in  about  the  same  parallel  as  the  north  of  Iceland. 

I  am  indebted  to  Professor  Heer  for  the  annexed  figure  of  this 
JS"orth  American  specimen  taken  from  the  original. 

"~ 

Fig.  202. 


pper  and  Lower  Miocene 
wer  Pliocene.    Val  d'Arno. 


Young  cone. 


Sequoia  Langsdorfti.    Fossil,  Mackenzie  Eiver,  lat.  65"  N. 
Sir  G.  Kichardson,  Voyage,  1851,  vol.  L  p.  186 ;  vol.  ii.  p.  408. 

a.  Branch  with  leaves,  one  year's  growth. 

&.  Under  side  of  a  leaf  magnified,  showing  punctuations  as  in  the  living  8.  sempetwwns. 

c.  Male  flowers.  d.  Carpets  of  the  cone.  e.  Seed. 

Among  the  ferns  met  with  in  profusion  at  Monod  is  the  Lastrcea 
stiriaca,  Unger,  which  has  a  wide  range  in  the  Miocene  period  from 
strata  of  the  age  of  (Eningen  to  the  lowest  part  of  the  Swiss 
molasse. 


264 


FOSSIL  PLANTS  OF 


[On.  XT. 


In  some  specimens,  as  shown  in  the  annexed  figure,  the  fructifica- 
tion is  distinctly  seen. 


Fig.  204. 


Lastrcea  stiriaca,  Ung.     (Heer's  Flora,  pi.  143,  fig.  8.) 

Natural  size.    Lower  and  Upper  Miocene.    Switzerland. 

a.  Specimen  from  Monod,  showing  the  position  of  the  sori  on  the  middle  of  the  tertiary 

nerves. 
&.  More  common  appearance,  where  the  sori  remain  and  the  nerves  are  obliterated. 

In  the  Upper  Miocene  flora  of  (Eningen  already  described  the  num- 
ber of  forest  trees  and  evergreen  shrubs  is  very  great.  Their  pre- 
dominance, however,  in  the  period  of  the  Lower  Miocene  was  still 
more  marked,  and  is  characteristic  of  subtropical  countries.  No  less 
than  two-thirds  of  all  the  ligneous  plants  were  evergreens. 

Among  other  features  which  cause  this  flora  to  resemble  that  of 

North  America  is  the  great  abun- 
dance of  trees  of  the  order  Amenta- 
ceae,  such  as  the  oak,  poplar,  alder, 
birch,  willow,  hornbeam,  plane,  &c. 

The  papilionaceous  plants,  of  which 
there  are  twenty-four  genera,  are  the 
most  abundantly  represented  of  all 
families,  both  in  the  Lower  and 
Upper  Miocene.  But  the  laurels,  of 
which  there  are  only  five  genera, 
have  contributed  most  leaves  to  the 
Miocene  strata.  Among  these  sev- 
eral species  of  Cinnamomum,  as  be- 
fore mentioned,  are  very  conspicuous. 
Besides  C.  polymorphism,  before 
figured,  p.  254,  another  species  also 
ranges  from  the  Lower  to  the  Upper 
Molasse  of  Switzerland,  and  is  very 
characteristic  of  dilTerent  deposits  of 

Cinnamorrwmllo8Sma*8leri,ILeer.  DapTi-  Brown  Coal  in  Germany.  It  has 
nogene  cinnamomifolia,  Unger.  Upper  been  called  Cinnamomum  RosmCLSS- 
and  Lower  Miocene,  Switzerland  and  .  „  ,  „  nr\*\ 

Germany.  ten  ty  Heer  (see  fig.  204). 


CH.  XV.]  MIOCENE  STRATA  OF  SWITZERLAND.  265 

This  plant  is  nearly  allied  to  a  living  North  Indian  species,  C.  euca- 
lyptoides.  The  leaves,  as  before  mentioned,  are  easily  recognized  as 
having  two  side  veins,  which  run  up  uninterruptedly  to  their  point. 

The  lowest  of  the  Swiss  Miocene  beds,  the  sandstone  of  Ralligen, 
on  the  Lake  of  Thun,  in  which  32  plants  have  been  found,  contains 
no  less  than  6  species  in  common  with  (Eningen — a  proportion  of  18 
in  a  hundred.  Among  them  we  find  Taxodium,  closely  allied  to  the 
deciduous  cypress  of  the  Mississippi,  also  a  pine,  an  arundo,  and  one 
of  the  Proteacese,  Dryandroides  lignitum. 

Alleged  difference  in  the  degree  of  affinity  of  the  Upper  Miocene  plants 
and  shells  to  the  living  creation. 

Before  concluding  my  remarks  on  the  fossil  Flora  and  Fauna  of 
Switzerland,  I  may  say  a  few  words  on  the  embarrassment  which 
some  geologists  have  felt  in  consequence  of  the  alleged  anomaly  of 
the  results  derived  from  the  study  of  the  fossil  shells  as  compared  to 
the  fossil  plants  and  insects.  Of  the  shells  of  the  marine  Molasse 
which  underlies  the  freshwater  deposit  of  (Eningen,  a  fourth  or 
more  than  a  fourth  have  been  declared  by  able  conchologists  to  be 
of  species  still  existing,  whereas  ah1  the  plants  and  insects  have 
been  said  to  differ  from  living  ones.  On  looking  more  closely  into 
the  evidence,  we  shall  perhaps  find  that  this  supposed  inconsistency 
disappears. 

Professor  Heer,  it  is  true,  does  not  identify  any  Miocene  plants 
with  living  species,  but  he  has  enumerated  72  species  which  he  terms 
"  homologous,"  40  of  them  known  by  their  fruits  as  well  as  their 
leaves  ;  and  although  he  is  opposed  to  the  doctrine  of  transmutation, 
he  admits  that  these  homologous  species  are  so  closely  allied  to  the 
nearest  forms  now  living,  that  the  latter  may  be  their  lineal  descend- 
ants. He  cannot,  he  says,  decide  "  whether  the  variation  has  been 
brought  about  by  some  influence  which  has  been  exerted  continuously 
for  ages,  or  whether  at  some  given  moment  of  past  time  the  old  types 
were  struck  with  a  new  image." 

Now  the  degree  of  relationship  here  implied  would  be  at  once  ac- 
cepted by  most  naturalists  as  constituting  specific  identity.  Let  us 
suppose  that  the  sessile  variety  of  the  common  oak,  Quercus  robur, 
had  been  only  known  to  us  as  a  fossil  from  (Eningen  and  not  as  a  liv- 
ing form,  and  that  the  other  living  variety,  in  which  the  flower  and 
acorns  are  supported  on  a  stalk,  was  the  only  form  now  existing.  The 
first  of  these  would,  according  to  the  method  adopted  in  Professor 
Heer's  work,  rank  as  an  extinct  Miocene  species ;  whereas  the  two 
forms  now  co-existing  in  European  forests  are  generally  regarded  by 
botanists  as  mere  varieties.  That  such  a  distinction  would  have  been 
made  by  Heer  we  are  entitled  to  infer  from  the  manner  in  which  he 
has  dealt  with  the  fossil  specimens  of  a  plant  called  by  him  Planera 
Ungeri.  To  the  leaves  and  fruit  of  this  tree,  which  is  allied  to  the 


266 


IDENTIFICATION  OF  FOSSIL  PLANTS. 


[On.  XV. 


elm,  linger  had  previously  given  the  name  of  P.  Richardi,  identify- 
ing it  with  a  tree  now  living  in  the  Caucasus  and  Crete ;   but  Heer 

Fig.  205. 


Fig.  206. 


Planera  Ricliardi^  Unger.    P.  Ungeri,  Heer. 

Upper  Miocene.    (Heer,  pi.  80,  Flora  Tert.  Helvetia.) 

a.  A  branch  from  (Eningen.  &.  Fruit  magnified.  c.  Leaf.  (Eningen. 

had  pointed  out  that  in  the  fossil  the  size  of  the  fruit  was  larger. 
When,  however,  in  1861,  the  Swiss  Professor  visited  with  me  the  rich 
herbarium  of  Kew,  Dr.  Hooker  showed  us  a  living  variety  of  P. 
Rickardi  in  which  the  fruit  was  fully  as  big  as  that  of  (Eningen,  so 
that  this  last  must  retain  linger' s  name,  and  this  example,  if  there 
were  no  other,  might  suffice  to  warn  us,  in  the  present  imperfect 
state  of  our  knowledge,  not  to  indulge  in  too  positive  a  belief  that  all 
the  Miocene  species  have  become  extinct. 

Out  of  the  72  homologous  species 
above  mentioned,  67  are  phsenoga- 
mous  and  only  5  cryptogamous ;  but 
it  may  well  be  doubted  whether 
among  the  49  Miocene  Cryptogamia 
described  in  Heer's  Flora  Tertiaria, 
a  much  greater  number,  perhaps 
more  than  half,  might  not  with  pro- 
priety have  received  (provisionally  at 
least)  the  names  of  living  plants. 
Heer  admits  that  the  majority  come 
very  near  to  existing  species,  and  we 
know  well  how  wide  is  the  geo- 
graphical range  of  the  ferns,  and 
still  more  of  flowerless  plants  of 
lower  grades,  such  as  mosses,  lich- 

a.  Part  of  a  leaf  of  Acer  trilobate  with     ens>  and  fun^  man7  SPecies  °f  wticn 

numerous  specimens  of  the  fungus    are  cosmopolitan,  and  therefore  fitted, 

called  Rhytisma  ^nduratum,  Heer. 


5.  Magnified  view  of  the  fungus. 
(Heer,   pi.  112,  fig.  7.)     Upper  Miocene, 
(Eningen. 


by  their  adaptability  to  varying  con- 
for  a  lone:  duration  in 


CH.  XV.]  MIOCENE  AND  LIVING  PLANTS.  267 

On  the  leaves  of  a  fossil  inaple,  Acer  trilobatum,  already  mentioned, 
fig.  183,  p.  253,  a  small  body  is  frequently  seen  resembling  the  living 
fungus  which  grows  on  maples,  called  by  Fries  Rhytisma  acerinum. 
It  is  tuberculated  and  crenulated  (see  the  magnified  figure,  b).  The 
fossil  has  made  so  deep  an  indentation  on  the  incumbent  and  subja- 
cent layer  of  marl  as  to  lead  Professor  Heer  to  infer  that  it  was  some- 
what thicker  than  the  living  form.  Instead,  therefore,  of  treating  it 
as  a  variety,  he  has  called  it  R.  induratum,  under  which  title  it  helps 
to  swell  the  list  of  extinct  Miocene  species. 

In  like  manner  there  is  a  minute  fungus,  called  by  Heer  Sphceria 
ceuthocarpoides,  which  spots  the  leaves  of  Populus  ovalis  at  (Eningen, 
very  closely  resembling  the  living  Sphceria  ceuthocarpa  of  Fries.  Some 
botanists  would  think  it  very  hazardous  to  assign  even  generic  names 
to  such  objects,  and  still  more  rash  to  decide  that  the  fossil  differed 
specifically  from  its  living  analogue. 

Another  of  these  fungi  forming  black  spots  on  the  fossil  leaves  of  a 
poplar  is  proved  in  like  manner  to  have  been  a  real  subtance,  and  not 
simply  the  effect  of  discoloration,  for  it  has  left  indentations  both  on  the 
under  and  overlying  layers  of  marl.  To  decide  that  it  is  not  a  living 
species  would  require  far  ampler  data.  Some  botanists  are  even  un- 
certain whether  as  much  can  be  said  of  the  Populus  latior  itself  of 
CEningen,  on  which  the  fungus  grew,  and  of  which  seven  varieties  are 
described  by  Heer,  some  of  them  coming  very  near  to  the  Populus 
monilifera  of  North  America. 

Similar  comments  might  be  made  on  the  long  list  of  homologous 
insects  given  by  Heer  from  the  Miocene  strata  of  Switzerland. 
Their  specific  distinctness  from  their  nearest  representatives  now  liv- 
ing might  appear  to  the  zoologist  in  a  very  different  light,  according 
to  the  state  of  mind  in  which  he  may  approach  their  study.  If  he  is 
reflecting  on  the  fact  that  all  the  Upper  Miocene  mammalia  and  a 
great  majority  of  the  testacea  are  extinct,  and  is  then  endeavoring  to 
decide  whether  a  fossil  and  a  recent  form,  between  which  there  is  a 
close  affinity,  should  be  regarded  as  varieties  or  distinct  species,«it 
may  seem  the  safest  course  to  incline  to  the  latter  alternative  ;  yet,  by 
giving  a  new  name  to  the  fossil  in  doubtful  cases,  a  serious  responsi- 
bility is  incurred,  as  the  naturalist  thereby  commits  himself  to  an  ab- 
solute negation  of  specific  identity  between  such  Miocene  and  living 
insects  and  plants.  If  it  be  right  to  exercise  extreme  caution  in  iden- 
tifying, it  is  equally  important  not  to  separate  individuals  which  may 
really  belong  to  the  same  species.  In  spite  of  the  soundness  and 
general  accuracy  of  the  conclusions  arrived  at  by  Professor  Heer  after 
such  great  and  conscientious  labors,  there  'appears  to  me  an  inconsis- 
tency in  one  of  his  results,  which  may  have  been  owing  to  an  unwill- 
ingness to  identify  Upper  Miocene  and  living  plants.  When  we 
consult  his  tabular  list  of  the  fossil  plants  of  Switzerland,  we  find  that 
a  great  number  of  species  pass  from  the  Aquitanian  Flora  to  that  of 
(Eningen,  which  are  as  distinct  from  each  other  in  age  as  are  the  Fon- 


268  THEORY  OF  A  MIOCENE  ATLANTIS.  [On.  XV. 

tainebleau  sands  from  the  Faluns  of  the  Loire.  But  scarcely  one 
plant  is  admitted  to  have  survived  the  shorter  interval  of  time  which 
separated  the  flora  of  CEningen  from  our  own  epoch.  I  say  shorter 
interval,  because,  as  we  have  seen,  p.  217,  all  the  shells  of  the  Fon- 
tainebleau  sands  differ  from  those  of  the  Faluns,  whereas  a  fifth  part, 
and  in  some  cases  a  third,  of  the  shells  of  falunian  deposits  are  still 
living.  If,  therefore,  the  differential  characters  of  the  plants  had  been 
measured  in  the  same  scale,  and  without  any  bias,  it  appears  to  me 
that  since  many  of  them  pass  from  a  lower  to  one  of  the  uppermost 
members  of  the  Miocene  group,  so  a  still  greater  number  should  have 
been  recognized  as  being  common  to  the  uppermost  Miocene  period 
and  the  living  creation. 

Theory  of  a  Miocene  Atlantis. — The  Swiss  plants  of  the  Miocene 
period  have  been  obtained  from  a  country  not  exceeding  one-fifth  of 
Switzerland  in  area,  yet  the  abundance  of  species  in  certain  genera 
and  families  best  adapted  for  preservation  in  a  fossil  state  is  so  great 
as  to  demonstrate  that  the  Miocene  was  richer  than  the  modern  flora, 
rich  and  varied  as  the  latter  is  well  known  to  be.  The  researches 
already  made  imply,  according  to  Heer,  that  in  the  phsenogamous 
class  alone  there  must  have  been  3000  Miocene  species,  and,  making 
due  allowance  and  deductions  on  account  of  those  which  are  limited 
to  certain  subordinate  members  of  the  Miocene  group,  and  which 
may  not  all  have  existed  at  once,  he  comes  to  the  conclusion  that  in 
no  equal  area  in  the  South  of  Europe  (in  Lombardy,  for  example,  or 
Sicily)  is  there  now  so  luxuriant  and  diversified  a  vegetation.  It  ex- 
ceeded in  variety  the  Southern  States  of  America,  such  as  Georgia 
and  the  Carolinas,  and  rivalled  that  of  tropical  countries,  such  as 
Jamaica  and  Bahia. 

The  majority  of  the  fossil  forms  are  allied  to  living  species  or 
genera,  but  there  are  certain  extinct  types,  specific  and  generic,  which 
have  a  wide  range  through  successive  tiers  of  strata  from  the  lowest 
Molasse  up  to  those  of  QEningen,  and  there  is  a  certain  unity  of  char- 
acter stamped  on  the  whole  Miocene  flora  in  spite  of  the  contrast  be- 
tween that  of  the  uppermost  and  lowest  formations.  The  proofs  of 
a  warmer  climate,  and  the  preponderance  of  trees  and  shrubs  over 
herbaceous  plants,  and  the  excess  of  evergreen  over  deciduous  species, 
are  characters  common  to  the  whole  flora,  but  which  are  intensified 
as  we  descend  to  the  inferior  deposits.  On  the  other  hand,  the  com- 
parative number  of  American  forms,  though  always  conspicuous,  is 
somewhat  lessened  in  the  lowest  beds.  The  living  American  types, 
says  Heer,  are  the  most  prominent ;  those  of  Europe  are  in  the  second 
rank ;  those  of  Asia  in  the  third ;  Africa  in  the  fourth ;  and  New 
Holland  in  the  fifth.  In  Europe  it  is  the  Mediterranean  region  which 
presents  the  greatest  number  of  analogous  species.  In  America,  the 
Southern  United  States,  such  as  Louisiana,  Florida,  Georgia,  and  the 
Carolinas;  in  Asia,  Japan,  and  the  countries  of  the  Caucasus  and 
Asia  Minor ;  in  Africa,  the  small  islands  in  the  Atlantic,  such  as  the 
Canaries  and  Madeira. 


CH.  XV.]  THEORY  OF  A  MIOCENE  ATLANTIS.  269 

If  we  consider  not  simply  a  mere  list  of  species  but  those  plants 
which  would  constitute  the  mass  of  the  vegetation,  the  European  part 
of  the  fossil  flora  is  thrown  still  more  in  the  background,  and  the  fore- 
ground is  occupied  by  America  with  its  numerous  evergreen  oaks, 
maples,  poplars,  planes,  Liquidambar,  Robinia,  Sequoia,  Taxodium, 
and  ternate-leaved  pines,  and  Japan  with  its  many  camphor  trees  and 
glyptostrobus,  the  Atlantic  Islands  with  their  laurels,  and  Asia  Minoi 
with  its  planera  and  Populus  mutabilis.*  During  the  Miocene  period 
in  Europe,  there  was  a  singular  coexistence  of  generic  types  of  plants 
which  are  now  peculiar  to  America,  or  to  Asia,  or  to  Africa,  or  Aus- 
tralia ;  in  a  word,  to  parts  of  the  globe  extremely  distant  from  each 
other.  This  fusion  of  the  characters  now  belonging  to  distinct  botan- 
ical provinces  becomes  more  marked  as  we  go  back  to  the  Lower 
Miocene  formations,  and  will  be  found  to  be  still  more  strikingly  ex- 
emplified in  the  antecedent  Eocene  and  Cretaceous  periods.  In  the 
Lower  Miocene  formations  of  Central  Europe  the  climate  seems  to 
have  been  not  only  hotter  but  more  uniform  and  humid,  and  this 
humidity  would  favor  the  formation  of  beds  of  lignite,  such  as  con- 
stitute the  Brown  Coal  of  Germany. 

The  large  number  of  American  genera  in  the  Miocene  flora  induced 
linger  to  suggest  that  the  present  basin  of  the  Atlantic  was  occupied 
by  land,  over  which  the  Miocene  plants  could  pass  freely,  and  this  hy- 
pothesis has  been  enlarged  and  advocated  with  great  ability  by  Heer. 
It  seems  at  the  first  glance  to  derive  much  support  from  the  fact  that 
it  is  the  eastern  or  Atlantic  side  of  North  America,  or  that  which  is 
nearest  to  Europe,  which  presents  the  greatest  number  of  vegetable 
forms  analogous  to  the  Miocene  flora.  But  Dr.  Asa  Gray,  following 
up  a  hint  thrown  out  by  Mr.  Bentham,  has  argued  with  great  force 
that  it  is  far  more  probable  that  the  plants,  instead  of  reaching  Eu- 
rope by  the  shortest  route  over  an  imaginary  Atlantis,  migrated  in  an 
opposite  direction,  and  took  a  course  four  times  as  long  across  Ameri- 
ca and  the  whole  of  Asia. 

If  the  evidence  in  the  botanical  scale  were  equally  balanced  in  favor 
of  these  two  opposite  theories,  a  geologist  would  not  hesitate  to  prefer 
that  of  Dr.  Asa  Gray  as  demanding  an  incomparably  smaller  amount  of 
change  in  physical  geography  since  the  close  of  the  Miocene  period. 
It  is  true  that  since  the  beginning  of  that  era  there  have  been  vast 
alterations  in  the  level  of  the  Alps  and  contiguous  regions,  as  we 
have  seen,  p.  260,  and  in  the  Mediterranean,  especially  the  Egean 
Sea,  p.  247.  And  there  was  perhaps,  as  the  late  Edward  Forbes 
contended,  an  extension  westward  of  European  and  North  African 
land  even  in  the  Pliocene  period.f  If,  instead  of  assigning  an 
almost  historical  date  to  a  continental  condition  of  the  area  between 
Africa  and  the  Southern  States  of  North  America,  such  as  might 


*  Heer  and  Gaudin,  p.  59. 

f  Sefe  Map,  vol.  i.  pi.  7.     Memoirs  of  Geol.  Survey,  &c.,  1846. 


270  THEORY  OF  A  MIOCENE  ATLANTIS.  [Cn.  XY. 

realise  the  story  of  the  Atlantis  spoken  of  by  the  Egyptian  priests  to 
Plato,  we  could  look  back  through  the  whole  interval  which  separates 
us  from  the  Eocene  or  Cretaceous  periods,  we  might  then  indeed 
freely  grant,  as  geologists,  any  amount  of  change  that  may  be  re- 
quired in  the  position  of  land  and  sea.  All  that  is  wanting  is  time 
for  the  gradual  development  of  a  long  series  of  subterranean  move- 
ments ;  that  being  conceded,  there  would  be  no  exaggeration  in  the 
lines  of  the  poet — 

"Earthquakes  have  raised  to  heaven  the  humble  vale, 
And  gulfs  the  mountain's  mighty  mass  entombed, 
And  where  the  Atlantic  rolls  wide  continents  have  bloomed." — Seattle. 

It  is  the  enormous  depth  and  width  of  the  Atlantic  which  makes  us 
shrink  from  the  hypothesis  of  a  migration  of  plants,  fitted  for  a  sub- 
tropical climate  in  the  Upper  Miocene  period,  from  America  to  Europe, 
by  a  direct  course  from  west  to  east.  Can  we  not  escape  from  this  dif- 
ficulty by  adopting  the  theory  that  the  forms  of  vegetation  common 
to  Recent  America  and  Miocene  Europe  first  extended  from  east  to 
west  across  North  America  and  passed  thence  by  Behring's  Straits  and 
the  Aleutian  Islands  to  Kamtschatka,  and  thence  by  land,  placed  be- 
tween the  40th  and  60th  parallels  of  latitude  where  the  Kurile  Islands 
and  Japan  are  now  situated,  and  thence  to  China,  from  which  they 
made  their  way  across  Asia  to  Europe. 

If  that  be  the  case,  the  breaks  in  a  once  continuous  province  of 
plants,  and  the  extinction  as  well  as  the  diminished  range  of  many 
species,  might  well  have  been  caused  by  the  mighty  revolutions  in 
physical  geography  which  we  know  to  have  occurred  in  various  parts 
of  this  area  in  Post-miocene  times. 

Professor  Oliver,  after  making  a  careful  analysis  of  Heer's  work, 
above  cited,  on  the  "  Tertiary  Flora  of  Switzerland,"  has  given  us  an 
able  essay  on  the  bearing  of  the  valuable  store  of  facts  therein  con- 
tained on  the  two  rival  theories  above  alluded  to.*  In  the  first  place 
he  has  thought  it  safer  to  set  aside  all  the  cryptogamia,  and  to  discard 
a  certain  number  of  the  phsenogamous  plants  as  having  been  doubt- 
fully determined  by  their  leaves  alone ;  but  after  these  deductions 
there  remain  about  800  plants  referred  to  196  genera  in  the  Swiss 
Miocene  flora.  It  is  of  course  understood  that  some  of  these  deter- 
minations are  very  doubtful  in  the  absence  of  fruit  or  flowers,  but 
the  positive  data  which  remain  are  amply  sufficient  for  sound 
generalizations,  and  we  need  not  fear  that  these  will  be  materially 
shaken  by  future  discoveries.  The  reasoning  is  the  more  to  be 
relied  on  because  in  so  great  a  number  of  genera  only  twenty-one 
are  extinct,  fifteen  of  these  being  monocotyledonous  and  six  dico- 
tyledonous. 

It  is  admitted  that  there  is  an  unquestionable  analogy  between  the 

*  Nat.  Hist.  Review,  1862,  p.  149. 


CH.  XV.]  THEORY  OF  A  MIOCENE  ATLANTIS.  271 

Miocene  flora  of  Central  Europe  and  the  Recent  flora  of  North 
America,  and  that  the  analogy  is  greater  than  between  the  same  fossil 
flora  and  that  now  existing  in  Europe.  But  in  the  first  place  it  is 
remarked  by  Dr.  Asa  Gray  that  the  Swiss  Miocene  plants  are  more 
like  those  of  Japan  than  they  are  like  those  now  living  in  Europe, 
which  at  once  suggests  the  idea  that  the  American  plants  may  have 
taken  a  westerly  instead  of  an  easterly  route.  In  the  next  place  it  is 
remarked  that,  if  we  travel  from  Europe  to  the  east,  the  farther  we  go 
the  more  we  find  the  living  vegetation  putting  on  the  characters  of 
the  Old  Miocene  flora.  Thus  in  passing  from  the  Mediterranean  to 
the  Levant,  the  Caucasus,  and  Persia,  we  meet,  says  Professor  Oliver, 
with  Chamcerops,  Platanus,  Liquidambar,  Pterocarya,  Juglans,  &c., 
&c.,  then  we  trace  along  the  Himalaya  and  through  China  other 
Miocene  genera,  the  eastern  part  of  the  Asiatic  continent  forming 
with  Japan  one  great  botanical  region.  In  the  Southern  American 
States  eighty-eight  of  the  Miocene  genera  are  now  represented ;  but  Pro- 
fessor Oliver  gives  a  table  to  show  that  if  we  take  Europe,  Asia,  and 
Japan  together,  as  before  suggested,  there  are  no  less  than  120  Recent 
genera  which  are  common  to  the  Swiss  Miocene  flora.  Moreover 
there  are  some  general  features  in  which  the  living  flora  of  Japan  is 
more  like  the  Old  Miocene  vegetation  of  Europe  than  is  the  living 
flora  of  America.  For  example,  the  nine  Tertiary  orders  which  are 
numerically  the  largest  are  the  following: — 1.  Gramineae  (grasses) ;  2. 
Composites ;  3.  Cyperacese  (sedges) ;  4.  Salicacese  (willows) ;  5.  Con- 
iferse  (pines) ;  6.  Leguminosse  ;  7,  Laurinea3  (laurels) ;  8.  Acerinese 
(maples) ;  and  9.  Proteacese.  The  six  first  of  these  are  included  in 
the  nine  largest  orders  of  Japan,  and  only  four  of  them,  namely, 
the  three  first  and  the  sixth,  in  the  largest  orders  of  the  Southern 
States  of  North  America ;  and  farther,  the  three  last  of  the  nine  are 
much  more  developed  in  Japan  than  in  the  Southern  States. 

Heer  estimates  the  proportion  of  ligneous  species  in  the  Swiss 
Miocene  as  exceeding  60  per  cent,  of  all  the  plants.  Professor  Oliver 
remarks  on  this  subject  that  in  Japan  they  constitute  40  per  cent,  of 
the  whole  flora,  and  only  22  per  cent,  in  that  of  the  Southern  United 
States.  There  are  seventy-seven  genera  common  to  the  recent  flora  of 
Japan  and  to  the  European  Miocene  strata,  and  nearly  the  same  num- 
ber are  common  to  the  tertiary  and  the  living  flora  of  Europe ;  but 
the  genera  which  are  common  in  these  two  instances  are  by  no  means 
the  same,  and  no  less  than  twenty-six  of  the  Japanese  list  are  wanting  in 
Europe,  having  become  extinct  there  since  the  Miocene  period.  Not 
a  few  of  these,  such  as  Cinnamomum  and  Glyptostrobus,  play  a  con- 
spicuous part  among  the  fossils. 

In  order  to  understand  the  disappearance  of  so  many  forms,  we 
have  only  to  call  to  mind  the  great  geographical  changes  already 
alluded  to,  which  are  known  to  have  taken  place  in  Eastern  Europe 
and  Western  Asia  since  the  Miocene  era.  It  seems  at  first  sight  an 
anomaly  that  the  plants  on  the  eastern  side  of  North  America  should 


272  THEORY  OF  A  MIOCENE  ATLANTIS.  [On.  XY. 

agree  more  closely  with  those  of  Japan  than  does  the  flora  of  the  in- 
tervening countries,  Oregon  and  California,  west  of  the  Rocky  Moun- 
tains. It  would  naturally  lead  us  to  conjecture  that  many  of  the 
Miocene  genera  of  Europe  now  found  only  on  the  Atlantic  side  of 
North  America  may  once  have  ranged  to  the  Pacific  side.  In  favor 
of  such  an  hypothesis,  it  may  be  mentioned  that  in  1859  Lesguereux 
discovered  in  a  fossil  state  in  Vancouver's  Island  and  in  Oregon  many 
of  the  Miocene  genera  which  are  no  longer  represented  in  the  flora 
now  living  on  the  west  side  of  the  Rocky  Mountains.  Among  these 
there  is  a  Cinnamomum  resembling  C.  Rossmassleri,  see  fig.  204,  a 
planer-tree,  like  Planera  Richardi,  a  Glyptostrobus  like  G.  (Eningemis, 
Br.,  and  a  fan  palm,  besides  willows  and  maples,  the  whole  assemblage 
implying  a  warmer  climate  in  Oregon  in  the  Miocene  period,  and  also 
pointing  to  the  spread  of  a  similar  vegetation  across  the  whole  Ameri- 
can continent  in  ancient  times. 

In  support  of  the  Atlantis  theory,  Heer  has  pointed  out  that  certain 
American  genera,  such  as  Oreodaphne,  closely  related  to  0.  fcetens  or 
the  Til,  also  Clethra,  Bystropogon,  Cedronella,  and  others,  are  com- 
mon to  the  Miocene  of  Europe,  and  to  the  flora  of  Madeira  and  Porto 
Santo,  and  to  that  of  the  Canaries  and  Azores.  Had  the  number  of 
genera  proper  to  these  islands,  especially  to  the  Azores,  been  very 
considerable,  this  argument  would  be  entitled  to  have  great  weight, 
for  such  Atlantic  islands  would  then  appear  to  have  been  the  last 
remnants  of  a  lost  continent  over  which  a  continuous  vegetation  once 
ranged  from  west  to  east.  But  Professor  Oliver  truly  observes  that 
the  botanical  types  having  the  geological  and  geographical  relations 
required  by  the  hypothesis  are  extremely  few  in  the  Atlantic  islands. 
Moreover  two  of  those  above  cited,  Clethra  and  Cedronella,  are  of  lit- 
tle or  no  value,  as  species  of  both  of  them  now  grow  in  Japan,  and 
some  of  the  other  plants  may  have  reached  the  Atlantic  islands  at  the 
time  when  these  were  united  with  Barbary,  and  Barbary  with  Europe, 
at  which  same  period  many  European  land-shells  and  plants  now 
flourishing  in  Madeira  and  Porto  Santo  may  have  migrated  thither. 

The  existence  of  a  continuous  land  communication  between  East- 
ern America  and  Western  Europe  in  the  Pliocene  period,  by  means 
of  which  many  plants  migrated,  before  the  Glacial  period,  from  one 
region  to  the  other,  was  suggested  by  Mr.  Darwin  in  his  "  Origin  of 
Species"  (chap,  xi.,  1859) ;  and  Dr.  Leidy  has  observed  that  a  like 
continuity  of  land  from  east  tb  west  is  implied  by  the  identity  of  some 
of  the  extinct  Pliocene  mammalia  of  the  .Niobrara  Valley  in  Nebraska 
with  those  of  a  corresponding  geological  age  in  Europe.  The  ideal 
map  given  by  Heer  of  the  Atlantis  represents  a  continent  as  large  as 
Europe  precisely  in  that  portion  of  the  Atlantic  Ocean  which  is  now 
the  broadest  and  deepest.*  The  depth  has  been  lately  shown  to 

*  Heer  and  Gaudin,  Flora  Tertiaria  Helvetise,  vol.  iii.  pi.  156,  fig.  9,  aud  Recher- 
ches  sur  le  Climat,  pi.  1,  fig.  9. 


CH.  XV.]  THEORY  OF  A  MIOCENE  ATLANTIS.  273 

range  in  the  central  parts  from  two  to  three  miles.  To  suppose  that 
a  continent,  therefore,  was  so  situated  up  to  the  close  of  the  Miocene 
period,  when  the  American  types,  as  seen  at  (Eningen,  were  most 
dominant,  would  imply  a  prodigious  amount  of  subsidence  in  a  com- 
paratively brief  period.  In  the  lifetime  of  a  single  generation  of  men, 
plants,  of  which  the  seeds  have  been  unintentionally  transported  to  a 
distant  coast,  have  made  their  way  for  many  miles  into  the  interior 
without  human  aid.  A  botanist,  therefore,  might  form  some  rude 
estimate  of  the  number  of  centuries  which  would  be  required  for  an 
assemblage  of  plants  to  spread  over  land  several  thousand  miles  in  ex- 
tent from  east  to  west ;  but  no  geologist  would  venture  to  estimate 
the  ages  required  to  convert  so  many  thousand  miles  of  land  into  a 
shallow  sea  and  then  turn  that  vast  shoal  into  a  sea-bottom  two  or 
three  miles  deep. 

Even  if  we  were  called  upon  to  imagine  that  the  Miocene  flora  origi- 
nated in  the  Southern  United  States,  in  Georgia  and  the  Carolinas  for 
example,  and  that  they  made  their  way  overland  westward  for  a 
distance  of  16,000  miles  to  Europe,  we  might  conceive  such  a  migra- 
tion to  be  performed  in  a  mere  fraction  of  the  period  which  it  would 
take  to  convert  Africa  or  North  America  into  an  ocean  as  deep  as  the 
Atlantic. 

Behring's  Straits  do  not  exceed  in  depth  and  width  the  Straits  of  Do- 
ver, so  that  the  former  union  of  North  America  with  Asia  would  demand 
only  a  slight  change  of  level,  and  the  present  existence  of  such  chains 
of  islands  as  the  Kurile  and  Aleutian  makes  it  easy  to  imagine  that 
there  may  have  been  a  post-miocene  connection  between  Kamt- 
schatka,  Japan,  and  China.  Independently,  therefore,  of  the  botanical 
arguments  in  favor  of  a  migration  from  east  to  west,  this  latter  theory 
involves  us  in  far  less  hazardous  speculations  as  to  geographical  change 
than  that  of  a  Miocene  Atlantis. 

We  are  not,  however,  entitled  to  take  for  granted  that  some  of  the 
American  types  may  not  have  crossed  to  Europe  in  high  Northern 
latitudes,  when  Greenland,  Iceland,  and  the  Hebrides  were  united  by 
a  continuous  land  communication.  And  in  support  of  this  view  it 
may  be  urged  that  a  Miocene  flora  has  been  discovered  in  several  parts 
of  the  Arctic  lands,  especially  in  Disco  Island,  in  Greenland,  lat. 
70°  N.,  and  in  Iceland,  and,  as  above  mentioned,  p.  242,  in  the 
Island  of  Mull  in  the  Hebrides.  But  in  the  first  place,  in  reference 
to  these  northern  miocene  deposits,  it  may  be  observed  that  palm  < 
and  other  tropical  forms  are  wanting ;  and  secondly,  the  depth  of 
the  ocean  in  the  regions  alluded  to  is  very  great.  Sir  L.  Mac- 
Clintock,  when  sounding  for  the  proposed  submarine  telegraph,  found 
a  depth  of  4092  feet  between  Scotland  and  Iceland,  and  again  a  depth 
of  no  less  than  9432  feet  between  Iceland  and  Greenland.  Possibly 
the  number  of  fathoms  might  not  be  so  great  if  a  survey  of  the  Arctic 
Seas  were  made  in  a  still  more  north-westerly  direction  from  Iceland 
to  Greenland,  but  we  have  no  data  at  present  which  favor  this  notion. 
18 


274:  THEORY  OF  A  MIOCENE  ATLANTIS.  [On.  XV. 

Upon  the  whole,  the  theory  which  derives  the  American  types 
from  the  east  instead  of  the  west  seems  by  far  the  most  natural,  and 
it  seems  to  acquire  still  more  claims  to  our  favor  when  we  study  the 
fossil  shells  and  corals  of  that  ancient  period  as  well  as  the  plants. 
In  1850,  Mr.  John  Carrick  Moore  pointed  out  that  certain  tertiary 
shells  of  San  Domingo  exhibited  affinities  to  the  miocene  shells  of 
Europe,*  and  that  although  such  of  the  San  Domingo  species  as 
agreed  with  the  living  were  chiefly  Atlantic  forms,  there  were  some 
so  closely  allied  to  the  existing  Pacific  fauna  as  to  lead  him  to  infer 
that  there  had  been  a  channel  in  Miocene  times  through  what  is  now 
the  Isthmus  of  Panama,  by  which  the  mollusca  could  have  migrated 
from  one  ocean  to  the  other.  Such  an  hypothesis,  he  observes,  will 
be  the  more  readily  accepted  when  we  consider  that  the  isthmus  no- 
where attains  an  elevation  exceeding  1000  feet,  which  is  not  half  the 
height  to  which  the  marine  Miocene  strata  of  San  Domingo  have 
been  uplifted  since  their  deposition. 

Similar  inferences  have  lately  been  drawn  by  Dr.  Duncan,f  from 
the  corals  of  San  Domingo,  Antigua,  Jamaica,  Barbadoes,  and  other 
West  Indian  islands.  They  are  allied  in  a  most  unequivocal  manner 
to  the  corals  of  the  Faluns  of  Vienna,  Bordeaux,  Dax,  Saucats, 
and  Turin,  while  at  the  same  time  the  forms  are  those  of  the  Pacific 
and  not  of  the  Caribbean  Sea  and  Atlantic.  Dr.  Duncan  concludes, 
therefore,  not  only  that  there  was  no  isthmus  of  Panama,  but  also 
that  there  was  no  great  barrier  of  land  or  Atlantic  continent  sepa- 
rating the  Miocene  seas  of  Europe  from  the  contemporaneous  seas  of 
the  West  Indies.  The  bearing  of  these  views  is  the  more  direct  on 
the  theory  of  an  Atlantis  before  discussed,  because  the  affinities  of 
the  marine  shells  and  the  corals  belong  precisely  to  that  period  (the 
Upper  Miocene),  when  the  flora  of  Europe  was  most  American. 
There  may  have  been,  as  Dr.  Duncan  supposes,  numerous  islands  in 
the  Atlantic,  large  and  small,  as  there  are  now  in  parts  of  the  Pacific 
and  Indian  Oceans,  where  corals  abound,  but  there  could  not  have 
been  that  continuity  of  land  which  is  represented  in  Heer's  ideal  map 
of  the  Atlantic  already  cited,  p.  272,  which  would  be  indispensable 
in  order  to  produce  an  affinity  in  so  many  genera  and  even  species  of 
plants  as  is  observed  between  the  Kecent  American  and  the  Swiss 
Miocene  flora. 

It  is  right,  however,  before  concluding  this  subject,  that  I  should 
warn  the  reader  that  much  of  the  reasoning  employed  by  those  who 
have  taken  part  in  discussing  the  probable  existence  of  a  Miocene 
Atlantis,  whether  as  advocates  or  opponents  of  the  hypothesis,  has 
proceeded  on  the  assumption  that  the  geographical  distribution  of 
genera  has  been  governed  by  laws  strictly  analogous  to  those  which 
govern  the  distribution  of  species.  When  Professor  Heer  speaks  of 
plants  called  by  him  homologous,  and  shows  that  about  half  of  these 

*  Quart.  Geol.  Journ.,  1850,  vol.  iv.  p.  43.  f  Ibid.  vol.  xix.  p.  455. 


CH.  XV.]  THEORY  OF  A  MIOCENE  ATLANTIS. 

are  common  to  Miocene  Europe  and  to  the  living  flora  of  America, 
and  that  this  is  more  especially  true  of  those  closely-allied  or  homo- 
logous species  which  are  known  by  their  fruits  as  well  as  their  leaves, 
the  force  of  his  argument  will  be  fully  appreciated  by  all  who  believe 
that  each  species  has  had  a  single  birthplace,  or  has  been  formed  in 
one  limited  geographical  area  from  which  it  may  have  migrated  to 
distant  parts  ;  for  Heer  supposes  the  homologous  living  species  to  be 
the  hereditary  descendants  of  their  closely-allied  Miocene  progenitors. 
But  when  the  reasoning  is  founded  on  plants  which  have  only  a 
generic  connection,  as  in  a  great  part  of  Heer's  work,  and  everywhere 
throughout  the  essay  of  Professor  Oliver,  its  force  depends  on  the 
previous  assumption  that,  not  only  the  individuals  of  a  species,  but 
also  the  different  species  of  a  genus,  have  radiated  from  certain  geo- 
graphical areas  which  constituted  the  original  starting-points  of  such 
genera.  This  is  not  the  place  to  enter  into  a  question  so  difficult  and 
unsettled  as  that  of  the  origin  of  species,  but  whether  we  adopt  or  re- 
ject the  doctrine  of  transmutation,  it  is  necessary  to  bear  in  mind, 
when  we  compare  the  recent  and  fossil  flora  and  endeavor  to  ascertain 
whether  the  miocene  plants  came  to  Europe  by  a  western  or  eastern 
route,  that  a  single  identical  or  very  closely-allied  species  is  of  more 
value  than  a  great  many  genera  represented  by  species  not  closely 
allied.  Thus,  for  example,  Heer  considers  the  walnut-tree  of  (Eningen 
called  Juglans  bilinica  to  be  homologous  with  the  living  American 
hickory,  Juglans  nigra,  and  that  another  Upper  Miocene  walnut  of 
Europe,  Juglans  vetusta,  is  homologous  with  our  common  walnut, 
J.  regia,  which  was  first  brought  into  Europe  from  Persia.  When, 
therefore,  the  Swiss  Professor  founds  on  the  one  an  argument  in  favor 
of  a  migration  across  an  Atlantic  continent  for  the  Miocene  walnuts 
of  Switzerland,  and  Professor  Oliver  founds  on  the  other  an  Asiatic 
route  for  the  same,  their  reasoning  is  logical  and  its  cogency  is  great 
in  proportion  to  the  identity  or  very  near  affinity  of  the  fossil  and 
recent  plants  which  are  compared.  But  several  other  Tertiary  wal- 
nuts of  Switzerland  have  a  comparatively  remote  bearing  on  the  ques- 
tion of  a  Miocene  Atlantis,  because  Juglans,  as  a  genus,  flourished  in 
Europe  in  the  Eocene,  and  even,  according  to  Goppert,  in  the  antece- 
dent Cretaceous  period.  Some,  therefore,  of  the  Miocene  species  of 
Juglans  may  have  come  from  indigenous  European  Eocene,  or  even 
Cretaceous  ancestors  ;  and  the  same  remark  applies  to  a  great  number 
of  the  genera  of  other  orders  and  classes  which  are  common  to  the 
Miocene  flora  of  Europe  and  to  older  tertiary  rocks.  Thus  eight  out 
of  232  fossil  species  of  Monte  Bolca,  a  locality  where  the  rocks  belong 
to  the  Nummulitic  or  Middle  Eocene  period,  pass  up  into  the  Miocene 
formations,  according  to  Massalongo  and  Heer.* 

The  Proteacese  also  abounded  in  the  Eocene  strata  of  England,  France, 
and  Italy,  and  in  the  cretaceous  rocks  at  Aix-la-Chapelle.     To  these 

*  Recherches,  &c.,  Heer  and  Gaudin,  p.  79. 


276  UPPER  MIOCENE— SIWALIK  HILLS.  [On.  XV. 

countries,  therefore,  rather  than  to  Australia  and  Africa,  we  ought  to 
look  for  the  origin  of  many  of  the  species  of  that  order  which  we  find 
both  in  Upper  and  Lower  Miocene  formations. 

But  notwithstanding  the  caution  which  we  must  use  in  our  specula- 
tions on  the  alleged  affinity  of  the  Miocene  flora  of  Europe  to  the  liv- 
ing plants  of  America  and  other  countries,  I  consider  the  generaliza- 
tions of  linger,  Asa  Gray,  Heer,  Oliver,  and  others  on  this  subject,  to 
be  most  important,  and  that  their  investigations  cannot  fail  to  throw 
great  light  on  the  past  history  of  species  and  genera  in  the  vegetable 
kingdom. 

UPPER    MIOCENE    FORMATIONS,  INDIA. 

Sub-Himalayan  or  Siwdlik  Hills. — The  Siwalik  Hills  lie  at  the 
southern  foot  of  the  Himalayan  chain,  rising  to  the  height  of  2000 
and  3000  feet.  Between  the  Jumna  and  the  Ganges  they  consist  of 
inclined  strata  of  sandstone,  shingle,  clay,  and  marl.  We  are  indebted 
to  the  indefatigable  researches  of  Dr.  Falconer  and  Sir  Proby  Cautley, 
continued  for  fifteen  years,  and  to  the  labors  of  other  scientific  officers 
in  the  Indian  service,  for  the  discovery  in  these  marls  and  sandstones  of 
a  great  variety  of  fossil  mammalia  and  reptiles,  together  with  many 
freshwater  shells.  Fifteen  species  of  shells  of  the  genera  Paludina, 
Melania,  Ampullaria,  and  Unio  were  shown  by  Falconer  and  Cautley 
in  1846  to  the  late  Professor  E.  Forbes,  who  pronounced  them  to  be 
all  extinct  or  unknown  species  with  the  exception  of  four,  which  are 
still  inhabitants  of  Indian  rivers.  Such  a  proportion  of  living  to  ex- 
tinct mollusca  agrees  well  with  the  usual  character  of  an  Upper  Mio- 
cene or  Falunian  fauna,  as  observed  in  Touraine,  or  in  the  basin  of 
Vienna  and  elsewhere. 

The  genera  of  mammalia  point  in  the  same  direction.  One  of 
them,  named  originally  Anoplotherium,  was  at  first  considered  to  sup- 
ply a  link  between  this  Indian  fauna  and  that  of  the  Eocene  period 
of  Europe,  but  it  is  now  recognized  to  belong  .to  the  genus  Chalico- 
therium  (or  Anisodon  of  Lartet),  a  pachyderm  intermediate  between 
the  Rhinoceros  and  Anoplothere,  and  characteristic  of  the  Upper  Mio- 
cene strata  of  Eppelsheim,  and  of  Sansans  in  the  Department  of  Gers 
in  the  South  of  France.  With  in  occurs  also  an  extinct  form  of  Hip- 
popotamus, called  Hexaprotodon,  and  a  species  of  Hippotherium  and 
pig,  also  two  species  of  Mastodon,  two  of  elephant,  and  three  other 
elephantine  proboscidians ;  none  of  them  agreeing  with  any  fossil 
forms  of  Europe,  and  being  intermediate  between  the  genera  Elephas 
and  Mastodon,  constituting  the  sub-genus  Stegodon  of  Falconer. 
With  these  are  associated  a  monkey,  allied  to  the  Semnopithecus 
entellus,  now  living  in  the  Himalaya,  and  many  ruminants.  Amongst 
these  last,  besides  the  giraffe,  camel,  antelope,  stag,  and  others,  we 
find  a  remarkable  new  type,  the  Sivatherium,  like  a  gigantic  four- 
horned  deer.  There  are  also  new  forms  of  carnivora,  both  feline  and 


On.  XV.]  UPPER  MIOCENE— SIWlLIK  HILLS.  277 

canine,  the  Machairodus  among  the  former,  also  hyaenas,  and  a  suburs 
ine  form  called  the  Hyaenarctos,  and  a  genus  allied  to  the  otter  (Enhy- 
driodon),  of  formidable  size. 

The  giraffe,  camel,  and  a  large  ostrich  may  be  cited  as  proofs  that 
there  were  formerly  extensive  plains  where  now  a  steep  chain  of  hills, 
with  deep  ravines,  runs  for  many  hundred  miles  east  and  west.  Among 
the  accompanying  reptiles  are  several  crocodiles,  some  of  huge  dimen- 
sions, and  one  not  distinguishable,  says  Dr.  Falconer,  from  a  species 
now  living  in  the  Ganges  (C.  Gangeticus),  and  there  is  still  another 
saurian  which  the  same  anatomist  has  identified  with  a  species  now 
inhabiting  India.  There  was  also  an  extinct  species  of  tortoise  of  gi- 
gantic proportions  (Colossochelys  Atlas),  the  curved  shell  of  which  was 
twelve  feet  three  inches  long  and  eight  feet  in  diameter,  the  entire 
length  of  the  animal  being  estimated  at  eighteen  feet,  and  its  probable 
height  seven  feet. 

That  some  of  the  reptiles  should,  as  well  as  many  of  the  shells, 
have  survived  from  the  Upper  Miocene  to  the  human  epoch,  need 
scarcely  excite  surprise,  for  we  have  no  reason  to  assume  that  the 
mean  temperature  of  India  in  the  Miocene  period  differed  materially 
from  that  which  now  prevails  ;  although  the  climate  must  have  been 
greatly  modified  by  the  revolution  which  has  since  occurred  in  the 
physical  geography  of  the  district.  The  heat  may  be  as  great  now, 
if  not  greater,  than  when  the  Sivatherium  and  Chalicotherium 
flourished. 

Numerous  fossils  of  the  Siwalik  type  have  also  been  found  in 
Perim  Island,  in  the  Gulf  of  Cambay,  and  among  these  a  species  of 
Dinotherium,  a  genus  so  characteristic  of  the  Upper  Miocene  period 
in  Europe. 

Atlantic  Islands. — Something  will  be  said  of  the  Upper  Miocene 
formations  of  marine  origin  in  Madeira,  the  Canary  Islands,  and  the 
Azores,  when  I  speak,  in  the  thirty-first  chapter,  of  the  volcanic  rocks 
of  those  countries. 

Older  Pliocene  and  Miocene  formations  in  the  United  States. — Be- 
tween the  Alleghany  Mountains,  formed  of  older  rocks,  and  the  Atlan- 
tic, there  intervenes,  in  the  United  States,  a  low  region  occupied  prin- 
cipally by  beds  of  marl,  clay,  and  sand,  consisting  of  the  cretaceous 
and  tertiary  formations,  and  chiefly  of  the  latter.  The  general  eleva- 
tion of  this  plain  bordering  the  Atlantic  does  not  exceed  100  feet, 
although  it  is  sometimes  several  hundred  feet  high.  Its  width  in  the 
middle  and  southern  States  is  very  commonly  from  100  to  150  miles. 
It  consists,  in  the  South,  as  in  Georgia,  Alabama,  and  South  Carolina, 
almost  exclusively  of  Eocene  deposits ;  but  in  North  Carolina,  Mary- 
land, Virginia,  Delaware,  more  modem  strata  predominate,  which, 
after  examining  them  in  1842,  I  supposed  to  be  of  the  age  of  the 
English  Crag  and  faluns  of  Touraine.*  If,  chronologically  speaking, 

*  Procee'd.  of  the  Geol.  Soc.,  vol.  iv.  Pt.  3,  1845,  p.  547. 


278  MIOCENE  STRATA  OF  VIRGINIA.  [On.  XV. 

they  can  be  truly  said  to  be  the  representatives  of  these  two  European 
formations,  they  may  range  in  age  from  the  Older  Pliocene  to  the 
Miocene  epoch,  according  to  the  classification  of  European  strata 
adopted  in  this  chapter. 

The  proportion  of  fossil  shells  agreeing  with  recent,  out  of  147 
species  collected  by  me,  amounted  to  about  17  per  cent,  or  one-sixth 
of  the  whole  ;  but  as  the  fossils  so  assimilated  were  almost  always  the 
same  as  species  now  living  in  the  neighboring  Atlantic,  the  number 
may  hereafter  be  augmented,  when  the  recent  fauna  of  that  ocean  is 
better  known.  In  different  localities,  also,  the  proportion  of  recent 
species  varied  considerably. 

On  the  banks  of  the  James  River,  in  Virginia,  about  twenty  miles 
below  Richmond,  .11  a  cliff  about  30  feet  high,  I  observed  yellow  and 
white  sands  overlying  an  Eocene  marl,  just  as  the  yellow  sands  of  the 
crag  lie  on  the  blue  London  clay  in  Suffolk  and  Essex  in  England.  In 
the  Virginian  sands,  we  find  a  profusion  of  an  Astarte  (A.  undulata, 
Conrad),  which  resembles  closely,  and  may  possibly  be  a  variety  of, 
one  of  the  commonest  fossils  of  the  Suffolk  Crag  (A.  bipartita)  ;  the 
other  shells  also,  of  the  genera  Natica,  Fissurella,  Artemis,  Lucina, 


20T.  Fig.  208. 


Fitlgur  canaUculatus.    Maryland.  Fmus  quadricostatus,  Say.    Maryland. 

Chama,  Pectunculus,  and  Pecten,  are  analogous  to  shells  both  of  the 
English  crag  and  French  faluns,  although  the  species  are  almost  all 
distinct.  Out  of  147  of  these  American  fossils  I  could  only  find  13 
species  common  to  Europe,  and  these  occur  partly  in  the  Suffolk 
Crag,  and  partly  in  the  faluns  of  Touraine ;  but  it  is  an  important 
characteristic  of  the  American  group,  that  it  not  only  contains  many 
peculiar  extinct  forms,  such  as  Fusus  quadricostatus,  Say  (see  fig, 
208),  and  Venus  tridacnoides,  abundant  in  these  same  formations,  but 
also  some  shells  which,  like  Fulgur  carica  of  Say  and  F.  canaliculatus 
(see  fig.  207),  Calyptrcea  costata,  Venus  mercenaria,  Lam.,  Modiola 
olandula,  Totten,  and  Pecten  magellanicus,  Lam.,  are  recent  species, 
yet  of  forms  now  confined  to  the  western  side  of  the  Atlantic — a  fact 
implying  that  some  traces  of  the  beginning  of  the  present  geographi- 


CH.  XV.]  LOWER  MIOCENE— NEBRASKA.  2Y9 

cal  distribution  of  mollusca  date  back  to  a  period  as  remote  as  that 
of  the  Miocene  strata. 

Of  ten  species  of  zoophytes  which  I  procured  on  the  banks  of  the 
James  Eiver,  one  was  formerly  supposed  by  Mr.  Lonsdale  to  be  iden- 
tical with  a  fossil  from  the  faluns  of  Touraine,  but  this  species  (see 
fig.  209)  proves  on  reexamination  to  be 
different,  and  to  agree  generically  with  a  ris-  209- 

coral  now  living  on  the  coast  of  the  Uni- 
ted States.  With  respect  to  climate,  Mr. 
Lonsdale  regards  these  corals  as  indicating 
a  temperature  exceeding  that  of  the  Medi- 
terranean, and  the  shells  would  lead  to 
similar  conclusions.  Those  occurring  on 
the  James  Kiver  are  in  the  37th  degree  of 
N.  latitude,  while  the  French  faluns  are  in 
the  47th ;  yet  the  forms  of  the  American  £*trarff"  f  <f 

1  /  Syn.  Anthophyllum 

fossils  would  scarcely  imply  so  warm  a  cli-         wmiamsburg,  Virginia. 
mate  as   must  have   prevailed  in  France 
when  the  Miocene  strata  of  Touraine  originated. 

Among  the  remains  of  fish  in  these  Post-eocene  strata  of  the  Uni- 
ted States  are  several  large  teeth  of  the  shark  family,  not  distinguish- 
able specifically  from  fossils  of  the  faluns  of  Touraine. 


LOWER   MIOCENE,    UNITED    STATES. 

Nebraska. — In  the  territory  of  Nebraska,  on  the  Upper  Missouri, 
near  the  Platte  Eiver,  lat.  42°  N.,  a  tertiary  formation  occurs,  con- 
sisting of  white  limestone,  marls,  and  siliceous  clay,  described  by  Dr. 
D.  Dale  Owen,*  in  which  many  bones  of  extinct  quadrupeds,  and  of 
chelonians  of  land  or  freshwater  forms,  are  met  with.  Among  these, 
Dr.  Leidy  describes  a  gigantic  quadruped,  called  by  him  Titanothe- 
rium,  nearly  allied  to  the  Palceotherium,  but  larger  than  any  of  the 
species  found  in  the  Paris  gypsum.  With  these  are  several  species 
of  the  genus  Oreodon,  Leidy,  uniting  the  characters  of  pachyderms 
and  ruminants  also ;  Eucrotaphus,  another  new  genus  of  the  same 
mixed  character ;  two  species  of  rhinoceros  of  the  sub-genus  Acero- 
therium,  a  Lower  Miocene  form  of  Europe  before  mentioned ;  two 
species  of  Archceotherium,  a  pachyderm  allied  to  Chceropotamus  and 
Hyracotherium ;  also  Pcebr other ium,  an  extinct  ruminant  allied  to 
Dorcatherium,  Kaup ;  also  Agriochcegus  of  Leidy,  a  ruminant  allied 
to  Merycopotamus  of  Falconer  and  Cautley ;  and,  lastly,  a  large  car- 
nivorous animal  of  the  genus  Machairodus,  the  most  ancient  example 
of  which  in  Europe  occurs  in  the  Lower  Miocene  strata  of  Auvergne, 
but  of  which  some  species  are  found  in  Pliocene  deposits.  The  tur- 

*  David  Dale  Owen,  Geol.  Survey  of  Wisconsin,  &c. ;  Philad.  1852. 


280 


MIDDLE  EOCENE  FORMATIONS. 


[On.  XVI. 


ties  are  referred  to  the  genus  Testudo,  but  have  some  affinity  to 
Emys.  On  the  whole,  the  Nebraska  formation  is  probably  newer 
than  the  Paris  gypsum,  and  referable  to  the  Lower  Miocene  period, 
as  above  defined. 


CHAPTER   XVI. 


EOCENE      FORMATIONS. 


Upper  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  mammalia — Boundary-line  between 
Lower  Miocene  and  Eocene — Fossils  of  Barton  Clay — British  Middle  Eocene — 
Shells,  nummulites,  fishes,  and  reptiles  of  tke  Bagshot  and  Bracklesham  beds — 
Vegetation  of  Middle  Eocene  period — Lower  Eocene  strata  of  England — Fossil 
plants  and  shells  of  the  London  Clay  proper — Strata  of  Kyson  in  Suffolk — Plas- 
tic clays  and  sands — Thanet  sands — Eocene  formations  of  France — Gypseous 
series  of  Montmartre  and  extinct  quadrupeds — Fossil  footprints — Calcaire  gros- 
sier — Miliolites — Lower  Eocene  in  France — Nummulitic  formations  of  Europe, 
Africa,  and  Asia  —Their  wide  extent — Referable  to  the  Middle  Eocene  period — 
Eocene  strata  in  the  United  States — Section  at  Claiborne,  Alabama — Colossal 
cetacean — Orbitoidal  limestone — Burr  stone. 

THE  strata  next  in  order  in  the  descending  series  are  those  which 
I  term  Upper  Eocene.  In  the  accompanying  map,  the  position  of 
several  Eocene  areas  is  pointed  out,  such  as  the  basin  of  the  Thames, 

Fig.  210. 
Map  of  the  principal  tertiary  basins  of  the  Eocene  period. 


sne  rocks  and  strata 
older  than  the  Devonian 
or  Old  Red  series. 


Eocene  formations. 


N.  B.  The  space  left  blank  is  occupied  by  secondary  formations  from  the  Devonian  or  old  rod 
sandstone  to  the  chalk  inclusive. 

part  of  Hampshire,  part  of  the  Netherlands,  and  the  country  round 
Paris.      The  three  last-mentioned   areas   contain  some  marine  and 


CH.  XVI.]  UPPER  EOCENE  FORMATIONS.  281 

freshwater  formations,  which  have  been  already  spoken  of  as  Lower 
Miocene,  but  their  superficial  extent  is  insignificant,  except  in  the 
Paris  basin  between  the  Seine  and  the  Loire. 


UPPER  EOCENE  FORMATIONS,  ENGLAND. 

The  following  table  will  show  the  order  of  succession  of  the  strata 
found  in  the  Tertiary  areas,  commonly  called  the  London  and  Hamp- 
shire basins.  (See  also  Table,  p.  103,  et  seq.) 

LOWER  MIOCENE. 

Thickness. 

Hempstead  beds,  Isle  of  Wight,  see  above,  p.  239,     -  -      170  feet. 

UPPER  EOCENE. 

A.  1.  Bembridge  Series— North  coast  of  Isle  of  Wight,        -  -  120 

A.  2.  Osborne  or  St.  Helen's  Series— ibid.,    -  -  100 

A.  3.  Headon  Series— Isle  of  Wight,  and  Hordwell  Cliff,  Hants,  -  170 

A.  4.  Barton  Clay,  Isle  of  Wight,  and  Barton  Ch'ffj  Hants,  -  -  300 

MIDDLE   EOCENE. 

B.   Bagshot  and  Bracklesham  Sands  and  Clays — London  and  Hants 

basins,         -  -      700 

LOWER  EOCENE. 

C.  1.  London  Clay  proper  and  Bognor  beds — London  and  Hants 

basins,  -  350  to  500 

C.  2.  Plastic  and  Mottled  Clays  and  Sands — London  and  Hants 

basins,  -  100 

C.  3.  Thanet  Sands — Reculvers,  Kent,  and  Eastern  part  of  London 

basin,  --  90 

The  true  relative  position  of  the  Hempstead  beds  and  of  the  Bem- 
bridge, A.  1,  and  the  Osborne  or  St.  Helen's  series,  A.  2,  were  not 
made  out  in  a  satisfactory  manner  till  Professor  Forbes  studied  them 
in  detail  in  1852.  The  true  place  of  the  Bagshot  sands,  B.,  and  of 
the  Thanet  sands,  C.  3,  was  first  accurately  ascertained  by  Mr.  Prest 
wich  in  1847  and  1852. 


UPPER  EOCENE,  ENGLAND. 

Bembridge  series,  A.  1. — These  beds  are  about  120  feet  thick,  and, 
as  before  stated  (p.  239),  are  conformable  with  the  Hempstead  beds, 
near  Yarmouth,  in  the  Isle  of  Wight.  They  consist  of  marls,  clays, 
and  limestones  of  freshwater,  brackish,  and  marine  origin.  Some  of 
the  most  abundant  shells,  as  Cyrena  semistriata  var.,  and  Paludina 
lenta,  fig.  176,  p.  240,  are  common  to  this  and  to  the  overlying  Hemp- 
stead  series ;  but  the  majority  of  the  species  are  distinct.  The  fol- 
lowing are  the  subdivisions  described  by  Professor  Forbes  : — 


282 


UPPER  EOCENE  FORMATIONS. 


xrr. 


a.  Upper  marls,  distinguished  by  the  abundance  of  Melania  turritissima,  Forbes 

(fig.  211). 

b.  Lower  marl,  characterized  by  CeritMum  mutabile,   Cyrena  pulchra,  &c.,  and 

by  the  remains  of  Trionyx  (see  fig.  212). 


Fig.  211. 


Fig.  212. 


Melania  turritissima,  i'orbes.        Fragment  of  Carapace  of  Trionyx. 
Bembridge.  Bembridge  Beds,  Isle  of  Wight. 

c.   Green  marls,  often  abounding  in  a  peculiar  species  of  oyster,  and  accompanied 
by  Cerithia,  Mytili,  an  Area,  a  Nucula,  &c. 


Fig.  213. 


Fig.  214. 


BvMmus  eltipUcus,  Sow.       ffettx  occlusa,  Edwards. 
Bembridge  Limestone.  Bembridge  Limestone, 

i  nat.  size.  Isle  of  Wight. 


Fig.  215. 


Paludina  orbicularls. 
Bembridge. 


d.  Bembridge  limestones,  compact  cream-colored  limestones  alternating  with  shales 
and  marls,  in  all  of  which  land-shells  are  common,  especially  at  Sconce,  near 


Fig.  216. 


Fig.  217. 


Fig.  21& 


PlanorMs  discus,  Edwards. 
Bembridge.    i  diam. 


Lymnea  longiseata.  Brard. 
Nat  size. 


Ohara  tuberculata* 
Bembridgo  Lime- 
stone, I.  of  Wight. 


CH.  XVL] 


UPPER  EOCENE  FORMATIONS. 


283 


Yarmouth,  as  described  by  Mr.  Edwards.  The  Bulimus  ellipticus,  fig.  213, 
and  Helix  occlusa,  fig.  214,  are  among  its  best  known  land-shells.  Paludina 
orbicularis,  fig.  215,  is  also  of  frequent  occurrence.  One  of  the  bands  is 
filled  with  a  little  globular  Paludina.  Among  the  freshwater  pulmonifera, 
Lymnea  longiscata  (fig.  217)  and  Planorbis  discus  (fig.  216)  are  the  most  gen- 
erally distributed :  the  latter  represents  or  takes  the  place  of  the  Planorbis 
euomphalus  (see  fig.  221),  of  the  more  ancient  Headon  series.  Char  a  tuber- 
culata  (fig.  218)  is  the  characteristic  Bembridge  gyrogonite. 

From  this  formation  on  the  shores  of  Whitecliff  Bay,  Dr.  Mantell 
obtained  a  fine  specimen  of  a  fan  palm,  Flabellaria,  Lamanonis, 
Brong.,  a  plant  first  obtained  from  beds  of  corresponding  age  in  the 
suburbs  of  Paris.  The  well-known  building-stone  of  Binstead,  near 
Hyde,  a  limestone  with  numerous  hollows  caused  by  Cyrence  which 
have  disappeared  and  left  the  moulds  of  their  shells,  belongs  to  this 
subdivision  of  the  Bembridge  series.  In  the  same  Binstead  stone  Mr. 
Pratt  and  the  Rev.  Darwin  Fox  first  discovered 
the  remains  of  mammalia  characteristic  of  the 
gypseous  series  of  Paris,  as  Palceotherium  mag- 
num (fig.  220),  P.  medium,  P.  minus,  P.  mimi- 
mum,  P.  curtum,  P.  crassum ;  also  Anoplo- 
therium  commune  (fig.  219),  A.  secundarium, 
Dichobune  cervinum,  and  Chceropotamus  Cu- 
vieri.  The  genus  Paleothere,  above  alluded  to, 
resembled  the  living  tapir  in  the  form  of  the 
head,  and  in  having  a  short  proboscis,  but  its 

&  *  '  .     Anoplotherium  commune. 

molar  teeth  were  more  like  those  01  the  rhi-     Binstead,  isle  of  wight 
noceros.      Paleotherium  magnum  was  of  the 
size  of  a  horse,  three  or  four  feet  high.     The  annexed  woodcut,  fig. 
220,  is  one  of  the  restorations  which  Cuvier  attempted  of  the  outline 

Fig.  220. 


Pig.  219. 


Lower  molar  tooth, 
nat.  size. 


Paleotherium,  magnum,  Cuvier. 


of  the  living  animal,  derived  from  the  study  of  the  entire  skeleton. 
As  the  vertical  range  of  particular  species  of  quadrupeds,  so  far  as 


284: 


UPPER  EOCENE  FORMATIONS. 


[CH.  XVI. 


our  knowledge  extends,  is  far  more  limited  than  that  of  the  testacea, 
the  occurrence  of  so  many  species  at  Binstead,  agreeing  with  fossils 
of  the  Paris  gypsum,  strengthens  the  evidence  derived  from  shells 
and  plants  of  the  synchronism  of  the  two  formations. 

Osborne  or  St.  Helen's  series,  A.  2. — This  group  is  of  fresh  and 
brackish-water  origin,  and  very  variable  in  mineral  character  and 
thickness.  Near  Ryde,  it  supplies  a  freestone  much  used  for  building, 
and  called  by  Professor  Forbes  the  Nettlestone  grit.  In  one  part 
ripple-marked  flagstones  occur,  and  rocks  with  fucoidal  markings. 
The  Osborne  beds  are  distinguished  by  peculiar  species  of  PaludincL, 
Melania,  and  Melanopsis,  as  also  of  Cypris  and  the  seeds  of  Cham. 

Headon  series,  A.  3. — These  beds  are  seen  both  in  Whitecliff  Bay 
and  in  Headon  Hill,  or  at  the  east  and  west  extremities  of  the  Isle 
of  Wight.  The  upper  and  lower  portions  are  freshwater,  and  the 
middle  of  mixed  origin,  sometimes  brackish  and  marine.  Everywhere 
PlanorUs  euomphalus,  fig.  221,  characterizes  the  freshwater  deposits, 


Fig.  221. 


Fig.  222. 


Planorbis  euomphalus,  Sow. 
Headon  HilL    i  diam. 


ffelix  labyrinthica,  Say.    Headon  Hill,  Isle  of  Wight; 
and  Hordwell  Cliff,  Hants — also  recent. 


just  as  the  allied  form,  P.  discus,  fig.  216,  does  the  Bembridge  lime- 
stone. The  brackish-water  beds  contain  Potamomya  plana,  Cerithium 
mutabile,  and  Potamides  cinctus  (fig.  44,  p.  30),  and  the  marine  beds 
Venus  (or  Oytherea)  incrassata,  a  species  common  to  the  Limburg 


Neritina  concava. 
Headon  series. 


Fig.  224 


Fig.  225. 


Lymnea  caudata. 
Headon  beds. 


Cerithiutn  concavum. 
Headon  series. 


beds  and  Gres  de  Fontainebleau,  or  the  Lower  Miocene  series.  The 
prevalence  of  salt-water  remains  is  most  conspicuous  in  some  of  the 
central  parts  of  the  formation.  Mr.  T.  Webster,  in  his  able  memoirs 


CH.  XVI.]  UPPER  EOCENE  FORMATIONS.  285 

on  the  Isle  of  Wight,  first  separated  the  whole  into  a  lower  fresh- 
water, an  upper  marine,  and  an  upper  freshwater  division. 

Among  the  shells  which  are  widely  distributed  through  the  Hea- 
don  series  are  JVeritina  concava  (fig.  223),  Lymnea  caudata  (fig.  224), 
and  Cerithium  concavum  (fig.  225).  Helix  labyrinthica,  Say  (fig. 
222),  a  land-sheh1  now  inhabiting  the  United  States,  was  discovered 
in  this  series  by  Mr.  Wood  in  Hordwell  Cliff".  It  is  also  met  with  in 
Headon  Hill,  in  the  same  beds.  At  Sconce,  in  the  Isle  of  Wight,  it 
occurs  in  the  Bembridge  series,  and  affords  a  rare  example  of  an 
Eocene  fossil  of  a  species  still  living,  though,  as  usual  in  such  cases, 
having  no  local  connection  with  the  actual  geographical  range  of  the 
species. 

The  lower  and  middle  portion  of  the  Headon  series  is  also  met  with 
in  Hordwell  Cliff  (or  Hordle,  as  it  is  often  spelt),  near  Lymington, 
Hants,  where  the  organic  remains  have  been  studied  by  Mr.  Searles 
Wood,  Dr.  Wright,  and  the  Marchioness  of  Hastings.  To  the  latter* 
we  are  indebted  for  a  detailed  section  of  the  beds,*  as  well  as  for  the 
discovery  of  a  variety  of  new  species  of  fossil  mammalia,  chelonians, 
and  fish ;  also,  for  first  calling  attention  to  the  important  fact  that 
these  vertebrata  differ  specifically  from  those  of  the  Bembridge  beds. 
Among  the  abundant  shells  of  Hordwell  are  Paludina  lenta  and  vari- 
ous species  of  Lymnea,  Planorbis,  Melania,  Cyclas,  and  Unio,  Pota- 
momya,  Dreissena,  &c. 

Among  the  chelonians  we  find  a  species  of  Emys,  and  no  less  than 
six  species  of  Trionyx ;  among  the  saurians  an  alligator  and  a 
crocodile  ;  among  the  ophidians  two  species  of  land-snakes  (Paleryx, 
Owen) ;  and  among  the  fish  Sir  P.  Egerton  and  Mr.  Wood  have  found 
the  jaws,  teeth,  and  hard  shining  scales  of  the  genus  Lepidosteus,  or 
bony  pike  of  the  American  rivers.  This  same  genus  of  freshwater 
ganoids  has  also  been  met  with  in  the  Hempstead  beds  in  the  Isle  of 
Wirrht.  The  bones  of  several  birds  have  been  obtained  from  Hord- 

O 

well,  and  the  remains  of  quadrupeds.  The  latter  belong  to  the  genera 
Paloplotherium  of  Owen,  Anoplotherium,  Anthracotherium,  Dichodon 
of  Owen  (a  new  genus  discovered  by  Mr.  A.  H.  Falconer),  Dichobune, 
Spalacodon,  and  Hycenodon.  The  latter  offers,  I  believe,  the  oldest 
known  example  of  a  true  carnivorous  animal  in  the  series  of  British 
fossils,  although  I  attach  very  little  theoretical  importance  to  the  fact, 
because  herbivorous  species  are  those  most  easily  met  with  in  a  fossil 
state  in  all  save  cavern  deposits.  In  another  point  of  view,  however, 
this  fauna  deserves  notice.  Its  geological  position  is  considerably 
lower  than  that  of  the  Bembridge  or  Montmartre  beds,  from  which 
it  differs  almost  as  much  in  species  as  it  does  from  the  still  more 
ancient  fauna  of  the  Lower  Eocene  beds  to  be  mentioned  in  the  sequel. 
It  therefore  teaches  us  what  a  grand  succession  of  distinct  assem- 
blages of  mammalia  flourished  on  the  earth  during  the  Eocene  period. 

*  Bulletin  Sou.  Geol.  de  France,  1852,  p.  191. 


286  UPPER  EOCENE  FORMATIONS.  [Cn.  XVI. 

Many  of  the  marine  shells  of  the  blackish-water  beds  of  the  above 
series,  both  in  the  Isle  of  Wight  and  Hordwell  Cliff,  are  common  to 
the  underlying  Barton  Clay ;  and,  on  the  other  hand,  there  are  some 
freshwater  shells,  such  as  Cyrena  obovata,  which  are  common  to  the 
Bembridge  beds,  notwithstanding  the  intervention  of  the  St.  Helen's 
series.  The  white  and  green  marls  of  the  Headon  series,  and  some 
of  the  accompanying  limestones,  often  resemble  the  Eocene  strata  of 
France  in  mineral  character  and  color  in  so  striking  a  manner,  as  to 
suggest  the  idea  that  the  sediment  was  derived  from  the  same  region, 
or  produced  contemporaneously  under  very  similar  geographical  cir- 
cumstances. 

At  Brockenhurst,  near  Lyndhurst,  in  the  New  Forest,  marine  strata 
have  recently  been  found,  containing  fifty-nine  shells,  of  which  many 
have  been  described  by  Mr.  Edwards.  These  beds  rest  on  the  Lower 
Headon,  and  are  considered  as  the  equivalent  of  the  middle  part  of 
the  Headon  series,  many  of  the  shells  being  common  to  the  brackish- 
water  or  Middle  Headon  beds  of  Colwell  and  Whitecliff  Bays,  such  as 
Cancellaria  muricata,  Sow.,  Fusus  labiatus,  Sow.,  <fec.  Baron  von 
Konen*  has  pointed  out  that  no  less  than  forty-six  out  of  the  fifty-nine 
Brockenhurst  shells,  or  a  proportion  of  78  per  cent.,  agree  with  species 
occurring  in  Dumont's  Lower  Tongrian  formation  in  Belgium.  This 
being  the  case,'  we  might  fairly  expect  that  if  we  had  a  marine  equiv- 
alent of  the  Bembridge  series,  or  of  the  contemporaneous  Paris 
gypsum,  we  should  find  it  to  contain  a  still  greater  number  of  shells 
common  to  the  Tongrian  beds  of  Belgium,  but  the  exact  correlation 
of  these  freshwater  groups  of  France,  Belgium,  and  Britain,  has  not 
yet  been  fully  made  out.  (  It  is  possible  that  the  Tongrian  of  Dumont 
may  be  newer  than  the  Bembridge  series,  and  therefore  referable  to 
the  Lower  Miocene,  according  to  the  classification  adopted  by  me  in 
Chapter  XIV.  p.  21V. 

If  ever  the  whole  series  should  be  complete,  we  must  be  prepared 
to  find  the  marine  equivalent  of  the  Bembridge  beds,  or  the  upper- 
most Eocene,  passing  by  imperceptible  shades  into  the  overlying 
lowest  Miocene  strata. 

Among  the  fossils  found  in  the  Middle  Headon  are  Cytherea  in- 
crassata  and  Cerithium  plicatum,  fig.  173,  p.  240.  These  shells,  espe- 
cially the  latter,  are  very  characteristic  of  the  Lower  Miocene,  and 
their  occurrence  in  the  Headon  series  has  been  cited  as  an  objection 
to  the  line  proposed  to  be  drawn  between  Miocene  and  Eocene. 
But  if  we  were  to  attach  importance  to  such  occasional  passages,  we 
should  soon  find  that  no  lines  of  division  could  be  drawn  anywhere, 
for  in  the  present  state  of  our  knowledge  of  the  Tertiary  series  there 
will  always  be  species  common  to  beds  above  and  below  our  boundary- 
lines. 

Both  in  Hordwell  Cliff  and  the  Isle  of  Wight,  the  Headon  beds 

*  Quart,  Geol.  Journ.,  vol.  xx.  p.  97.     1864. 


CH.  XVI.] 


SHELLS  OF  THE  BAKTON  CLAY. 


287 


Fig.  226. 


rest  on  white  sands,  used  for  making  glass,  and  constituting  the  up- 
per member  of  the  Barton  series,  A.  4,  p.  281,  next  to  be  mentioned. 
White  sands  and  Barton  clay,  A.  4  (Table,  p.  281). — In  one  of  the 
upper  sandy  beds  of  this  formation,  Dr.  Wright  found  Chama 
squamosa  in  great  plenty.  The  same  sands  contain  impressions  of 
many  marine  shells  (especially  in  Whitecliff  Bay)  common  to  the  up- 
per Bagshot  sands  afterwards  to  be  described.  The  underlying  Bar- 
ton clay  has  yielded  about  252  marine  shells,  more 
than  half  of  them,  according  to  Mr.  Prestwich,  pecu- 
liar ;  and  only  about  one  in  twenty  being  common  to 
the  London  clay  proper,  a  much  older  Eocene  group 
(see  p.  291),  with  which  the  Barton  clay  was  formerly 
confounded.  About  one-third  of  the  Barton  clay 
shells  agree  specifically  with  those  of  the  calcaire 
grossier  of  the  Paris  basin.*  It  is  nearly  a  century 
since  Brander  published,  in  1766,  an  account  of  the 
organic  remains  collected  from  these  Barton  and  Hord- 
well  Cliffs,  and  his  excellent  figures  of  the  shells  then  deposited  in  the 
British  Museum  are  justly  admired  by  conchologists  for  their  accuracy. 

SHELLS  OF  THE  BARTON  CLAY,  HANTS. 

Certain  foraminifera  called  Nummulities  begin,  when  we  study  the 
tertiary  formations  in  a  descending  order,  to  make  their  first -appear- 


Fig.  22T. 


Fig.  228. 


Fig.  229. 


Fig.  230. 


Mitra  scabra.         Valuta  anibigua.         Typhis  piwgens. 
Fig.  231.  Fig.  232.  Fig.  233. 


Valuta  athleta.    Barton 
and  Bracklesham. 


Fig.  234. 


Terebellum  fusi- 
forme.  Barton 
and  Brackles- 

hain. 


Terebellum  so- 
pita,  Brandner, 
Lam. 

Seraphs  convo- 
lutum,  Mont£ 


Cardita  sulsata. 


Crassatella  suleata. 


*  Quart.  Geol.  Journ.,  vol.  xiii.  p.  134.     London  1857. 


288  MIDDLE  EOCENE,  ENGLAND.         [On.  XVI. 

ance  in  these  Barton  beds.  A  small  species  called  Nummulites 
variolaria  is  found  both  on  the  Hampshire  coast  and  in  beds  of  the 
same  age  in  "Whitecliff  Bay,  in  the  Isle  of  Wight.  Several  marine 
shells,  such  as  Carbula  pisum,  are  common  to  the  Barton  beds  and  the 
Hempstead  or  Lower  Miocene  series,  and  a  still  greater  number,  as  be- 
fore stated,  are  common  to  the  Headon  series. 


MIDDLE    EOCENE,  ENGLAND. 

Bagshot  and  Bracklesham  beds,  B.— The  Bagshot  beds,  consisting 
chiefly  of  siliceous  sand,  occupy  extensive  tracts  round  Bagshot,  in 
Surrey,  and  in  the  New  Forest,  Hampshire.  They  may  be  separated 
into  three  divisions,  the  upper  and  lower  consisting  of  light  yellow 
sands,  and  the  central  of  dark  green  sands  and  brown  clays,  the  whole 
reposing  on  the  London  clay  proper.*  The  uppermost  division  is 
probably  very  nearly  related  in  age  to  the'  Barton  series.  Although 
the  Bagshot  beds  are  usually  devoid  of  fossils,  they  contain  marine 
shells  in  some  places,  among  which  Venericardia  planicosta  (see  fig. 
235)  is  abundant,  with  Turritella  sulcifera  and  Nummulites  Icevigata 
(see  fig.  239,  p.  289). 

Fig.  285. 


Venericardia  planicosta,  Lam. 
Cardita  planicosta,  Deshayes. 

At  Bracklesham  Bay,  near  Chichester,  in  Sussex,  the  characteristic 
shells  of  this  member  of  the  Eocene  series  are  best  seen ;  among 
others,  the  huge  Cerithium  giganteum,  so  conspicuous  in  the  calcaire 
grossier  of  Paris,  where  it  is  sometimes  two  feet  in  length.  The 
volutes  and  cowries  of  this  formation,  as  well  as  the  lunulites  and 
corals,  seem  to  favor  the  idea  of  a  warm  climate  having  prevailed, 
which  is  borne  out  by  the  discovery  of  a  serpent  Palceophis  typhoeus 
(see  fig.  236),  exceeding,  according  to  Professor  Owen,  twenty  feet 
in  length,  and  allied  in  its  osteology  to  the  Boa,  Python,  Coluber, 
and  Hydrus.  The  compressed  form  and  diminutive  size  of  certain 

*  Prestwich,  Quart.  Geol.  Journ.,  vol.  iii.  p.  386. 


CH.  XVI.] 


MIDDLE  EOCENE,  ENGLAND. 


caudal  vertebras  indicate  so  much  anology  with  Hydrus  as  to  induce 
Professor  Owen  to  pronounce  this  extinct  ophidian  to  have  been 
marine.*  He  had  previously  combated  with  much  success  the  evi- 

Fig.  286. 


PalmopJtis  typhoeus,  Owen ;  an  Eocene  sea-serpent    Bracklesham. 
a,  &.  Vertebra,  with  long  neural  spine  preserved,    c.  Two  vertebrae  in  natural  articulation. 

dence  advanced  to  prove  the  existence  in  the  Northern  Ocean  of 
huge  sea-serpents  in  our  own  times,  but  he  now  contends  for  the  for- 
mer existence  in  the  British  Eocene  seas  of  less  gigantic  serpents, 
when  the  climate  was  probably  more  genial ;  for  amongst  the  compan- 
ions of  the  sea-snake  of  Bracklesham  was  an  extinct  Gavial  (Gavialis 
Dixoni,  Owen),  and  a  numerous  fish,  such  as  now  frequent  the  seas 
of  warm  latitudes,  as  the  ostraceont  fish,  of  which  a  spine  is  figured 
(see  fig.  237),  and  gigantic  rays  of  the  genus  Myliobates  (see  fig. 
238).' 

Fig.  23T 


Defensive  spine  of  an  Ostraceon,  or  fish  of  the  family  Bali&Uda. 
Bracklesham.    Dixon's  Fossils  of  Sussex,  pi.  11,  fig.  26. 


Fig.  238. 


Dental  plates  of  MyUobates  Edwardsi. 
Bracklesham  Bay.    Ibid.,  pi.  8. 


NummuUtes  (Nummularia)  Icevigata. 

Bracklesham.    Ibid.,  pi.  8. 
a.  Section  of  the  nummulite. 
&.  Group,  with  an  individual  showing  the  exterior 

of  the  shell. 


The  teeth  of  sharks  also,  of  the  genera  Carcharodon,  Otodus, 
Lamna,  Galeoccrdo,  and  others,  are  abundant.  (See  figs.  240, 241,  242, 
243.)  The  Nummulites  Icevigata  (see  fig.  239),  so  characteristic  of 


*  Palaeont.  Soc.  Monograph.  Kept.,  Ft.  ii.  p.  61. 
19 


290 


BRACKLESHAM  BEDS. 


[Gu.  XVI. 


the  lower  beds  of  the  calcaire  grossier  in  France,  where  it  sometimes 
forms  stony  layers,  as  near  Compiegne,  is  very  common  at  Brackle- 
sham,  together  with  JV.  scdbra  and  N.  variolaria.  Out  of  193  species 
of  testacea  procured  from  the  Bagshot  and  Bracklesham  beds  in 
England,  126  occur  in  the  calcaire  grossier  in  France.  It  was  clearly, 
therefore,  coeval  with  that  part  of  the  Parisian  series  more  nearly  than 
with  any  other. 


Fig.  240. 


Tig.  241. 


Fig.  242. 


Fig.  248. 


Carcharodon  heterodon, 


Otodus  obUquus,     Lamna  elegant^      GaUocerdo  latidens 

Agass. 
Teeth  of  sharks  from  Bracklesham  Bay. 


Fig.  244. 


Marine  Shells  of  Bracklesham  Beds. 

Fig.  246.'  Fig.  246.  Fig.  24T. 


Pl&urotoma  att&nu- 
ata,  Sow. 


Fig.  248. 


Valuta,  Sel-       Turritella       Luaina  eerrato,  Dixon.       Conus  deper- 
se'iensis,       multisulcata,  Magnified. 

Edwards.  Lam. 


VEGETATION    OF    MIDDLE    EOCENE    PERIOD. 

The  plants  of  Alum  Bay  in  the  Isle  of  Wight,  and  of  Bournemouth, 
on  the  south  coast  of  Hampshire,  imbedded  in  white  clays  of  the 
Middle  Eocene  series,  bear  a  great .  resemblance  generally  to  those  of 
the  Miocene  period,  as  described  in  the  last  chapter ;  but  the  species 
are  with  very  few  exceptions  quite  distinct.  Forty  of  these  are  men- 
tioned by  MM.  de  la  Harpe  and  Gaudin,  among  which  the  Proteacese 


CH.  XVI.]  LOWER  EOCENE  FORMATIONS,  ENGLAND.  291 

(Dryandra,  &c.),  and  the  fig  tribe  are  abundant,  as  well  as  the  cinna- 
mon and  several  other  laurineae,  with  some  papilionaceous  plants.  On 
the  whole  they  remind  the  botanist  of  the  types  of  tropical  India  and 
Australia.* 

Heer  has  mentioned  several  species  which  are  common  to  this  Alum 
Bay  flora  and  that  of  Monte  Bolca,  near  Verone,  so  celebrated  for  its 
fossil  fish,  and  where  the  strata  contain  nummulites  and  other  Middle 
Eocene  fossils.f  He  has  particularly  alluded  to  Aralia  primigenia,  De 
la  Harpe ;  Daphnogene  Veronensis,  Massalongo  sp. ;  and  Ficus  grana- 
dilla,  Mass,  sp.,  as  among  the  species  common  to  and  characteristic  of 
the  Isle  of  Wight  and  Italian  Eocene  beds ;  and  he  observes  that  in 
the  flora  of  this  period  those  forms  of  a  temperate  climate  which  con- 
stitute a  marked  feature  in  the  European  Miocene  formations,  such  as 
the  willow,  poplar,  birch,  alder,  elm,  hornbeam,  oak,  fir,  and  pine, 
are  wanting.  The  American  types  are  also  absent,  or  much  more 
feebly  represented  than  in  the  Miocene  period.  The  number  of  exotic 
forms  which  are  common  to  the  Eocene  and  Miocene  strata  of  Europe 
demonstrate  the  remoteness  of  the  times  in  which  the  geographical 
distribution  of  living  plants  originated.  A  great  majority  of  the 
Eocene  genera  have  disappeared  from  our  temperate  climates,  but  not 
the  whole  of  them ;  and  they  must  all  have  exerted  some  influence  on 
the  assemblage  of  species  which  succeeded  them.  Many  of  these  are 
indeed  so  closely  allied  to  the  flora  now  surviving  as  to  make  it  ques- 
tionable, even  in  the  opinion  of  naturalists  opposed  to  the  doctrine  of 
transmutation,  whether  they  are  not  genealogically  related  the  one  to 
the  other, 

LOWER   EOCENE    FORMATIONS,    ENGLAND. 

London  Clay  proper  (C.  1,  Table,  p.  281). — This  formation  under- 
lies the  preceding,  and  consists  of  tenacious  brown  and  bluish-gray 
clay,  with  layers  of  concretions  called  septaria,  which  abound  chiefly 
in  the  brown  clay,  and  are  obtained  in  sufficient  numbers  from  sea- 
cliffs  near  Harwich,  and  from  shoals  off  the  Essex  coast,  to  be  used 
for  making  Roman  cement.  The  principal  localities  of  fossils  in  the 
London  Clay  are  Highgate  Hill,  near  London,  the  island  of  Sheppey, 
and  Bognor  in  Hampshire.  Out  of  133  fossil  shells,  Mr.  Prestwich 
found  only  20  to  be  common  to  the  calcaire  grossier  (from  which  600 
species  have  been  obtained),  while  33  are  common  to  the  "Lits 
Coquilliers"  (p.  304),  in  which  200  species  are  known  in  France. 
We  may  presume,  therefore,  that  the  London  clay  proper  is  older 
than  the  calcaire  grossier.  This  may  perhaps  remove  a  difficulty 
which  M.  Adolphe  Brongniart  has  experienced  when  comparing  the 
Eocene  Flora  of  the  neighborhoods  of  London  and  Paris.  The  fossil 

*  Heer,  Climat  et  Vegetation  du  Pays  Tertiaire,  p.  172. 

f  For  remarks  on  the  Monte  Bolca  rocks,  see  below,  Chap.  XXXII. 


292  LOWER  EOCENE  FORMATIONS,   ENGLAND.  [Cn.  XVL 

species  of  the  Island  of  Sheppey,  he  observes,  indicate  a  much,  more 
tropical  climate  than  the  Eocene  Flora  of  France.  Now  the  latter 
had  deen  derived  principally  from  the  Uppermost  Eocene  or  gypseous 
series,  and  resembles  the  vegetation  of  the 
borders  of  the  Mediterranean  rather  than 
that  of  an  equatorial  region ;  whereas  the 
older  flora  of  Sheppey  belongs  to  an  ante- 
cedent epoch,  separated  from  the  period  of 
the  Paris  gypsum  by  all  the  Barton  and  Bag- 
shot  series — in  short,  by  the  equivalents  of 
the  great  nummulitic  series  of  continental 
writers. 

Mr.  Bowerbank,  in  a  valuable  publication 
on  the  fossil  fruits  and  seeds  of  the  island 
*Oipti#t*,-Row.    of  Sheppey,  near  London,  has  described  no 
Fossil  fruit  of  palm,  from  Shep-  less    than   thirteen   fruits  'of  palms   of  the 

pey. 

recent  type  Nipa,   now  only  found  in  the 

Molucca  and  Philippine  Islands  and  in  Bengal  (see  fig.  249).  In 
the  delta  of  the  Ganges,  Dr.  Hooker  observed  the  large  nuts  of 
Nipa  fruticans  floating  in  such  numbers  in  the  various  arms  of 
that  great  river,  as  to  obstruct  the  paddle-wheels  of  steamboats. 
These  plants  are  allied  to  the  cocoa-nut  tribe  on  the  one  side,  and  on 
the  other  to  the  Pandanus,  or  screw-pine.  The  fruits  of  other  palms 
besides  those  of  the  cocoa-nut  tribe  are  also  met  with  in  the  clay  of 
Sheppey ;  also  three  species  of  Anona,  or  custard  apple ;  and  cucur- 
bitaceous  fruits  (of  the  gourd  and  melon  family)  are  in  considerable 
abundance.  Fruits  of  various  species  of  Acacia  are  in  profusion,  and 
these,  although  less  decidedly  tropical,  imply  a  warm  climate. 

The  contiguity  of  land  may  be  inferred  not  only  from  these  vege- 
table productions,  but  also  from  the  teeth  and  bones  of  crocodiles 
and  turtles,  since  these  creatures,  as  Dean  Conybeare  remarked,  must 
have  resorted  to  some  shore  to  lay  their  eggs.  Of  turtles  there  were 
numerous  species  referred  to  extinct  genera.  These  are,  for  the  most 
part,  not  equal  in  size  to  the  largest  living  tropical  turtles.  A  sea- 
snake,  which  must  have  been  thirteen  feet  long,  of  the  genus  Paloco- 
phis  before  mentioned  (p.  289),  has  also  been  described  by  Professor 
Owen  from  Sheppey,  of  a  different  species  from  that  of  Bracklesham. 
A  true  crocodile,  also,  Crocodilus  toliapicus,  and  another  saurian  more 
nearly  allied  to  the  gavial,  accompany  the  above  fossils;  also  the 
relics  of  several  birds  and  quadrupeds.  One  of  these  last  belongs  to 
the  new  genus  Hyracotherium  of  Owen,  of  the  hog  tribe,  allied  to 
Chseropotamus  ;  another  is  a  Lophiodon  ;  a  third  a  pachyderm  called 
Coryphodon  eoccenus  by  Owen,  larger  than  any  existing  tapir.  All 
these  animals  seem  to  have  inhabited  the  banks  of  the  great  river 
which  floated  down  the  Sheppey  fruits.  They  imply  the  existence  of 
a  mammiferous  fauna  antecedent  to  the  period  when  nummulites  flour- 
.shed  in  Europe  and  Asia,  and  therefore  before  the  Alps,  Pyrenees, 


CH.  XVI.]  FOSSIL  SHELLS  OF  THE  LONDON   CLAY. 


293 


and  other  mountain-chains  now  forming  the  backbones  of  great  con- 
tinents, were  raised  from  the  deep ;  nay,  even  before  a  part  of  the  con- 
stituent rock  masses  now  entering  into  the  central  ridges  of  these 
chains  had  been  deposited  in  the  sea. 

The  marine  shells  of  the  London  clay  confirm  the  inference  deriva- 
ble from  the  plants  and  reptiles  in  favor  of  a  high  temperature.  Thus 
many  species  of  Conus  and  Valuta  occur,  a  large  Cyprcea,  C.  ovifor- 
miSj  a  very  large  Rostellaria  (fig.  252),  a  species  of  Cancellaria,  six 
species  of  Nautilus  (fig.  254),  besides  other  Cephalopoda  of  extinct 
genera,  one  of  the  most  remarkable  of  which  is  the  Belosepia  *  (fig. 
255).  Among  many  characteristic  bivalve  shells  are  Leda  amyg- 
daloides  (fig.  256)  and  Cryptodon  angulatum  (fig.  257),  and  among 
the  Radiata  a  star-fish  called  Astropecten  (fig.  258). 


Fig.  250. 


FOSSIL    SHELLS    OF   THE    LONDON    CLAY. 
Fig.  251.  Fig.  252. 


Voluta  nodosa,  Sow. 
Highgate. 


Phorus  extensus, 
Sow.     Highgate. 


Fig.  253. 


Nautilus  centraUs,  Sow.    Highgate. 
Fig.  254. 


Rostellaria  ampla,  Brander.    £  of  nat.  size ; 
also  found  in  the  Barton  clay. 

Fig.  255. 


Aturia  ziczac,  Brown  and  Edwards. 
Syn.  Nautilus  ziczac,  Sow. 
London  clay.    Sheppey. 


Belosepia,  sepioidea,    De  Blainv. 
London  Clay.    Sheppey. 


*  For  description  of  Eocene  Cephalopoda,  see  Monograph  by  F.  E.  Edwards, 
Palaeontograph.  Soc.,  1849. 


294  STRATA  OF  KYSON  IN  SUFFOLK.  [On.  XVI. 

Fig.  256.  Pig.  287.  Tig.  258. 


Leda  amygdaloides.  Cryptodon  angulatum.  Astropecten  crispatus. 

Highgate.  London  clay.    Hornsea.  E.  Forbes.    Sheppey. 

These  fossils  are  accompanied  by  a  sword-fish  (Tetrapterus  priscus, 
Agassiz),  about  eight  feet  long,  and  a  saw-fish  (Pristis  bisulcatus,  Ag.), 
about  ten  feet  in  length ;  genera  now  foreign  to  the  British  seas.  On 
the  whole,  no  less  than  fifty  species  of  fish  have  been  described  by  M. 
Agassiz  from  these  beds  in  Sheppey,  and  they  indicate,  in  his  opinion, 
a  warm  climate. 

Strata  of  Kyson  in  Suffolk. — At  Kyson,  a  few  miles  east  of 
Woodbridge,  a  bed  of  Eocene  clay,  twelve  feet  thick,  underlies  the 
red  crag.  Beneath  it  is  a  deposit  of  yellow  and  white  sand,  of  consider- 
able interest,  in  consequence  of  many  peculiar  fossils  contained  in  it. 
Its  geological  position  is  probably  the  lowest  part  of  the  London  clay 
proper.  In  this  sand  have  been  found  remains  of  an  opossum  (Didel- 
phys)  (see  fig.  259),  and  an  insectivorous  bat  (fig.  260),  together  with 
many  teeth  of  fishes  of  the  shark  family.  Mr.  Colchester,  in  1840,  ob- 
tained other  mammalian  relics  from  Kyson,  among  which  Professor 
Owen  has  recognized  several  teeth  of  the  genus  Hyracotherium  (fig. 
261),  and  the  vertebrae  of  a  large  serpent,  probably  a  Palceophis. 

Fig.  259.  Fig.  260.  Fig.  261. 


Molar  tooth  and  part  of  jaw          Molars  of  insectivorous  bats,  Molar  of 

of  opossum.  twice  nat.  size.  Hyracotherium. 

From  Kyson.*  From  Kyson,  Suffolk. 

As  the  remains  both  of  the  Hyracotherium  and  Palceophis  were  after- 
wards met  with  in  the  London  clay,  as  before  remarked,  these  fossils 
confirm  the  opinion  previously  entertained,  that  the  Kyson  sand  be- 
longs to  the  Lower  Eocene  period.  A  fossil  lower  jaw  with  teeth  from 
the  same  bed  was  at  first  referred  by  Professor  Owen,  in  1840,  to  a 
monkey  called  Macacus  eoccenus,  and  afterwards  JEopithecus  ;  but  he 
has  since  (1862)  retracted  this  opinion,  and,  on  reexainination,  and 
with  more  ample  materials  at  his  command,  has  pronounced  it  to  be- 
long to  a  Hyracotherium.  There  is  now,  therefore,  no  Eocene  monkey 
known  to  palaeontologists  unless  M.  Eiitimeyer  is  right  in  referring  to 

*  Annals  of  Nat.  Hist.,  vol.  iv.  No.  23,  Nov.  1839. 


CH.  XVI.]          LOWER  EOCENE  FORMATIONS,   ENGLAND.  395 

this  family  a  small  fragment  of  a  jaw  with  three  molar  teeth,  found  in 
the  Upper  Eocene  strata  of  the  Swiss  Jura. 

Plastic  or  mottled  clays  and  sands  (C.  2,  p.  281). — The  clays  called 
plastic,  which  lie  immediately  below  the  London  clay,  received  their 
name  originally  in  France  from  being  often  used  in  pottery.  Beds  of 
the  same  age  (the  Woolwich  and  Reading  series  of  Prestwich)  are 
used  for  the  like  purposes  in  England.* 

No  formations  can  be  more  dissimilar  on  the  whole  in  mineral  char- 
acter than  the  Eocene  deposits  of  England  and  Paris ;  those  of  our 
own  island  being  almost  exclusively  of  mechanical  origin, — accumula- 
tions of  mud,  sand,  and  pebbles  ;  while  in  the  neighborhood  of  Paris 
we  find  a  great  succession  of  strata  composed  of  limestones,  some  of 
them  siliceous,  and  of  crystalline  gypsum  and  siliceous  sandstone,  and 
sometimes  of  pure  flint  used  for  millstones.  Hence  it  is  by  no  meaus 
an  easy  task  to  institute  an  exact  comparison  between  the  various 
members  of  the  English  and  French  series,  and  to  settle  their  respec- 
tive ages.  It  is  clear  that,  on  the  sites  both  of  Paris  and  London,  a 
continual  change  was  going  on  in  the  fauna  and  flora  by  the  coming 
in  of  new  species  and  the  dying  out  of  others  ;  and  contemporaneous 
changes  of  geographical  conditions  were  also  in  progress  in  conse- 
quence of  the  rising  and  sinking  of  the  land  and  bottom  of  the  sea. 
A  particular  subdivision,  therefore,  of  the  time  was  occasionally  repre- 
sented in  one  area  by  land,  in  another  by  an  estuary,  in  a  third  by  the 
sea,  and  even  where  the  conditions  were  in  both  areas  of  a  marine 
character,  there  was  often  shallow  water  in  one,  and  deep  sea  in 
another,  producing  the  want  of  agreement  in  the  state  of  animal  life. 

But  in  regard  to  that  division  of  the  Eocene  series  which  we  have 
now  under  consideration,  we  find  an  exception  to  the  general  rule,  for, 
whether  we  study  it  in  the  basins  of  London,  Hampshire,  or  Paris, 
we  recognize  everywhere  the  same  mineral  character.  This  uniformity 
of  aspect  must  be  seen  in  order  to  be  fully  appreciated,  since  the  beds 
consist  simply  of  mottled  clays  and  sand,  with  lignite  and  well-rolled 
flint  pebbles,  derived  from  the  chalk,  and  varying  in  size  from  that  of 
a  pea  to  an  egg.  These  strata  may  be  seen  in  the  Isle  of  Wight  in 
contact  with  the  chalk,  or  in  the  London  basin,  at  Reading,  Black- 
heath,  and  Woolwich.  In  some  of  the  lowest  of  them,  banks  of 
oysters  are  observed,  consisting  of  Ostrea  bellovacina,  so  common  in 
France  in  the  same  relative  position,  and  Ostrea  edulina,  scarcely  dis- 
tinguishable from  the  living  eatable  species.  In  the  same  beds  at 
Bromley,  Dr.  Buckland  found  one  large  pebble  to  which  five  full- 
grown  oysters  were  affixed,  in  such  a  manner  as  to  show  that  they  had 
commenced  their  first  growth  upon  it,  and  remained  attached  to  it 
through  life. 

In  several  places,  as  at  Woolwich  on  the  Thames,  at  Newhaven  in 
Sussex,  and  elsewhere,  a  mixture  of  marine  and  freshwater  testacea 

*  Prestwich,  Waterbearing  Strata  of  London,  1851. 


296 


LOWER  EOCENE  FORMATIONS,  ENGLAND.          [On.  XVI. 


distinguishes  this  member  of  the  series.     Among  the  latter,  Melania 
inquinata  (see  fig.  263)  and  Cyrena  cuneiformis  (see  fig.  262)  are  very 


Fig.  262. 


Fig.  263. 


Oyrena  cuneiformis,  Min.  Con. 
Natural  size. 


Melania  inquinata,  Des.    Nat.  size. 
Syn.  Ceriihiwm  melanoides,  Min  Con. 


common,  as  in  beds  of  corresponding  age  in  France.  They  clearly  indi- 
cate points  where  rivers  entered  the  Eocene  sea.  Usually  there  is  a  mix- 
ture of  brackish  freshwater,  and  marine  shells,  and  sometimes,  as  at 
Woolwich,  proofs  of  the  river  and  the  sea  having  successively  pre- 
vailed on  the  same  spot.  At  New  Charlton,  in  the  suburbs  of  Wool- 
wich, M.  de  la  Condamine  discovered  in  1849,  and  pointed  out  to 
me,  a  layer  of  sand  associated  with  well-rounded  flint  pebbles  in  which 
numerous  individuals  of  the  Cyrena  tellinella  were  seen  standing  end- 
wise with  both  their  valves  united,  the  posterior  extremity  of  each 
shell  being  uppermost,  as  would  happen  if  the  mollusks  had  died  in 
their  natural  position.  I  have  described  *  a  bank  of  sandy  mud,  in 
the  delta  of  the  Alabama  River  at  Mobile,  on  the  borders  of  the  Gulf 
of  Mexico,  where  in  1846  I  dug  out  at  low  tide  specimens  of  living 
species  of  Cyrena  and  of  a  Gnathodon,  which  were  similarly  placed 
with  their  shells  erect,  or  in  a  position  which  enables  the  animal  to 
protrude  its  siphon  upwards  and  draw  in  or  reject  water  at  pleasure. 
The  water  at  Mobile  is  usually  fresh,  but  sometimes  brackish.  At 
Woolwich  a  body  of  river-water  must  have  flowed  permanently  into 
the  sea  where  the  Cyrence  lived,  and  they  may  have  been  killed  sud- 
denly by  an  influx  of  pure  salt  water,  which  invaded  the  spot  when 
the  river  was  low,  or  when  a  subsidence  of  land  took  place.  Traced 
in  one  direction,  or  eastward  toward  Herne  Bay,  the  Woolwich  beds 


Second  Visit  to  the  United  States,  vol.  ii.  p.  104. 


CH.  XVI.]         EOCENE  STRATA  IN  FRANCE.  297 

assume  more  and  more  of  a  marine  character  ;  while  in  an  opposite, 
or  south-western  direction,  they  become,  as  near  Chelsea  and  other 
places,  more  freshwater,  and  contain  Unio,  Paludina,  and  layers  of 
lignite,  so  that  the  land  drained  by  the  ancient  river  seems  clearly  to 
have  been  to  the  south-west  of  the  present  site  of  the  metropolis. 

Before  the  minds  of  geologists  had  become  familiar  with  the  theory 
of  the  gradual  sinking  of  the  land,  and  its  conversion  into  sea  at  dif- 
ferent periods,  and  the  consequent  change  from  shallow  to  deep  water, 
the  freshwater  and  littoral  character  of  this  inferior  group  appeared 
strange  and  anomalous.  After  passing  through  hundreds  of  feet  of 
London  clay,  proved  by  its  fossils  to  have  been  deposited  in  deep  salt 
water,  we  arrive  at  beds  of  fluviatile  origin,  and  in  the  same  underly- 
ing formation  masses  of  shingle,  attaining  at  Blackheath,  near  London, 
a  thickness  of  50  feet,  indicate  the  proximity  of  land,  where  the  flints 
of  the  chalk  were  rolled  into  sand  and  pebbles,  and  spread  continu- 
ously over  wide  spaces.  Such  shingle  always  appears  at  the  bottom 
of  the  series,  whether  in  the  Isle  of  Wight,  or  in  the  Hampshire  or 
London  basins.  It  may  be  asked  why  they  did  not  constitute  simple 
narrow  littoral  zones,  such  as  we  might  look  for  on  an  ancient  sea- 
shore. In  reply  Mr.  Prestwich  has  suggested  that  such  zones  of 
shingle  may  have  been  slowly  formed  on  a  large  scale  at  the  period 
of  the  Thanet  sands  (C.  3,  p.  281),  and  while  the  land  was  sinking 
the  well-rolled  pebbles  may  have  been  dispersed  simultaneously  over 
considerable  areas,  and  exposed  during  gradual  submergence  to  the 
action  of  the  waves  of  the  sea,  aided  occasionally  by  tidal  currents 
and  river  floods. 

Thanet  sands  (C.  3,  p.  281). — The  mottled  or  plastic  clay  of  the 
Isle  of  Wight  and  Hampshire  is  often  seen  in  actual  contact  with  the 
chalk,  constituting  in  such  places  the  lowest  member  of  the  British 
Eocene  series.  But  at  other  points  another  formation  of  marine 
origin,  characterized  by  a  somewhat  different  assemblage  of  organic 
remains,  has  been  shown  by  Mr.  Prestwich  to  intervene  between  the 
chalk  and  the  Woolwich  series.  For  these  beds  he  has  proposed  the 
name  of  "  Thanet  Sands,"  because  they  are  well  seen  in  the  Isle  of 
Thanet,  in  the  northern  part  of  Kent,  and  on  the  seacoast  between 
Herne  Bay  and  the  Reculvers,  where  they  consist  of  sands  with  a 
few  concretionary  masses  of  sandstone,  and  contain  among  other 
fossils  Pholadomya  cuneata,  Cyprina  Morrisii,  Corbula  longirostris, 
Scalaria  Bowerb&rikii,  &c.  The  greatest  thickness  of  these  beds  is 
about  90  feet. 

GENERAL   TABLE    OF   FRENCH    EOCENE    STRATA. 

UPPER  EOCENE. 

French  subdivisions.  English  equivalents. 

A.  1.   Gypseous  series  of  Montmartre.          1.  Bembridge  series,  p.  281. 
A.  2.   Calcaire  silicieux,    or    Travertin       2.   Osborne  and  Headon  series,  p.  284. 
Inferieur. 


298  EOCENE  STRATA  IN  FRANCE.         [Cn.  XVI. 

A.  3.   Gres  de  Beauchamp,  or  Sables       3.  White  sand  and  clay  of  Barton 
Moyens.  Hants. 


MIDDLE  EOCENE. 


B.  1.   Calcaire  Grossier.  1.  Bagshot  and  Bracklesham  beds. 

B.  2.  Soissonnais  Sands,   or   Lits  Co-       2.   Wanting, 
quilliers. 


LOWER   EOCENE. 


C.  1.  Argile  de  Londres  at  base  of  Hill  1.  London  Clay. 

of  Cassel,  near  Dunkirk.  2.  Plastic  clay  and  sand  with  lignite 
C.  2.  Argile  plastique  and  lignite.  (Woolwich  and  Reading  series). 

C.  3.   Sables  de  Bracheux.  3.   Thanet  sands. 

The  tertiary  formations  in  the  neighborhood  of  Paris  consists  of  a 
series  of  marine  and  freshwater  strata,  alternating  with  each  other, 
and  filling  up  a  depression  in  the  chalk.  The  area  which  they  occupy 
has  been  called  the  Paris  basin,  and  is  about  180  miles  in  its  greatest 
length  from  north  to  south,  and  about  90  miles  in  breadth  from  east 
to  west  (see  Map,  p.  221).  MM.  Cuvier  and  Brongniart  attempted,  in 
1810,  to  distinguish  five  different  groups,  comprising  three  freshwater 
and  two  marine,  which  were  supposed  to  imply  that  the  waters  of  the 
ocean,  and  of  rivers  and  lakes,  had  been  by  turns  admitted  into  and 
excluded  from  the  same  area.  Investigations  since  made  in  the 
Hampshire  and  London  basins  have  rather  tended  to  confirm  these 
views,  at  least  so  far  as  to  show  that  since  the  commencement  of  the 
Eocene  period  there  have  been  great  movements  of  the  bed  of  the 
sea,  and  of  the  adjoining  lands,  and  that  the  superposition  of  deep 
sea  to  shallow  water  deposits  (the  London  clay,  for  example,  to  the 
Woolwich  beds)  can  only  be  explained  by  referring  to  such  move- 
ments. Nevertheless,  it  appears,  from  the  researches  of  M.  Constant 
Prevost,  that  some  of  the  minor  alternations  and  intermixtures  of 
freshwater  and  marine  doposits,  in  the  Paris  basin,  may  be  accounted 
for  by  imagining  both  to  have  been  simultaneously  in  progress,  in 
the  same  bay  of  the  same  sea,  or  a  gulf  into  which  many  rivers 
entered. 

Gypseous  series  of  Montmartre. — To  enlarge  on  the  numerous  sub- 
divisions of  the  Parisian  strata  would  lead  me  beyond  my  present  lim- 
its ;  I  shall  therefore  give  some  examples  only  of  the  most  important 
formations  enumerated  in  the  foregoing  Table. 

Beneath  the  Ores  de  Fontainebleau,  often  called  "  Upper  marine 
sands,"  and  belonging  to  the  Lower  Miocene,  as  before  stated,  we  find, 
in  the  neighborhood  of  Paris,  a  series  of  white  and  green  marls,  with 
subordinate  beds  of  gypsum,  A.,  Table,  p.  297.  These  are  most 
largely  developed  in  the  central  parts  of  the  Paris  basin,  and,  among 
other  places,  in  the  hill  of  Montmartre,  where  its  fossils  were  first 
studied  by  Cuvier. 

The  gypsum  quarried  there  for  the  manufacture  of  plaster  of  Paris 


CH.  XVI.]  MAMMALIA  OF  PARIS  GYPSUM.  299 

occurs  as  a  granular  crystalline  rock,  and  together  with  the  associated 
marls,  contains  land  and  fluviatile  shells,  together  with  the  hones  and 
skeletons  of  birds  and  quadrupeds.  Several  landplants  are  also  met 
with,  among  which  are  fine  specimens  of  the  fan  palm  or  palmetto 
tribe  (Fldbellaria).  The  remains  also  of  freshwater  fish,  and  of  croc- 
odiles and  other  reptiles,  occur  in  the  gypsum.  The  skeletons  of 
mammalia  are  usually  isolated,  often  entire,  the  most  delicate  extremi- 
ties being  preserved ;  as  if  the  carcases,  clothed  with  their  flesh  and 
skin,  had  been  floated  down  soon  after  death,  and  while  they  were  still 
swollen  by  the  gases  generated  by  their  first  decomposition.  The  few 
accompanying  shells  are  of  those  light  kinds  which  frequently  float  on 
the  surface  of  rivers,  together  with  wood. 

M.  Prevost  has  therefore  suggested  that  a  river  may  have  swept 
away  the  bodies  of  animals,  and  the  plants  which  lived  on  its  borders, 
or  in  the  lakes  which  it  traversed,  and  may  have  carried  them  down 
into  the  centre  of  the  gulf  into  which  flowed  the  waters  impregnated 
with  sulphate  of  lime.  We  know  that  the  Fiume  Salso  in  Sicily 
enters  the  sea  so  charged  with  various  salts  that  the  thirsty  cattle 
refuse  to  drink  of  it.  A  stream  of  sulphureous  water  as  white  as 
milk,  descends  into  the  sea  from  the  volcanic  mountain  of  Idienne 
on  the  east  of  Java ;  and  a  great  body  of  hot  water,  charged  with 
sulphuric  acid,  rushed  down  from  the  same  volcano  on  one  occasion, 
and  inundated  a  large  tract  of  country,  destroying,  by  its  noxious  prop- 
erties, all  the  vegetation.*  In  like  manner  the  Pusanibio,  or  "  Vin- 
egar River,"  of  Columbia,  which  rises  at  the  foot  of  Purace,  an 
extinct  volcano,  7500  feet  above  the  level  of  the  sea,  is  strongly  im- 
pregnated with  sulphuric  and  hydrochloric  acids  and  with  oxide  of 
iron.  We  may  easily  suppose  the  waters  of  such  streams  to  have 
properties  noxious  to  marine  animals,  and  in  this  manner  the  entire 
absence  of  marine  remains  in  the  ossiferous  gypsum  may  be  explained.! 
There  are  no  pebbles  or  coarse  sand  in  the  gypsum  ;  a  circumstance 
which  agrees  well  with  the  hypothesis  that  these  beds  were  precipi- 
tated from  water  holding  sulphate  of  lime  in  solution,  and  floating  the 
remains  of  different  animals. 

In  this  formation  the  relics  of  about  fifty  species  of  quadrupeds, 
including  the  genera  Paleotherium  (see  fig.  220),  Anoplotherium  (see 
fig.  219),  and  others,  have  been  found,  all  extinct,  and  nearly  four- 
fifths  of  them  belonging  to  the  Perissodactyle  or  odd-toed  division  of 
the  order  Pachydermata,  which  now  contains  only  four  living  genera, 
namely,  rhinoceros,  tapir,  horse,  and  hyrax.  With  them  a  few 
carnivorous  animals  are  associated,  among  which  are  the  Hycenodon 
dasyuroides,  a  species  of  dog,  Canis  Parisiensis,  and  a  weasel,  Cyn- 
odon  Parisiensis.  Of  the  Rodentia  are  found  a  squirrel ;  of  the 


*  Leyde  Magaz.  voor  Wetensch.  Konst  en  Lett.,  partie  v.  cahier  i.  p.  71.    Cited 
by  Rozet,  Journ.  de  Geologic,  torn.  i.  p.  43. 

\  M.  C.  Prevost,  Submersions  Iteratives,  &c.     Note  23. 


300 


MAMMALIA  OF  PARIS  GYPSUM. 


[On.  XVL 


Cheiroptera,  a  bat ;  while  the  Marsupialia  (an  order  now  confined  to 
America,  Australia,  and  some  contiguous  islands)  are  represented  by 
an  opposum. 

Of  birds,  about  ten  species  have  been  ascertained,  the  skeletons  of 
some  of  which  are  entire.  None  of  them  are  referable  to  existing 
species.*  The  same  remark  applies  to  the  fish,  according  to  MM. 
Cuvier  and  Agassiz,  as  also  to  the  reptiles.  Among  the  last  are  croc- 
odiles and  tortoises  of  the  genera  JEmys  and  Trionyx. 

The  tribe  of  land  quadrupeds  most  abundant  in  this  formation  is 
such  as  now  inhabits  alluvial  plains  and  marshes,  and  the  banks  of 
rivers  and  lakes,  a  class  most  exposed  to  suffer  by  river  inundations. 
Among  these  were  several  species  of  Paleotherium,  a  genus  before 
alluded  to  (p.  283).  These  were  associated  with  the  Anoplotherium, 
a  tribe  intermediate  between  pachyderms  and  ruminants.  One  of 
the  three  divisions  of  this  family  was  called  by  Cuvier  Xiphodon. 
Their  forms  were  slender  and  elegant,  and  one,  named  Xiphodon 
gracile  (fig.  264),  was  about  the  size  of  the  chamois ;  and  Cuvier  in- 


Fig.  264. 


Xiphodon  graeile,  or  Anoplotherium  gracile,  Cuvier.    Eestored  outline. 

ferred  from  the  skeleton  that  it  was  as  light,  graceful,  and  agile  as  the 
gazelle. 

When  the  French  osteologist  declared,  in  the  early  part  of  the 
present  century,  that  all  the  fossil  quadrupeds  of  the  gypsum  of  Paris 
were  extinct,  the  announcement  of  so  startling  a  fact,  on  such  high 
authority,  created  a  powerful  sensation,  and  from  that  time  a  new  im- 
pulse was  given  throughout  Europe  to  the  progress  of  geological  in- 
vestigation. Eminent  nuturalists,  it  is  true,  had  long  before  main- 
tained that  the  shells  and  zoophytes  met  with  in  many  ancient  Euro- 
pean rocks  had  ceased  to  be  inhabitants  of  the  earth,  but  the  majority 
even  of  the  educated  classes  continued  to  believe  that  the  species  of 
animals  and  giants,  now  contemporary  with  man,  were  the  same  as 
those  which  oeen  called  into  being  when  the  planet  itself  was  created. 

*  Cuvier,  Oss.  Foss.,  torn.  iii.  p.  255. 


CH.  XVL]  FOSSIL  FOOTPRINTS.  301 

It  was  easy  to  throw  discredit  upon  the  new  doctrine  by  asking 
whether  corals,  shells,  and  other  creatures  previously  unknown,  were 
not  annually  discovered  ?  and  whether  living  forms  corresponding  with 
the  fossils  might  not  yet  be  dredged  up  from  seas  hitherto  unexamined  ? 
But  from  the  era  of  the  publication  of  Cuvier's  "  Ossements  Fossiles," 
and  still  more  his  popular  Treatise  called  "  A  Theory  of  the  Earth," 
sounder  views  began  to  prevail.  It  was  clearly  demonstrated  that 
most  of  the  mammalia  found  in  the  gypsum  of  Montmartre  differed 
even  generically  from  any  now  known  to  exist,  and  the  extreme  improba- 
bility that  any  of  them,  especially  the  larger  ones,  would  ever  be  found 
surviving  in  continents  yet  unexplored,  was  made  manifest.  Moreover, 
the  non-admixture  of  a  single  living  species  in  the  midst  of  so  rich  a 
fossil  fauna  was  a  striking  proof  that  there  had  existed  in  that 
region  a  state  of  the  earth's  surface  zoologically  unconnected  with  the 
present. 

Fossil  footprints. — There  are  three  superimposed  masses  of  gypsum 
in  the  neighborhood  of  Paris,  separated  by  intervening  deposits  of 
laminated  marl.  In  the  uppermost  of  the  three  in  the  valley  of  Mont- 
morency  M.  Desnoyers  discovered  in  1859  many  footprints  of  animals 
occurring  at  no  less  than  six  different  levels.*  The  gypsum  to  which 
they  belong  varies  from  thirty  to  fifty  feet  in  thickness,  and  is  that 
which  has  yielded  to  the  naturalist  the  largest  number  of  bones  and 
skeletons  of  mammalia,  birds,  and  reptiles.  I  visited  the  quarries, 
soon  after  the  discovery  was  made  known,  with  M.  Desnoyers,  who 
also  showed  me  large  slabs  in  the  Museum  at  Paris,  where,  on  the  up- 
per planes  of  stratification,  the  indented  footmarks  were  seen,  while 
corresponding  casts  in  relief  appeared  on  the  lower  surfaces  of  the 
strata  of  gypsum  which  were  immediately  superimposed.  A  thin  film 
of  marl,  which  before  it  was  dried  and  condensed  by  pressure  must 
have  represented  a  much  thicker  layer  of  soft  mud,  intervened  be- 
tween the  beds  of  solid  gypsum.  On  this  mud  the  animals  had 
trodden,  and  made  impressions  which  had  penetrated  to  the  gypseous 
mass  below,  then  evidently  unconsolidated.  Tracks  of  the  Anoplo- 
therium  with  its  bisulcate  hoof,  and  the  trilobed  footprints  of  Paleo- 
therium,  were  seen  of  different  sizes,  corresponding  to  those  of  several 
species  of  these  genera  which  Cuvier  had  reconstructed,  while  in  the 
the  same  beds  were  footmarks  of  carnivorous  mammalia.  The  tracks 
also  of  fluviatile,  lacustrine,  and  terrestrial  tortoises  (Emys,  Trionyx, 
&c.),  have  been  discovered,  also  those  of  crocodiles,  iguanas,  geckos, 
and  great  batrachians,  and  the  footprints  of  a  huge  bird,  apparently  a 
wader,  of  the  size  of  the  gastornis,  to  be  mentioned  in  the  sequel. 
There  were  likewise  impressions  of  the  feet  of  other  creatures,  some 
of  them  clearly  distinguishable  from  any  of  the  fifty  extinct  types  of 
mammalia,  of  which  the  bones  have  been  found  in  the  Paris  gypsum. 

*  Sur  des  Empreintes  de  Pas  d'Animaux,  par  M.  J.  Desnoyers.     Compte  Rendu 
de  1'Institut,  1859. 


302  FOSSIL  FOOTPKINTS  IN  THE  [On.  XVI. 

The  whole  assemblage,  says  Desnoyers,  indicate  the  shores  of  a  lake, 
or  several  small  lakes  communicating  with  each  other,  on  the  borders 
of  which  many  species  of  Pachyderms  wandered,  and  beasts  of 
prey  which  occasionally  devoured  them.  The  toothmarks  of  these 
last  had  been  detected  by  palaeontologists  long  before  on  the  bones  and 
skulls  of  Paleotheres  entombed  in  the  gypsum. 

These  footmarks  have  revealed  to  us  new  and  unexpected  proofs 
that  the  air-breathing  fauna  of  the  Upper  Eocene  period  in  Europe 
far  surpassed  in  the  number  and  variety  of  its  species  the  largest  es- 
timate which  had  previously  been  formed  of  it.  We  may  now  feel 
sure  that  the  mammalia,  reptiles,  and  birds,  which  have  left  portions 
of  their  skeletons  as  memorials  of  their  existence  in  the  solid  gypsum, 
constituted  but  a  part  of  the  then  living  creation.  Similar  inferences 
may  be  drawn  from  the  study  of  the  whole  succession  of  geological 
records.  In  each  district  the  monuments  of  periods  embracing  thou- 
sands, and  probably  in  some  instances  millions  of  years,  are  totally 
wanting.  Even  in  the  volumes  which  are  extant  the  greater  number  of 
the  pages  are  missing  in  any  given  region,  and  where  they  are  found 
they  contain  but  few  and  casual  entries  of  the  physical  events  or  liv- 
ing beings  of  the  times  to  which  they  relate.  It  may  also  be  re- 
marked that  the  subordinate  formations  met  with  in  two  neighbor- 
ing countries,  such  as  France  and  England  (the  minor  Tertiary  groups 
above  enumerated),  commonly  classed  as  equivalents  and  referred  to 
corresponding  periods,  may  nevertheless  have  been  by  no  means 
strictly  coincident  in  date.  Though  called  contemporaneous,  it  is 
probable  that  they  were  often  separated  by  intervals  of  hundreds  of 
thousands  of  years.  We  may  compare  them  to  double  stars,  which 
appear  single  to  the  naked  eye  because  seen  from  a  vast  distance  in 
space,  and  which  really  belong  to  one  and  the  same  stellar  system 
though  occupying  places  in  space  extremely  remote  if  estimated  by 
our  ordinary  standard  of  terrestrial  measurements. 

Calcaire  siliceux,  or  Travertin  inferieur  (A.  2,  p.  297). — This  com- 
pact siliceous  limestone  extends  over  a  wide  area.  It  resembles  a 
precipitate  from  the  waters  of  mineral  springs,  and  is  often  traversed 
by  small  empty  sinuous  cavities.  It  is,  for  the  most  part,  devoid  of 
organic  remains,  but  in  some  places  contains  freshwater  and  land 
species,  and  never  any  marine  fossils.  The  calcaire  siliceux  and  the 
calcaire  grossier  usually  occupy  distinct  parts  of  the  Paris  basin,  the 
one  attaining  its  fullest  development  in  those  places  where  the  other  is 
of  slight  thickness.  They  are  described  by  some  writers  as  alternat- 
ing with  each  other  toward  the  centre  of  the  basin,  as  at  Sergy  and 
Osny. 

The  gypsum,  with  its  associated  marls  before  described,  is  in  great- 
est force  toward  the  centre  of  the  basin,  where  the  calcaire  grossier 
and  calcaire  siliceux  are  less  fully  developed. 

Ores  de  Beauchamp,  or  Sables  moyens  (A.  3,  p.  298). — In  some  parts 
of  the  Paris  basin,  sands  and  marls,  called  the  Gres  de  Beauchamp,  or 


On.  XVI.] 


EOCENE  STRATA  OF  FRANCE. 


303 


Sables  moyens,  divide  the  gypseous  beds  from  the  calcaire  grossier 
proper.  These  sands,  in  which  a  small  nummulite  (JV.  variolaria)  is 
very  abundant,  contain  more  than  300  species  of  marine  shells,  many 
of  them  peculiar,  but  others  common  to  the  next  division. 

Calcaire  grossier,  upper  and  middle  (B.  1,  p.  298). — The  upper  divis- 
ion of  this  group  consists  in  great  part  of  beds  of  compact,  fragile 
limestone,  with  some  intercalated  green  marls.  The  shells  in  some 
parts  are  a  mixture  of  Cerithium,  Cyclostoma,  and  Corbula  ;  in  others 
Limnea,  Cerithium,  Paludina,  <fec.  In  the  latter,  the  bones  of  reptiles 
and  mammalia,  Paleotherium  and  Lophiodon,  have  been  found.  The 
middle  division,  or  calcaire  grossier  proper,  consists  of  a  coarse  lime- 
stone, often  passing  into  sand.  It  contains  the  greater  number  of  the 
fossil  shells  which  characterize  the  Paris  basin.  No  less  than  400  dis- 
tinct species  have  been  procured  from  a  single  spot  near  Grignon, 
where  they  are  embedded  in  a  calcareous  sand,  chiefly  formed  of  com- 
minuted shells,  in  which,  nevertheless,  individuals  in  a  perfect  state  of 
preservation,  both  of  marine,  terrestrial,  and  freshwater  species,  are 
mingled  together.  Some  of  the  marine  shells  may  have  lived  on  the 
spot ;  but  the  Cyclostoma  and  Limnea  must  have  been  brought  thither 
by  rivers  and  currents,  and  the  quantity  of  triturated  shells  implies 
considerable  movement  in  the  waters. 

Nothing  is  more  striking  in  this  assemblage  of  fossil  testacea 
than  the  great  proportion  of  species  referable  to  the  genus  Cerithium 
(see  figures,  p.  240).  There  occur  no  less  than  137  species  of  this 
genus  in  the  Paris  basin,  and  almost  all  of  them  in  the  calcaire  gros- 
sier. Most  of  the  living  Cerithia  inhabit  the  sea  near  the  mouths  of 
rivers,  where  the  waters  are  brackish  ;  so  that  their  abundance  in  the 
marine  strata  now  under  consideration  is  in  harmony  with  the  hy- 
pothesis that  the  Paris  basin  formed  a  gulf  into  which  several  rivers 
flowed. 

In  some  parts  of  the  calcaire  grossier  round  Paris,  certain  beds 
occur  of  a  stone  used  in  building,  and  called  by  the  French  geologists 


EOCENE    FORAMINIFERA. 


Calcarina  rarispina,  Desh. 
5.  Natural  size,    «,  c.  Same  magnified. 


Fig.  266. 


Spirolina  stenostoma,  Desh. 
B.  Natural  size.    A,  C,  D.  Same  magnified. 


304: 


EOCENE  FORAMINIFERA. 

Fig.  26T. 


[On.  XVI 


Trilocnlina  irtflata,  Been. 
b.  Natural  size.    «,  c,  d.  Same  magnified. 


Clavulina  corrugata,  Desh. 
er.  Natural  size.    &,  c.  Same  magnified. 

"  Miliolite  limestone."  It  is  almost  entirely  made  up  of  millions  of 
microscopic  shells,  of  the  size  of  minute  grains  of  sand,  which  all 
belong  to  the  class  Foraminifera.  Figures  of  some  of  these  are  given 
in  the  annexed  woodcut.  As  this  miliolitic  stone  never  occurs  in  the 
Faluns,  or  Upper  Miocene  strata  of  Brittany  and  Touraine,  it  often 
furnishes  the  geologist  with  a  useful  criterion  for  distinguishing  the 
detached  Eocene  and  Miocene  formations  scattered  over  those  and 
other  adjoining  provinces.  The  discovery  of  the  remains  of  Paleo- 
therium  and  other  mammalia  in  some  of  the  upper  beds  of  the  cal- 
caire  grossier  shows  that  these  land  animals  began  to  exist  before  the 
deposition  of  the  overlying  gypseous  series  had  commenced. 

Lower  Calcaire  grossier,  or  Glauconie  grossiere  (B.  1,  p.  298). — The 
lower  part  of  the  calcaire  grossier,  which  often  contains  much  green 
earth,  is  characterized  at  Auvers,  near  Pontoise,  to  the  north  of  Paris, 
and  still  more  in  the  environs  of  Compiegne,  by  the  abundance  of 
nummulites,  consisting  chiefly  of  N.  Icevigata,  N.  scabra,  and  N.  La- 
marcki,  which  constitute  a  large  proportion  of  some  of  the  stony 
strata,  though  these  same  foraminifera  are  wanting  in  beds  of  similar 
age  in  the  immediate  environs  of  Paris. 

Soissonnais  sands,  or  Lits  coquilliers  (B.  2,  p.  298). — Below  the 
preceding  formation,  shelly  sands  are  seen,  of  considerable  thickness, 
especially  at  Cuisse-Lamotte,  near  Compiegne,  and  other  localities  in 
the  Soissonnais,  about  fifty  miles  N.  E.  of  Paris,  from  which  about  300 
species  of  shells  have  been  obtained,  many  of  them  common  to  the 
calcaire  grossier  and  the  Bracklesham  beds  of  England,  and  many 
peculiar.  The  Nummulites  planulata  is  very  abundant,  and  the 
most  characteristic  shell  is  the  Nerita  conoidea,  Lam.,  a  fossil  which 
has  a  very  wide  geographical  range ;  for,  as  M.  d'Archiac  remarks, 


CH.  XVI. ]         MIDDLE  EOCENE  FORMATIONS  OF  FRANCE.  395 

Fig.  269. 


N&rita  conoidea,  Lam. 
Syn.  N.  SchmidelUana,  Chemnitz. 

it  accompanies  the  nummulitic  formation  from  Europe  to  India,  hav- 
ing been  found  in  Cutch,  near  the  mouths  of  the  Indus,  associated 
with  Nummulites  scabra.  No  less  than  33  shells  of  this  group  are 
said  to  be  identical  with  shells  of  the  London  clay  proper,  yet,  after 
visiting  Cuisse-Lamotte  and  other  localities  of  the  "  Sables  inferieurs  " 
of  Archiac,  I  agree  with  Mr.  Prestwich,  that  the  latter  are  probably 
newer  than  the  London  clay,  and  perhaps  older  than  the  Bracklesham 
beds  of  England.  The  London  clay  seems  to  be  unrepresented  in  the 
Paris  basin,  unless  partially  so,  by  these  sands.*  One  of  the  shells 
of  the  sandy  beds  of  the  Soissonnais  is  adduced  by  M.  Deshayes  as 
an  example  of  the  changes  which  certain  species  underwent  in  the 
successive  stages  of  their  existence.  It  seems  that  different  varieties 

O 

of  the  Cardium  porulosum  are  ^characteristic  of  different  formations. 

Fig.  270. 


Cardium  porulosum.    Paris  and  London  basins. 

In  the  Soissonnais  this  shell  acquires  but  a  small  volume,  and  has 
many  peculiarities,  which  disappear  in  the  lowest  beds  of  the  calcaire 
grossier.  In  these  the  shell  attains  its  full,  size,  with  many  distinctive 
characters,  which  are  again  modified  in  the  uppermost  beds  of  the 
calcaire  grossier ;  and  these  last  modifications  of  form  are  preserved 
throughout  the  "  upper  marine  "  (or  Lower  Miocene)  series.f 


LOWER  EOCENE  FORMATIONS  OF  FRANCE. 

Argile  plastique  (C.  2,  p.  298).— At  the  base  of  the  tertiary  system 
in  France  are  extensive  deposits  of  sands,  with  occasional  beds  of  clay 

*  D' Archiac,  Bulletin,  torn.  x. ;  and  Prestwick,  Geol.  Quart.  Journ.,  1847,  p.  377. 
f  Coquilles  caracteristiques  des  Terrains,  1831. 
20 


306       LOWER  EOCENE  FORMATIONS  OF  FRANCE.    [Cn.  XVI. 

used  for  pottery,  and  called  "argile  plastique."  Fossil  oysters  (Ostrea 
bellovacina)  abound  in  some  places,  and  in  others  there  is  a  mixture  of 
fluviatile  shells,  such  as  Cyrena  cuneiformis  (fig.  262,  p.  296),  Melania 
inquinata  (fig.  263),  and  others,  frequently  met  with  in  beds  occupying 
the  same  position  in  the  valley  of  the  Thames.  Layers  of  lignite  also 
accompany  the  inferior  clays  and  sands. 

Immediately  upon  the  chalk  at  the  bottom  of  all  the  tertiary  strata 
in  France  there  generally  is  a  conglomerate  or  breccia  of  rolled  and 
angular  chalk-flints,  cemented  by  cilicious  sand.  These  beds  appear 
to  be  of  littoral  origin,  and  imply  the  previous  emergence  of  the  chalk, 
and  its  waste  by  denudation.  In  the  year  1855,  the  tibia  and  femur  of 
a  large  bird  equalling  at  least  the  ostrich  in  size  were  found  at  Meudon, 
near  Paris,  at  the  base  of  the  Plastic  clay.  This  bird,  to  which  the 
name  of  Gastornis  Parisiensis  has  been  assigned,  appears,  from  the 
Memoirs  of  MM.  Hebert,  Lartet,  and  Owen,  to  belong  to  an  extinct 
genus.  Professor  Owen  refers  it  to  the  class  of  wading  land  birds 
rather  than  to  an  aquatic  species.* 

That  a  formation  so  much  explored  for  economical  purposes  as  the 
Argile  Plastique  around  Paris,  and  the  clays  and  sands  of  correspond- 
ing age  near  London,  should  never  have  afforded  any  vestige  of  a 
feathered  biped  previously  to  the  year  1855,  shows  what  diligent 
search  and  what  skill  in  osteological  interpretation  are  acquired  before 
the  existence  of  birds  of  remote  ages  can  be  proved  by  more  decisive 
evidence  than  their  footprints. 

Sables  de  Bracheux  (C.  3,  p.  298). — The  marine  sands  called  the 
Sables  de  Bracheux  (a  place  near  Beauvais),  are  considered  by  M. 
Hebert  to  be  older  than  the  Lignites  and  Plastic  clay,  and  to  concide 
in  age  with  the  Thanet  Sands  of  England.  At  La  Fere,  in  the  De- 
partment of  the  Aisne,  in  a  deposit  of  this  age,  a  fossil  skull  has  been 
found  of  a  quadruped  called  by  Blainville  Arctocyon  primcevus,  and 
supposed  by  him  to  be  related  both  to  the  bear  and  to  the  Kinkajou 
(Cercoleptes).  This  creature  appears  to  be  the  oldest  known  tertiary 
mammifer. 

Nummulitic  formation  of  Europe,  Asia,  <&c. — When  I  visited  Bel- 
gium and  French  Flanders  in  1851,  with  a  view  of  comparing  the  ter- 
tiary strata  of  those  countries  with  the  English  series,  I  found  that 
all  the  beds  between  the  Lower  Miocene  or  Limburg  formations  and 
the  Lower  Eocene  or  London  clay  proper,  might  be  conveniently  divided 
into  three  sections,  distinguished,  among  other  palseontological  char- 
acters, by  three  different  species  of  nummulities,  N.  variolaria  in  upper 
beds,  N.  Icevigata  in  the  middle,  and  N.  planulata  in  the  lower.  Af- 
ter I  had  adopted  this  classification,  I  found,  what  I  had  overlooked  or 
forgotten,  that  the  superposition  of  these  three  species  in  the  order 
here  assigned  to  them  had  been  previously  recognized  in  the  North 
of  France,  in  1842,  by  Viscount  d'Archiac.  The  same  author,  in 

*  Quart.  Geol.  Journ.,  vol.  xii.  p.  204,  1856. 


CH.  XVI.]  NUMMULITIC  EOCENE  STRATA.  307 

the  valuable  monograph  published  by  him  in  1853,*  has  observed 
that  a  somewhat  similar  distribution  of  these  and  other  species  in 
time,  prevails  very  widely  in  the  South  of  France  and  in  the 
Pyrenees,  as  well  as  in  the  Alps  and  Apennines,  and  in  Istria — the 
lowest  nummulitic  beds  being  characterized  by  fewer  and  smaller 
species,  the  middle  by  a  greater  number  and  by  those  which  individ- 
ually attain  the  largest  dimensions,  and  the  uppermost  beds  again  by 
small  species. 

In  the  treatise  alluded  to,  M.  d'Archiac  describes  no  less  than  fifty- 
two  species  of  this  genus,  and  considers  that  they  are  all  of  them  char- 
acteristic of  those  tertiary  strata  which  I  have  called  Middle  Eocene. 
In  very  few  instances  at  least  do  certain  species  diverge  from  this 
narrow  limit,  whether  into  incumbent  or  subjacent  tertiary  formations, 
one  or  two  species  only,  of  which  Numnmulites  intermedia,  also  a 
Middle  Eocene  form,  is  an  example,  ascend  into  the  Lower  Miocene, 
but  it  seems  doubtful  whether  any  of  them  descend  to  the  level  of 
the  London  clay.  Certainly  they  have  never  been  traced  so  low 
down  as  the  marine  beds,  coeval  with  the  Plastic  clay  or  Lignite,  in 
any  country  of  which  the  geology  has  been  well  worked  out.  This 
conclusion  is  a  very  unexpected  result  of  recent  inquiry,  since  for 
many  years  it  was  a  matter  of  controversy  whether  the  nummulitic 
rocks  of  the  Alps  and  Pyrenees  ought  not  to  be  regarded  as  cretace- 
ous rather  than  Eocene.  The  late  M.  Alex.  Brongniart  first  declared 
the  specific  identity  of  many  shells  of  the  marine  Eocene  strata  near 
Paris,  and  those  of  the  nummulitic  formation  of  Switzerland,  although 
he  obtained  these  last  from  the  summit  of  the  Diablerets,  one  of  the 
loftiest  of  the  Swiss  Alps,  which  rises  more  than  10,000  feet  above 
the  level  of  the  sea. 

The  nummulitic  limestone  of  the  Alps  is  often  of  great  thickness, 
and  is  immediately  covered  by  another  series  of  strata  of  dark-col- 
ored slates,  marls,  and  fucoidal  sandstones,  to  the  whole  of  which  the 
provincial  name  of  "  flysch"  has  been  given  in  parts  of  Switzerland. 
The  researches  of  Sir  Roderick  Murchison  in  the  Alps  in  1847  have 
shown  that  all  these  tertiary  strata  enter  into  the  disturbed  and  lof- 
tiest portion  of  the  Alpine  chain,  to  the  upheaval  of  which  they  enable 
us  therefore  to  assign  a  comparatively  modern  date. 

The  nummulitic  formation,  with  its  characteristic  fossils,  plays  a  far 
more  conspicuous  part  than  any  other  tertiary  group  in  the  solid 
framework  of  the  earth's  crust,  whether  in  Europe,  Asia,  or  Africa. 
It  often  attains  a  thickness  of  many  thousand  feet,  and  extends  from 
the  Alps  to  the  Carpathians,  and  is  in  full  force  in  the  north  of 
Africa,  as,  for  example,  in  Algeria  and  Morocco.  It  has  also  been 
traced  from  Egypt,  where  it  was  largely  quarried  of  old  for  the  build- 
ing of  the  Pyramids,  into  Asia  Minor,  and  across  Persia  by  Bagdad 
to  the  mouths  of  the  Indus.  It  occurs  not  only  in  Cutch,  but  in  the 

*  Animaux  Foss.  du  Groupe  nummul.  de  1'Inde.     Paris,  1853. 


308 


NUMMULITIC  FORMATIONS. 


[On.  XVI. 


mountain  ranges  which  separate  Scinde  from  Persia,  and  which  form 
the  passes  leading  to  Caboul ;  and  it  has  been  followed  still  farther 
eastward  into  India,  as  far  as  eastern  Bengal  and  the  frontiers  of 
China. 

Fig.  271. 


Fig.  272. 


Nummulites  PuscM,  D'Archiac.    Peyrehorade,  Pyrenees. 
a.  External  surface  cf  one  of  the  nummulites,  of  which  longitudinal  sections  are  seen  in  the 

limestone. 
5.  Transverse  section  of  same. 

Dr.  T.  Thompson  found  nummulites  at  an  elevation  of  no  less  than 
16,500  feet  above  the  level  of  the  sea,  in  Western  Thibet. 

One  of  the  species,  which  I  myself  found  very  abundant  on  the 
flanks  of  the  Pyrenees,  in  a  compact  crystalline 
marble  (fig.  271),  is  called  by  M.  d'Archiac 
Nummulites  Puschi.  The  same  is  also  very 
common  in  rocks  of  the  same  age  in  the  Car- 
pathians. 

Another  large  species  (see  fig.  272),  Num- 
mulites exponens,  J.  Sow.,  occurs  not  only  in 
the  South  of  France,  near  Dax,  but  in  Ger- 
many, Italy,  Asia  Minor,  and  in  Cutch  ;  also  in 
the  mountains  of  Sylhet,  on  the  frontiers  of 
China. 

In  many  of  the  distant  countries  above  alluded  to,  in  Cutch,  for 
example,  some  of  the  same  shells,  such  as  Nerita  conoidea  (fig.  269), 
accompany  the  nummulites,  as  in  France. 

The  opinion  of  many  observers,  that  the  Nummulitic  formation 
belongs  partly  to  the  cretaceous  era,  seems  chiefly  to  have  arisen 
from  confounding  an  allied  genus,  Orbitoides,  with  the  true  Num- 
mulite. 

When  we  have  once  arrived  at  the  conviction  that  the  nummulitic 
formation  occupies  a  middle  place  in  the  Eocene  series,  we  are  struck 
with  the  comparatively  modern  date  to  which  some  of  the  greatest 
revolutions  in  the  physical  geography  of  Europe,  Asia,  and  Northern 
Africa  must  be  referred.  All  the  mountain  chains,  such  as  the  Alps, 
Pyrenees,  Carpathians,  and  Himalayas,  into  the  composition  of  whose 
central  and  loftiest  parts  the  nummulitic  strata  enter  bodily,  could 
have  had  no  existence  till  after  the  Middle  Eocene  period.  During 
that  period  the  sea  prevailed  where  these  chains  now  rise,  for  num- 


Nummulites  ewponens. 
Sow.    Europe  and  Asia. 


CH.  XVI.]          EOCENE  STRATA  IN  THE  UNITED  STATES.  399 

mulites  and  their  accompanying  testacea  were  unquestionably  inhabit- 
ants of  salt  water.  Before  these  events,  comprising  the  conversion 
of  a  wide  area  from  a  sea  to  a  continent,  England  had  been  peopled, 
as  I  before  pointed  out  (p.  294),  by  various  quadrupeds,  by  herbiv- 
orous pachyderms,  by  insectivorous  bats,  and  by  opossums. 

Almost  all  the  extinct  volcanoes  which  preserve  any  remains  of 
their  original  form,  or  from  the  craters  of  which  lava  streams  can  be 
traced,  are  more  modern  than  the  Eocene  fauna  now  under  consider- 
ation ;  and  besides  these  superficial  monuments  of  the  action  of  heat, 
Plutonic  influences  have  worked  vast  changes  in  the  texture  of  rocks 
within  the  same  period.  Some  members  of  the  nummulitic  and 
overlying  tertiary  strata  called  flysch  have  actually  been  converted  in 
the  central  Alps  into  crystalline  rocks,  and  transformed  into  marble, 
quartz-rock,  mica-schist,  and  gneiss.* 


EOCENE    STRATA   IN   THE    UNITED    STATES. 

In  North  America  the  Eocene  formations  occupy  a  large  area  bor- 
dering the  Atlantic,  which  increases  in  breadth  and  importance  as  it 
is  traced  southward  from  Delaware  and  Maryland  to  Georgia  and 
Alabama.  They  also  occur  in  Louisiana  and  other  States  both  east 
and  west  of  the  valley  of  the  Mississippi.  At  Claiborne  in  Alabama, 
no  less  than  four  hundred  species  of  marine  shells,  with  many  echino- 
derms  and  teeth  of  fish,  characterize  one  member  of  this  system. 
Among  the  shells,  the  Cardita  planicosta,  before  mentioned  (fig.  235, 
p.  288),  is  in  abundance ;  and  this  fossil  and  some  others  identical 
with  European  species,  or  very  nearly  allied  to  them,  make  it  highly 
probable  that  the  Claiborne  beds  agree  in  age  with  the  central  or 
Bracklesham  group  of  England,  and  with  the  calcaire  grossier  of 
Paris.f 

Higher  in  the  series  is  a  remarkable  calcareous  rock,  formerly 
called  "  the  nummulite  limestone,"  from  the  great  number  of  discoid 
bodies  resembling  nummulites  which  it  contains,  fossils  now  referred 
by  A.  d'Orbigny  to  the  genus  Orbitoides,  which  has  been  demon- 
strated by  Dr.  Carpenter  to  belong  to  the  foraminifera.f  That  natu- 
ralist, moreover,  is  of  opinion  that  the  Orbitoides  alluded  to  (0. 
Mantelli)  is  of  the  same  species  as  one  found  in  Cutch  in  the  Middle 
Eocene  or  nummulitic  formation  of  India.  The  following  section 
will  enable  the  reader  to  understand  the  position  of  three  subdivis- 
ions of  the  Eocene  series,  Nos.  1,  2,  and  3,  the  relations  of  which  I 


*  Murchison,  Quart.  Journ.  of  Geol.  Soc.,  vol.  v.,  and  Lyell,  vol.  vi.,  1850.  An- 
niversary Address. 

t  See  paper  by  the  Author,  Quart.  Journ.  Geol.  Soc.,  vol.  iv.  p.  12 ;  and  Second 
Visit  to  the  U.  S.,  vol.  ii.  p.  59. 

$  Quart.  Journ.  Geol.  Soc.,  vol.  vi.  p.  32. 


310  EOCENE  STRATA  IN  THE  UNITED  STATES.          [Cn.  XVI. 

ascertained  in  Clarke  County,  between  the  rivers  Alabama  and  Tom- 
beckbee. 

The  lowest  set  of  strata,  No.  1,  having  a  thickness  of  more  than 
100  feet,  comprise  marly  beds,  in  which  the  Ostrea  sellceformis  occurs, 
a  shell  ranging  from  Alabama  to  Virginia,  and  being  a  representative 
form  of  the  Ostrea  flabellula  of  the  Eocene  group  of  Europe.  In 
other  beds  of  No.  1,  two  European  shells,  Oardita  planicosta,  before 
mentioned,  and  Solarium  canaliculatum,  are  found  with  a  great  many 
other  species  peculiar  to  America.  Numerous  corals  also,  and  the 
remains  of  placoid  fish  and  of  rays,  occur,  and  the  "  swords "  (fig. 
237,  p.  289),  as  they  are  called,  of  sword-fishes,  all  bearing  a  great 
generic  likeness  to  those  of  the  Eocene  strata  of  England  and  France. 

No.  2  (fig.  273)  is  a  white  limestone,  sometimes  soft  and  argilla 


Fig.  273. 


1.  Sand,  marl,  &c.,  with  numerous  fossils.  \ 

2.  White  or  rotten  limestone,  with  Zeuglodon.       I  Eocene. 
8.  Orbitoidal,  or  so-called  nummulitic  limestone.    > 

4.  Overlying  formation  of  sand  and  clay  without  fossils.    Age  unknown. 

ceous,  but  in  parts  very  compact  and  calcareous.  It  contains  several 
peculiar  corals,  and  a  large  nautilus  allied  to  N.  ziczac ;  also  in  its 
upper  bed  a  gigantic  cetacean,  called  Zeuglodon  by  Owen.* 

The  colossal  bones  of  this  cetacean  are  so  plentiful  in  the  interior 
of  Clarke  County  as  to  be  characteristic  of  the  formation.  The  ver- 
tebral column  of  one  skeleton  found  by  Dr.  Buckley  at  a  spot  visited 
by  me,  extended  to  the  length  of  nearly  70  feet,  and  not  far  off"  part 
of  another  backbone  nearly  50  feet  long  was  dug  up.  I  obtained 
evidence,  during  a  short  excursion,  of  so  many  localities  of  this  fossil 
animal  within  a  distance  of  10  miles,  as  to  lead  me  to  conclude  that 
they  must  have  belonged  to  at  least  forty  distinct  individuals. 

Professor  Owen  first  pointed  out  that  this  huge  animal  was  not  rep- 
tilian, since  each  tooth  was  furnished  with  double  roots  (see  fig.  274), 
implanted  in  corresponding  double  sockets ;  and  his  opinion  of  the 
cetacean  nature  of  the  fossil  was  afterwards  confirmed  by  Dr.  "Wyman 
and  Dr.  R.  W.  Gibbes.  That  it  was  an  extinct  mammal  of  the  whale 
tribe  has  since  been  placed  beyond  all  doubt  by  the  discovery  of  the 
entire  skull  of  another  fossil  species  of  the  same  family,  having  the 

*  See  paper  by  R.  W.  Gibbes,  Journ.  of  Acad.  Nat.  Sci.  Philad.,  vol.  i.,  1847. 


CH.  XVI.]          EOCENE  STRATA  IN  THE  UNITED  STATES. 
Fig.  274.  Fig.  275. 


Zeuglodon  cetoides,  Owen. 
JBasilosaurus,  Harlan. 
Fig.  274.  Molar  tooth,  natural  size.  Fig.  275.  Vertebra,  reduced. 

double  occipital  condyles  only  met  with  in  mammals,  and  the  convo- 
luted tympanic  bones  which  are  characteristic  of  cetaceans. 

Near  the  junction  of  No.  2  and  the  incumbent  limestone,  No.  3, 
next  to  be  mentioned,  are  strata  characterized  by  the  following  shells : 
Spondylus  dumosus  (Plagiostoma  dumosum,  Morton),  Pecten  Poul- 
soni,  Pecten  perplanus,  and  Ostrea  cretacea. 

No.  3  (fig.  273)  is  a  white  limestone,  for  the  most  part  made  up  of 
the  Orbitoides  of  D'Orbigny  before  mentioned  (p.  309),  formerly  sup- 
posed to  be  a  nummulite,  and  called  JV.  Mantelli,  mixed  with  a  few 
lunulites,  some  small  corals,  and  shells.*  The  origin,  therefore,  of 
this  cream-colored  soft  stone,  like  that  of  our  white  chalk,  which  it 
much  resembles,  is,  I  believe,  due  to  the  decomposition  of  these 
foraminifera.  The  surface  of  the  country  where  it  prevails  is  some- 
times .  marked  by  the  absence  of  wood,  like  our  chalk  downs,  or  is 
covered  exclusively  by  the  Juniperus  Virginiana,  as  certain  chalk  dis- 
tricts in  England  by  the  yew  tree  and  juniper. 

Some  of  the  shells  of  this  limestone  are  common  to  the  Claiborne 
beds,  but  many  of  them  are  peculiar. 

It  will  be  seen  in  the  section  (fig.  273,  p.  310)  that  the  strata  Nos. 
1,  2,  3  are,  for  the  most  part,  overlaid  by  a  dense  formation  of  sand 
or  clay  without  fossils.  In  some  points  of  the  bluff  or  cliff  of  the 
Alabama  River,  at  Claiborne,  the  beds  Nos.  1,  2  are  exposed  nearly 
from  top  to  bottom,  whereas  at  other  points  the  newer  formation,  No. 
4,  occupies  the  face  of  nearly  the  whole  cliff.  The  age  of  this  over- 
lying mass  has  not  yet  been  determined,  as  it  has  hitherto  proved 
destitute  of  organic  remains. 

The  burr-stone  strata  of  the  Southern  States  contain  so  many 
fossils  agreeing  with  those  of  Claiborne,  that  it  doubtless  belongs  to 
the  same  part  of  the  Eocene  group,  though  I  was  not  fortunate 
enough  to  see  the  relations  of  the  two  deposits  in  a  continuous  sec- 

*  Lyell,  Quart.  Journ.  Geol.  Soc.,  1847,  vol.  iv.  p.  15. 


312  CRETACEOUS  GROUP.  [Cn.  XVII. 

tion.  Mr.  Tuomey  considers  it  as  the  lower  portion  of  the  series. 
It  may,  perhaps,  be  a  form  of  the  Claiborne  beds  in  places  where 
lime  was  wanting,  and  where  silex,  derived  from  the  decomposition 
of  felspar,  predominated.  It  consists  chiefly  of  slaty  clays,  quartzose 
sands,  and  loam,  of  a  brick-red  color,  with  layers  of  cellular  chert  or 
burr-stone,  used  in  some  places  for  mill-stones. 


CHAPTER   XVII. 

CRETACEOUS      GROUP. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods — Whether  certain  forma- 
tions in  Belgium  and  France  are  of  intermediate  age — Pisolitic  limestone — Divis- 
ions of  the  Cretaceous  series  in  North- Western  Europe — Maestricht  beds — Chalk 
of  Faxoe — White  chalk — Its  geographical  extent  and  origin — Formed  in  an  open 
and  deep  sea — How  far  derived  from  shells  and  corals — A  similar  rock  now  in 
progress  in  the  depths  of  the  Atlantic  made  up  of  Globigerinae — Origin  of  Flint 
hi  Chalk — Siliceous  Diatomaceae  of  the  Atlantic — By  what  intermittent  action 
the  alternate  layers  of  white  chalk  and  flint  may  have  been  caused — Pot- 
stones  of  Horstead — Isolated  pebbles  of  quartz  and  foreign  rocks  in  chalk — 
Fossils  of  the  Upper  Cretaceous  rocks  —  Echinoderms,  Mollusca,  Bryozoa, 
Sponges— Upper  Greensand  and  Gault — Blackdown  beds — Flora  of  the  Upper 
Cretaceous  period — Fossil  plants  of  Aix-la-Chapelle — Large  proportion  of  Dico- 
tyledonous Angiosperms — Their  coexistence  with  large  extinct  genera  of  reptiles 
— Chalk  of  South  of  Europe — Hippurite  limestone — Cretaceous  rocks  of  the 
United  States. 

HAVING  treated  in  the  preceding  chapters  of  the  tertiary  strata,  we 
have  next  to  speak  of  the  uppermost  of  the  secondary  groups,  com- 
monly called  the  chalk  or  the  cretaceous  strata,  from  ere ta,  the  Latin 
name  for  that  remarkable  white  earthy  limestone,  which  constitutes 
an  upper  member  of  the  group  in  those  parts  of  Europe  where  it  was 
first  studied.  The  marked  discordance  in  the  fossils  of  the  tertiary, 
as  compared  with  the  cretaceous  formations,  has  long  induced  many 
geologists  to  suspect  that  an  indefinite  series  of  ages  elapsed  between 
the  respective  periods  of  their  origin.  Measured,  indeed,  by  such  a 
standard,  that  is  to  say,  by  the  amount  of  change  in  the  Fauna  and 
Flora  of  the  earth  effected  in  the  interval,  the  time  between  the 
Cretaceous  and  Eocene  may  have  been  as  great  as  that  between  the 
Eocene  and  Recent  periods,  to  the  history  of  which  the  last  seven 
chapters  have  been  devoted.  Several  fragmentary  deposits  have  been 
met  with  here  and  there,  in  the  course  of  the  last  half  century,  of  an 
age  intermediate  between  the  white  chalk  and  the  plastic  clays  and 
sands  of  the  Paris  and  London  districts,  monuments  which  have  the 
same  kind  of  interest  to  a  geologist  which  certain  mediaeval  records 
excite  when  we  study  the  history  of  nations.  For  both  of  them 


CH.  XVII.]  PISOLITIC  LIMESTONE  OF  FRANCE.  3^3 

throw  light  on  ages  of  darkness,  preceded  and  followed  by  others  of 
which  the  annals  are  comparatively  well  known  to  us.  But  these 
newly-discovered  records  do  not  fill  up  the  wide  gap,  some  of  them 
being  closely  allied  to  the  Eocene,  and  others  to  the  Cretaceous  type, 
while  none  appear  as  yet  to  possess  so  distinct  and  characteristic  a 
fauna  as  may  entitle  them  to  hold  an  independent  place  in  the  great 
chronological  series. 

Among  the  formations  alluded  to,  the  Thanet  Sands  of  Prestwich 
have  been  sufficiently  described  in  the  last  chapter,  and  classed  as 
Lower  Eocene.  To  the  same  tertiary  series  belong  the  Belgian  for- 
mations, called  by  Professor  Dumont,  Landenian  and  Heersian, 
although  the  latter  may  be  of  higher  antiquity  than  the  Thanet 
Sands.  On  the  other  hand,  the  Maestricht  and  Faxoe  limestones 
are  very  closely  connected  with  the  chalk,  to  which  also  the  Pisolitic 
limestone  of  France  has  been  referred  by  high  authorities. 

The  Lower  Landenian  beds  of  Belgium  consist  of  marls  and  sands, 
often  containing  much  green  earth,  called  glauconite.  They  may  be 
seen  at  Tournay,  and  at  Angres,  near  Mons,  and  at  Orp-le-Grand, 
Lincent,  and  Landen  in  the  ancient  province  of  Hesbaye,  in  Belgium, 
where  they  supply  a  durable  building-stone,  yet  one  so  light  as  to  be 
easily  transported.  Some  few  shells  of  the  genus  Pholadomya,  Sca- 
laria,  and  others,  agree  specifically  with  fossils  of  the  Thanet  Sands ; 
but  most  of  them,  such  as  Astarte  incequilatera,  Nyst,  are  peculiar. 
In  the  building-stone  of  Orp-le-Grand,  I  found  a  Cardiaster,  a  genus 
which,  according  to  Professor  E.  Forbes,  was  previously  unknown  in 
rocks  newer  than  the  cretaceous. 

Still  older  than  the  Lower  Landenian  is  the  marl,  or  calcareous 
glauconite,  of  the  village  of  Heers,  near  Waremme,  in  Belgium ;  also 
seen  at  Marlinne  in  the  same  district,  where  I  have  examined  it.  It 
has  been  sometimes  classed  with  the  cretaceous  series,  although  as 
yet  it  has  yielded  no  forms  of  a  decidedly  cretaceous  aspect,  such  as 
Ammonite,  Baculite,  Belemnite,  Hippurite,  &c.  The  species  of 
shells  are  for  the  most  part  new ;  but  it  contains,  according  to  M. 
Hebert,  Pholadomya  cuneata,  an  Eocene  fossil,  and  he  assigns  it  with 
confidence  to  the  tertiary  series. 

Pisolitic  limestone  of  France. — Geologists  have  been  still  more  at 
variance  respecting  the  chronological  relations  of  this  rock,  which  is 
met  with  in  the  neighborhood  of  Paris,  and  at  places  north,  south, 
east,  and  west  of  that  metropolis,  as  between  Vertus  and  Laversines, 
Meudon,  and  Montereau.  It  is  usually  in  the  form  of  a  coarse  yel- 
lowish or  whitish  limestone,  and  the  total  thickness  of  the  series  of 
beds  already  known  is  about  100  feet.  Its  geographical  range,  ac- 
cording to  M.  Hebert,  is  not  less  than  45  leagues  from  east  to  west, 
and  35  from  north  to  south.  Within  these  limits  it  occurs  in  small 
patches  only,  resting  unconformably  on  the  white  chalk.  It  was 
originally  regarded  as  cretaceous  by  M.  E.  de  Beaumont,  on  the 
ground  of  its  having  undergone,  like  the  white  chalk,  extensive  denu- 


314  CLASSIFICATION  OF  CRETACEOUS  ROCKS.         [Cn.  XVII. 

dation  previous  to  the  Eocene  period ;  but  many  able  palaeontologists, 
and  among  others  MM.  C.  d'Orbigny,  Deshayes,  and  d'Archiac,  dis- 
puted this  conclusion,  and,  after  enumerating  54  species  of  fossils, 
declared  that  their  appearance  was  more  tertiary  than  cretaceous. 
More  recently,  M.  Hebert,  having  found  the  Pecten  quadricostatus,  a 
cretaceous  species,  in  this  same  pisolitic  rock,  at  Montereau  near 
Paris,  and  some  few  other  fossils  common  to  the  Maestricht  chalk, 
and  to  the  Baculite  limestone  of  the  Cotentin,  in  Normandy,  classed 
it  as  an  upper  member  of  the  cretaceous  group,  an  opinion  since 
adopted  by  M.  Alcide  d'Orbigny,  who  has  carefully  examined  the 
fossils.  The  Nautilus  Danicus,  fig.  278,  and  two  or  three  other  spe- 
cies found  in  this  rock,  are  frequent  in  that  of  Faxoe  in  Denmark,  but 
as  yet  no  Ammonites,  Hamites,  Scaphites,  Turrulites,  Baculites,  or 
Hippurites  have  been  met  with.  The  proportion  of  peculiar  species, 
many  of  them  of  tertiary  aspect,  is  confessedly  large ;  and  great 
aqueous  erosion  suffered  by  the  white  chalk,  before  the  pisolitic  lime- 
stone was  formed,  affords  an  additional  indication  of  the  two  deposits 
being  widely  separated  in  time.  The  pisolitic  formation,  therefore, 
may  eventually  prove  to  be  somewhat  more  intermediate  in  date  be- 
tween the  secondary  and  tertiary  epochs  than  the  Maestricht  rock. 

It  should,  however,  be  observed,  that  all  the  above-mentioned 
strata,  from  the  Thanet  Sands  to  the  Pisolitic  limestone  inclusive, 
and  even  the  Maestricht  rock,  next  to  be  described,  exhibit  marks 
of  denudation  experienced  at  various  dates,  subsequently  to  the  con- 
solidation of  the  white  chalk.  This  fact  helps  us  in  some  degree  to 
explain  the  remarkable  break  in  the  sequence  of  European  rocks, 
between  the  secondary  and  tertiary  eras,  for  many  strata  which  once 
existed  have  doubtless  been  swept  away. 


CLASSIFICATION    OF   THE    CRETACEOUS    ROCKS. 

The  cretaceous  group  has  generally  been  divided  into  an  Upper 
and  a  Lower  series,  each  of  them  comprising  several  subdivisions, 
distinguished  by  peculiar  fossils,  and  sometimes  retaining  a  uniform 
mineral  character  throughout  wide  areas.  The  Upper  series  is  often 
called  familiarly  the  chalk,  and  the  Lower  the  greensand,  the  last- 
mentioned  name  being  derived  from  the  green  color  imparted  to  cer- 
tain strata  by  grains  of  chloritic  matter.  The  following  table  com- 
prises the  names  of  the  subdivisions  most  commonly  adopted  : — - 

UPPER  CRETACEOUS. 

A.  1.  Maestricht  beds  and  Faxoe  limestones. 

2.  White  chalk  with  flints. 

3.  Chalk  marl,  or  gray  chalk  slightly  argillaceous. 

4.  Upper  Greensand,  occasionally  with  beds  of  chert,  and  with  chloritic  marl 

(craie  chloritee  of  French  authors)  in  the  upper  portion. 

5.  Gault,  including  the  Blackdown  beds. 


CH.  XVII.]  MAESTRICHT  BEDS. 

LOWER  CRETACEOUS  (or  Neocomiari). 

B.  1.   Lower  Greensand — green  sand,  iron  sand,  clay,  and  occasional  beds  of  lime- 
stone (Kentish  Rag). 
2.   Wealden  beds  or  Weald  clay  and  Hastings  sands.* 

Maestricht  Beds. — On  the  banks  of  the  Meuse,  at  Maestricht,  re- 
posing on  ordinary  white  chalk  with  flints,  we  find  an  upper  calca- 
.reous  formation  about  100  feet  thick,  the  fossils  of  which  are,  on  the 
whole,  very  peculiar,  and  all  distinct  from  tertiary  species.  Some  few 
are  of  species  common  to  the  inferior  white  chalk,  among  which  may 
be  mentioned  Belemnites  mucronatus  (fig.  290,  p.  325)  and  Pecten 
quadricostatus,  a  shell  regarded  by  many  as  a  mere  variety  of  P. 
quinquecostatus  (see  fig.  305,  p.  327).  Besides  the  Belemnite  there 
are  other  genera,  such  as  Baculite  and  Hamite,  never  found  in  strata 
newer  than  the  cretaceous,  but  frequently  met  with  in  these  Maestricht 
beds.  On  the  other  hand,  Valuta,  Fasciolaria,  and  other  genera  of 
univalve  shells,  usually  met  with  only  in  tertiary  strata,  occur. 

The  upper  part  of  the  rock,  about  20  feet  thick,  as  seen  in  St. 
Peter's  Mount,  in  the  suburbs  of  Maestricht,  abounds  in  corals  and 
Bryozoa,  often  detachable  from  the  matrix ;  and  these  beds  are  suc- 
ceeded by  a  soft  yellowish  limestone  50  feet  thick,  extensively  quar- 
ried from  time  immemorial  for  building.  The  stone  below  is  whiter, 
and  contains  occasional  nodules  of  gray  chert  or  chalcedony. 

M.  Bosquet,  with  whom  I  examined  this  formation  (August,  1850), 
pointed  out  to  me  a  layer  of  chalk  from  two  to  four  inches  thick, 
containing  green  earth  and  numerous  encrinital  stems,  which  forms 
the  line  of  demarcation  between  the  strata  containing  the  fossils 
peculiar  to  Maestricht  and  the  white  chalk  below.  The  latter  is  dis- 
tinguished by  regular  layers  of  black  flint  in  nodules,  and  by  several 
shells,  such  as  Terebratula  carnea  (see  fig.  301),  wholly  wanting  in 
beds  higher  than  the  green  band.  Some  of  the  organic  remains,  how- 
ever, for  which  St.  Peter's  Mount  is  celebrated,  occur  both  above  and 
below  that  parting  layer,  and,  among  others,  the  great  marine  reptile 
called  Mosasaurus  (see  fig.  276),  a  saurian  supposed  to  have  been  24 
feet  in  length,  of  which  the  entire  skull  and  a  great  part  of  the  skele- 
ton have  been  found.  Such  remains  are  chiefly  met  with  in  the  soft 

*  M.  Alcide  d'Orbigny,  in  his  valuable  work  entitled  Paleontologie  Frangaise,  has 
adopted  new  terms  for  the  French  subdivisions  of  the  Cretaceous  Series,  which,  so 
far  as  they  can  be  made  to  tally  with  English  equivalents,  seem  explicable  thus  : — 

Etage  Danien.  Maestricht  beds. 

"  Senonien.  White  chalk,  and  chalk  marl. 

"  Turonien.  Part  of  the  chalk  marl. 

"  Cenomanien.  Upper  Greensand. 

"  Albien.  Gault. 

"  Aptien.  Upper  part  of  Lower  Greensand. 

"  Neocomien.  Lower  part  of  same. 

"  Neocomien  inferieur.     Wealden  beds  and  contemporaneous  marine  strata. 


316 


CHALK  OF  FAXOE. 
Fig.  276. 


[On.  XVII. 


Fig.  277. 


Mosasaurus  Cam/peri.    Original  more  than  three  feet  long. 

freestone,  the  principal  member  of  the  Maestricht  beds.  Among  the 
fossils  common  to  the  Maestricht  and  white  chalk  may  be  instanced 
the  echinoderm,  fig.  277. 

I  saw  proofs  of  the  previous  denudation  of  the  white  chalk  ex- 
hibited in  the  lower  bed  of  the  Maestricht 
formation  in  Belgium,  about  30  miles  S.W. 
of  Maestricht,  at  the  village  of  Jendrain, 
where  the  base  of  the  newer  deposit  con- 
sisted chiefly  of  a  layer  of  well-rolled, 
black,  chalk-flint  pebbles,  in  the  midst  of 
which  perfect  specimens  of  Thecidea  ra- 
dians and  Belemnites  mucronatus  are  im- 
bedded. 

Chalk  of  Faxoe. — In  the  island  of  See- 
land,  in  Denmark,  the  newest  member  of 
the  chalk  series,  seen  in  the  sea-cliffs  at 

Stevensklint  resting  on  white  chalk  with  flints,  is  a  yellow  lime- 
stone, a  portion  of  which,  at  Faxoe,  where  it  is  used  as  a  building- 
stone,  is  composed  of  corals,  even  more  conspicuously  than  is  usually 

Fig.  278. 


Hemipneustes  radiatus,  Ag. 

Spatangus  radiatus,  Lam. 

Chalk  of  Maestricht  and  white 

chalk. 


Nautilus  fianicutt,  Schl.    Faxoe,  Denmark. 


CH.  XVII.] 


WHITE  CHALK. 


317 


§ 


observed  in  recent  coral  reefs.  It  has  been  quarried  to  the  depth  of 
more  than  40  feet,  but  its  thickness  is  unknown.  The  imbedded 
shells  are  chiefly  casts,  many  of  them  of  univalve  mollusca,  which  are 
usually  very  rare  in  the  white  chalk  of  Europe.  Thus,  there  are  two 
species  of  Cyprcea,  one  of  Oliva,  two  of  Mitra,  four  of  the  genus 
Cerithium,  six  of  Fusus,  two  of  Trochus,  one  Patella,  one  Emargi- 
nula,  &c. ;  on  the  whole,  more  than  thirty  univalves,  spiral  or  patelli- 
form.  At  the  same  time,  some  of  the  accompany- 
ing bivalve  shells,  echinoderms,  and  zoophytes  are 
specifically  identical  with  fossils  of  the  true  Creta- 
ceous series.  Among  the  cephalopoda  of  Faxoe 
may  be  mentioned  Baculites  Faujasii  and  Belem- 
nites  mucronatus,  shells  of  the  white  chalk.  The 
Nautilus  Danicus  (see  fig.  278)  is  characteristic 
of  this  formation ;  and  it  also  occurs  in  France  in 
the  calcaire  pisolitique  of  Laversin  (Department 
of  Oise). 

The  claws  and  entire  skull  of  a  small  crab, 
Brachyurus  rugosus  (Schlottheim),  are  scattered  | 
through  the  Faxoe  stone,  reminding  us  of  similar  | 
crustaceans  enclosed  in  the  rocks  of  modern  coral  § 
reefs.  Some  small  portions  of  this  coralline  for- 
mation consist  of  white  earthy  chalk ;  it  is  there-  g» 
fore  clear  that  this  substance  must  have  been  pro-  § 
duced  simultaneously — a  fact  of  some  importance,  | 
as  bearing  on  the  theory  of  the  origin  of  white  * 
chalk ;  for  the  decomposition  of  such  corals  as  we  £ 
see  at  Faxoe  is  capable,  we  know,  of  forming  white  | 
mud,  undistinguishable  from  chalk,  and  which  we  § 
may  suppose  to  have  been  dispersed  far  and  wide  3 
through  the  ocean,  in  which  such  reefs  as  that  of  a 
Faxoe  grew.  g 

White  chalk  (see  Tab.,  p.  314  et  seq.).— The  § 
highest  beds  of  chalk  in  England  and  France  con-  p 
sist  of  a  pure,  white,  calcareous  mass,  usually  too 
soft  for  a  building-stone,  but  sometimes  passing 
into  a  more  solid  state.  It  consists,  almost  purely, 
of  carbonate  of  lime ;  the  stratification  is  often 
obscure,  except  where  rendered  distinct  by  inter- 
stratified  layers  of  flint,  a  few  inches  thick,  occa- 
sionally in  continuous  beds,  but  oftener  in  nodules, 
and  recurring  at  intervals  from  two  to  four  feet 
distant  from  each  other. 

This  upper  chalk  is  usually  succeeded,  in  the 
descending  order,  by  a  great  mass  of  white  chalk 
without  flints,  below  which  comes  the  chalk  marl,  in  which  there  is  a 
slight  admixture  of  argillaceous  matter.     The  united  thickness  of  the 


g 
$ 

-   2, 


i 


318  ANIMAL  ORIGIN  OF  WHITE  CHALK.  [Cn.  XVII. 

three  divisions  in  the  south  of  England  equals,  in  some  places,  1000 
feet. 

The  foregoing  section  (fig.  279)  will  show  the  manner  in  which  the 
white  chalk  extends  from  England  into  France,  covered  by  the  ter- 
tiary strata  described  in  former  chapters,  and  reposing  on  lower  cre- 
taceous beds. 

Geographical  extent  and  origin  of  the  White  Chalk. — The  area  over 
which  the  white  chalk  preserves  a  nearly  homogeneous  aspect  is  so 
vast,  that  the  earlier  geologists  despaired  of  discovering  any  analogous 
deposits  of  recent  date.  Pure  chalk,  of  nearly  uniform  aspect  and 
composition,  is  met  with  in  a  northwest  and  southeast  direction,  from 
the  north  of  Ireland  to  the  Crimea,  a  distance  of  about  1140  geo- 
graphical miles,  and  in  an  opposite  direction  it  extends  from  the  south 
of  Sweden  to  the  south  of  Bordeaux,  a  distance  of  about  840  geo- 
graphical miles.  In  Southern  Russia,  according  to  Sir  R.  Murchison, 
it  is  sometimes  600  feet  thick,  and  retains  the  same  mineral  charac- 
ter as  in  France  and  England,  with  the  same  fossils,  including  Inoce- 
ramus  Cuvieri,  Belemnites  mucronatus,  and  Ostrea  vesicularis. 

But  it  would  be  an  error  to  imagine  that  the  chalk  was  ever  spread 
out  continuously  over  the  whole  of  the  space  comprised  within  these 
limits,  although  it  prevailed  in  greater  or  less  thickness  over  large 
portions  of  that  area.  On  turning  to  those  regions  of  the  Pacific 
where  coral  reefs  abound,  we  find  some  archipelagoes  of  lagoon 
islands,  such  as  that  of  the  Dangerous  Archipelago,  for  instance,  and 
that  of  Radack,  with  several  adjoining  groups,  which  are  from  1100 
to  1200  miles  in  length,  and  300  or  400  miles  broad ;  and  the  space 
to  which  Flinders  proposed  to  give  the  name  of  the  Coralline  Sea  is 
still  larger,  for  it  is  bounded  on  the  east  by  the  Australian  barrier — 
all  formed  of  coral  rock — on  the  west  by  New  Caledonia,  and  on  the 
north  by  the  reefs  of  Louisiade.  Although  the  islands  in  these  areas 
may  be  thinly  sown,,  the  mud  of  the  decomposing  zoophytes  and 
foraminifera  may  be  scattered  far  and  wide  by  oceanic  currents. 
That  this  mud  would  sometimes  resemble  chalk  I  have  already 
hinted,  when  speaking  of  the  Faxoe  limestone,  p.  316,  and  it  was 
also  remarked  in  an  early  part  of  this  volume,  that  even  some  of  that  chalk, 
which  appears  to  an  ordinary  observer  quite  destitute  of  organic  re- 
mains, is  nevertheless,  when  seen  under  the  microscope,  full  of  frag- 
ments of  corals,  bryozoa,  and  sponges ;  together  with  the  valves  of 
entomostraca,  the  shells  of  foraminifera,  and  still  more  minute  infu- 
soria. (See  p.  26). 

Now  it  had  been  often  suspected,  before  these  discoveries,  that  white 
chalk  might  be  of  animal  origin,  even  where  every  trace  of  organic 
structure  had  vanished.  This  bold  idea  was  partly  founded  on  the 
fact,  that  the  chalk  consisted  of  carbonate  of  lime,  such  as  would 
result  from  the  decomposition  of  testacea,  echini,  and  corals ;  and 
partly  on  the  passage  observable  between  these  fossils  when  half  de- 
composed and  chalk.  But  this  conjecture  seemed  to  many  naturalists 


CH.  XVII.]  ANIMAL  ORIGIN  OF  WHITE  CHALK.  319 

quite  vague  and  visionary,  until  its  probability  was  strengthened  by 
new  evidence  brought  to  light  by  modern  geologists. 

We  learn  from  Captain  Nelson  that  in  the  Bermuda  Islands,  and  in 
the  Bahamas,  there  are  many  basins  or  lagoons  almost  surrounded  and 
enclosed  by  reefs  of  coral.  At  the  bottom  of  these  lagoons  a  soft 
white  calcareous  mud  is  formed,  not  merely  from  the  comminution  of 
corallines  (or  calcareous  plants)  and  corals,  together  with  the  exuviae 
of  foraminifera,  mollusks,  echinoderms,  and  crustaceans,  but  also,  as 
Mr.  Darwin  observed  upon  studying  the  coral  islands  of  the  Pacific, 
from  the  faecal  matter  ejected  by  echinoderms,  conchs,  and  coral-eat- 
ing fish.  In  the  West  Indian  seas,  the  conch  (S  trombus  gigas)  adds 
largely  to  the  chalky  mud  by  means  of  its  faecal  pellets  composed  of 
minute  grains  of  soft  calcareous  matter,  exhibiting  some  organic  tissue. 
Mr.  Darwin  describes  gregarious  fishes  of  the  genus  Scarus,  seen 
through  the  clear  waters  of  the  coral  regions  of  the  Pacific  browsing 
quietly  in  great  numbers  on  living  corals,  like  grazing  herbs  of  gram- 
inivorous quadrupeds.  On  opening  their  bod- 
ies, their  intestines  were  found  to  be  filled  with  Fi£-  28°- 
impure  chalk.  This  circumstance  is  the  more  in 
point  when  we  recollect  how  the  fossilist  was 
formerly  puzzled  by  meeting,  in  chalk,  with  cer- 
tain bodies,  called  "  larchcones,"  which  were 
afterwards  recognized  by  Dr.  Buckland  to  be 
the  excrement  of  fish.  Such  spiral  coprolites 
(fig.  280),  like  the  scales  and  bones  of  fossil  fish 
in  the  chalk,  are  composed  chiefly  of  phosphate 
of  lime. 

In  the  Bahamas,  the  angel-fish,  and  the  unicorn  or  trumpet-fish,  and 
many  others,  feed  on  shellfish,  or  on  corals. 

The  mud  derived  from  the  sources  above  mentioned  may  be  actu- 
ally seen  in  the  Maldiva  Atolls  to  be  washed  out  of  the  lagoons 
through  narrow  openings  leading  from  the  lagoon  to  the  ocean,  and 
the  waters  of  the  sea  are  discolored  by  it  for  some  distance.  When 
dried,  this  mud  is  very  like  common  chalk,  and  might  probably  be 
made  by  a  modern  pressure  to  resemble  it  still  more  closely.* 

Mr.  Dana,  when  describing  the  elevated  coral  reef  of  Oahu,  in  the 
Sandwich  Islands,  says  that  some  varieties  of  the  rock  consist  of 
aggregated  shells,  imbedded  in  a  compact  calcareous  base  as  firm  in 
texture  as  any  secondary  limestone ;  while  others  are  like  chalk,  hav- 
ing its  color,  its  earthy  fracture,  its  soft  homogeneous  texture,  and  be- 
ing an  equally  good  writing  material.  The  same  author  describes,  in 
several  growing  coral  reefs,  a  similar  formation  of  modern  chalk,  un- 
distinguishable  from  the  ancient,  f  The  extension  over  a  wide  sub- 

*  See  Nelson,  Geol.  Trans.,  1837,  vol.  v.  p.  108  ;  and  Geol.  Quart.  Journ.,  1853, 
p.  200. 

f  Geol.  of  U.  S.  Exploring  Exped.,  p.  252.     1849. 


320 


ANIMAL  ORIGIN  OF  WHITE  CHALK. 


[Cn.  XVH. 


marine  area,  of  the  calcareous  matrix  of  the  chalk,  as  well  as  of  the 
imbedded  fossils,  would  take  place  more  readily  in  consequence  of 
the  low  specific  gravity  of  the  shells  of  mollusca  and  zoophytes,  when 
compared  with  ordinary  sand  and  mineral  matter.  The  mud  also  de- 
rived from  their  decomposition  would  be  much  lighter  than  argillace- 
ous and  inorganic  mud,  and  very  easily  transported  by  currents,  espe- 
cially in  salt  water. 

But  the  analogy  of  existing  coral  reefs  would  better  illustrate  such 
formations  as  the  Oolitic  limestones,  to  be  described  in  Chapters  XX. 
and  XXI.,  which  consists  in  great  part  of  compact  rock,  than  the  soft 
and  unconsolidated  white  chalk.  A  new  light  has  recently  been 
thrown  upon  the  origin  of  the  latter  deposit  by  the  deep  soundings 
made  in  the  North  Atlantic,  previous  to  laying  down,  in  1858,  the 
electric  telegraph  between  Ireland  and  Newfoundland.  At  depths 
sometimes  exceeding  two  miles,  the  mud  forming  the  floor  of  the 
ocean  was  found,  when  examined  by  Professor  Huxley,  to  be  almost 
entirely  composed  (more  than  nineteen-twentieths  of  the  whole)  of 
minute  Rhizopods,  or  foraminiferous  shells  of  the  genus  Globigerina, 
especially  the  species  of  Globigerina  bulloides  (see  fig.  281).  In  the 
remainder  of  the  mud  the  organic  bodies  next  in  quantity  were  the 
siliceous  shells  called  Polycystinece,  and  next  to  them  the  siliceous 
skeletons  of  plants  called  Diatomacece  (figs.  282,  283,  284),  and 
occasionally  some  siliceous  spiculse  of  sponges  (fig.  285),  were  inter- 
mixed. 


Fig.  281. 


Fig.  282. 


Fig.  283.      Fig.  284.    Fig. 


Organic  bodies  forming  the  ooze  of  the  bed  of  the  Atlantic  at  great  depth3. 
Fig.  281.    Globigerina  bulloides.    Calcareous  Rhisopod. 

282.  Actinocyclas.          | 

283.  Pinnularia.  f    Siliceous  Diatoms. 
28\    Eunotia  Widens.     ' 

235.    Spicula  of  sponge,       Siliceous  sponge. 

In  1860,  shells  of  the  same  Globigerina  were  observed  by  Sir  Leo- 
pold MacClintoch  and  Dr.  Wallich,  during  the  cruise  of  the  "  Bulldog," 
to  form,  over  other  wide  areas  of  the  Atlantic,  a  proportion  of  about 
95  per  cent,  of  the  mud,  both  between  the  Faroe  Islands  and  Iceland, 
and  between  Iceland  and  Greenland.  The  consistency  of  the  ooze 
brought  up  from  great  depths  in  these  areas  is  described  as  akin  to 
that  of  putty.  On  the  surface  were  found  living  Globigerinse,  while 
immediately  below  were  countless  calcareous  grains,  the  relics  of  by- 
gone generations.  Each  of  these  grains,  as  will  be  seen  by  the  mag- 
nified drawing,  instead  of  being  solid,  consists  of  a  collection  of  cells, 
and  as  similar  Globigerinse  form  a  large  part  of  the  white  chalk,  their 


CH.  XVII.]  CHALK  FLINTS,   HOW  FORMED.  321 

structure,  as  Mr.  Dana  lias  well  observed,  helps  us  to  understand  the 
imperfect  aggregation  of  that  remarkable  rock.  At  the  same  time 
the  continued  growth  of  these  Bhizopods  over  a  wide  extent  of  deep 
ocean  enables  us  to  conceive  how  formerly  in  European  areas  a  vast 
thickness  of  cretaceous  limestone,  very  uniform  in  composition,  and 
devoid  of  sand,  pebbles,  terrestrial  and  freshwater  plants  and  shells, 
and  all  other  signs  of  a  neighboring  continent,  may  have  been  formed. 
That  white  chalk  is  now  forming  in  the  depths  of  the  ocean,  may  now 
be  regarded  as  an  ascertained  fact,  because  the  Globigerina  bulloides 
is  specifically  undistinguishable  from  a  fossil  which  constitutes  a  large 
portion  of  the  chalk  of  Europe.  It  is  not  figured  (p.  26)  among  the 
cretaceous  foraminifera  discovered  by  Mr.  Lonsdale  in  1835,  because  it 
occurs  for  the  most  part  in  fragments  in  the  white  chalk,  and  the 
perfect  shell  was  not  well  understood  before  it  was  obtained  living  from 
the  bed  of  the  Atlantic.  The  Rosalina  figured  in  the  same  page  some- 
what resembles  externally  a  Globigerina,  but  it  differs  in  the  arrange- 
ment of  its  cells. 

Chalk  Flints. — The  origin  of  the  layers  of  flint,  whether  in  con- 
tinuous sheets  or  in  the  form  of  nodules,  has  always  been  found  more 
difficult  to  account  for  than  that  of  the  white  chalk.  In  modern 
coral  reefs  no  such  siliceous-  masses  are  known  to  be  forming.  But 
here  again  the  late  deep-sea  soundings  have  suggested  a  very  proba- 
ble source  of  such  mineral  matter.  During  the  cruise  of  the  "  Bull- 
dog," already  alluded  to,  it  was  ascertained  that  while  the  calcareous 
GlobigerincB  had  almost  exclusive  possession  of  certain  tracts  of  the 
sea-bottom,  they  were  wholly  wanting  in  others,  as  between  Green- 
land and  Labrador.  Dr.  Wallich  supposes  that  they  flourished  in 
those  spaces  where  they  may  derive  nutriment  from  organic  and 
other  matter,  brought  from  the  south  by  the  warm  waters  of  the 
Gulf  Stream,  and  that  they  may  be  absent  where  the  effects  of  that 
great  current  are  not  felt.  In  several  of  the  spaces  where  the  calcare- 

O 

ous  Ehizopods  are  wanting,  the  microscopic  plants  called  Diatomacece, 
before  mentioned  (figs.  282,  284),  the  solid  parts  of  which  are  siliceous, 
monopolize  the  ground  at  a  depth  of  nearly  400  fathoms,  or  2400  feet. 
Mr.  Dana  also  has  reminded  us  that  in  the  soundings  made  in  the 
Sea  of  Kamtschatka  Professor  Bailey  found  the  same  microscopic 
vegetable  organisms  in  as  great  profusion  as  are  the  Globigerinse  in 
the  Atlantic,  and  he  adds  that  when  such  Diatomacese  decompose, 
the  alkaline  waters  of  the  ocean  can  take  up  and  hold  in  solution 
only  a  minute  portion  of  the  silica  set  free,  so  that  an  opportunity 
would  be  given  for  the  remainder  to  form  concretionary  nodules,  or 
to  aggregate  round  any  foreign  body  as  a  nucleus,  especially  when 
such  a  body  is  undergoing  chemical  change  or  decomposition.  This 
would  explain  the  frequent  occurrence  of  fossils  within  nodules  of  flint, 
and  the  silicification  of  various  organisms.*  In  some  parts  of  the 

*  Dana's  Geology,  p.  489. 
21 


322 


POTSTONES  AT  HORSTEAD. 


[Cn.  XVII. 


Southern  Hemisphere  likewise,  as  Captain  Maury  observes,  in  lat.  13° 
S.,  long.  16°  E.,  for  example,  siliceous  Diatomaceae  and  sponge  spicules 
are  the  predominant  forms  instead  of  calcareous  Rhizopods. 

If  it  be  asked  how  the  Diatomacese  above  alluded  to  can  obtain  a 
constant  supply  of  silex  in  solution,  I  may  remind  the  reader  of  the 
decomposition  of  felspathic  rocks  mentioned  above  (p.  42)  as  a  copi- 
ous source  of  that  mineral.  Almost  all  the  great  rivers  which  flow 
into  the  ocean  must  contain  some  of  it,  and  springs  charged  with 
silex  in  solution  must  rise  up  in  many  parts  of  the  bed  of  the  ocean 
as  they  do  on  dry  land. 

Dr.  Buckland  endeavored  formerly  to  account  for  the  recurrence,  at 
so  many  distinct  levels,  of  beds  of  nodular  or  tabular  flint  in  the  chalk, 
by  supposing  the  periodical  accumulation  of  widely  extended  layers 
of  mud,  made  up  of  calcareous  and  siliceous  matter.  When  a  stratum 
five  or  six  feet  or  more  in  thickness  had  accumulated,  its  partial  con- 
solidation took  place,  during  which  the  heavier  silex  sank  to  the  bot- 
tom, forming  nodules,  or,  if  it  was  in  sufficient  quantity,  continuous 
layers.*  But  the  thickness  of  the  masses  of  chalk  intervening  be- 
tween some  of  the  strata  of  flint  has  always  made  this  hypothesis 
somewhat  unsatisfactory,  although  such  segregation  of  siliceous  matter 
helps  us  to  conceive  how  isolated  and  scattered  flinty  nodules  may 
sometimes  be  formed  in  the  midst  of  a  calcareous  matrix.  To  explain 
a  regular  succession  of  flinty  layers,  we  must  seek  out  some  intermit- 
tent action,  favoring  alternately  the  deposition  of  calcareous  and  siliceous 
matter.  Many  centuries  would  probably  be  required  for  the  growth  of 
microscopic  organisms  sufficient  in  quantity  to  form  a  bed  of  white  chalk 

Fig.  286. 


From  a  drawing  by  Mrs.  Gunn. 
View  of  a  chalk-pit  at  Horstead,  near  Norwich,  showing  the  position  of  the  potstones. 

*  Geol.  Trans.,  First  Series,  vol.  iv.  p.  413. 


CH.  XVII.]  PEBBLES  IN  CHALK.  323 

several  feet,  and  sometimes  yards  in  thickness.  We  may  imagine  that 
after  a  lapse  of  many  years  or  centuries,  changes  took  place  in  the 
direction  of  the  marine  currents,  favoring  at  one  time  a  supply  in  the 
same  area  of  siliceous,  and  at  another  of  calcareous  matter  in  excess, 
giving  rise  in  the  one  case  to  a  preponderance  of  Globigerinse,  and  in 
the  other  of  Diatomacese. 

A  more  difficult  enigma  is  presented  by  the  occurrence  of  certain 
huge  flints,  or  potstones,  as  they  are  called  in  Norfolk,  occurring  singly, 
or  arranged  in  nearly  continuous  columns  at  right  angles  to  the  ordi- 
nary and  horizontal  layers  of  small  flints.  I  visited,  in  the  year  1825, 
an  extensive  range  of  quarries  then  open  on  the  River  Bure,  near  Hor- 
stead,  about  six  miles  from  Norwich,  which  afforded  a  continuous  sec- 
tion, a  quarter  of  a  mile  in  length,  of  white  chalk,  exposed  to  the 
depth  of  twenty-six  feet,  and  covered  by  a  thick  bed  of  gravel.  The 
potstones,  many  of  them  pear-shaped,  were  usually  about  three  feet 
in  height  and  one  foot  in  their  traversed  diameter,  placed  in  ver- 
tical rows,  like  pillars  at  irregular  distances  from  each  other,  but 
usually  from  20  to  30  feet  apart,  though  sometimes  nearer  together, 
as  in  the  above  sketch.  These  rows  did  not  terminate  downwards  in 
any  instance  which  I  could  examine,  nor  upwards,  except  at  the  point 
where  they  were  cut  off  abruptly  by  the  bed  of  gravel.  On  breaking- 
open  the  potstones,  I  found  an  internal  cylindrical  nucleus  of  pure 
chalk,  much  harder  than  the  ordinary  surrounding  chalk,  and  not 
crumbling  to  pieces  like  it,  when  exposed  to  the  winter's  frost.  At 
the  distance  of  half  a  mile,  the  vertical  piles  of  potstones  were  much 
farther  apart  from  each  other.  Dr.  Buckland  has  described  very  simi- 
lar phenomena  as  characterizing  the  white  chalk  on  the  north  coast 
of  Antrim,  in  Ireland.* 

These  pear-shaped  masses  of  flint  often  resemble  in  shape  and  size 
the  large  sponges  called  Neptune's  cups  (Spongia  patera,  Hardw.), 
which  grow  in  the  seas  of  Sumatra ;  and  if  we  could  suppose  a  series 
of  such  gigantic  sponges  to  be  separated  from  each  other,  like  trees  in 
a  forest,  and  the  individuals  of  each  successive  generation  to  grow  on 
the  exact  spot  where  the  parent  sponge  died  and  was  enveloped  in  cal- 
careous mud,  so  that  they  should  become  piled  one  above  the  other  in 
a  vertical  column,  their  -growth  keeping  space  with  the  accumulation 
of  the  enveloping,  calcareous  mud,  a  counterpart  of  the  phenomena  of 
the  Horstead  potstones  might  be  obtained. 

Single  pebbles  in  chalk.— The  general  absence  of  sand  and  pebbles 
in  the  white  chalk  has  been  already  mentioned ;  but  the  occurrence 
here  and  there,  in  the  south-east  of  England,  of  a  few  isolated  pebbles 
of  quartz  and  green  schist,  some  of  them  2  or  3  inches  in  diameter,  has 
justly  excited  much  wonder.  If  these  had  been  carried  to  the  spots 
where  we  now  find  them  by  waves  or  currents  from  the  lands  once 
bordering  the  cretaceous  sea,  how  happened  it  that  no  sand  or  mud 

*  Geol.  Trans.,  First  Series,  vol.  iv.  p.  413.     "  On  Paramoudra,  &c." 


324  PEBBLES  IN  CHALK.  [On.  XVII. 

were  transported  thither  at  the  same  time  ?  We  cannot  conceive  such 
rounded  stones  to  have  been  drifted  like  erratic  blocks  by  ice  (see 
Chaps.  X.,  XL),  for  that  would  imply  a  cold  climate  in  the  Cretaceous 
period  —  a  supposition  inconsistent  with  the  luxuriant  growth  of  large 
chambered  univalves,  numerous  corals,  and  many  fish,  and  other  fossils 
of  tropical  forms. 

Now  in  Keeling  Island,  one  of  those  detached  masses  of  coral  which 
rise  up  in  the  wide  Pacific,  Captain  Ross  found  a  single  fragment  of 
greenstone,  where  every  other  particle  of  matter  was  calcareous  ;  and 
Mr.  Darwin  concludes  that  it  must  have  come  there  entangled  in  the 
roots  of  a  large  tree.  He  reminds  us  that  Chamisso,  the  distinguished 
naturalist  who  accompanied  Kotzebue,  affirms  that  the  inhabitants  of 
the  Radack  archipelago,  a  group  of  lagoon  islands  in  the  midst  of  the 
Pacific,  obtained  stones  for  sharpening  their  instruments  by  searching 
the  roots  of  trees  which  are  cast  up  on  the  beach.* 

It  may  perhaps  be  objected,  that  a  similar  mode  of  transport 
cannot  have  happened  in  the  cretaceous  sea,  because  fossil  wood  is 
very  rare  in  the  chalk.  Nevertheless  wood  is  sometimes  met  with, 
and  in  the  same  parts  of  the  chalk  where  the  pebbles  are  found,  both 
in  soft  stone  and  in  a  silicified  state  in  flints.  In  these  cases  it  has 
often  every  appearance  of  having  been  floated  from  a  distance,  being 
usually  perforated  by  boring-shells,  such  as  the  Teredo  and  Fistu- 


The  only  other  mode  of  transport  which  suggested  itself  is  sea- 
weed. Dr.  Beck  informs  me  that  in  the  Lym-Fiord,  in  Jutland,  the 
Fucus  vesiculosuSj  often  called  kelp,  sometimes  grows  to  the  height 
of  10  feet,  and  the  branches  rising  from  a  single  root  form  a  cluster 
several  feet  in  diameter.  When  the  bladders  are  distended,  the  plant 
becomes  so  buoyant  as  to  float  up  loose  stones  several  inches  in 
diameter,  and  these  are  often  thrown  by  the  waves  high  up  on  the 
beach.  The  Fucus  giganteus  of  Solander  (Macrocystes  pyrifera, 
Hooker),  so  common  in  Terra  del  Fuego,  was  descried  by  Captain 
Cook  as  attaining  the  length  of  360  feet,  although  the  stem  is  not 
much  thicker  than  a  man's  thumb.  Dr.  Hooker  found  the  same  sea- 
weed 700  feet  long.  J  It  is  often  met  with  floating  at  sea,  with  shells 
attached,  several  hundred  miles  from  the  spots  where  it  grew.  Some 
of  these  plants,  says  Mr.  Darwin,  were  found  adhering  to  large  loose 
stones  in  the  inland  channels  of  Terra  del  Fuego,  during  the  voyage 
of  the  "  Beagle  "  in  1834  ;  and  that  so  firmly,  that  the  stones  were 
drawn  up  from  the  bottom  into  the  boat,  although  so  heavy  that  they 
could  scarcely  be  lifted  in  by  one  person.  Some  fossil  sea-weeds  have 
been  found  in  the  Cretaceous  formation,  but  none,  as  yet,  of  large  size. 

But  we  must  not  imagine  that  because  pebbles  are  so  rare  in  the 


*  Darwin,  p.  649.    Kotzebue's  First  Voyage,  vol.  iii.  p.  155. 
f  Mantell,  Geol.  of  S.E.  of  England,  p.  96. 
j  Flora  Antarctica,  vol.  ii.  p.  464. 


CH.  XVII.]    "     FOSSILS  OF  UPPER  CRETACEOUS  ROCKS. 


325 


white  chalk  of  England  and  France  there  are  no  proofs  of  sand, 
shingle,  and  clay  having  been  accumulated  contemporaneously  even 
in  European  seas.  The  siliceous  sandstone,  called  "  upper  quader  " 
by  the  Germans,  overlies  white  argillaceous  chalk  or  "  planer-kalk," 
a  deposit  resembling  in  composition  and  organic  remains  the  chalk 
marl  of  the  English  series.  This  sandstone  contains  as  many  fossil  shells 
common  to  our  white  chalk  as  could  be  expected  in  a  sea-bottom 
formed  of  such  different  materials.  It  sometimes  attains  a  thickness 
of  600  feet,  and,  by  its  jointed  structure  and  vertical  precipices,  plays 
a  conspicuous  part  in  the  picturesque  scenery  of  Saxon  Switzerland, 
near  Dresden. 


FOSSILS  OF  THE  UPPER  CRETACEOUS  ROCKS. 

Among  the  fossils  of  the  white  chalk,  echinoderms  are  very  numer- 
ous ;  and  some  of  the  genera,  like  Ananchytes  (see  fig.  287),  are  ex- 
Fig.  28T. 


Ananchytes  ovata.    White  chalk,  upper  and  lower. 
a.  Side  view. 

5.  Bottom  of  the  shell  on  which  both  the  oral  and  anal  apertures  are  placed; 
the  anal  being  more  round,  and  at  the  smaller  end. 

clusively  cretaceous.     Among  the  Crinoidea,  the  Marsupite  (fig.  294) 
is  a  characteristic  genus.     Among  the  mollusca,  the  cephalopoda,  or 


Fig.  28a 


Fig.  289. 


Micraster  cor-angwnum. 
White  chalk. 


Galerites  albogalerus,  Lam. 
White  chalk. 


Fig.  290. 


a.  JSelemnites  mucronatus.    Syn.  BelemniteHn  inucronata. 

5.  Same,  showing  internal  structure.    Mtiestricht,  Faxoe,  and  white  chalk. 


326 


FOSSILS  OF  UPPER  CRETACEOUS  ROCKS.         [Cn.  XVII. 


chambered  univalves,  of  the  genera  Ammonite,  Scapliite,  Belemnite 
(fig.  290),  Baculite  (291-293),  and  Turrilite  (296,  297),  with  other 


Fig.  291. 


Saeulites 


Upper  Greensand,  or  chloritic  marl,  craie  chloritee.    France. 
A.  d'Orb.,  Terr.  Cret 


Fig.  293. 


Portion  of  Saculites  Favfiasii.  Portion  of  Saaulites  anceps. 

Maestricht  and  Faxoe  beds  and  white  chalk.       Maestricht  and  Faxoe  beds  and  white  chalk. 


Fig.  294. 


Mw*wpites  MilUri. 
White  chalk. 


Fig.  295. 


Scaphites  cequalis.    Chloritic  marl 
of  Upper  Greensand,  Dorsetshire. 


Fig.  290. 


Fig.  297. 


TurriUtes  costatus. 
Chalk. 


a.  Fragment  of  Turrilites  costatua. 
Chalk  marl. 


Bame,  showing  the  foliated  border 
of  the  partition  of  the  chambers. 


allied  forms,  present  a  great  contrast  to  the  testacea  of  the  same  class 
in  the  Tertiary  and  Recent  periods. 


CH.  XVII.]         FOSSILS  OF  UPPER  CRETACEOUS  ROCKS. 


327 


Among  the  brachiopoda  in  the  white  chalk,  the  Terebratulce  are 
very  abundant.  These  shells  are  known  to  live  at  the  bottom  of  the 
sea,  where  the  water  is  tranquil  and  of  some  depth  (see  figs.  298, 
299,  300,  301,  302).  With  these  are  associated  some  forms  of  oyster 


Fig.  298. 


Fig.  299. 


Fig.  301. 


Terebratulina  striata. 
Upper  white  chalk. 


Rhynchonella       Magas  pumila,  Sow. 
octoplicata.  Upper  white  chalk. 

(Var.  of  T.  plicatiUs.} 
Upper  white  chalk. 


Terebratula 

carnea. 
Upper  white  chalk. 


(see  figs.  309,  310,  311),   and   other  bivalves   (figs.  303,  304,  305, 
306,  307). 


Fig.  302. 


Fig.  304. 


Terebratula  biplicata, 
Sow.    Upper  cretaceous. 


Crania  Parisiensis, 
inferior  or  attached 

valve. 
Upper  white  chalk. 


Pecten  Beaveri,  reduced  to 
one-third  diameter. 

Lower  white  chalk  and  chalk 
marl.  Maidstone. 


Fig.  805. 


Fig.  306. 


Fig.  307. 


Pecten  5-eostatus. 

White  chalk,  Upper  and 

Lower  Green  sands. 


Plagiostoma  Hoperi,  Sow. 

Syn.  Lima  ffoperi. 
White  chalk  and  Upper  Greensand. 


Lima  spinosa,  Sow. 

Syn.  Spondylus  spinosus. 

Upper  white  chalk. 


Among  the  bivalve  mollusca,  no  form  marks  the  Cretaceous  era  in 
Europe,  America,  and  India,  in  a  more  striking  manner  than  the 
extinct  genus  Inoceramus  (Catillus  of  Lam. ;  see  fig.  308),  the  shells 
of  which  are  distinguished  by  a  fibrous  texture,  and  are  often  met 
with  in  fragments,  having,  probably,  been  extremely  friable. 

Of  the  singular  family  called  JRudistes,  by  Lamarck,  hereafter  to 
be  mentioned  as  extremely  characteristic  of  the  chalk  of  Southern 


328  MOLLUSCA,  BRYOZOA,  SPONGES. 

Fig.  808,  Fig.  809. 


[Cn.  XVH. 


Inoceramus  Lamarckii. 
Syn.  CaUllus  LamarcJcii. 
White  chalk.    (Dixon's  Geol.  Sussex, 
Tab.  28,  fig.  29.) 

Fig.  810. 


Ostrea  vesicularis.    Syn.  Gryphcea  globosa. 
Upper  chalk  and  Upper  Greensand. 


Fig.  811 


Ostrea  colwnba. 

Syn.  Cfryphcea  columba. 

CTpper  Greensand. 


Ostrea  carinata.    Chalk  marl,  Upper  and 
Lower  Greensand. 


Fig.  813. 


Fig.  815. 


Fig.  814 


BadioUtes  Mortoni,  Mantell.    Houghton,  Sussex.    White  chalk. 

Diameter  one-seventh  nat.  size. 
Fig.  812.    Two  individuals  deprived  of  their  upper  valves,  adhering  together. 

313.  Same  seen  from  above. 

314.  Transverse  section  of  part  of  the  wall  of  the  shell,  magnified  to  show  the  structure. 

315.  Vertical  section  of  the  same. 

On  the  side  where  the  shell  is  thinnest,  there  is  one  external  furrow  and  corresponding  inter- 
nal ridge,  a,  &,  figs.  312,  813;  but  they  are  usually  less  prominent  than  in  these  figures.  This 
species  was  first  referred  by  Mantell  to  Hippurites,  afterwards  to  the  genus  Radiolites.  I  have 
never  seen  the  upper  valve.  The  specimen  above  figured  was  discovered  by  the  late  Mr.  Dixon. 


CH.  xvn.] 


MOLLUSCA,   BRYOZOA,   SPONGES. 


329 


Europe,  a  single  representative  only  (fig.  312)  has  been  discovered  in 
the  white  chalk  of  England. 


Fig.  316. 


Escharina  oceani. 
a.  Natural  size. 
5.  Part  of  the  same  magnified. 

White  chalk. 


Eschara  disticha. 
a.  Natural  size. 
Portion  magnified. 
White  chalk. 


VentricuUtea  rodiatus. 

MantelL 

Syn.  Ocellaria  radiata, 
D'Orb.    White  chalk. 


Fig.  820. 


Fig.  819. 


A  branching  sponge  in  a  flint,  from  the  white  chalk. 
From  the  collection  of  Mr.  Bowerbank. 


Siphonia  pyriformis. 
Blackdown  beds. 


330  FOSSILS  OF  UPPER  CRETACEOUS  BEDS.  [Ca  XVII. 

With  these  mollusca  are  associated  many  Bryozoa,  such  as  Eschara 
and  EschaTina  (figs.  316,  317),  which  are  alike  marine,  and,  for  the 
most  part,  indicative  of  a  deep  sea.  These  and  other  organic  bodies, 
especially  sponges,  such  as  Ventriculites  (fig.  318),  are  dispersed  in- 
differently through  the  soft  chalk  and  hard  flint,  and  some  of  the 
flinty  nodules  owe  their  irregular  forms  to  enclosed  sponges  such  as 
fig.  319  a,  where  the  hollows  in  the  exterior  are  caused  by  the 
branches  of  a  sponge,  seen  on  breaking  open  the  flint  (fig.  319  b). 

The  remains  of  fishes  of  the  Upper  Cretaceous  formations  consist 
chiefly  of  teeth  of  the  shark  family  of  genera,  in  part  common  to  the 
tertiary,  and  partly  distinct.  To  the  latter  belongs  the  genus  Ptycho- 
dus  (fig.  321),  which  is  allied  to  the  living  Port  Jackson  Shark,  Ces- 
tracion  Phillippi,  the  anterior  teeth  of  which  (see  fig.  322  a)  are 
sharp  and  cutting,  while  the  posterior  or  palatal  teeth  (b)  are  flat,  and 
analogous  to  the  fossil  (fig.  321). 

Fig.  822. 


Pig.  821. 


Palatal  tooth  of 

Ptychodus  decurrens. 

Lower  white  chalk. 

Maidstone. 


Cestracion  Phillippi  ;  recent. 
Port  Jackson.    Buckland,  Bridgewater  Treatise,  pi.  27  d. 

But  we  meet  with  no  bones  of  land  animals,  nor  any  terrestrial  or 
fluviatile  shells,  nor  any  plants,  except  sea-weeds,  and  here  and  there  a 
piece  of  drift-wood.  All  the  appearances  concur  in  leading  us  to  con- 
clude that  the  white  chalk  was  the  product  of  an  open  sea  of  consider- 
able depth. 

The  existence  of  turtles  and  oviparous  saurams,  and  of  a  Pterodactyl 
or  winged  lizard,  found  in  the  white  chalk  of  Maidstone,  implies,  no 
doubt,  some  neighboring  land ;  but  a  few  small  islets  in  mid-ocean, 
like  Ascension,  formerly  so  much  frequented  by  migratory  droves  of 
turtle,  might  perhaps  have  afforded  the  required  retreat  where  these  crea- 
tures laid  their  eggs  in  the  sand,  or  from  which  the  flying  species  may 
have  been  blown  out  to  sea.  Of  the  vegetation  of  such  islands  we 
have  scarcely  any  indication,  but  it  consisted  partly  of  cycadaceous 
plants ;  for  a  fragment  of  one  of  these  was  found  by  Capt.  Ibbetson 
in  the  Chalk  Marl  of  the  Isle  of  Wight,  and  is  referred  by  A.  Brong- 


CH.  XVII.]  UPPER  GREENSAND.  33} 

niart  to  Clathraria  Lyellii,  Mantell,  a  species  common  to  the  ante- 
cedent Wealden  period. 

'The  Pterodactyl  of  the  Kentish  chalk,  above  alluded  to,  was  of 
gigantic  dimensions,  measuring  16  feet  6  inches  from  tip  to  tip  of  its 
outstretched  wings.  Some  of  its  elongated  bones  were  at  first  mis- 
taken by  able  anatomists  for  those  of  birds ;  of  which  class  no  osse- 
ous remains  have  as  yet  been  derived  from  the  white  chalk,  although 

Fossils  of  the  Upper  Greensand. 

823.  Fig.  324. 


a.  Terebrirostra  lyra,     )   Upper  Greensand.  Ammonites  Bhotomageiisis. 

&.  Same,  seen  in  profile,     f      France.  Upper  Greensand. 

they  have  been  found  (as  will  be  seen  in  the  annexed  figures)  in  the 
Upper  Greensand. 

Upper  Greensand  (A.  4,  Table,  p.  314). — The  lower  chalk  without 
flints  passes  gradually  downwards,  in  the  south  of  England,  into  an 
argillaceous  limestone,  "  the  chalk  marl,"  already  alluded  to,  in  which 
ammonites  and  other  cephalopoda,  so  rare  in  the  higher  parts  of  the 
series,  appear.  This  marly  deposit  passes  in  its  turn  into  beds  called 
the  Upper  Greensand,  containing  green  particles  of  sand  of  a  chloritic 
mineral.  In  parts  of  Surrey,  calcareous  matter  is  largely  intermixed, 
forming  a  stone  called  Jirestone.  In  the  cliffs  of  the  southern  coast 
of  the  Isle  of  Wight,  this  upper  greensand  is  100  feet  thick,  and  con- 
tains bands  of  siliceous  limestone  and  calcareous  sandstone  with  no- 
dules of  chert. 

The  Upper  Greensand  is  regarded  by  Mr.  Austen  and  Mr.  D.  Sharpe 
as  a  littoral  deposit  of  the  Chalk  Ocean,  and,  therefore,  contempora- 
neous with  part  of  the  chalk  marl,  and  even,  perhaps,  with  some  part 
of  the  white  chalk.  For  as  the  land  went  on  sinking,  and  the  cretace- 
ous sea  widened  its  area,  white  mud  and  chloritic  sand  were  always 
forming  somewhere,  but  the  line  of  sea-shore  was  perpetually  varying 
its  position.  Hence,  though  both  sand  and  mud  originated  simul- 
taneously, the  one  near  the  land,  the  other  far  from  it,  the  sands  and 
in  every  locality  where  a  shore  became  submerged  might  constitute 
the  underlying  deposit. 

Gault. — The  lowest  member  of  the  Upper  Cretaceous  group, 
usually  about  100  feet  thick  in  the  S.E.  of  England,  is  provincially 
termed  Gault.  It  consists  of  a  dark  blue  marl,  sometimes  intermixed 
with  greensand.  Many  peculiar  forms  of  cephalopoda,  such  as  the 


332        FLORA  OF  UPPER  CRETACEOUS  PERIOD    |CH- 

Hamite  (fig.  325)  and  Scaphite,  with  other  fossils,  characterize  this 
formation,  which,  small  as  is  its  thickness,  can  be  traced  by  its 
organic  remains  to  distant  parts  of  Europe,  as,  for  example,  to  the 
Alps. 

Fig.  825. 


Ancyloceras  spinigerwn,  D'Orb.    Syn.  ffamites  spiniger,  Sow.    Near  Folkestone.    Gault. 

The  BlacJcdown  beds  in  Devonshire,  celebrated  for  containing  many 
species  of  fossils  not  found  elsewhere,  have  been  commonly  referred 
to  the  Upper  Greensand,  which  they  resemble  in  mineral  character ; 
but  Mr.  Sharpe  has  suggested,  and  apparently  with  reason,  that  they 
are  rather  the  equivalent  of  the  Gault,  and  were  probably  formed  on 
the  shores  of  the  sea,  in  the  deeper  parts  of  which  the  fine  mud  called 
Gault  was  deposited.  Several  Blackdown  species  are  common  to  the 
Lower  Cretaceous  series,  as,  for  example,  Trigonia  caudata,  fig.  334,  p. 
344.  We  learn  from  M.  d'Archiac,  that  in  France,  at  Mons,  in  the 
valley  of  the  Loire,  strata  of  greensand  occur  of  the  same  age  as  the 
Blackdown  beds,  and  containing  many  of  the  same  fossils.  They  are 
also  regarded  as  of  littoral  origin  by  M.  d'Archiac.* 

The  phosphate  of  lime,  found  near  Farnham,  in  Surrey,  and  near 
Cambridge,  in  such  abundance  as  to  be  used  largely  by  the  agricul- 
turist for  fertilizing  soils,  occurs  in  the  Upper  Greensand.  It  is  doubt- 
less of  animal  origin,  and  partly  coprolitic,  derived  from  the  excre- 
ment of  fish  and  reptiles.  In  this  formation  near  Cambridge  the  late 
M.  Louis  Barrett  discovered,  in  1858,  the  remains  of  a  bird,  which  was 
rather  larger  than  the  common  pigeon,  and  probably  of  the  Order 
Natatores,  and  which,  like  most  of  the  Gull  tribe,  had  well-developed 
wings.  Portions  of  the  metacarpus,  metatarsus,  tibia,  and  femur  have 
been  detected,  and  the  determinations  of  Mr.  Barrett  have  been  con- 
firmed by  Professor  Owen. 


FLORA    OF    THE    UPPER    CRETACEOUS    PERIOD. 

As  the  upper  cretaceous  rocks  of  Europe  are,  for  the  most  part,  of 
purely  marine  origin,  and  formed  in  deep  water  far  from  the  nearest 
shore,  land-plants  of  this  period,  as  we  might  naturally  have  antici- 

*  Hist,  des  Progress  de  la  Geol.,  &c.,  vol.  iv.  p.  360.     1851. 


CH.  XVII.]  AT  AIX-LA-CHAPELLE.  333 

pated,  are  very  rarely  met  with.  In  the  neighborhood  of  Aix-la-Cha- 
pelle,  however,  an  important  exception  occurs,  for  there  certain  white ' 
sands,  400  feet  in  thickness,  contain  the  remains  of  terrestrial  plants 
in  a  beautiful  state  of  preservation.  These  have  been  diligently  col- 
lected and  studied  by  Dr.  Debey,  and  as  they  afford  the  only  example 
yet  known  of  a  terrestrial  flora  older  than  the  Eocene,  in  which  the 
great  divisions  of  the  vegetable  kingdom  are  represented  in  nearly  the 
same  proportions  as  in  our  own  times,  they  deserve  particular  atten- 
tion. Dr.  Debey  estimates  the  number  of  species  as  amounting  to 
more  than  two  hundred,  of  which  sixty-seven  are  cryptogamous, 
chiefly  ferns,  twenty  species  of  which  can  be  well  determined,  most 
of  them  being  in  fructification.  The  cicatrices  on  the  bark  of  one  or 
two  are  supposed  to  indicate  tree-ferns.  Of  thirteen  genera  three  are 
still  existing,  namely,  Grleichenia,  now  inhabiting  the  Cape  of  Good 
Hope  and  New  Holland ;  Lygodium,  now  living  in  Japan,  Java,  and 
North  America ;  and  Asplenium,  a  cosmopolite  form.  Among  the 
phaenogamous  plants  the  Conifers  are  abundant,  the  most  common  be- 
longing to  a  genus  called  Cycadopteris  by  Debey,  and  hardly  separable 
from  Sequoia  (or  Wellingtonia),  of  which  both  the  cones  and  branches 
are  preserved.  When  I  visited  Aix,  I  found  the  silicified  wood  of  this 
plant  very  plentifully  dispersed  through  the  white  sands  in  the  pits 
near  that  city.  In  one  silicified  trunk  200  rings  of  annual  growth  had 
been  counted.  Species  of  Araucaria  like  those  of  Australia  are  also 
found.  Cycads  are  extremely  rare,  and  of  Monocotyledons  there  are 
but  few.  No  palms  have  been  recognized  with  certainty,  but  the  genus 
Pandanus,  or  screw  pine,  has  been  distinctly  made  out.  The  number 
of  the  Dicotyledonous  Angiosperms  is  the  most  striking  feature  in  so 
ancient  a  flora.* 

Among  them  we  find  the  familiar  forms  of  the  Oak,  Fig,  and  Wal- 
nut, Quercus,  Ficus,  and  Juglans,  of  the  latter  both  the  nuts  and  leaves ; 
also  several  genera  of  the  Myrtacese.  But  the  predominant  order  is 

*  la  this  and  subsequent  remarks  on  fossil  plants  I  shall  often  use  Dr.  Lindley's 
terms,  as  most  familiar  in  this  country ;  but  as  those  of  M.  A.  Brongniart  are 
much  cited,  it  may  be  useful  to  geologists  to  give  a  table  explaining  the  corre- 
sponding names  of  groups  so  much  spoken  of  in  palaeontology. 

Brongniart.  Lindley. 

1.  Cryptogamous  araphi-  1 

gens,     or    cellular  >•     Thallogens.  Lichens,  sea-weeds,  fungi, 

cryptogamic.  ) 

2.  Cryptogamous     aero-        Acrogens.  Mosses,  equisetums,  ferns,  lyco- 

gens.  podiums, — Lepidodendron. 

3.  Dicotyledonous   gym-        Gymnogens.          Conifers  and  Cycads. 

nosperms. 

4.  Dicot.  Angiosperms.  Exogens.  Composite,    Ieguminoss9,  um- 

belliferae,  crucifcrse,  heaths, 
&c.  All  native  European 
trees  except  conifers. 

5.  Monocotyledons.  Endogens.  Palms,    lilies,    aloes,    rushes, 

grasses,  &c. 


334  FLORA  OF  UPPER  CRETACEOUS  PERIOD.         [On.  XVII. 

the  Proteacese,  of  which  there  are  between  sixty  and  seventy  species, 
many  of  extinct  genera,  but  some  referred  to  the  following  living  forms 
— Dryandra,  Grevillea,  Hakea,  Banksia,  Persoonia — all  now  belonging 
to  Australia,  and  Leucospermum,  species  of  which  form  small  bushes 
at  the  Cape. 

The  epidermis  of  the  leaves  of  many  of  these  Aix  plants,  especially 
of  the  Proteacese,  is  so  perfectly  preserved  in  an  envelope  of  fine  clay 
that  under  the  microscope  the  stomata,  or  polygonal  cellules,  can  be 
detected,  and  their  peculiar  arrangement  is  identical  with  that  known 
to  characterize  some  living  Proteacese  (Grevillea,  for  example).  An  oc- 
casional admixture  of  Fucoids  and  Zosterites  attests,  like  the  shells, 
the  presence  of  saltwater. 

Of  insects  Dr.  Debey  has  obtained  about  ten  species  of  the  families 
CurculionidsD  and  Carabidse. 

The  age  of  the  beds  containing  this  remarkable  assemblage  of 
plants  was  for  a  long  time  matter  of  dispute.  They  were  at  first 
erroneously  referred  to  the  Middle  Tertiary,  and  afterwards  to  the 
Lower  Cretaceous  series,  but  they  are  in  truth  the  equivalents  of  the 
white  chalk  and  Chalk  Marl,  or  Senonien  of  D'Orbigny.  Such  was 
Ferdinand  Romer's  opinion  in  1853,*  and  after  examining  the  coun- 
try in  1857,  I  satisfied  myself  that  he  was  right,  although  the  white 
siliceous  sands  of  the  lower  beds,  and  the  green  grains  in  the  upper 
part  of  the  formation,  caused  it  to  differ  in  mineral  character  from  our 
white  chalk. 

In  travelling  from  Maestricht  to  Aix-la-Chapelle,  we  first  pass 
from  the  Maestricht  beds  to  white  chalk,  with  flints,  about  300  feet 
thick,  next  to  which,  in  descending  order,  we  find  chalk  without  flints, 
and  Chalk  Marl;  and  below  this  again,  greensand,  which  contains 
Belemnitella  mucronata  (fig.  290,  p.  325),  and  other  fossils,  showing 
that  it  is  not  the  equivalent  of  the  English  Upper  Greensand.  Below 
this  are  the  white  and  yellow  sands  of  Aix,  about  400  feet  thick,  which 
rest  immediately  on  ancient  Devonian  rocks,  highly  inclined.  Some  of 
the  sand  in  the  lower  beds  has  concreted  into  solid  masses  of  sandstone, 
like  the  German  Quader  Sandstein. 

Beds  of  fine  clay,  with  fossil  plants,  and  with  seams  of  lignite  and 
even  perfect  coal,  are  intercalated.  Floating  wood,  containing  perfo- 
rating shells,  such  as  Pholas,  and  Gastrochcena  also  occur.  There  are 
likewise  a  few  beds  of  a  yellowish  brown  limestone,  with  marine  shells, 
which  enable  us  to  identify  the  lowest  with  the  highest  plant-beds. 
Among  these  shells  are  Pecten  quadricostatus,  and  several  others  which 
are  common  to  the  upper  and  lower  part  of  the  series,  and  a  Trigonia, 
called  by  some  of  the  Aix  naturalists  T.  alacformis,  which,  as  M.  Bos- 
quet pointed  out  to  me,  agrees  far  better  in  character  with  D'Orbigny's 
T.  limbata,  a  shell  of  the  white  chalk.  On  the  whole  the  organic  re- 

*  F.  Romer,  Kreidebildung  der  Gegend  von  Aachen.    Deutsch.  Geol.  Gesellsch. 
vii.  534. 


CH.  XVII.]         FLORA  OF  UPPER  CRETACEOUS  PERIOD.  335 

mains  and  the  geological  position  of  the  strata  prove  distinctly  that  in 
the  neighborhood  of  Aix-la-Chapelle,  a  gulf  of  the  ancient  cretaceous 
sea  was  bounded  by  land  composed  of  Devonian  rocks.  These  rocks 
consisted  of  quartzose  and  schistose  beds,  the  first  of  which  supplied 
white  sand  and  other  argillaceous  mud  to  a  river  which  entered  the 
sea  at  this  point,  carrying  down  in  its  turbid  waters  much  drift-wood 
and  the  leaves  of  plants.  Occasionally,  when  the  force  of  the  river 
abated,  marine  shells  of  the  genera  Trigonia,  Turritella,  Pecten,  &c., 
established  themselves  in  the  same  area,  and  plants  allied  to  Zostera 
and  Fucus  grew  on  the  bottom. 

Before  the  cretaceous  flora  of  Aix-la-Chapclle  was  known,  a  few 
leaves  of  a  dicotyledonous  and  angiospermous  genus  called  "  Cred- 
neria,"  were  known  in  the  "  Quader  Sandstein  "  and  "  Planer  Kalk," 
of  Germany,  rocks  corresponding  in  age  to  the  white  chalk  and  gault 
of  England.  But  such  fossil  plants  were  the  only  representatives  in 
rocks  older  than  the  Eocene  period  of  those  Exogens  which  now  con- 
stitute three-fourths  of  the  living  vegetation  of  the  globe. 

M.  Adolphe  Brongniart,  when  dividing  the  whole  fossiliferous  series 
into  three  groups  in  reference  solely  to  fossil  plants,  has  named  the 
primary  strata  "  the  age  of  acrogens ; "  the  secondary,  exclusive  of  the 
cretaceous,  "  the  age  of  gymnosperms  ; "  and  the  third,  comprising  the 
cretaceous  and  tertiary,  "  the  age  of  angiosperms."  He  considers  the 
cretaceous  flora  as  displaying  a  transitional  character  from  that  of  a 
secondary  to  that  of  a  tertiary  vegetation.  Coniferce  and  Cycadece  (or 
Gymnogens)  still  flourished,  as  in  the  preceding  oolitic  and  triassic 
epochs ;  while,  together  with  these,  some  well-marked  leaves  of  dico- 
tyledonous angiosperms  appeared.  But  now  that  the  fossil  plants  of 
Aix-la-Chapelle  are  with  certainty  referred  to  an  Upper  Cretaceous 
era,  the  line  dividing  the  ages  of  gymnosperms  and  of  angiosperms 
seems  to  run  between  the  Lower  and  Upper  Cretaceous  formations,  or 
between  the  Lower  Greensand  and  the  sand  of  Aix. 

The  resemblance  of  the  flora  of  Aix-la-Chapelle  to  the  tertiary  and 
living  floras  in  the  proportional  number  of  dicotyledonous  angiosperms 
as  compared  to  the  gymnogens,  is  a  subject  of  no  small  theoretical  in- 
terest, because  we  can  now  affirm  that  these  Aix  plants  flourished  be- 
fore the  rich  reptilian  fauna  of  the  secondary  rocks  had  ceased  to  exist, 
The  Ichthyosaurus,  Pterodactyl,  and  Mosasaurus  were  of  coeval  date 
with  the  oak,  the  walnut,  and  the  fig.  Speculations  have  often  been 
hazarded  respecting  a  connection  between  the  rarity  of  Exogens  in  the 
older  rocks  and  a  peculiar  state  of  the  atmosphere.  A  denser  air,  it 
was  suggested,  had  in  earlier  times  been  alike  adverse  to  the  well  be- 
ing of  the  higher  order  of  flowering  plants,  and  of  the  quick-breath- 
ing animals  such  as  mammalia  and  birds,  while  it  was  favorable  to  a 
cryptogamic  and  gymnospermous  flora,  and  to  a  predominance  of  rep- 
tile life.  But  we  now  learn  that  there  is  no  incompatibility  in  the  co- 
existence of  a  vegetation  like  that  of  the  present  globe,  and  some  of 
the  most  remarkable  forms  of  the  extinct  reptiles  of  the  age  of  gymno- 
sperms. 


336 


HIPPURITE  LIMESTONE 


[Cn.  XVIL 


If  the  passage  seem  at  present  to  be  somewhat  sudden  from  the  flora 
of  the  Lower  to  that  of  the  Upper  Cretaceous  period,  the  abruptness 
of  the  change  will  probably  disappear  when  we  are  better  acquainted 
with  the  fossil  vegetation  of  the  Lower  Greensand,  and  with  that  of 
the  Gault  and  Tipper  Greensand. 


826< 


HIPPURITE    LIMESTONE. 

Difference  between  the  chalk  of  the  North  and  South  of  Europe.  — 
By  the  aid  of  the  three  tests  of  relative  age,  namely,  superposition, 
mineral  character,  and  fossils,  the  geologist  has  been  enabled  to  refer 
to  the  same  Cretaceous  period  certain  rocks  in  the  north  and  south 
of  Europe,  which  differ  greatly  both  in  their  fossil  contents  and  in 
their  mineral  composition  and  structure. 

If  we  attempt  to  trace  the  cretaceous  deposits  from  England  and 
France  to  the  countries  bordering  the  Mediterranean,  we  perceive, 
in  the  first  place,  that  the  chalk  and  greensand  in  the  neighborhood 
of  London  and  Paris  form  one  great  continuous  mass,  the  straits  of 
Dover  being  a  trifling  interruption,  a  mere  valley  with  chalk  cliffs  on 
both  sides.  We  then  observe  that  the  main  body  of  the  chalk  which 
surrounds  Paris  stretches  from  Tours  to  near  Poitiers  (see  the  annexed 

map,  fig.  326,  in  which  the   shaded 
part  represents  chalk). 

Between  Poitiers  and  La  Rochelle, 
the  space  marked  A  on  the  map  sepa- 
rates two  regions  of  chalk.  This  space 
is  occupied  by  the  Oolite  and  certain 
other  formations  older  than  the  Chalk, 
.and  has  been  supposed  by  M.  E.  de 
Beaumont  to  have  formed  an  island 
in  the  cretaceous  sea.  South  of  this 
space  we  again  meet  with  a  formation 
which  we  at  once  recognize  by  its 
mineral  character  to  be  chalk,  although 
there  are  some  places  where  the  rock 
becomes  oolitic.  The  fossils  are,  upon 
the  whole,  very  similar  ;  especially 
certain  species  of  the  genera  Spatan- 
gus,  Ananchytes,  Cidarites,  Nucula, 
Ostrea,  Gryphwa  (Exogyra),  Pecten, 
Plagiostoma  (Lima),  Trigonia,  Catil- 
lus  (Inoceramus),  and  Terebratula.* 
But  Ammonites,  as  M.  d'Archiac  observes,  of  which  so  many  species 


*  D'Archiac,  Sur  la  Form.  Cretacee  de  S.-O.  do  la  France,  Mem.  de  la  Soc.  Geol. 
de  France,  torn.  ii. 


CH.  XVII.] 


OF  SOUTH  OF  EUROPE. 


337 


are  met  with  in  the  chalk  of  the  north  of  France,  are  scarcely  ever 
found  in  the  southern  region;  while  the  genera  Hamite,  Turrilite, 
and  Scaphite,  and  perhaps  Belemnite,  are  entirely  wanting. 

On  the  other  hand,  certain  forms  are  common  in  the  south  which 
are  rare  or  wholly  unknown  in  the  north  of  France.  Among  these 
may  be  mentioned  many  Hippurites,  Sphcerulites,  and  other  members 
of  that  great  family  of  mollusc*  called  Rudistes  by  Lamarck,  to  which 
nothing  analogous  has  been  discovered  in  the  living  creation,  but 
which  is  quite  characteristic  of  rocks  of  the  Cretaceous  era  in  the 


Fig.  82T. 


Pig.  828. 


a.  RadioUtes  radiosa,  D'Orb. 
Z>.  Upper  valve  of  same, 

White  chalk  of  France. 


Badiolites  fottaceua,  D'Orb. 
Syn.  SphceruUtes  agorici- 

formis,  Blainv. 
White  chalk  of  France. 


Fig. 


Hippurites  organisans,  Desmoulins. 

Upper  chalk:— chalk  marl  of  Pyrenees ? * 

a.  Young  individual ;  when  full  grown  they  occur  in  groups  adhering 

laterally  to  each  other. 

&.  Upper  side  of  the  upper  valve,  showing  a  reticulated  structure  in 
those  parts,  &,  where  the  external  coating  is  worn  off. 

c.  Upper  end  or  opening  of  the  lower  and  cylindrical  valve. 

d.  Cast  of  the  interior  of  the  lower  conical  valve. 


*  D'Orbigny's  Paleontologie  Frai^aise,  pi.  533. 
22 


338  AMERICAN  CRETACEOUS  ROCKS.  [On.  XVII 

south  of  France,  Spain,  Sicily,  Greece,  and  other  countries  bordering 
the  Mediterranean. 

The  species  called  ffippurites  organisans  (fig.  329)  is  more  abun- 
dant than  any  other  in  the  south  of  Europe ;  and  the  geologist  should 
make  himself  well  acquainted  with  the  cast  d,  which  is  far  more  com- 
mon in  many  compact  marbles  of  the  Upper  Cretaceous  period  than 
the  shell  itself,  this  having  often  wholly  disappeared.  The  flutings, 
or  smooth,  rounded,  longitudinal  ribs,  representing  the  form  of  the 
interior,  are  wholly  unlike  the  Hippurite  itself,  and  in  some  individu- 
als attain  a  great  size  and  length. 

Between  the  region  of  chalk  last  mentioned,  in  which  Perigueux 
is  situated,  and  the  Pyrenees,  the  space  B  intervenes.  (See  Map,  fig. 
326.)  Here  the  tertiary  strata  cover,  and  for  the  most  part  conceal, 
the  cretaceous  rocks,  except  in  some  spots  where  they  have  been  laid 
open  by  the  denudation  of  the  newer  formations.  In  these  places 
they  are  seen  still  preserving  the  form  of  a  white  chalky  rock,  which 
is  charged  in  part  with  grains  of  greensand.  Even  as  far  south  as 
Tercis,  on  the  Adour,  near  Dax,  cretaceous  rocks  retain  this  charac- 
ter. I  examined  them  in  1828,  and  M.  Grateloup  found  in  them 
Ananchytes  ovata  (fig.  287,  p.  325),  and  other  fossils  of  the  English 
chalk,  together  with  Hippurites. 


CRETACEOUS    ROCKS    IN   THE    UNITED    STATES. 

If  we  pass  to  the  American  continent,  we  find  in  the  State  of  New 
Jersey  a  series  of  sandy  and  argillaceous  beds  wholly  unlike  our 
Upper  Cretaceous  system ;  which  we  can,  nevertheless,  recognize  as 
referable,  palaeontologically,  to  the  same  division. 

That  they  were  about  the  same  age  generally  as  the  European 
chalk  and  greensand,  was  the  conclusion  to  which  Dr.  Morton  and 
Mr.  Conrad  came  after  their  investigation  of  the  fossils  in  1834.  The 
strata  consist  chiefly  of  greensand  and  green  marl,  with  an  overlying 
coralline  limestone  of  a  pale  yellow  color,  and  the  fossils,  on  the 
whole,  agree  most  nearly  with  those  of  the  Upper  European  series, 
from  the  Maestricht  beds  to  the  gault  inclusive.  I  collected  sixty 
shells  from  the  New  Jersey  deposits  in  1841,  five  of  which  were  iden- 
tical with  European  species — Ostrea  larva,  0.  vesicularis,  Gryphcea 
costata,  Pecten  quinque-costatus,  Belemnites  mucronatus.  As  some  of 
these  have  the  greatest  vertical  range  in  Europe,  they  might  be  ex- 
pected more  than  any  others  to  recur  in  distant  parts  of  the  globe. 
Even  where  the  species  were  different,  the  generic  forms,  such  as  the 
Baculite  and  certain  sections  of  Ammonites,  as  also  the  Inoceramus 
(see  above,  fig.  308,  p.  328),  and  other  bivalves,  have  a  decidedly  cre- 
taceous aspect.  Fifteen  out  of  the  sixty  shells  above  alluded  to  were 
regarded  by  Professor  Forbes  as  good  geographical  representatives  of 
well-known  cretaceous  fossils  of  Europe.  The  correspondence,  there- 


CH.  XVII.]  CRETACEOUS  ROCKS.  339 

fore,  is  not  small,  when  we  reflect  that  the  part  of  the  United  States 
where  these  strata  occur  is  between  3000  and  4000  miles  distant  from 
the  chalk  of  Central  and  Northern  Europe,  and  that  there  is  a  differ- 
ence of  ten  degrees  in  the  latitude  of  the  places  compared  on  oppo- 
site sides  of  the  Atlantic.* 

Fish  of  the  genera  Lamna,  Galeus,  and  Carcharodon  are  common 
to  New  Jersey  and  the  European  cretaceous  rocks.  So  also  is  the 
genus  Mosasaurus  among  reptiles.  The  vertebra  of  a  Plesiosaurus,  a 
reptile  known  in  the  English  chalk,  had  often  been  cited  on  the  au- 
thority of  Dr.  Harlan  as  occurring  in  the  cretaceous  marl,  at  Mullica 
Hill,  in  New  Jersey.  But  Dr.  Leidy  has  since  shown  that  the  bone 
in  question  is  not  saurian  but  cretaceous,  and  whether  it  can  truly  lay 
claim  to  the  high  antiquity  assigned  to  it,  is  a  point  still  open  to  dis- 
cussion. The  discovery  of  another  mammal  of  the  seal  tribe  (Steno- 
rhynchus  vetus,  Leidy),  from  a  lower  bed  in  the  cretaceous  series  in 
New  Jersey,  appears  to  rest  on  better  evidence.f 

From  New  Jersey  the  cretaceous  rocks  extend  southward  to  North 
Carolina  and  Georgia,  cropping  out  at  intervals  from  beneath  the  ter- 
tiary strata,  between  the  Appalachian  Mountains  and  the  Atlantic. 
They  then  sweep  round  the  southern  extremity  of  that  chain,  in  Ala- 
bama and  Mississippi,  and  stretch  northward  again  to  Tennessee  and 
Kentucky.  They  have  also  been  traced  far  up  the  valley  of  the  Mis- 
souri, as  far  north  as  lat.  48°,  or  to  Fort  Mandan  ;  so  that  already  the 
area  which  they  are  ascertained  to  occupy  in  North  America  may 
perhaps  equal  their  extent  in  Europe,  and  exceeds  that  of  any  other 
fossiliferous  formation  in  the  United  States.  So  little  do  they  resem- 
ble mineralogically  the  European  white  chalk,  that  in  North  America, 
limestone  is  upon  the  whole  an  exception  to  the  rule ;  and,  even  in 
Alabama,  where  I  saw  a  calcareous  member  of  this  group,  composed 
of  marl-stone,  it  was  more  like  the  English  and  French  Lias  than  any 
other  European  secondary  deposit. 


*  See  a  paper  by  the  Author,  Quart.  Journ.  Geol.  Soc.,  vol.  i.  p.  79. 

•f  In  the  Principles  of  Geology,  ninth  ed.  p.  145,  I  cited  Dr.  Leidy  of  Philadel- 
phia as  having  described  (Proceedings  of  Acad.  Nat.  Sci.  Philad.,  1851)  two  species 
of  cetacea  of  a  new  genus  which  he  called  Priscodelphimts,  from  the  greensand  of 
New  Jersey.  In  1853  I  saw  the  two  vertebrae  at  Philadelphia  on  which  this  new 
genus  was  founded,  and  afterwards,  with  the  aid  of  Mr.  Conrad,  traced  one  of  them 
to  a  Miocene  marl  pit  in  Cumberland  County,  New  Jersey.  The  other  (the  Plesio- 
saurus of  Harlan),  labelled  "  Mullica  Hill"  in  the  Museum,  would  no  doubt  be  an 
upper  cretaceous  fossil,  if  really  derived  from  that  locality,  but  its  mineral  condition 
makes  the  point  rather  doubtful.  The  tooth  of  Stenorhynchus  vetus  figured  by 
Leidy  from  a  drawing  of  Conrad's  (Proceed,  of  Acad.  Nat.  Sci.  Philad.,  1853,  p. 
377),  was  found  by  Samuel  R.  Wetherill,  Esq.,  in  the  greensand  1£  mile  southeast 
of  Burlington.  This  gentleman  related  to  me  and  Mr.  Conrad,  in  1853,  the  circum- 
stances under  which  he  met  with  it,  associated  with  Ammonites  placenta,  Ammon- 
ites Delawarensis,  Trigonia  thoracica,  &c.  The  tooth  has  been  mislaid,  but  not 
until  it  had  excited  much  interest  and  had  been  carefully  examined  by  good  zoolo- 
gists. 


340  CRETACEOUS  ROCKS.    '  [Cn.  XVII. 

At  the  base  of  the  system  in  Alabama,  I  found  dense  masses  of 
shingle,  perfectly  loose  and  unconsolidated,  derived  from  the  waste 
of  palaeozoic  (or  carboniferous)  rocks,  a  mass  in  no  way  distinguish- 
able, except  by  its  position,  from  ordinary  alluvium,  but  covered  with 
marls  abounding  in  Inocerami. 

In  Texas,  according  to  R  Homer,  the  chalk  assumes  a  new  litho- 
logical  type,  a  large  portion  of  it  consisting  of  hard  siliceous  lime- 
stone, but  the  organic  remains  leave  no  doubt  in  regard  to  its  age, 
the  Baculites  anceps  and  10  other  European  species  occurring  there. 
Fossil  plants  from  New  Jersey,  and  others,  obtained  from  the  creta- 
ceous rocks  by  Messrs.  Meek  and  Hayden  in  Nebraska,  include,  ac- 
cording to  Dr.  Newberry,  many  genera  of  dicotyledonous  angiosperms 
in  the  same  way  as  does  the  flora  of  Aix-la-Chapelle,  above  described, 
p.  335. 

In  South  America  the  cretaceous  strata  have  been  discovered  in 
Columbia,  as  at  Bogota  and  elsewhere,  containing  Ammonites,  Ha- 
mites,  Inocerami,  and  other  characteristic  shells.* 

In  the  south  of  India,  also,  at  Pondicherry,  Yerdachellum,  and 
Trinconopoly,  Messrs.  Kaye  and  Egerton  have  collected  fossils  be- 
longing to  the  cretaceous  system.  Taken  in  connection  with  those 
from  the  United  States,  they  prove,  says  Prof.  E.  Forbes,  that  those 
powerful  causes  which  stamped  a  peculiar  character  on  the  forms  of 
marine  animal  life  at  this  period,  exerted  their  full  intensity  through 
the  Indian,  European,  and  American  seas.f  Here,  as  in  North  and 
South  America,  the  cretaceous  character  can  be  recognized  even 
where  there  is  no  specific  identity  in  the  fossils  ;  and  the  same  may 
be  said  of  the  organic  type  of  those  rocks  in  Europe  and  India  which 
occur  next  to  the  chalk  in  the  ascending  and  descending  order, 
namely,  the  Eocene  and  the  Oolitic. 

*  Proceed,  of  the  Geol.  Soc.,  vol.  iv.  p.  391. 
f  See  Forbes,  Quart.  GeoL  Journ.,  vol.  i.  p.  79. 


CH.  XVIII.]  LOWER  GREENSAND. 


CHAPTER   XVIH. 

LOWER   CRETACEOUS    AND    WEALDEN   FORMATIONS. 

Lower  Greensand — Term  "Neocomian" — Atherfield  section,  Isle  of  Wight — Fos- 
sils of  Lower  Greensand — Palaeontological  relations  of  the  Upper  and  Lower  Cre- 
taceous strata — Wealden  Formation — Freshwater  strata  intercalated  between  two 
marine  groups — Weald  Clay  and  Hastings  Sand — Tunbridge  rocks — Fossil  shells, 
fish,  and  plants  of  Wealden — Their  relation  to  the  Cretaceous  type — Geographi- 
cal extent  of  Wealden — Movements  in  the  earth's  crust  to  which  the  Wealden 
owed  its  origin  and  submergence. 

THE  term  "  Lower  Greensand  "  has  hitherto  been  most  commonly 
applied  to  such  portions  of  the  Cretaceous  series  as  are  older  than 
the  Gault.  But  the  name  has  often  been  complained  of  as  incon- 
venient, and  not  without  reason,  since  green  particles  are  wanting  in 
a  large  part  of  the  strata  so  designated,  even  in  England,  and  wholly 
so  in  some  European  countries.  Moreover,  a  subdivision  of  the 
Upper  Cretaceous  group  has  likewise  been  called  Greensand,  and  to 
prevent  confusion  the  terms  Upper  and  Lower  Greensand  were  intro- 
duced. Such  a  nomenclature  naturally  leads  the  uninitiated  to  sup- 
pose that  the  two  formations  so  named  are  of  somewhat  coordinate 
value,  which  is  so  far  from  being  true,  that  the  Lower  Greensand,  in 
its  widest  acceptation,  embraces  a  series  nearly  as  important  as  the 
whole  Upper  Cretaceous  group,  from  the  Gault  to  the  Maestricht  beds 
inclusive ;  while  the  Upper  Greensand  is  but  one  subordinate  member 
of  this  same  group.  Many  eminent  geologists  have,  therefore,  pro- 
posed the  term  "  Neocomian  "  as  a  substitute  for  Lower  Greensand ; 
because,  near  Neufchatel  (Neocomum),  in  Switzerland,  these  Lower 
Greensand  strata  are  well  developed,  entering  largely  into  the  structure 
of  the  Jura  mountains.  By  the  same  geologists  the  Wealden  beds  are 
usually  classed  as  "  Lower  Neocomian,"  a  classification  which  will  not 
appear  inappropriate  when  we  have  explained,  in  the  sequel,  the  inti- 
mate relation  of  the  Lower  Greensand  and  Wealden  fossils. 

Dr.  Fitton,  to  whom  we  are  indebted  for  an  excellent  monograph 
on  the  Lower  Cretaceous  (or  Greensand)  formation  as  developed  in 
England,  gives  the  following  as  the  succession  of  rocks  seen  in  parts 
of  Kent : 

No.  1.   Sand,  white,  yellowish,  or  ferruginous,  with  concretion 

of  limestone  and  chert,        -  -  70  feet. 

2.  Sand  with  green  matter,  -  70  to  100  feet. 

3.  Calcareous  stone,  called  Kentish  rag,    -  -  60  to  80  feet. 


342  ATHERFIELD  SECTION,  ISLE  OF  WIGHT.        [CH.  XVIII. 

In  his  detailed  description  of  the  fine  section  displayed  at  Ather- 
field,  in  the  south  of  the  Isle  of  Wight,  we  find  the  limestone  wholly 
wanting ;  in  fact,  the  variations  in  the  mineral  composition  of  this 
group,  even  in  contiguous  districts,  is  very  great ;  and  on  comparing 
the  Atherfield  beds  with  corresponding  strata  at  Hythe,  in  Kent,  dis- 
tant 95  miles,  the  whole  series  presents  a  most  dissimilar  aspect.* 

On  the  other  hand,  Professor  E.  Forbes  has  shown  that  when  the 
sixty-three  strata  at  Atherfield  are  severally  examined,  the  total  thick- 
ness of  which  he  gives  as  843  feet,  there  are  some  fossils  which  range 
through  the  whole  series,  others  which  are  peculiar  to  particular 
divisions.  As  a  proof  that  all  belong  chronologically  to  one  system, 
he  states  that  whenever  similar  conditions  are  repeated  in  overlying 
strata  the  same  species  reappear.  Changes  of  depth,  or  of  the  min- 
eral nature  of  the  sea-bottom,  the  presence  or  absence  of  lime  or  of 
peroxide  of  iron,  the  occurrence  of  a  muddy,  or  a  sandy,  or  a  gravelly 
bottom,  are  marked  by  the  banishment  of  certain  species  and  the  pre- 
dominance of  others.  But  these  differences  of  conditions  being  min- 
eral, chemical,  and  local  in  their  nature,  have  nothing  to  do  with  the 
extinction,  throughout  a  large  area,  of  certain  animals  or  plants.  The 
rule  laid  down  by  this  eminent  naturalist  for  enabling  us  to  test  the 
arrival  of  a  new  state  of  things  in  the  animate  world,  is  the  repre- 
sentation by  new  and  different  species  of  corresponding  genera  of 
mollusca  or  other  beings.  When  the  forms  proper  to  loose  sand  or 
soft  clay,  or  to  a  stony  or  calcareous  bottom,  or  to  a  moderate  01 
great  depth  of  water,  recur  with  all  the  same  species,  the  interval  of 
time  has  been,  geologically  speaking,  small,  however  dense  the  mass 
of  matter  accumulated.  But  if,  the  genera  remaining  the  same,  the 
species  are  changed,  we  have  entered  upon  a  new  period ;  and  no 
similarity  of  climate,  or  of  geographical  and  local  conditions,  can 
then  recall  the  old  species  which  a  long  series  of  destructive  causes  in 
the  animate  and  inanimate  world  has  gradually  annihilated.  On  pass- 
ing from  the  Lower  Greensand  to  the  Gault,  we  suddenly  reach  one 
of  these  new  epochs,  scarcely  any  of  the  fossil  species  being  common 
to  the  lower  and  upper  cretaceous  systems,  a  break  in  the  chain  im- 
plying no  doubt  many  missing  links  in  the  series  of  geological  monu- 
ments, which  we  may  some  day  be  able  to  supply. 

One  of  the  largest  and  most  abundant  shells  in  the  lowest  strata  of 
the  Lower  Greensand,  as  displayed  in  the  Atherfield  section,  is  the 
large  Perna  Mulleti,  of  which  a  reduced  figure  is  here  given  (fig.  330). 

In  the  south  of  England,  during  the  accumulation  of  the  Lower 
Greensand  above  described,  the  bed  of  the  sea  appears  to  have  been 
continually  sinking,  from  the  commencement  of  the  period  when  the 
freshwater  Wealden  beds  were  submerged,  to  the  deposition  of  those 
strata  on  which  the  gault  immediately  reposes. 

*  Dr.  Fitton,  Quart.  Geol.  Journ.,  vol.  i.  p.  179,  ii.  p.  65,  and  iii.  p.  289,  where 
comparative  sections  and  a  valuable  table  showing  the  vertical  range  of  the  various 
fossils  of  the  Lower  Greensand  at  Atherfield  are  given. 


CH.  XVIII.] 


FOSSILS  OF  LOWER  GREENSAND. 


343 


Pebbles  of  quartzose  sandstone,  jasper,  and  flinty  slate,  together 
with  grains  of  chlorite  and  mica,  speak  plainly  of  the  nature  of  the 


Fig.  830. 


Perna  Mulleti.    Desh.  and  Leym. 
a.  Exterior.  Z>.  Part  of  hinge  of  upper  valve. 

preexisting  rocks,  from  the  wearing  down  of  which  the  Greensand 
beds  were  derived.  The  land,  consisting  of  such  rocks,  was  doubt- 
less submerged  before  the  origin  of  the  white  chalk,  a  deposit  which 
originated  in  a  more  open  sea,  and  in  clearer  waters. 

The  fossils  of  the  Lower  Cretaceous  are  for  the  most  part  specific- 
ally distinct  from  those  of  the  Upper  Cretaceous  strata. 

Among  the  former  we  often  meet  with  the  genus  Scaphites  or 
Ancyloceras  (fig.  331),  which  has  been  aptly  described  as  an  ammo- 


Fig.  331. 


Fig.  332. 


Ancyloceras  gigas,  D'Orb. 


Nautilus  plicatus,  Sow.,  in 
Fitton's  Monog. 


nite  more  or  less  uncoiled ;  also  a  furrowed  Nautilus,  JV.  plicatus 
(fig.  332),  Trigonia  caudata  (fig.  334),  likewise  found  in  the  Black- 
down  beds  (see  above,  p.  332),  and  Gervillia,  a  bivalve  genus  allied  to 


UPPER  AND  LOWER  CRETACEOUS  ROCKS.        [Cn.  XVIII. 


Avicula ;   also   the  remarkable   shell  Diceras  Lonsdalii,  eminently 
characteristic  of  the  ferruginous  beds  of  the  Lower  Greensand  in 


Fig.  888. 


Fig.  834. 


Fig.  885. 


O&rvUUa,  anceps,  Desh. 
Lower  Greensand. 


Trigonia  caudata,  Agass. 
Lower  Greensand. 


Terebratula  sella, 

Sow.    Lower 

Greensand. 


Wilts.  This  genus  is  closely  allied  to  Chama,  and  the  cast  of  the 
interior  has  been  compared  to  the  horns  of  a  goat.  The  same  shell 
has  been  referred  by  some  authors  to  Caprotina,  and  by  others  to 
JRequienia. 

Fig.  886. 


Diceras  Lonsdalii.    Lower  Greensand,  Wilts. 
a.  The  bivalve  shell.  &.  Cast  of  the  same. 

PalcBontological  relation  of  the  Upper  and  Lower  Cretaceous  Rocks. 
— Professor  Ramsay  has  deduced  from  an  analysis  of  tables  drawn  up 
by  Mr.  Etheridge  of  the  fossils  of  the  Cretaceous  series  of  Great  Britain 
the  following  conclusions  : — First,  that  a  great  number  of  species  are 
common  to  the  different  subdivisions  of  the  Upper  Cretaceous  group, 
such  as  the  Gault,  Upper  Greensand,  White  Chalk,  &c. 

Secondly,  that  there  is  a  great  break  between  the  Lower  and  Upper 
Cretaceous  series,  for  of  280  species  of  all  kinds  of  animal  remains 
known  in  the  Lower  Cretaceous,  233  are  peculiar,  and  51,  or  only 
about  18  per  cent.,  pass  from  the  Lower  Greensand  to  the  Gault  and 
overlying  strata. 

The  same  geologist  adds :  "  This  break  and  disappearance  of  so 
many  species  in  succession  is  accompanied  by  a  stratigraphical  break 
as  well ;  for  round  the  Weald  it  is  known  that  in  some  of  the  very 
few  exposures  of  junctions  the  Gault  has  been  seen  lying  on  eroded 
surfaces  of  Lower  Greensand,  while  in  the  western  and  middle  parts 
of  England,  on  the  west  and  north  of  the  great  chalk  escarpment, 
the  frequent  and  sudden  overlaps  of  the  Lower  Greensand  by  the 


CH.  XVIII.]  WEALDEN  FORMATION.  34.5 

Gault  leave  no  doubt  that  the  upper  formation  lies  actually  uncon- 
formably  on  the  lower,  and  the  time  occupied  by  the  denudation  has 
been  with  us  unrepresented  by  any  stratified  formation."  *  Yet 
while  there  is  so  much  difference  between  the  organic  remains  of  the 
Upper  and  Lower  Cretaceous  rocks,  the  Cretaceous  series,  palaeon- 
tologically  considered,  forms  an  independent  whole,  having  scarcely 
any  species  in  common  with  the  Oolitic  series  which  preceded  it,  or 
with  the  Eocene  which  followed.  Thus,  by  referring  to  the  tables 
above  mentioned,  we  observe  that  521  species  are  enumerated  as 
known  in  the  Upper  Chalk  of  England,  all  of  which,  with  the  excep- 
tion of  Terebratula  caput-serpentis,  and  a  few  Foraminifera,  had  become 
extinct  before  the  beginning  of  the  Eocene  epoch,  as  represented  by 
the  Thanet  sands. 

On  the  other  hand,  when  the  lowest  marine  strata  or  Atherfield 
beds  of  the  Cretaceous  series  are  compared  with  the  marine  forma- 
tions of  the  Upper  Oolite,  we  find  that  no  British  species  pass  from  one 
to  the  other,  and  we  know  that  this  change  in  the  organic  world  coin- 
cides in  date  with  that  enormous  lapse  of  time  during  which  the  fresh- 
water formations  of  the  Wealden  and  Purbeck,  more  than  1500  feet  in 
thickness,  were  deposited. 


WEALDEN   FORMATION. 

Beneath  the  Lower  Greensand  in  the  S.E.  of  England,  a  freshwater 
formation  is  found,  called  the  Wealdon  (see  Nos.  5  and  6,  Map,  fig. 
3  5  5,  p.  357),  which,  although  it  occupies  a  small  horizontal  area  in 
Europe,  as  compared  to  the  White  Chalk  and  Greensand,  is  neverthe- 
less of  great  geological  interest,  since  the  imbedded  remains  give  us 
some  insight  into  the  nature  of  the  terrestrial  fauna  and  flora  of  the 
Lower  Cretaceous  epoch.  The  name  of  Wealden  was  given  to  this 
group  because  it  was  first  studied  in  parts  of  Kent,  Surrey,  and  Sus- 
sex, called  the  Weald  (see  Map,  p.  357)  ;  and  we  are  indebted  to  Dr. 
Mantell  for  having  shown,  in  1822,  in  his  "  Geology  of  Sussex,"  that 
the  whole  group  was  of  fluviatile  origin.  In  proof  of  this  he  called 
attention  to  the  entire  absence  of  Ammonites,  Belemnites,  Terebratulse, 
Echinites,  Corals,  and  other  marine  fossils,  so  characteristic  of  the 
Cretaceous  rocks  above,  and  of  the  Oolitic  strata  below,  and  to  the 
presence  in  the  Weald  of  Paludinae,  Melanise,  and  various  fluviatile 
shells,  as  well  as  the  bones  of  terrestrial  reptiles  and  the  trunks  and 
leaves  of  land-plants. 

The  evidence  of  so  unexpected  a  fact  as  the  infra-position  of  a  dense 
mass  of  purely  freshwater  origin  to  a  deep-sea  deposit  (a  phenomenon 
with  which  we  have  since  become  familiar)  was  received,  at  first,  with 
no  small  doubt  and  incredulity.  But  the  relative  position  of  the  beds 

*  Ramsay,  Anniversary  Address,  Geol.  Quart.  Journ.,  vol.  xx.  p.  58, 


346 


WEALD  CLAY. 


[Cn.  XVIH. 


is  unequivocal ;  the  Weald  Clay  being  distinctly  seen  to  pass  beneath 
the  Lower  Greensand  in  various  parts  of  Surrey,  Kent,  and  Sussex, 
and  to  reappear  in  the  Isle  of  Wight  at  the  base  of  the  Cretaceous 
series,  being,  no  doubt,  continuous  far  beneath  the  surface,  as  indicated 
by  the  dotted  lines  in  the  annexed  diagram,  fig.  337. 


Sussex. 


a.  Chalk.       6.  Greensand.        c.  "Weald  Clay.       d.  Hastings  Sand.       e.  Purbeck  Beds. 

The  Wealden  is  divisible  into  two  minor  groups  : 

Greatest  known 

thickness. 

1st.  Weald  Clay — blue  and  brown  clay  and  shale,  sometimes  includ- 
ing thin  beds  of  sand  and  shelly  limestone  with  Paludina,       600  feet. 
2d.    Hastings  Sand — chiefly  arenaceous,  but  in  which  occur  some 

clays  and  calcareous  grits,*  -  -    740      " 

Another  freshwater  formation,  called  the  Purbeck,  consisting  of  vari- 
ous limestones  and  marls,  containing  distinct  species  of  molluscs,  Cyp- 
rides,  and  other  fossils,  lies  immediately  beneath  the  Wealden  in  the 
south-east  of  England.  As  it  is  now  found  to  be  more  nearly  related, 
by  its  organic  remains,  to  the  Oolitic  than  to  the  Cretaceous  Series,  it 
will  be  treated  of  in  the  twentieth  chapter. 


Weald  Clay. 

The  upper  division,  or  Weald  Clay,  is  of  purely  freshwater  origin. 
Its  highest  beds  are  not  only  conformable,  as  Dr.  Fitton  observes,  to 
the  inferior  strata  of  the  Lower  Greensand,  but  of  similar  mineral 
composition.  To  explain  this,  we  may  suppose,  that,  as  the  delta  of 
a  great  river  was  tranquilly  subsiding,  so  as  to  allow  the  sea  to  en- 
croach upon  the  space  previously  occupied  by  freshwater,  the  river 
still  continued  to  carry  down  the  same  sediment  into  the  sea.  In 
confirmation  of  this  view  it  may  be  stated,  that  the  remains  of  the 
Iguanodon  Mantelli,  a  gigantic  terrestrial  reptile,  very  characteristic 
of  the  Wealden,  has  been  discovered  near  Maidstone,  in  the  overly- 
ing Kentish  rag,  or  marine  limestone  of  the  Lower  Greensand.  Hence 
we  may  infer,  that  some  of  the  saurians  which  inhabited  the  country  of 
the  great  river  continued  to  live  when  part  of  the  country  had  become 
submerged  beneath  the  sea.  Thus,  in  our  own  times,  we  may  sup- 
pose the  bones  of  large  alligators  to  be  frequently  entombed  in  recent 

*  Dr.  Fitton,  Geol.  Trans.,  Second  Series,  vol.  iv.  p.  320. 


CH.  XVHI.] 


WEALD  CLAY. 


34:7 


freshwater  strata  in  the  delta  of  the  Ganges.  But  if  part  of  that 
delta  should  sink  down  so  as  to  be  covered  by  the  sea,  marine  forma- 
tions might  begin  to  accumulate  in  the  same  space  where  freshwater 
beds  had  previously  been  formed ;  and  yet  the  Ganges  might  still 
pour  down  its  turbid  waters  in  the  same  direction,  and  carry  seaward 
the  carcases  of  the  same  species  of  alligator,  in  which  case  their 
bones  might  be  included  in  marine  as  well  as  in  subjacent  freshwater 
strata. 

The  Iguanodon,  first  discovered  by  Dr.  Mantell,  has  left  more  of  its 
remains  in  the  Weald  en  strata  of  the  south-eastern  counties  and  Isle 
of  Wight  than  has  any  other  genus  of  associated  saurians.  It  was  an 
herbivorous  reptile,  and  regarded  by  Cuvier  as  more  extraordinary 
than  any  with  which  he  was  acquainted ;  for  the  teeth,  though  bear- 
ing a  great  analogy,  in  their  general  form  and  crenated  edges  (see  figs. 
338  a,  338  6),  to  the  modern  Iguanas  which  now  frequent  the  tropi- 

Fig.  m 


Fig.  888.    a,  Z>.  Tooth  of  Iguanodon  Mantelli. 

889.    a.  Partially  worn  tooth  of  young  individual  of  the  same. 
&.   Crown  of  tooth  in  adult,  worn  down.    (Mantell.) 

cal  woods  of  America  and  the  West  Indies,  exhibit  many  striking 
and  important  differences.  It  appears  that  they  have  often  been  worn 
by  the  process  of  mastication  ;  whereas  the  existing  herbivorous  rep- 
tiles clip  and  gnaw  off  the  vegetable  productions  on  which  they  feed, 
but  do  not  chew  them.  Their  teeth  frequently  present  an  appearance 
of  having  been  chipped  off,  but  never,  like  the  fossil  teeth  of  the  Igua- 
nodon, have  a  flat  ground  surface  (see  fig.  339  6),  resembling  the 
grinders  of  herbivorous  mammalia.  Dr.  Mantell  computes  that  the 
teeth  and  bones  of  this  species  which  passed  under  his  examination  dur- 
ing twenty  years  must  have  belonged  to  no  less  than  seventy-one  dis- 
tinct individuals,  varying  in  age  and  magnitude  from  the  reptile  just 
burst  from  the  egg,  to  one  of  which  the  femur  measured  twenty-four 


348 


FOSSILS  OF  THE 


[Cn.  XVIII. 


inches  in  circumference.  Yet,  notwithstanding  that  the  teeth  were  more 
numerous  than  any  other  bones,  it  is  remarkable  that  it  was  not  until 
the  relics  of  all  these  individuals  had  been  found,  that  a  solitary  ex- 
ample of  part  of  a  jawbone  was  obtained.  More  recently  remains 
both  of  the  upper  and  the  lower  jaw  have  been  met  with  in  the  Hast- 
ings beds  in  Tilgate  Forest.  Their  size  was  somewhat  greater  than 
had  been  anticipated,  and  Dr.  Mantell,  who  does  not  agree  with  Pro- 
fessor Owen  that  the  tail  was  short,  estimates  the  probable  length  of 
some  of  these  saurians  at  between  50  and  60  feet.  The  largest  femur 
yet  found  measures  4  feet  8  inches  in  length,  the  circumference  of 
the  shaft  being  25  inches,  and  if  measured  round  the  condyles,  42 
inches. 

Occasionally  bands  of  limestone,  called  Sussex  Marble,  occur  in  the 
Weald  Clay,  almost  entirely  composed  of  a  species  of  Paludina,  closely 
resembling  the  common  P.  vivipara  of  English  rivers. 

Shells  of  the  Cypris,  a  genus  of  Crustaceans  before  mentioned  (p. 
31)  as  abounding  in  lakes  and  ponds,  are  also  plentifully  scattered 
through  the  clays  of  the  Wealden,  sometimes  producing,  like  plates  of 
mica,  a  thin  lamination  (see  fig.  342).  Similar  cypris-bearing  marls 
are  found  in  the  lacustrine  tertiary  beds  of  Auvergne  (see  above 
p.  224). 


Fig.  340. 


Tig.  341. 


Fig.  842. 


Cypris 

spinigera, 

Fitton. 


Cypris  Valdensis,  Fitton. 
(C.  fata,  Min.  Con.  485.) 


Weald  clay  with  Cyprides. 


Hastings  Sands. 

This  lower  division  of  the  Wealden  consists  of  sand,  sandstone, 
calciferous  grit,  clay,  and  shale  ;  the  argillaceous  strata,  notwithstand- 
ing the  name,  predominating  somewhat  over  the  arenaceous,  as  will 
be  seen  by  reference  to  the  following  section,  drawn  up  by  Messrs.  Drew 
and  Foster,  of  the  Government  Survey  of  Great  Britain : 


Hastings  Sand.-1 


Names  of  Subordinate 
Formations. 

Tunbridge  Wells 
Sand, 

Wadhurst  Clay, 
Ashdown  Sand, 
Ashburnham  Beds,  - 


Mineral  Composition 
of  the  Strata. 


•j  Sandstone  and  loam, 


Thickness 
in  Feet. 


150 


Blue  and  brown  shale  and  clay 

with  a  little  calc-grit,  -        100 

j  Hard  sand  with  some  beds  of 

"j       calc-grit,        -  '  '  -        160 

j  Mottled  white  and  red  clay  with 

"j      some  sandstone,        -  -        330 


CH.  XVIII.]  WEALDEN  GROUP.  349 

The  picturesque  scenery  of  the  "  High  Rocks  "  and  other  places 
in  the  neighborhood  of  Tunbridge  is  caused  by  the  steep  natural 
cliffs,  to  which  a  hard  be  of  white  sand,  occurring  in  the  upper  part  of 
the  Tunbridge  Wells  Sand,  mentioned  in  the  preceding  table,  gives  rise. 
Mr.  Drew  found  this  bed  of  "rock-sand"  to  vary  in  thickness  from  25 
to  48  feet.  Large  masses  of  it,  which  were  by  no  means  hard  or 
capable  of  making  a  good  building-stone,  form,  nevertheless,  project- 
ing rocks  with  perpendicular  faces,  and  resist  the  degrading  action 
of  the  river  because,  says  Mr.  Drew,  they  present  a  solid  mass  with- 
out planes  of  division.*  The  calcareous  sandstone  and  grit  of  Til- 
gate  Forest  near  Cuckfield,  in  which  the  remains  of  the  Tguanodon  and 
Hylseosaurus  were  first  found  by  Dr.  Mantell,  constitute  an  upper 
member  of  the  Tunbridge  Wells  Sand,  while  the  "  sand-rock  "  of  the 
Hastings  cliffs,  about  100  feet  thick,  is  one  of  the  lower  members  of 
the  same.  The  reptiles,  which  are  very  abundant  in  this  division, 
consist  partly  of  saurians,  referred  by  Owen  and  Mantell  to  eight 
genera,  among  which,  besides  those  already  enumerated,  we  find  the 
Megalosaurus  and  Plesiosaurus.  The  Pterodactyl  also,  a  flying  rep- 
tile, is  met  with  in  the  snme  strata,  and  many  remains  of  Chelonians 
of  the  genera  Trionyx  and  fimys,  now  confined  to  tropical  regions. 

The  fishes  of  the  Wealden  are  chiefly  referable  to  the  Ganoid  and 
Placoid  orders.  Among  them  the  teeth  and  scales  of  Lepidotus  are 
most  widely  diffused  (see  fig.  343).  These  ganoids  were  allied  to  the 


Fig. 


Lepidotua  ManMU,  Agass.    Wealden. 
a.  Palate  and  teeth.  &.  Bide  view  of  teeth.  c.  Scale. 

Lepidosteus,  or  Gar-pike,  of  the  American  rivers.  The  whole  body  was 
covered  with  large  rhomboidal  scales,  very  thick,  and  having  the  ex- 
posed part  coated  with  enamel.  Most  of  the  species  of  this  genus  are 
supposed  to  have  been  either  river-fish,  or  inhabitants  of  the  sea  at  the 
mouth  of  estuaries. 

The  shells  of  the  Hastings  beds  belong  to  the  genera  Melanopsis, 
Melania,  Paludina,  Cyrena,  Cyclas,  Vnio  (see  fig.  344),  and  others, 
which  inhabit  rivers  or  lakes ;  but  one  band  has  been  found  at  Pun- 
field,  in  Dorsetshire,  indicating  a  brackish  state  of  the  water,  where 
the  genera  Corbula  (see  fig.  345),  Mytilus,  and  Ostrea  occur ;  and  in 

*  Quart.  Geol.  Journ.,  1861,  vol.  xvii.  p.  274. 


350 


WEALDEN  FOSSILS. 


[Cn.  XVIII. 


some  places  this  bed  becomes  purely  marine,  the  species  being  for  the 
most  part  peculiar,  but  several  of  them  well-known  Lower  Greensand 

Fig.  844. 


Fig.  846. 


Oorbula  alata,  Fitton.    Magnified. 
In  brackish-water  beds  of  the  Hast- 
ings Sands,  Punfield  Bay. 


Uhio  Valdenste,  Mant 

Isle  of  Wight  and  Dorsetshire ;  in  the  lower  beds 
of  the  Hastings  Sands. 

fossils,  among  which  Ammonites  Deshayesii  may  be  mentioned.  These 
facts  show  how  closely  related  were  the  faunas  of  the  Wealden  and 
Cretaceous  periods. 

At  different  heights  in  the  Hastings  Sand,  we  find  again  and  again 
slabs  of  sandstone  with  a  strong  ripple-mark,  and  between  these  slabs 
beds  of  clay  many  yards  thick.  In  some  places,  as  at  Stammerham, 
near  Horsham,  there  are  indications  of  this  clay  having  been  exposed 
so  as  to  dry  and  crack  before  the  next  layer  was  thrown  down  upon 
it.  The  open  cracks  in  the  clay  have  served  as  moulds,  of  which  casts 
have  been  taken  in  relief,  and  which  are,  therefore,  seen  on  the  lower 
surface  of  the  sandstone  (see  fig.  346). 

Fig.  846. 


Underside  of  slab  of  sandstone  about  one  yard  in  diameter. 
Stammerham,  Sussex. 

Near  the  same  place  a  reddish  sandstone  occurs  in  which  are  in- 
numerable traces  of  a  fossil  vegetable,  apparently  Sphenopteris,  the 
stems  and  branches  of  which  are  disposed  as  if  the  plants  were  stand- 


CH.  XVIU.] 


AREA  OF  THE  WEALDEN. 


351 


Fig.  347. 


Sphenopteris  gracilis  (Fitton),  from  the 

Hastings  Sands  near  Tunbridge  "Wells. 

a,  A  portion  of  the  same  magnified. 


ing  erect  on  the  spot  where  they  originally  grew,  the  sand  having  been 
gently  deposited  upon  and  around  them ;  and  similar  appearances 
have  been  remarked  in  other  places  in  this  formation.*  In  the  same 
division  also  of  the  Wealden,  at  Cuckfield,  is  a  bed  of  gravel  or  con- 
glomerate, consisting  of  water-worn  pebbles  of  quartz  and  jasper,  with 
rolled  bones  of  reptiles.  These  must  have  been  drifted  by  a  current, 
probably  in  water  of  no  great  depth. 

From  such  facts  we  may  infer  that, 
notwithstanding  the  great  thickness 
of  this  division  of  the  Wealden,  the 
whole  of  it  was  a  deposit  in  water  of 
a  moderate  depth,  and  often  extremely 
shallow.  This  idea  may  seem  start- 
ling at  first,  yet  such  would  be  the 
natural  consequence  of  a  gradual  and 
continuous  sinking  of  the  ground  in 
an  estuary  or  bay,  into  which  a  great 
river  discharged  its  turbid  waters. 
By  each  foot  of  subsidence,  the  fun- 
damental rock  would  be  depressed  one  foot  farther  from  the  surface ; 
but  the  bay  would  not  be  deepened,  if  newly  deposited  mud  and  sand 
should  raise  the  bottom  one  foot.  On  the  contrary,  such  new  strata  of 
sand  and  mud  might  be  frequently  laid  dry  at  low  water,  or  overgrown 
for  a  season  by  a  vegetation  proper  to  marshes. 

Area  of  the  Wealden. — In  regard  to  the  geographical  extent  of  the 
Wealden,  it  cannot  be  accurately  laid  down ;  because  so  much  of  it  is 
concealed  beneath  the  newer  marine  formations.  It  has  been  traced 
about  200  English  miles  from  west  to  east,  from  the  coast  of  Dorset- 
shire to  near  Boulogne,  in  France ;  and  nearly  200  miles  from  northwest 
to  southeast,  from  Surrey  and  Hampshire  to  Beauvais,  in  France.  If 
the  formation  be  continuous  throughout  this  space,  which  is  very 
doubtful,  it  does  not  follow  that  the  whole  was  contemporaneous ;  be- 
cause, in  all  likelihood,  the  physical  geography  of  the  region  under- 
went frequent  changes  throughout  the  whole  period,  and  the  estuary  may 
have  altered  its  form,  and  even  shifted  its  place.  Dr.  Dunker,  oi 
Cassel,  and  H.  von  Meyer,  in  an  excellent  monograph  on  the  Weal- 
dens  of  Hanover  and  Westphalia,  have  shown  that  they  correspond 
so  closely,  not  only  in  their  fossils,  but  also  in  their  mineral  characters, 
with  the  English  series,  that  we  can  scarcely  hesitate  to  refer  the 
whole  to  one  great  delta.  Even  then,  the  magnitude  of  the  deposit 
may  not  exceed  that  of  many  modern  rivers.  Thus,  the  delta  of  the 
Quorra  or  Niger,  in  Africa,  stretches  into  the  interior  for  more  than 
170  miles,  and  occupies,  it  is  supposed,  a  space  of  more  than  300 
miles  along  the  coast,  thus  forming  a  surface  of  more  than  25,000 


*  Mantell,  Geol.  of  S.  E.  of  England,  p.  244. 

|  Fitton,  Geol.  of  Hastings,  p.  58,  who  cites  Lander's  Travels. 


352  LOWER  CRETACEOUS  AND  WEALDEN  FLORA.      [Cn.  XVIII. 

square  miles,  or  equal  to  about  one  half  of  England.*  Besides,  we 
know  not,  in  such  cases,  how  far  the  fluviatile  sediment  and  organic 
remains  of  the  river  and  the  land  may  be  carried  out  from  the  coast, 
and  spread  over  the  bed  of  the  sea.  I  have  shown,  when  treating  of 
the  Mississippi,  that  a  more  ancient  delta,  including  species  of  shells, 
such  as  now  inhabit  Louisiana,  has  been  upraised,  and  made  to 
occupy  a  wide  geographical  area,  while  a  newer  delta  is  forming ;  * 
and  the  possibility  of  such  movements,  and  their  effects,  must  not  be 
lost  sight  of  when  we  speculate  on  the  origin  of  the  Wealden. 

If  it  be  asked  where  the  continent  was  placed  from  the  ruins  of 
which  the  Wealden  strata  was  derived,  and  by  the  drainage  of  which 
a  great  river  was  fed,  we  are  half  tempted  to  speculate  on  the  former 
existence  of  the  Atlantis  of  Plato.  The  story  of  the  submergence 
of  an  ancient  continent,  however  fabulous  in  history,  must  have  been 
true  again  and  again  as  a  geological  event. 

The  real  difficulty  consists  in  the  persistence  of  a  large  hydrographi- 
cal  basin,  from  whence  a  great  body  of  fresh  water  was  poured  into  the 
sea,  precisely  at  a  period  when  the  neighboring  area  of  the  Wealden 
was  gradually  going  downward  1000  feet  or  more  perpendicularly. 
If  the  adjoining  land  participated  in  the  movement,  how  could  it  es- 
cape being  submerged,  or  how  could  it  retain  its  size  and  altitude  so 
as  to  continue  to  be  the  source  of  such  an  inexhaustible  supply  of 
fresh  water  and  sediment?  In  answer  to  this  question,  we  are  fairly 
entitled  to  suggest  that  the  neighboring  land  may  have  been  station- 
ary, or  may  even  have  undergone  a  contemporaneous  slow  upheaval. 
There  may  have  been  an  ascending  movement  in  one  region,  and  a 
descending  one  in  a  contiguous  parallel  zone  of  country ;  just  as  the 
northern  part  of  Scandinavia  is  now  rising,  while  the  middle  portion 
(that  south  of  Stockholm)  is  unmoved,  and  the  southern  extremity  in 
Scania  is  sinking,  or  at  least  has  sunk  within  the  historical  period.f 
We  must,  nevertheless,  conclude,  if  we  adopt  the  above  hypothesis, 
that  the  depression  of  the  land  became  general  throughout  a  large  part 
of  Europe  at  the  close  of  the  Wealden  period,  and  this  subsidence 
brought  in  the  cretaceous  ocean. 

The  flora  of  the  Wealden  and  the  Lower  Greensand  is  characterized 
by  a  great  abundance  of  Coniferse,  Cycadese,  and  Ferns,  and  by  the 
absence  of  leaves  and  fruits  of  dicotyledonous  angiosperms.  The  dis- 
covery, in  1855,  in  the  Hastings  beds  of  the  Isle  of  Wight,  of 
Gyrogonites,  or  spore-vessels  of  the  Chara,  supplied  a  link  between 
the  secondary  and  tertiary  flora  which  was  previously  wanting. 

*  See  above,  p.  84 ;  and  Second  Visit  to  the  U.  S.,  vol.  ii.  chap,  xxxiv. 
f  See  the  Author's  Anniversary  Address,  Geol.  Soc.,  1850,  Quart.  Geol.  Journ. 
vol.  vi.  p.  52. 


CH.  XIX.]  INLAND   CHALK  CLIFFS  IN  NORMANDY.  353 


CHAPTER  XIX. 

DENUDATION  OF  THE  CHALK  AND  WEALDEN. 

Physical  geography  of  certain  districts  composed  of  Cretaceous  and  Wealden  strata 
— Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy — Outstanding  pillars  and 
needles  of  chalk — Denudation  of  the  chalk  and  Wealden  in  Surrey,  Kent,  and 
Sussex — Chalk  once  continuous  from  the  North  to  the  South  Downs — Anticlinal 
axis  and  parallel  ridges — Longitudinal  and  transverse  valleys — Chalk  escarp- 
ments— Rise  and  denudation  of  the  strata  gradual — Ridges  formed  by  harder, 
valleys  by  softer  beds — At  what  periods  the  Weald  Yalley  was  denuded — Why  no 
alluvium,  or  wreck  of  the  chalk,  in  the  central  district  of  the  Weald — Successive 
periods  of  marine  denudation — The  latest  of  these  posterior  to  the  Upper  Miocene 
era— Elephant-bed,  Brighton — Sangatte  Cliff — The  great  escarpments  and  trans- 
verse valleys  of  the  chalk  mainly  due  to  the  waves  and  tides  of  the  sea — Paroxys- 
mal causes  unnecessary  for  explaining  the  external  configuration  of  the  Wealden. 

ALL  the  fossiliferous  formations  may  be  studied  by  the  geologist  in 
two  distinct  points  of  view :  1st,  in  reference  to  their  position  in  the 
series,  their  mineral  character  and  fossils ;  and,  2dly,  in  regard  to 
their  physical  geography,  or  the  manner  in  which  they  now  enter,  as 
mineral  masses,  into  the  external  structure  of  the  earth ;  forming  the 
bed  of  lakes  and  seas,  or  the  surface  or  foundation  of  hills  and  valleys, 
plains  and  table-lands.  Some  account  has  already  been  given,  on  the 
first  head,  of  the  Tertiary,  the  Cretaceous,  and  the  Wealden  strata ; 
and  we  now  proceed  to  consider  certain  features  in  the  physical  geogra- 
phy of  these  groups  as  they  occur  in  parts  of  England  and  France. 

The  hills  composed  of  white  chalk  in  the  S.  E.  of  England  have  a 
smooth  rounded  outline,  and,  being  usually  in  the  state  of  sheep-pas- 
tures, are  free  from  trees  or  hedgerows  ;  so  that  we  have  an  opportu- 
nity of  observing  how  the  valleys  by  which  they  are  drained  ramify  in 
all  directions,  and  become  wider  and  deeper  as  they  descend.  Although 
these  valleys  are  now  for  the  most  part  dry,  except  during  heavy  rains 
and  the  melting  of  snow,  they  may  have  been  due  to  aqueous  denu- 
dation, having  been  excavated  when  the  chalk  emerged  gradually  from 
the  sea.  This  opinion  is  confirmed  by  the  occasional  occurrence  of 
what  appear  to  be  long  lines  of  inland  cliffs,  in  which  the  strata  are 
cut  off  abruptly  in  steep  and  often  vertical  precipices.  The  true  na- 
ture of  such  escarpments  is  nowhere  more  obvious  than  in  parts  of  Nor- 
mandy, where  the  river  Seine  and  its  tributaries  flow  through  deep  wind- 
ing valleys,  hollowed  out  of  chalk  horizontally  stratified.  Thus,  for  ex- 
ample, if  we  follow  the  Seine  for  a  distance  of  about  30  miles  from  An- 
delys  to  Elboeuf,  we  find  the  valley  flanked  on  both  sides  by  a  steep  slope 
of  chalk,  with  numerous  beds  of  flint,  the  formation  being  laid  open  for  a 
thickness  of  about  250  and  300  feet.  Above  the  chalk  is  an  overlying 
23 


354 


INLAND  CHALK-CLIFFS  IN  NORMANDY. 

Fig.  348. 


[Cn.  XIX. 


Section  across  Valley  of  Seine. 

mass  of  sand,  gravel,  and  clay,  from  30  to  100  feet  thick.  The  two  op- 
posite slopes  of  the  hills  a  and  6,  fig.  348,  where  the  chalk  appears  at 
the  surface,  are  from  2  to  4  miles  apart,  and  they  are  often  perfectly 
smooth  and  even,  like  the  steepest  of  our  downs  in  England ;  but  at 
many  points  they  are  broken  by  one,  two,  or  more  ranges  of  vertical 
and  even  overhanging  cliffs  of  bare  white  chalk  with  flints.  At  some 
points  detached  needles  and  pinnacles  stand  in  the  line  of  the  cliffs,  or 
in  front  of  them,  as  at  c,  fig.  348.  On  the  right  bank  of  the  Seine,  at 
Andelys,  one  range,  about  2  miles  long,  is  seen  varying  from  50  to  100 
feet  in  perpendicular  height,  and  having  its  continuity  broken  by  a  num- 
ber of  dry  valleys  or  coombs,  in  one  of  which  occurs  a  detached  rock  or 
needle,  called  the  Tete  d'Homme  (see  figs.  349,  350).  The  top  of  this 
rock  presents  a  precipitous  face  toward  every  point  of  the  compass ;  its 
vertical  height  being  more  than  20  feet  on  the  side  of  the  downs,  and  40 
toward  the  Seine,  the  average  diameter  of  the  pillar  being  36  feet.  Its 
composition  is  the  same  as  that  of  the  larger  cliffs  in  its  neighborhood, 
namely,  white  chalk,  having  occasionally  a  crystalline  texture  like  mar- 
ble, with  layers  of  flint  in  nodules  and  tabular  masses.  The  flinty  beds 


Fig.  349. 


View  of  the  Tete  d'Homme,  Andelys,  seen  from  above. 

often  project  in  relief  4  or  5  feet  beyond  the  white  chalk,  which  is  gen- 
erally in  a  state  of  slow  decomposition,  either  exfoliating  or  being  cov- 
ered with  white  powder,  like  the  chalk  cliffs  on  the  English  coast ;  and, 
as  in  them,  this  superficial  powder  contains  in  some  places  common  salt. 
Other  cliffs  are  situated  on  the  right  bank  of  the  Seine,  opposite  Tour- 
nedos,  between  Andelys  and  Pont  de  1'Arche,  where  the  precipices  are 


CH.  XIX.]  CLIFFS  OF  CHALK  IN  NORMANDY. 

Fig.  850. 


355 


Side  view  of  the  Tete  d'Homme.    White  chalk  with  flints. 

from  50  to  80  feet  high. :  several  of  their  summits  terminate  in  pinnacles ; 
and  one  of  them,  in  particular,  is  so  completely  detached  as  to  present  a 
perpendicular  face  50  feet  high  toward  the  sloping  down.  On  these  cliffs 
several  ledges  are  seen,  which  mark  so  many  levels  at  which  the  waves  of 
the  sea  may  be  supposed  to  have  encroached  for  a  long  period.  At  a 
still  greater  height,  immediately  above  the  top  of  this  range,  are  three 
much  smaller  cliffs,  each  about  4  feet  high,  with  as  many  intervening 
terraces,  which  are  continued  so  as  to  sweep  in  a  semicircular  form 
round  an  adjoining  coomb,  like  those  in  Sicily  before  described  (p.  76). 
If  we  then  descend  the  river  from  Vatteville  to  a  place  called  Senne- 
ville,  we  meet  with  a  singular  needle  about  50  feet  high,  perfectly  iso- 
lated on  the  escarpment  of  chalk  on  the  right  bank  of  the  Seine  (see  fig. 
351).  Another  conspicuous  range  of  inland  cliffs  is  situated  about  12 


Fig.  851. 


Fig.  852. 


Chalk  pinnacle  at  Senneville. 


Koches  d'Orival,  Elbcenf. 


miles  below  on  the  left  bank  of  the  Seine,  beginning  at  Elboeuf,  and 
comprehending  the  Roches  d'Orival  (see  fig.  352).  Like  those  before 
described,  it  has  an  irregular  surface,  often  overhanging,  and  with  beds 


356 


CLIFFS  OF  CHALK  IN  NOKMANDY. 


[CH.  XIX 


of  flint  projecting  several  feet.  Like  them,  also,  it  exhibits  a  white 
powdery  surface,  and  consists  entirely  of  horizontal  chalk  with  flints. 
It  is  40  miles  inland,  its  height,  in  some  parts,  exceeds  200  feet,  and 
its  base  is  only  a  few  feet  above  the  level  of  the  Seine.  It  is  broken,  in 
one  place,  by  a  pyramidal  mass  or  needle,  200  feet  high,  called  the 
Roche  de  Pignon,  which  stands  out  about  25  feet  in  front  of  the  upper 
portion  of  the  main  cliffs,  with  which  it  is  united  by  a  narrow  ridge 
about  40  feet  lower  than  its  summit  (see  fig.  353).  Like  the  detached 

Fig.  353. 


View  of  the  Koche  de  Pignon,  seen  from  the  south. 

rocks  before  mentioned  at  Senneville,  Vatteville,  and  Andelys,  it  may  be 
compared  to  those  needles  of  chalk  which  occur  on  the  coast  of  Nor- 
mandy* (see  fig.  354),  as  well  as  in  the  Isle  of  Wight  and  in  Purbeck. 


Needle  and  Arch  of  Etretat,  in  the  chalk  cliffs  of  Normandy. 
Height  of  Arch  100  feet    (Passy.)t 

The  foregoing -description  and  drawings  will  show,  that  the  evidence 
of  certain  escarpments  of  the  chalk  having  been  originally  sea-cliffs,  is 
far  more  full  and  satisfactory  in  France  than  in  England.  If  it  be  asked 
why,  in  the  interior  of  our  own  country,  we  meet  with  no  ranges  of 
precipices  equally  vertical  and  overhanging,  and  no  isolated  pillars  or 
needles,  we  may  reply  that  the  greater  hardness  of  the  chalk  in  Nor- 
mandy may,  no  doubt,  be  the  chief  cause  of  this  difference.  But  the 

*  An  account  of  these  cliffs  was  read  by  the  author  to  the  British  Assoa  at 
Glasgow,  Sept.  1840. 

f  Seine-Infe'rieure,  p.  142,  and  pi.  6,  fig.  1. 


GIL  XIX.]    DENUDATION  OF  THE  CHALK  AND  WEALDEN.        35? 

frequent  absence  of  all  signs  of  littoral  denudation  in  the  valley  of  the 
Seine  itself  is  a  negative  fact  of  a  far  more  striking  and  perplexing  char- 
acter. The  cliffs,  after  being  almost  continuous  for  miles,  are  then  wholly 
wanting  for  much  greater  distances,  being  replaced  by  a  green  sloping 
down,  although  the  beds  remain  of  the  same  composition,  and  are  equally 
horizontal ;  and  although  we  may  feel  assured  that  the  manner  of  the 
upheaval  of  the  land,  whether  intermittent  or  not,  must  have  been  the 
same  at  those  intermediate  points  where  no  cliffs  exist,  as  at  others  where 
they  are  so  fully  developed.  But,  in  order  to  explain  such  apparent 
anomalies,  the  reader  must  refer  again  to  the  theory  of  denudation,  as 
expounded  in  the  6th  chapter ;  where  it  was  shown,  first,  that  the  under- 
mining force  of  the  waves  and  marine  currents  varies  greatly  at  different 
parts  of  every  coast ;  secondly,  that  precipitous  rocks  have  often  decom- 
posed and  crumbled  down ;  and  thirdly,  that  terraces  and  small  clifls 
may  occasionally  lie  concealed  beneath  a  talus  of  detrital  matter. 

Denudation  of  the  Weald  Valley. — No  district  is  better  fitted  to  illus- 
trate the  manner  in  which  a  great  series  of  strata  may  have  been  up- 
heaved and  gradually  denuded  than  the  country  intervening  between  the 
North  and  South  Downs.  This  region,  of  which  a  ground-plan  is  given 
in  the  accompanying  map  (fig.  355),  comprises  within  it  the  whole  of 
Sussex,  and  parts  of  the  counties  of  Kent,  Surrey,  and  Hampshire.  The 
space  in  which  the  formations  older  than  the  White  Chalk,  or  those 
from  the  Gault  to  the  Hastings  sands  inclusive,  crop  out,  is  bounded 
everywhere  by  a  great  escarpment  of  chalk,  which  is  continued  on  the 
opposite  side  of  the  channel  in  the  Bas  Boulonnais  in  France,  where  it 
forms  the  semicircular  boundary  of  a  tract  in  which  older  strata  also  ap- 
pear at  the  surface.  The  whole  of  this  district  may  therefore  be  consid- 
ered geologically  as  one  and  the  same. 

Fig.  355. 


Jfeaefyfleatl 

ENGLISH  CHANNEL 


Geological  map  of  the  southeast  of  Endand  and  part  of  France,  exhibiting  the  denudation 
of  the  Weald. 


1.  IlBlij  Tertiary. 

2.  I 1  Chalk  and  upper  greensand. 

3.  MM»  Gault. 

4.  ^^3  Lower  Greenland. 


Weald  clay. 
Hastings  sande. 


358         DENUDATION  OF  THE  CHALK  AND  WEALDEN.    [Ca  XIX 


The  space  here  inclosed  within  the  escarpment  of  the  chalk  affords  an 
example  of  what  has  been  sometimes  called  a  "  valley  of  elevation" 
(more  properly  "  of  denudation")  ;  where  the  strata,  partially  removed  by 
aqueous  excavation,  dip  away  on  all  sides  from  a  central  axis.  Thus,  it 


ea 

co   og 

6C.2 

S  S 


CH.  XIX.]  TKANSVEKSE   VALLEYS.  359 

is  supposed,  that  the  area  now  occupied  by  the  Hastings  sand  (No.  6) 
was  once  covered  by  the  Weald  clay  (No.  5),  and  this  again  by  the 
Greensand  (No.  4),  and  this  by  the  Gault  (No.  3)  ;  and,  lastly,  that  the 
Chalk  (No.  2)  extended  originally  over  the  whole  space  between  the 
North  and  the  South  Downs.  This  theory  will  be  better  understood  by 
consulting  the  annexed  diagram  (fig.  356),  where  the  dark  lines  represent 
what  now  remains,  and  the  fainter  ones  those  portions  of  rock  which  are 
believed  to  have  been  carried  away. 

At  each  end  of  the  diagram  the  tertiary  strata  (No.  1)  are  exhibited 
reposing  on  the  chalk.  In  the  middle  are  seen  the  Hastings  sands  (No.  6.) 
forming  an  anticlinal  axis,  on  each  side  of  which  the  other  formations 
are  arranged  with  an  opposite  dip.  It  has  been  necessary,  however,  in 
order  to  give  a  clear  view  of  the  different  formations,  to  exaggerate  the 
proportional  height  of  each  in  comparison  to  its  horizontal  extent :  and  a 
true  scale  is  therefore  subjoined  in  another  diagram  (fig.  357),  in  order 
to  correct  the  erroneous  impression  which  might  otherwise  be  made  on 
the  reader's  mind.  In  this  section  the  distance  between  the  North  and 
South  Downs  is  represented  to  exceed  forty  miles ;  for  the  Valley  of  the 
Weald  is  here  intersected  in  its  longest  diameter,  in  the  direction  of  a 
line  between  Lewes  and  Maidstone. 

Through  the  central  portion,  then,  of  the  district  supposed  to  be  de- 
nuded runs  a  great  anticlinal  line,  having  a  direction  nearly  east  and 
west,  on  both  sides  of  which  the  beds  5,  4,  3,  and  2,  crop  out  in  succession. 
But,  although,  for  the  sake  of  rendering  the  physical  structure  of  this 
region  more  intelligible,  the  central  line  of  elevation  has  alone  been  in- 
troduced, as  in  the  diagrams  of  Smith,  Mantell,  Conybeare,  and  others, 
geologists  have  always  been  well  aware  that  numerous  minor  lines  of 
dislocation  and  flexure  run  parallel  to  the  great  central  axis. 

In  the  central  area  of  the  Hastings  sand  the  strata  have  undergone  the 
greatest  displacement ;  one  fault  being  known,  where  the  vertical  shift  of 
a  bed  of  calcareous  grit  is  no  less  than  60  fathoms.*  Much  of  the  pic- 
turesque scenery  of  this  district  arises  from  the  depth  of  the  narrow  valleys 
and  ridges  to  which  the  sharp  bends  and  fractures  of  the  strata  have 
given  rise ;  but  it  is  also  in  part  to  be  attributed  to  the  excavating  power 
exerted  by  water,  especially  on  the  interstratified  argillaceous  beds. 

Besides  the  series  of  longitudinal  valleys  and  ridges  in  the  Weald, 
there  are  valleys  which  run  in  a  transverse  direction,  passing  through  the 
chalk  to  the  basin  of  the  Thames  on  the  one  side,  and  to  the  English 
Channel  on  the  other.  In  this  manner  the  chain  of  the  North  Downs  is 
broken  by  the  rivers  Wey,  Mole,  Darent,  Medway,  and  Stour ;  the  South 
Downs  by  the  Arun,  Adur,  Ouse,  and  Cuckmere.f  If  these  transverse 
hollows  could  be  filled  up,  all  the  rivers,  observes  Dr.  Conybeare,  would 
be  forced  to  take  an  easterly  course,  and  to  empty  themselves  into  the 
sea  by  Romney  Marsh  and  Pevensey  Levels.]; 

*  .Fitton,  Geol.  of  Hastings,  p.  65.         f  Conybeare,  Outlines  of  GeoL  p.  81. 


360 


CHALK  ESCAKPMENTS. 


[On. 


Mr.  Martin  has  suggested  that  the  great  cross  fractures  of  the  chalk, 
which  have  become  river  channels,  have  a  remarkable  correspondence 
on  each  side  of  the  valley  of  the  Weald  ;  in  several  instances  the  gorges 
in  the  North  and  South  Downs  appearing  to  be  directly  opposed  to  each 
other.  Thus,  for  example,  the  defiles  of  the  Wey  in  the  North  Downs, 
and  of  the  Arun  in  the  South,  seemed  to  coincide  in  direction  ;  and  in 

like  manner,  the  Ouse  corre- 
sponds to  the  Darent,  and  the 
Cuckmere  to  the  Medway.* 

Although  these  coincidences 
may,  perhaps,  be  accidental,  it 
is  by  no  means  improbable,  as 
hinted  by  the  author  above 
mentioned,  that  great  amount 
of  elevation  towards  the  centre 
of  the  Weald  district  gave  rise 
to  transverse  fissures.  And  as 
the  longitudinal  valleys  were 
connected  with  that  linear  move- 
ment which  caused  the  anti- 
clinal lines  running  east  and 
west,  so  the  cross  fissures  migh 
have  been  occasioned  by  the 
intensity  of  the  upheaving  force 
towards  the  centre  of  the  line. 

But  before  treating  of  the 
manner  in  which  the  upheaving 
movement  may  have  acted,  T 
shall  endeavor  to  make  the 
reader  more  intimately  acquaint- 
ed with  the  leading  geographi- 
cal features  of  the  district,  so 
far  as  they  are  of  geological  in- 
terest. 

In  whatever  direction  we  travel 
from  the  tertiary  strata  of  the 
basins  of  London  and  Hamp- 
I  -g  shire  towards  the  valley  of  the 
Weald,  we  first  ascend  a  slope 
of  white  chalk,  with  flints,  and 
then  find  ourselves  on  the  sum- 
mit of  a  declivity  consisting,  for 
the  most  part,  of  different  mem- 
bers of  the  chalk  formation ; 
below  which  the  upper  green- 


Geol.  of  Western  Sussex,  p.  61. 


CH.  XIX.] 


TKANSVEKSE   VALLEYS. 


361 


sand,  and  sometimes,  also,  the  gault,  crop  out.  This  steep  declivity, 
is  the  great  escarpment  of  the  chalk  before  mentioned,  which  overhangs 
a  valley  excavated  chiefly  out  of  the  argillaceous  or  marly  bed,  termed 
Gault  (No.  3).  The  escarpment  is  continuous  along  the  southern  ter- 
mination of  the  North  Downs,  and  may  be  traced  from  the  sea,  at 
Folkestone,  westward  to  Guildford  and  the  neighborhood  of  Petersfield, 
and  from  thence  to  the  termination  of  the  South  Downs  at  Beachy 
Head.  In  this  precipice  or  steep  slope  the  strata  are  cut  off  abruptly, 
and  it  is  evident  that  they  must  originally  have  extended  farther.  In 
the  wood-cut  (fig.  358,  p.  360),  part  of  the  escarpment  of  the  South 
Downs  is  faithfully  represented,  where  the  denudation  at  the  base  of 
the  declivity  has  been  somewhat  more  extensive  than  usual,  in  conse- 
quence of  the  upper  and  lower  greensand  being  formed  of  very  inco- 
herent materials,  the  former,  indeed,  being  extremely  thin  and  almost 
wanting. 

The  geologist  cannot  fail  to  recognize  in  this  view  the  exact  likeness 
of  a  sea-cliff ;  and  if  he  turns  and  looks  in  an  opposite  direction,  or 
eastward,  towards  Beachy  Head  (see  fig.  359),  he  will  see  the  same  line 


Fig.  359. 


Chalk  escarpment,  as  seen  ft-om  the  hill  above  Steyning,  Sussex.    The  castle  and  village 
of  Bramber  in  the  foreground. 

of  heights  prolonged.  Even  those  who  are  not  accustomed  to  specu- 
late on  the  former  changes  which  the  surface  has  undergone  may  fancy 
the  broad  and  level  plain  to  resemble  the  flat  sands  which  were  laid  dry 
by  the  receding  tide,  and  the  different  projecting  masses  of  chalk  to  be 
the  headlands  of  a  coast  which  separated  the  different  bays  from  each 
other. 

Occasionally  in  the  North  Downs  sand-pipes  are  intersected  in  the 
slope  of  the  escarpment,  and  have  been  regarded  by  some  geologists 
as  more  modern  than  the  slope ;  in  which  case  they  might  afford  an 
argument  against  the  theory  of  these  slopes  having  originated  as  sea- 
cliffs  or  river-cliffs.  But  when  we  observe  the  great  depth  of  many 
sand-pipes,  those  near  Sevenoaks,  for  example,  we  perceive  that  the 
lower  termination  of  such  pipes  must  sometimes  appear  at  the  sur- 
face far  from'  the  summit  of  an  escarpment,  whenever  portions  of  the 
chalk  are  cut  away. 

In  regard  to  the  transverse  valleys  before  mentioned,  as  intersecting 
the  chalk  hills,  some  idea  of  them  may  be  derived  from  the  subjoined 


TRANSVERSE   VALLEYS. 


[OH.  XIX. 


sketch  (fig.  360)  of  the  gorge  of  the  River  Adur,  taken  from  the  sum- 
mit of  the  chalk-downs,  at  a  point  in  the  bridle-way  leading  from  the 
towns  of  Bramber  and  Steyning  to  Shorehain.  If  the  reader  will  refer 
again  to  the  view  given  in  a  former  woodcut  (fig.  358,  p.  360),  he 
will  there  see  the  exact  point  where  the  gorge  of  which  I  am  now 
speaking  interrupts  the  chalk  escarpment.  A  projecting  hill,  at  the 
point  a,  hides  the  town  of  Steyning,  near  which  the  valley  commences 

where  the  Adur  passes  directly 
to  the  sea  at  Old  Shoreham.  The 
river  flows  through  a  nearly  level 
plain,  as  do  most  of  the  others 
which  intersect  the  hills  of  Surrey, 
Kent,  and  Sussex ;  and  it  is  evi- 
dent that  these  openings  could 
not  have  been  produced  by  rivers, 
except  under  conditions  of  physi- 
cal geography  entirely  different 
from  those  now  prevailing.  In- 
deed, many  of  the  existing  rivers, 
like  the  Ouse  near  Lewes,  have 
filled  up  arms  of  the  sea,  instead 
of  deepening  the  hollows  which 
they  traverse. 

That  the  place  of  some,  if  not 
of  all,  the  gorges  running  north 
and  south,  has  been  originally  de- 
termined by  the  fracture  and  dis- 
placement of  the  rocks,  seems  the 
more  probable,  when  we  reflect  on 
the  proofs  obtained  of  a  ravine 
running  east  and  west,  which 
branches  off  from  the  eastern  side 
of  the  valley  of  the  Ouse  just 
mentioned,  and  which  is  undoubt- 
edly due  to  dislocation.  This  ra- 
vine is  called  "  the  Coomb"  (fig. 
361),  and  is  situated  in  the  sub- 
urbs of  the  town  of  Lewes.  It 
was  first  traced  out  by  Dr.  Man- 
tell,  in  whose  company  I  exam- 
ined it.  The  steep  declivities  on 
each  side  are  covered  with  green 
turf,  as  is  the  bottom,  which  is 
perfectly  dry.  No  outward  signs 
of  disturbance  are  visible ;  and 
the  connection  of  the  hollow  with 
subterranean  movements  would 


3 

II 


XIX.] 


COOMB  NEAR  LEWES. 


363 


not  have  been  suspected  by  the  geologist,  had  not  the  evidence  of  great 
convulsions  been  clearly  exposed  in  the  escarpment  of  the  valley  of  the 


Fig.  861. 


The  Coomb,  near  Lew< 


Ouse,  and  the  numerous  chalk-pits  worked  at  the  termination  of  the 
Coomb.  By  the  aid  of  these  we  discover  that  the  ravine  coincides  pre- 
cisely with  a  line  of  fault,  on  one  side  of  which  the  chalk  with  flints  (a, 
fig.  362)  appears  at  the  summit  of  the  hill,  while  it  is  thrown  down  to 
the  bottom  on  the  other. 


Fault  coinciding  with  the  Coomb,  in  the  Cliff-hill  near  Lewes.    Mantell. 
a.  Chalk  with  flints.  &.  Lower  chalk. 


In  order  to  account  for  the  manner  in  which  the  five  groups  of  strata, 
2,  3,  4,  5,  6,  represented  in  the  map,  fig.  355,  and  in  the  section,  fig.  356, 
may- have  been  brought  into  their  present  position,  the  following  hypoth- 
esis has  been  suggested  : — Suppose  the  five  formations  to  lie  in  horizontal 
stratification  at  the  bottom  of  the  sea ;  then  let  a  movement  from  below 
press  them  upwards  into  the  form  of  a  flattened  dome,  and  let  the  crown 
of  this  dome  be  afterwards  cut  off,  so  that  the  incision  should  penetrate  to 
:he  lowest  of  the  five  groups.  The  different  beds  would  then  be  exposed 
on  the  surface,  in  the  manner  exhibited  in  the  map,  fig.  355.* 

*  See  illustrations  of  this  theory,  by  Dr.  Fitton,  Geol.  Sketch  of  Hastings. 


364:  PROMINENCE   OF  HARDER  STRATA.  [On.  XIX 

The  quantity  of  denudation,  or  removal  by  water,  of  stratified  masses 
assumed  to  have  once  reached  continuously  from  the  North  to  the  South 
Downs  is  so  enormous,  that  the  reader  may  at  first  be  startled  by  the 
boldness  of  the  hypothesis.  But  the  difficulty  will  disappear  when  once 
sufficient  time  is  allowed  for  the  gradual  rising  and  sinking  of  the 
strata  at  many  successive  geological  periods,  during  which  the  waves 
and  currents  of  the  ocean,  and  the  power  of  rain,  rivers,  and  land-floods, 
might  slowly  accomplish  operations  which  no  sudden  diluvial  rush  of 
waters  could  possibly  effect. 

Among  other  proofs  of  the  action  of  water,  it  may  be  stated  that  the 
great  longitudinal  valleys  follow  the  outcrop  of  the  softer  and  more 
incoherent  beds,  while  ridges  or  lines  of  cliff  usually  occur  at  those 
points  where  the  strata  are  composed  of  harder  stone.  Thus,  for  ex- 
ample, the  chalk  with  flints,  together  with  the  subjacent  upper  green- 
sand,  which  is  often  used  for  building,  under  the  provincial  name 
of  "  firestone,"  have  been  cut  into  a  steep  cliff  on  that  side  on  which 
the  sea  encroached.  This  escarpment  bounds  a  deep  valley,  exca- 
vated chiefly  out  of  the  soft  argillaceous  bed,  termed  gault  (No.  3, 
map,  p.  35*7).  In  some  places  the  upper  greensand  is  in  a  loose 
and  incoherent  state,  and  there  it  has  been  as  much  denuded  as 
the  gault ;  as,  for  example,  near  Beachy  Head  ;  but  farther  to  the 
westward  it  is  of  great  thickness,  and  contains  hard  beds  of  blue 
chert  and  calcareous  sandstone  or  firestone.  Here,  accordingly,  we 
find  that  it  produces  a  corresponding  influence  on  the  scenery  of  the 
country;  for  it  runs  out  like  a  step  beyond  the  foot  of  the  chalk 
hills,  and  constitutes  a  lower  terrace,  varying  in  breadth  from  a  quar 
ter  of  a  mile  to  three  miles,  and  following  the  sinuosities  of  the  chalk 
escarpment.* 

Fig.  363. 


a.  Chalk  with  flints.  5.  Chalk  without  flints, 

c.  Upper  greensand,  or  flrestone.  d.  Gault 

It  is  impossible  to  desire  a  more  satisfactory  proof  that  the  escarp- 
ment is  due  to  the  excavating  power  of  water  during  the  rise  of  the 
strata,  or  during  their  rising  and  sinking  at  successive  periods ;  for 
I  have  shown,  in  my  account  of  the  coast  of  Sicily  (p.  76),  in  what 
manner  the  encroachments  of  the  sea  tend  to  efface  that  succession 
of  terraces  which  must  otherwise  result  from  the  intermittent  up- 
heaval of  a  coast  preyed  upon  by  the  waves.  During  the  inter- 

*  Sir  R.  Murchison,  Geol.  Sketch  of  Sussex,  Ac.,  Geol.  Trans.,  Second  Series, 
vol.  ii.  p.  93. 


CH.  XIX.]  DENUDATION  OF  THE  WEALD. 

val  between  two  elevatory  movements,  the  lower  terrace  will  usually  be 
destroyed,  wherever  it  is  composed  of  incoherent  materials  ;  whereas 
the  sea  will  not  have  time  entirely  to  sweep  away  another  part  of  the 
same  terrace,  or  lower  platform,  which  happens  to  be  composed  of 
rocks  of  a  harder  texture,  and  capable  of  offering  a  firmer  resistance  to 
the  erosive  action  of  water.  As  the  yielding  clay  termed  gault  would 
be  readily  washed  away,  we  find  its  outcrop  marked  everywhere  by  a 
valley  which  skirts  the  base  of  the  chalk-hills,  and  which  is  usually 
bounded  on  the  opposite  side  by  the  lower  greensand ;  but  as  the 
upper  beds  of  this  last  formation  are  most  commonly  loose  and  inco- 
herent, they  also  have  usually  disappeared  and  increased  the  breadth 
of  the  valley.  In  those  districts,  however,  where  chert,  limestone, 
and  other  solid  materials  enter  largely  into  the  composition  of  this 
formation  (No.  4,  map,  p.  357),  they  give  rise  to  a  range  of  hills 
parallel  to  the  chalk,  which  sometimes  rival  the  escarpment  of  the 
chalk  itself  in  height,  or  even  surpass  it,  as  in  Leith  Hill,  near  Dork- 
ing. This  ridge  often  presents  a  steep  escarpment  toward  the 
soft  argillaceous  deposit  called  the  Weald  clay  (as  above,  No.  5, 
fig.  356,  p.  358),  which  usually  forms  a  broad  valley,  separating  the 
lower  greensand  from  the  Hastings  sands  or  Forest  Ridge  ;  but  where 
subordinate  beds  of  sandstone  of  a  firmer  texture  occur,  the  uniform- 
ity of  the  plain  of  No.  5  is  broken  by  waving  irregularities  and 
hillocks. 

Pluvial  action. — In  considering,  however,  the  comparative  destruc- 
tibility  of  the  harder  and  softer  rocks,  we  must  not  underrate  the 
power  of  rain.  The  chalk-downs,  even  on  their  summits,  are  usually 
covered  with  unrounded  chalk-flints,  such  as  might  remain  after  mass- 
es of  white  chalk  had  been  softened  and  removed  by  water.  This 
superficial  accumulation  of  the  hard  or  siliceous  materials  of  dis- 
integrated strata  may  be  due  in  no  small  degree  to  pluvial  action;  for 
during  extraordinary  rains  a  rush  of  water  charged  with  calcareous 
matter,  of  a  milk-white  color,  may  be  seen  to  descend  even  gently 
sloping  hills  of  chalk.  If  a  layer  no  thicker  than  the  tenth  of  an  inch 
be  removed  once  in  a  century,  a  considerable  mass  may  in  the  course 
of  indefinite  ages  melt  away,  leaving  nothing  save  a  stratum  of  flinty 
nodules  to  attest  its  former  existence.  A  bed  of  fine  clay  some- 
times covers  the  surface  of  slight  depressions  in  the  white  chalk, 
which  may  represent  the  aluminous  residue  of  the  jock,  after  the 
pure  carbonate  of  lime  has  been  dissolved  by  rain-water,  charged  with 
excess  of  carbonic  acid  derived  from  decayed  vegetable  matter.  The 
acidulous  waters  sometimes  descend  through  "  sand-pipes  "  and  "  swal- 
low-holes "  in  the  chalk,  so  that  the  surface  may  be  undermined,  and 
cavities  may  be  formed  or  enlarged,  even  by  that  part  of  the  drainage 
which  is  subterranean.* 

*  See  above,  p.  82,  83,  "  Sand-pipes  in  Chalk ;"  and  Prestwich,  Geol.  Quart. 
Journ.,  vol.  x.  p.  222. 


366  THEORY  OF  FRACTURE  AND  UPHEAVAL.          |_CH- 

Lines  of  Fracture. — Mr.  Martin,  in  his  work  on  the  geology  of  West- 
ern Sussex,  published  in  1828,  threw  much  light  on  the  structure  of 
the  Wealden  by  tracing  out  continuously  for  miles  the  direction  of 
many  anticlinal  lines  and  cross  fractures ;  and  the  same  course  of 
investigation  has  since  been  followed  out  in  greater  detail  by  Mr. 
Hopkins.  The  geologist  and  mathematician  last  mentioned  has  shown 
that  the  observed  direction  of  the  lines  of  flexure  and  dislocation  in 
the  Weald  district  coincide  with  those  which  might  have  been  antici- 
pated theoretically  on  mechanical  principles,  if  we  assume  certain  sim- 
ple conditions  under  which  the  strata  were  lifted  up  by  an  expansive 
subterranean  force.* 

His  opinion,  that  both  the  longitudinal  and  transverse  lines  of  frac- 
ture may  have  been  produced  simultaneously,  accords  well  with  that 
expressed  by  M.  Thurmann,  in  his  work  on  the  anticlinal  ridges  and 
valleys  of  elevation  of  the  Bernese  Jura.f  For  the  accuracy  of  the 
map  and  sections  of  the  Swiss  geologist  I  can  vouch,  from  personal 
examination,  in  1835,  of  part  of  the  region  surveyed  by  him.  Among 
other  results  at  which  he  arrived,  it  appears  that  the  breadth  of  the 
anticlinal  ridges  and  dome-shaped  masses  in  the  Jura  is  invariably 
great  in  proportion  to  the  number  of  the  formations  exposed  to  view ; 
or,  in  other  words,  to  the  depth  to  which  the  superimposed  groups  of 
secondary  strata  have  been  laid  open.  (See  fig.  71,  p.  55,  for  structure 
of  Jura.)  He  also  remarks,  that  the  anticlinal  lines  are  occasionally 
oblique  and  cross  each  other,  in  which  case  the  greatest  dislocation  of 
the  beds  takes  place.  Some  of  the  cross  fractures  are  imagined  by  him 
to  have  been  contemporaneous  with  others  subsequent  to  the  longi- 
tudinal ones. 

I  have  assumed,  in  the  former  part  of  this  chapter,  that  the  rise  of 
the  Weald  was  gradual,  whereas  many  geologists  have  attributed  its 
elevation  to  a  single  effort  of  subterranean  violence.  There  appears 
to  them  such  a  unity  of  effect  in  this  and  other  lines  of  deranged 
strata  in  the  southeast  of  England,  such  as  that  of  the  Isle  of  Wight, 
as  is  inconsistent  with  the  supposition  of  a  great  number  of  separate 
movements  recurring  after  lotig  intervals  of  time.  But  we  know  that 
earthquakes  are  repeated  throughout  a  long  series  of  ages  in  the  same 
spots,  like  volcanic  eruptions.  The  oldest  lavas  of  Etna  were  poured 
out  many  thousands,  perhaps  myriads  of  years  before  the  newest,  and 
yet  they,  and  the  movements  accompanying  their  emission,  have  pro- 
duced a  symmetrical  mountain ;  and  if  rivers  of  melted  matter  thus 
continue  to  flow  upwards  in  the  same  direction,  and  towards  the  same 
point,  for  an  indefinite  lapse  of  ages,  what  difficulty  is  there  in  con- 
ceiving that  the  subterranean  volcanic  force,  occasioning  the  rise  or  fall 
of  certain  parts  of  the  earth's  crust,  may,  by  reiterated  movements, 
produce  the  most  perfect  unity  of  result  ? 

*  GeoL  Soc.  Proceed.  No.  74,  p.  363,  1841,  and  G.  S.  Trans.,  2d  Series,  vol.  vii. 
•}  Soulevemens  Jurassiques.     1832. 


CH.  XIX.]     PERIODS  OF  DENUDATION  IN  THE   WEALD.  367 

At  what  periods  the  Weald  valley  was  denuded. —  We  may  next 
inquire  at  what  time  the  denudation  of  the  Weald  was  effected,  and 
we  shall  find,  on  considering  all  the  facts  brought  to  light  by  recent 
investigation,  that  it  was  accomplished  in  the  course  of  so  long  a 
series  of  ages,  that  the  greatest  revolutions  in  the  physical  geography 
of  the  globe,  yet  known  to  us,  have  taken  place  within  the  same 
lapse  of  time.  It  has  now  been  ascertained,  that  part  of  the  denu- 
dation of  the  Weald  was  completed  before  the  British  Eocene  strata, 
and  consequently  before  the  nummulitic  rocks  of  Europe  and  Asia  were 
formed.  The  date,  therefore,  of  part  of  the  changes  now  under  contem- 
plation was  long  antecedent  to  the  existence  of  the  Alps,  Pyrenees,  and 
many  other  European  and  Asiatic  mountain-chains,  and  even  to  the 
accumulation  of  large  portions  of  their  component  materials  beneath 
the  sea. 

M.  Elie  de  Beaumont  suggested,  in  1833,  that  there  was  an  island 
in  the  Eocene  sea  in  the  area  now  occupied  by  the  French  and 
English  Wealden  strata,  and  he  gave  a  map  or  hypothetical  restora- 
tion of  the  ancient  geography  of  that  region  at  the  era  alluded  to.* 
Mr.  Prestwich  has  since  shown  that  the  materials  of  which  the  lower 
tertiary  beds  of  England  are  made  up,  and  their  manner  of  resting 
on  the  chalk,  imply,  that  such  an  island,  or  several  islands  and  shoals, 
composed  of  Chalk,  Upper  Greensand,  Gault,  and  probably  of  some 
of  the  Lower  Cretaceous  rocks,  did  exist  somewhere  between  the  present, 
North  and  South  Downs.  The  undermined  cliffs  and  shores  of  those 
lands  supplied  the  flints,  which  the  action  of  the  waves  rounded  into 
pebbles,  such  as  now  form  the  Woolwich  and  Blackheath  shingle- 
beds  below  the  London  Clay.  It  is  supposed,  that  the  land  referred 
to  was  drained  by  rivers  flowing  into  the  Eocene  sea,  and  whence 
the  brackish  and  freshwater  deposits  of  Woolwich  and  other  contem- 
poraneous strataf  were  derived.  The  large  size  of  some  of  the  rolled 
flints  (eight  inches  and  upwards  in  diameter)  of  the  Blackheath  shingle 
demonstrates  the  proximity  of  land.  Such  heavy  masses  could  not 
have  been  transported  from  great  distances,  whether  they  owe  their 
shape  to  waves  breaking  on  a  sea-beach,  or  to  rivers  descending  a  steep 
slope.  # =..- 

In  the  annexed  diagram  (fig.  364)  Mr.  Prestwich  has  represented 
a  section  from  near  Saffron  Walden,  in  Essex,  to  the  Weald,  passing 
north  and  south  through  Godstone,  in  which  we  see  how  the  chalk, 
c,  had  been  disturbed  and  denuded  before  the  lower  Eocene  beds,  ft, 
were  deposited.  Some  small  patches  of  the  last-mentioned  beds,  &', 
consisting  of  clay  and  sand,  extend  occasionally,  as  in  this  instance, 
to  the  very  edge  of  the  escarpment  of  the  North  Downs,  proving  that 
the  surface  of  the  white  chalk,  now  covered  with  tertiary  strata,  is 
the  same  which  originally  constituted  the  bottom  of  the  Eocene  sea. 

*  M4m.  de  la  Soc.  G6ol.  de  France,  vol.  i.  part  i.  p.  Ill,  pL  7,  fig.  8. 
f  See  p.  296,  above. 


ISLANDS  IN  THE  EOCENE   SEA. 
Fig.  864. 


[On.  XIX. 


Section  showing  that  the  Weald  had  heen  denuded  of  chalk  before  the  Lower  Eocene  strata  were 

deposited. 

8.  Eelative  position  of  Saffron  Walden. 

G.  Chalk-escarpment  above  Godstone,  surmounted  by  a  patch  of  the  Lower  Tertiary  beds,  &'. 
a.  London  Clay.  6,  &'.  Lower  Tertiaries.  c.  Chalk. 

d.  Upper  Greensand.          e.  Gault.  /  Lower  Greensand  and  Wealden. 

as.  Point  at  which  the  present  upper  and  under  surfaces  of  the  chalk,  if  they  were  prolonged 
would  converge. 

It  is  therefore  inferred,  that,  if  we  prolong  southwards  the  upper  and 
under  surfaces  of  the  chalk,  along  the  dotted  line  in  the  above  section, 
they  would  converge  at  the  point  x ;  therefore,  beyond  that  point,  no 
white  chalk  existed  at  the  time  when  the  Eocene  beds,  6,  bf,  were  formed. 
In  other  words,  the  central  parts  of  the  Wealden,  south  of  x,  were  already 
bared  of  their  original  covering  of  chalk,  or  had  only  some  slight  patches 
of  that  rock  scattered  over  them. 

The  island,  or  islands,  in  the  Eocene  sea  may  be  represented  in  the 
annexed  diagram  (fig.  365) ;  but  doubtless  the  denudation  extended 


Fig.  865. 


Sea. 


<L 


Island  in  the  Eocene  Sea. 
a.  Chalk,  Upper  Greensand,  and  Gault.  &.  Lower  Greensand. 


c.  Wealden. 


farther  in  width  and  depth  before  the  close  of  the  Eocene  period,  and  the 
waves  may  have  cut  into  the  Lower  Greensand,  and  perhaps  in  some 
places  into  the  Wealden  strata. 

According  to  this  view  the  mass  of  cretaceous  and  subcretaceous  rocks, 
planed  off  by  the  waves  and  currents  in  the  area  between  the  North  and 
South  Downs  before  the  origin  of  the  oldest  Eocene  beds,  may  have  been 
as  voluminous  as  the  mass  removed  by  denudation  since  the  commence- 
ment of  the  Eocene  era. 

But  the  reader  may  ask,  why  is  it  necessary  to  assume  that  so  much 
white  chalk  first  extended  continuously  over  the  Wealden  beds  in  this 
part  of  England,  and  was  then  removed  ?  May  we  not  suppose  that  land 
began  to  exist  between  the  North  and  South  Downs  at  a  much  earlier 
epoch  ;  and  that  the  upper  Wealden  beds  rose  in  the  midst  of  the  Creta- 
ceous Ocean,  so  as  to  check  the  accumulation  of  white  chalk,  and  limit  it 
to  the  deeper  water  of  adjoining  areas  ?  This  hypothesis  has  often  been 
advanced,  and  as  often  rejected ;  for,  had  there  been  shoals  or  dry  land 


CH.  XIX.]  WEALD,   WHEN  DENUDED.  369 

BO  near,  the  white  chalk  would  not  have  remained  unsoiled,  or  without 
intermixture  of  mud  and  sand  ;  nor  would  organic  remains  of  terrestrial, 
fluviatile,  or  littoral  origin  have  been  so  entirely  wanting  in  the  strata  of 
the  North  and  South  Downs,  where  the  chalk  terminates  abruptly  in  the 
escarpments.  It  is  admitted  that  the  fossils  now  found  there  belong  ex- 
clusively to  classes  which  inhabit  a  deep  sea.  Moreover,  the  uppermost 
beds  of  the  Wealden  group,  as  Mr.  Prestwich  has  remarked,  would  not 
have  been  so  strictly  conformable  with  the  lowest  beds  of  the  Lower 
Greensand  had  the  strata  of  the  Wealden  undergone  upheaval  before  the 
deposition  of  the  incumbent  cretaceous  series. 

But,  although  we  must  assume  that  the  white  chalk  was  once  contin- 
uous, over  what  is  now  the  Weald,  it  by  no  means  follows  that  the  first 
denudation  was  subsequent  to  the  entire  Cretaceous  era.  Most  probably 
it  commenced  before  a  large  portion  of  the  Maestricbt  beds  were  formed, 
or  while  they  were  in  progress.  I  have  already  stated  (p.  316,  above), 
that  in  parts  of  Belgium  I  observed  rolled  pebbles  of  chalk-flints  very 
abundant  in  the  lowest  Maestricht  beds,  where  these  last  overlie  the  white 
chalk,  showing  at  how  early  a  date  the  chalk  was  upraised  from  deep 
water  and  exposed  to  aqueous  abrasion. 

Guided  by  the  amount  of  change  in  organic  life,  we  may  estimate  the 
interval  between  the  Maestricht  beds  and  the  Thanet  Sands  to  have  been 
nearly  equal  in  duration  to  the  time  which  elapsed  between  the  depo- 
sition of  those  same  Thanet  Sands  and  the  Glacial  period.  If  so,  it 
would  be  idle  to  expect  to  be  able  to  make  ideal  restorations  of  the  innu- 
merable phases  in  physical  geography  through  which  the  southeast  of 
England  must  have  passed  since  the  Weald  began  to  be  denuded.  In 
less  than  half  the  same  lapse  of  time  the  aspect  of  the  whole  European 
area  has  been  more  than  once  entirely  changed.  Nevertheless,  it  may  be 
useful  to  enumerate  some  of  the  known  fluctuations  in  the  physical  con- 
formation of  the  Weald  and  the  regions  immediately  adjacent  during  the 
period  alluded  to. 

First,  we  have  to  carry  back  our  thoughts  to  those  very  remote  move- 
ments which  first  brought  up  the  white  chalk  from  a  deep  sea  into 
exposed  situations  where  the  waves  could  plane  off  certain  portions,  as 
expressed  in  diagram  (fig.  364),  before  the  British  Lower  Eocene  beds 
originated. 

Secondly,  we  have  to  take  into  account  the  gradual  wear  and  tear  of 
the  chalk  and  its  flints,  to  which  the  Thanet  sands  bear  witness,  as  well  as 
the  subsequent  Woolwich  and  Blackheath  shingle-beds,  occasionally  50 
feet  thick,  and  composed  of  rolled  flint-pebbles. 

Thirdly,  at  a  later  period  a  great  subsidence  took  place,  by  which  the 
shallow-water  and  freshwater  beds  of  Woolwich  and  other  Lower  Eocene 
deposits  were  depressed  (see  above,  p.  296)  so  as  to  allow  the  London 
Clay  and  Bagshot  series,  of  deep-sea  origin,  to  accumulate  over  them. 
The  amount  of  this  subsidence,  according  to  Mr.  Prestwich,  exceeded  800 
feet  in  the  London,  and  1800  feet  in  the  Hampshire  or  Isle  of  Wight 
basin ;  and  if  so,  the  intervening  area  of  the  Weald  could  scarcely  fail  to 
24 


370  PERIODS  OF  WEALD  DENUDATION.  [On.  XIX. 

share  in  the  movement,  and  some  parts  at  least  of  the  island  before 
spoken  of  (fig.  365,  p.  368)  would  become  submerged. 

Fourthly.  After  the  London  clay  and  the  overlying  Bagshot  sands 
had  been  deposited,  they  appear  to  have  been  upraised  in  the  London 
basin,  during  the  Eocene  period,  and  their  conversion  into  land  in  the 
north  seems  to  have  preceded  the  upheaval  of  beds  of  corresponding 
age  in  the  south,  or  in  the  Hampshire  basin ;  because  none  of  the  fluvio- 
marine  Eocene  strata  of  Hordwell  and  the  Isle  of  Wight  (described  in 
Chap.  XVI.)  are  found  in  any  part  of  the  London  area. 

Fifthly.  The  fossils  of  the  alternating  marine,  brackish,  and  fresh- 
water beds  of  Hampshire,  of  Middle  and  Upper  Eocene  date,  bear 
testimony  to  rivers  draining  adjacent  lands,  and  to  the  existence  of 
numerous  quadrupeds  in  those  lands.  Instead  of  these  phenomena, 
the  signs  of  an  open  sea  might  naturally  have  been  expected,  as  a 
consequence  of  the  vast  subsidence  of  the  Middle  Eocene  beds  before 
mentioned,  had  not  some  local  upheaval  taken  place  at  the  same  time 
in  the  Isle  of  Wight,  or  in  regions  immediately  adjacent.  Whatever 
hypothesis  be  adopted,  we  are  entitled  to  assume  that  during  the 
Middle  and  Upper  Eocene  periods  there  were  risings  and  sinkings  of 
land,  and  changes  of  level  in  the  bed  of  the  sea  in  the  southeast  of 
England,  and  that  the  movements  were  by  no  means  uniform  over 
the  whole  area  during  these  periods.  The  extent  and  thickness  of 
the  missing  beds  in  the  Weald  should  of  itself  lead  us  to  look  for 
proofs  of  that  area  having,  by  repeated  oscillations,  changed  its  level 
frequently,  and,  oftener  than  any  adjoining  area,  been  turned  from 
sea  into  land  and  land  into  sea ;  for  the  submergence  and  emergence 
of  land  augment,  beyond  any  other  cause,  the  wasting  and  removing 
power  of  water,  whether  of  the  waves  and  tides  or  of  rivers  and 
land-floods. 

Sixthly.  The  Lower  Miocene  strata  of  the  Isle  of  Wight  (or  the 
Hempstead  beds  before  described)  have  been  upraised  several  hundred 
feet  above  the  level  of  the  sea  in  which  they  were  originally  formed. 
This  upward  movement  may  have  occurred,  in  great  part  at  least, 
during  the  Miocene  period,  when  a  large  part  of  Europe  is  supposed 
to  have  become  land,  as  before  suggested  (p.  242).  Hence  we  are 
entitled  to  speculate  on  the  probability  of  revolutions  in  the  physical 
geography  of  the  adjoining  Weald  in  times  intermediate  between 
the  deposition  of  the  Hempstead  beds  and  the  origin  of  the  Suffolk 
crag. 

Seventhly.  We  have  already  seen  (p.  235)  that  certain  ferruginous 
sands  lie  in  patches  on  the  North  Downs,  some  of  them  from  20  to  40 
feet  in  thickness,  and  referable  by  their  fossils  to  the  same  age  as  the 
Diest  sands  of  Belgium.  They  are  probably  somewhat  older  than  the 
coralline  crag  of  Suffolk,  and,  as  before  explained,  may  constitute  the 
only  representative  in  the  British  Isles  of  the  Upper  Miocene  or 
Falunian  epoch.  It  is  clear,  from  the  relative  position  of  the  sands  in 
question  on  the  North  Downs  to  the  Lower  Eocene  deposits  of  the 


CH.  XIX.]  WEALD,  WHEN  DENUDED. 

London  clay,  Woolwich,  and  Thanet  series,  that,  before  the  waters  of 
the  Upper  Miocene  sea  spread  over  this  region  and  south  of  the 
Thames,  all  those  Eocene  strata  had  been  much  wasted  and  often  re- 
duced to  mere  isolated  outliers  scattered  over  the  chalk.  After  the 
ferruginous  sands  were  thrown  down  the  bed  of  the  sea  must  have 
been  again  raised  500  or  600  feet,  in  order  that  the  North  Downs 
might  attain  their  present  elevation. 

We  learn  from  these  discoveries  how  impossible  it  may  often  be 
to  demonstrate  the  former  presence  of  the  sea  on  any  given  area  by 
organic  remains,  or  by  sea-beaches.  Long  and  diligent  inquiries  had 
been  made  before  the  year  1856,  for  sea-shells  of  recent  or  crag 
species,  and  for  the  signs  of  old  sea-margins  within  the  area  of  the 
North  and  South  Downs  and  the  Wealden,  or  on  Nos.  2,  3,  4,  5,  6, 
and  7  of  the  map  (p.  357) ;  but  in  vain,  until  at  last  a  few  shells  and 
casts  of  others  prove  incontestibly  the  sojourn  of  the  Older  Pliocene 
or  Upper-  Miocene  sea  in  those  very  spaces.  We  must  now,  there- 
fore, admit  the  retreat  of  its  waters  to  have  been  an  event  as  modern 
as  the  Upper  Miocene,  if  not  the  Pliocene  period.  It  follows  that  in 
many  cases  the  land  may  have  sunk  and  have  emerged  again  without 
retaining  on  its  surface  any  monuments  of  the  kind  usually  demanded 
as  indispensable  to  warrant  our  speculating  on  marine  denudation  as 
a  great  modifying  cause  in  the  physical  geography  of  the  globe. 

Eighthly.  But  we  have  still  to  consider  another  vast  interval  of 
time,  that  which  separated  the  end  of  the  Miocene  from  the  end  of 
the  Newer  Pliocene  era — a  lapse  of  ages  which,  if  measured  by  the 
fluctuations  experienced  in  the  marine  fauna,  may  have  sufficed  to 
submerge  and  reelevate  whole  continents  by  a  process  as  slow  as 
that  which  is  now  operating  to  upraise  Sweden  and  depress  Greenland. 

Lastly.  The  reader  must  recall  to  mind  what  was  said,  in  Chap- 
ters XI.  and  XII.  respecting  the  vast  geographical  changes  of  Post- 
pliocene  date,  especially  those  relating  to  the  glacial  drift  and  its 
far-transported  materials.  A  wide  extent  of  the  British  Isles  appears 
to  have  been  under  the  sea  during  some  part  or  other  of  that  epoch. 
Most  of  the  submerged  areas  were  afterwards  converted  into  dry 
land,  now  several  hundred  and  in  Wales  more  than  thirteen  hundred 
feet  high,  as  proved  by  marine  fossil  shells.  It  seems  highly  prob- 
able that  the  Wealden  area  was  dry  land  when  the  most  charac- 
teristic northern  drift  originated,  no  traces  of  northern  erratics 
having  been  met  with  farther  south  than  Highgate,  near  London. 
But  it  by  no  means  follows  that  the  area  of  the  Weald  was  stationary 
during  all  these  ages.  It  may  have  been  raised  and  depressed,  and  its 
surface  may  have  been  modified  by  rain,  rivers,  and  floods  caused 
by  the  sudden  melting  of  deep  snow  again  and  again  during  the 
Glacial  era.* 

*  In  my  Geological  Evidences  of  the  Antiquity  of  Man,  pp.  276,  278,  I  have 
given  maps  illustrating  the  changes  hi  physical  geography  which  have  taken  place 


372  WEALD,  WHEN  DENUDED.  [On.  XIX. 

It  was  long  ago  observed  by  Dr.  Mantell  that  no  vestige  of  the 
chalk  and  its  flints  has  been  seen  on  the  central  ridge  of  the  Weald  or 
on  the  Hastings  Sands,  but  merely  gravel  and  loam  derived  from  the 
rocks  in  situ  in  the  neighborhood.  This  distribution  of  alluvium, 
especially  the  absence  of  chalk-flints  in  the  central  district,  agrees 
well  with  the  theory  of  denudation  before  set  forth ;  for  by  referring 
to  fig.  356  (p.  358),  the  reader  will  see  that  had  the  chalk  (No.  2) 
been  once  continuous,  and  covered  everywhere  with  flint-gravel, 
this  gravel  would  be  the  first  to  be  carried  away  from  the  highest  part 
of  the  dome  long  before  any  of  the  gault  (No.  3)  was  laid  bare. 
Now,  if  some  ruins  of  the  chalk  remain  at  first  on  the  gault,  these 
would  be,  in  a  great  degree,  cleared  away  before  any  part  of  the  lower 
greensand  (No.  4)  is  denuded.  Thus  in  proportion  to  the  number 
and  thickness  of  the  groups  removed  in  succession,  is  the  probability 
lessened  of  our  finding  any  remnants  of  the  highest  groups  strewed 
over  the  bared  surface  of  the  lowest. 

But  it  is  objected,  that,  had  the  sea  at  one  or  several  periods  been 
the  agent  of  denudation,  we  should  have  found  ancient  sea-beaches 
at  the  foot  of  the  escarpments,  and  other  signs  of  oceanic  erosion. 
As  a  general  rule,  the  wreck  of  the  white  chalk  and  its  flints  can 
only  be  traced  to  slight  distances  from  the  escarpments  of  the  North 
and  South  Downs.  Even  where  exceptions  occur,  and  where  flints 
are  seen  two  or  three  miles  from  the  nearest  chalk,  they  are  so  angular 
as  to  be  regarded  by  many  as  indicating  fluviatile  rather  than  marine 
denudation.  Without  wishing  to  gainsay  the  doctrine  that  many  of 
the  last  superficial  changes  of  the  Weald  may  have  been  due  to  rain 
and  rivers,  combined  with  successive  upheaval  and  depression  of  land, 
I  may,  nevertheless,  remind  the  reader  that,  in  the  absence  of  organic 
remains,  it  is  often  impossible  to  distinguish  between  gravel  formed 
in  the  bed  of  a  river  and  that  which  accumulates  on  a  sea-beach. 
For  if  we  examine  the  broken  flints  at  the  base  of  a  cliff,  in  places 
where  they  are  not  peculiarly  exposed  to  the  continuous  and  violent 
action  of  the  waves,  we  may  observe  that  they  retain  much  angularity. 
This  may  be  seen  between  the  Old  Harry  rocks  in  Dorsetshire  and 
Christchurch  in  Hampshire.  Throughout  the  greater  part  of  that 
line  of  coast  the  cliffs  are  composed  of  tertiary  strata,  capped  by  a 
dense  covering  of  gravel  formed  of  flints  slightly  abraded.  As  the 
waste  of  the  cliffs  is  rapid,  the  old  materials  are  gradually  changed  for 
new  ones  on  the  beach ;  nevertheless  we  have  here  an  example  of 
angles  being  retained  after  two  periods  of  attrition ;  first,  that  during 
which  the  gravel  was  spread  originally  over  the  Eocene  deposits ;  and 
secondly,  when  the  Eocene  sands  and  clays  were  undermined  and  the 
modern  cliff  and  sea-beach  formed.  As  to  the  angularity  of  the  flints, 
it  has  been  thought  by  some  authorities  to  imply  great  violence  in 

in  Post-pliocene  times,  availing  myself  of  the  maps  and  memoirs  of  Mr.  Trimmer, 
Mr.  Godwin-Austen,  and  others. 


CH.  XIX.] 


ELEPHANT-BED. 


373 


the  removing  power,  especially  in  those  cases  where  well-rounded 
pebbles  washed  out  of  Eocene  strata  are  likewise  found  broken,  some- 
times with  sharp  edges,  and  often  with  irregular  pieces  chipped  out 
of  them  as  if  by  a  smart  blow.  Such  fractured  pebbles  occur  not  un- 
frequently  in  the  drift  of  the  valley  of  the  Thames.  In  explanation  I 
may  remark  that,  in  the  Blackheath  and  other  Eocene  shingle-beds, 
hard  egg-shaped  flint-pebbles  may  be  found  in  such  a  state  of  decom- 
position as  to  break  in  the  same  manner  on  the  application  of  a  mod- 
erate blow,  such  as  stones  might  encounter  in  the  bed  of  a  swollen 
river  or  on  a  sea-coast. 

Angular  flint-breccia  is  not  confined  to  the  Weald,  nor  to  the  trans- 
verse gorges  in  the  chalk,  but  extends  along  the  neighboring  coast 
from  Brighton  to  Rottingdean,  where  it  was  called  by  Dr.  Mantell 
"  the  elephant-bed,"  because  the  bones  of  the  mammoth,  E.  primigenius, 
abound  in  it  with  those  of  the  horse,  and,  more  rarely,  the  rhinoceros, 
R.  tichorhinus.  The  following  is  a  section  of  this  formation  as  it  ap- 
pears in  the  Brighton  cliff.* 

Fig.  366. 


A.  Chalk  with  layers  of  flint  dipping  slightly  to  the  south. 

&.  Ancient  beach,  consisting  of  fine  sand,  from  one  to  four  feet  thick,  covered  by  shingle  from 

five  to  eight  feet  thick  of  pebbles  of  chalk-flint,  granite,  and  other  rocks,  with  broken 

shells  of  recent  marine  species,  and  bones  of  cetacea. 
C.  Elephant-bed,  about  fifty  feet  thick,  consisting  of  layers  of  white  chalk  rubble,  with  broken 

chalk-flints,  often  more  confusedly  stratified  than  is  represented  in  this  drawing,  in  which 

deposit  are  found  bones  of  ox,  deer,  horse,  and  mammoth. 
d.  Sand  and  shingle  of  modern  beach. 

To  explain  this  section  we  must  suppose  that,  after  the  excavation 
of  the  cliff  A,  the  beach  of  sand  and  shingle  6  was  formed  by  the 
long-continued  action  of  the  sea.  The  presence  of  Littorina  littorea 
and  other  recent  littoral  shells,  determines  the  modern  date  of  the 
accumulation.  The  overlying  beds  are  composed  of  such  calcareous 

*  See  also  Sir  R.  Murchison,  Geol.  Quart.  Journ.,  vol.  vii.  p.  365. 


WEALD,  HOW  DENUDED.  [On.  XIX. 

rubble  and  flints,  rudely  stratified,  as  are  often  conspicuous  in  parts  of 
the  Norfolk  coast,  where  they  are  associated  with  glacial  drift,  and 
were  probably  of  contemporaneous  origin.  Similar  flints  and  chalk- 
rubble  have  been  recently  traced  by  Sir  Roderick  Murchison  to  Folke- 
stone and  along  the  face  of  the  cliffs  at  Dover,  where  the  teeth  of  the 
fossil  elephant  have  been  detected. 

Mr.  Prestwich  also  has  shown  that  at  Sangatte,  near  Calais,  on  the 
coast  exactly  opposite  Dover,  a  similar  water-worn  beach,  with  an 
incumbent  mass  of  angular  flint-breccia,  is  visible.  I  have  myself 
visited  this  spot,  and  found  the  deposit  strictly  analogous  to  that  of 
Brighton.  The  fundamental  ancient  beach  has  been  uplifted  more 
than  ten  feet  above  its  original  level.  The  flint-pebbles  in  it  have 
evidently  been  rounded  at  the  base  of  an  ancient  chalk-cliff,  the  course 
of  which  can  still  be  traced  inland,  nearly  parallel  with  the  present 
shore,  but  with  a  space  intervening  between  them  of  about  one-third 
of  a  mile  in  its  greatest  breadth. 

Of  a  somewhat  older  date  than  the  Brighton  beach  are  some  large 
erratic  blocks,  the  greatest  number  of  which  are  seen  at  Pagham  and 
Selsea,  fifteen  miles  south  of  Chichester,  consisting  of  granite  and  many 
other  rocks  which  are  not  of  northern  origin,  but  which  seem  to  have 
been  drifted  into  their  present  site  by  coast-ice  from  Normandy  and 
Brittany.  They  overlie  a  Post-pliocene  deposit  of  marine  origin. 
Like  the  Brighton  beach,  they  help  to  prove  that  during  the  Glacial 
period  a  sea-coast  bounded  the  elevated  district  of  the  Weald  to  the 
south  of  the  present  South  Downs. 

Professor  Ramsay,*  and  some  other  able  geologists,  who  fully 
admit  that  the  denudation  of  the  Wealden  area  and  that  of  the 
North  and  South  Downs  was  mainly  effected  by  the  agency  of  the 
sea,  incline,  nevertheless,  to  the  opinion  that  the  great  escarpments 
of  the  chalk  may  have  been  due  to  pluvial  and  fluviatile  erosion, 
the  sea,  when  it  last  retired,  having  left  the  secondary  strata  planed 
off  at  one  and  the  same  level.  But  this  hypothesis  seems  to  me  un- 
tenable, because,  assuming  that  the  last  of  the  submarine  areas  due 
to  denudation  had  an  even  and  level  surface  before  it  emerged,  I 
cannot  imagine  that  great  superficial  inequalities  would  not  have 
been  produced  by  the  waves  and  tides  of  the  sea  during  the  time 
when  the  chalk,  gault,  greensand,  and  other  formations,  some  com- 
posed of  harder  and  some  of  softer  materials,  were  raised  gradually 
above  the  waters,  The  scooping  out  of  the  great  longitudinal  valleys 
must  have  commenced  during  such  upheaval ;  and  as  to  the  transverse 
valleys,  if  it  be  true,  as  Mr.  Jukes  has  suggested,  that  they  originated 
at  a  very  remote  era  by  fluviatile  erosion,  when  the  chalk  extended 
farther  towards  the  central  axis  of  the  Wealden  than  now,  still  the 
subsequent  deepening  of  these  valleys  must  have  been  due  in  part  to 

*  See  Professor  Ramsay's  Physical  Geology  and  Geography  of  Great  Britain,  2d 
ed. :  London,  1864. 


CH.  XIX.]  DENUDATION  OF  THE  WEALD.  375 

tidal  action.  As  to  the  power  of  mere  atmospheric  causes,  we  have 
only  to  endow  them  with  a  small  portion  of  the  force  ascribed  to  them 
by  the  geologists  in  question,  and  we  can  have  no  difficulty  in  explain- 
ing how  all  traces  of  the  sea  in  the  shape  of  littoral  shells  or  beach 
deposits  should  have  disappeared.  Shells,  once  strewed  over  ancient 
shores,  may  have  decomposed  so  as  to  make  it  impossible  for  us  to 
assign  an  exact  palseontological  date  to  the  period  of  emergence ;  but 
the  leading  inequalities  of  hill  and  dale,  the  long  lines  of  escarpment, 
the  longitudinal  and  transverse  valleys,  may  still  be  mainly  due  to  the 
power  of  the  waves  and  currents  of  the  sea. 

In  despair  of  solving  the  problem  of  the  present  geographical  con- 
figuration and  geological  structure  of  the  Weald  by  an  appeal  to 
ordinary  causation,  some  geologists  have  been  fain  to  invoke  the  aid 
of  imaginary  "  rushes  of  salt  water  "  over  the  land  during  the  sudden 
upthrow  of  the  bed  of  the  sea,  when  the  anticlinal  axis  of  the  Weald 
was  formed.  Others  refer  to  vast  bodies  of  fresh  water  breaking 
forth  from  subterranean  reservoirs,  when  the  rocks  were  riven  by 
earthquake  shocks  of  intense  violence.  The  singleness  of  the  cause 
and  the  unity  of  the  result  are  emphatically  insisted  upon :  the  catas- 
trophe was  abrupt,  tumultuous,  transient,  and  paroxysmal ;  fragments 
of  stone  were  swept  along  to  great  distances  without  time  being 
allowed  for  attrition ;  alluvium  was  thrown  down  unstratified,  and 
often  in  strange  situations,  on  the  flanks  or  on  the  summits  of  hills, 
while  the  lowest  levels  were  left  bare.  The  convulsion  was  felt  simul- 
taneously over  so  wide  an  area,  that  all  the  individuals  of  certain  spe- 
cies of  quadrupeds  were  at  once  annihilated  ;  yet  the  event  was  com- 
paratively modern,  for  the  species  of  testacea  now  living  were  already 
in  existence. 

This  hypothesis  is  untenable  and  unnecessary.  In  the  present 
chapter  I  have  endeavored  to  show  how  numerous  have  been  the 
periods  of  geographical  change,  and  how  vast  their  duration.  Evi- 
dence to  this  effect  is  afforded  by  the  relative  position  of  the  chalk 
and  overlying  tertiary  deposits ;  by  the  nature,  character,  and  posi- 
tion of  the  tertiary  strata ;  and  by  the  overlying  alluvia  of  the  Weald 
and  adjacent  countries.  As  to  the  superficial  detritus,  its  insignifi- 
cance in  volume,  when  compared  to  the  missing  rocks,  should  never 
be  lost  sight  of.  A  mountain-mass  of  solid  matter,  hundreds  of 
square  miles  in  extent,  and  hundreds  of  yards  in  thickness,  has  been 
carried  away  bodily.  To  what  distance  it  has  been  transported  we 
know  not,  but  certainly  beyond  the  limits  of  the  Weald.  For  achiev- 
ing such  a  task,  if  we  are  to  judge  by  analogy,  all  transient  and  sud- 
den agency  is  hopelessly  inadequate.  There  is  one  power  alone  which 
is  competent  to  the  task,  namely,  the  mechanical  force  of  water  in 
motion,  operating  gradually  and  for  ages.  We  have  seen  in  the  sixth 
chapter  that  every  stratified  portion  of  the  earth's  crust  is  a  monu- 
ment of  denudation  on  a  grand  scale,  always  effected  slowly ;  for  each 
superimposed  stratum,  however  thin,  has  been  successively  and  sepa- 


3T6  DENUDATION  OF  THE  WEALD.  [On.  XIX. 

rately  elaborated.  Every  attempt,  therefore,  to  circumscribe  the  time 
in  which  any  great  amount  of  denudation,  ancient  or  modern,  has 
been  accomplished,  draws  with  it  the  gratuitous  rejection  of  the  only 
kind  of  machinery  known  to  us  which  possesses  the  adequate  power. 
If,  then,  at  every  epoch,  from  the  most  ancient  to  the  Pliocene  in- 
clusive, voluminous  masses  of  matter,  such  as  are  missing  in  the 
Weald,  have  been  transferred  from  place  to  place,  and  always  re- 
moved gradually,  it  seems  extravagant  to  imagine  an  exception  in  the 
very  region  where  we  can  prove  the  first  and  last  acts  of  denudation 
to  have  been  separated  by  so  vast  an  interval  of  time.  Here,  might 
we  say,  if  anywhere  within  the  range  of  geological  inquiry,  we  have 
time  enough,  and  without  stint,  at  our  command. 


CH.  XX.]  DIVISIONS  OF  THE  OOLITE. 


CHAPTER  XX. 

JURASSIC    GROUP. PURBECK    BEDS    AND    OOLITE. 

The  Purbeck  beds  a  member  of  the  Jurassic  group — Subdivisions  of  that  group — 
Physical  geography  of  the  Oolite  in  England  and  France — Upper  Oolite — Purbeck 
beds — New  genera  of  fossil  mammalia  in  the  Middle  Purbeck  of  Dorsetshire — 
Dirt-bed  or  ancient  soil — Fossils  of  the  Purbeck  beds — Portland  stone  and  fossils 
— Lithographic  stone  of  Solenhofen — Archaeopteryx — Middle  Oolite — Coral  rag — 
Zoophytes — Nerinaean  limestone — Diceras  limestone — Oxford  clay,  Ammonites, 
and  Belemnites — Kelloway  Rock — Lower  Oolite,  Crinoideans — Great  Oolite  and 
Bradford  clay — Stonesfield  slate — Fossil  mammalia — Resemblance  to  an  Austra- 
lian fauna — Northamptonshire  slates — Yorkshire  Oolitic  coal-field — Brora  coal — 
Fuller's  earth — Inferior  Oolite  and  fossils — Palaeontological  relations  of  the  sev- 
eral subdivisions  of  the  Oolitic  group. 

IMMEDIATELY  below  the  Hastings  Sands  (the  inferior  member  of  the 
Wealden,  as  defined  in  Chapter  XVIII.),  we  find  in  Dorsetshire,  an- 
other remarkable  freshwater  formation,  called  the  Purbeck,  because  it 
was  first  studied  in  the  sea-cliffs  of  the  peninsula  of  Purbeck  in  Dorset- 
shire. These  beds  were  formerly  grouped  with  the  Wealden,  but  some 
organic  remains  recently  discovered  in  certain  intercalated  marine  beds 
show  that  the  Purbeck  series  has  a  close  affinity  to  the  Oolitic  group, 
of  which  it  may  be  considered  as  the  newest  or  uppermost  member. 

In  England  generally,  and  in  the  greater  part  of  Europe,  both  the 
Wealden  and  Purbeck  beds  are  wanting,  and  the  marine  cretaceous  group 
is  followed  immediately,  in  the  descending  order,  by  another  series  called 
the  Jurassic.  In  this  term,  the  formations  commonly  designated  as  "  the 
Oolite  and  Lias  "  are  included,  both  being  found  in  the  Jura  Mountains. 
The  Oolite  was  so  named  because  in  the  countries  where  it  was  first  ex- 
amined, the  limestones  belonging  to  it  had  an  oolitic  structure  (p.  12). 
These  rocks  occupy  in  England  a  zone  which  is  nearly  30  miles  in  aver- 
ao-e  breadth,  and  extends  across  the  island,  from  Yorkshire  in  the  north- 

e  >  ' 

east,  to  Dorsetshire  in  the  southwest.  Their  mineral  characters  are  not 
uniform  throughout  this  region ;  but  the  following  are  the  names  of  the 
principal  subdivisions  observed  in  the  central  and  southeastern  parts 
of  England : 


Upper - 


Middle  H 


OOLITE. 

a.  Purbeck  beds. 

b.  Portland  stone  and  sand. 

c.  Kimmeridge  clay. 

d.  Coral  rag. 

e.  Oxford  clay,  and  Kelloway  rock. 


]/.  Cornbrash  and  Forest  marble. 
T          j  g.  Great  Oolite  and  Stonesfield  slate. 
er  1  h.  Fuller's  earth. 

(>   Inferior  Oolite. 
The  Lias  then  succeeds  to  the  Inferior  Oolite. 


378  PHYSICAL   GEOGRAPHY  OF  THE   OOLITE.  [Ca  XX. 

The  Upper  oolitic  system  of  the  above  table  has  usually  the  Kimrae- 
ridge  clay  for  its  base  ;  the  Middle  oolitic  system,  the  Oxford  clay.  The 
Lower  system  reposes  on  the  Lias,  an  argillo-calcareous  formation,  which 
some  include  in  the  Lower  Oolite,  but  which  will  be  treated  of  separately 
in  the  next  chapter.  Many  of  these  subdivisions  are  distinguished  by  pe- 
culiar organic  remains ;  and,  though  varying  in  thickness,  may  be  traced 
in  certain  directions  for  great  distances,  especially  if  we  compare  the  part 
of  England  to  which  the  above-mentioned  type  refers  with  the  northeast 
of  France  and  the  Jura  mountains  adjoining.  In  that  country,  distant 
above  400  geographical  miles,  the  analogy  to  the  accepted  English  type, 
notwithstanding  the  thinness  or  occasional  absence  of  the  clays,  is  more 
perfect  than  in  Yorkshire  or  Normandy. 

Physical  geography. — The  alternation,  on  a  grand  scale,  of  distinct  for- 
mations of  clay  and  limestone  has  caused  the  oolitic  and  liassic  series  to 
give  rise  to  some  marked  features  in  the  physical  outline  of  parts  of  Eng- 
land and  France.  Wide  valleys  can  usually  be  traced  throughout  the 
long  bands  of  country  where  the  argillaceous  strata  crop  out ;  and  be- 
tween these  valleys  the  limestones  are  observed,  composing  ranges  of  hills 
or  more  elevated  grounds.  These  ranges  terminate  abruptly  on  the  side  on 
which  the  several  clays  rise  up  from  beneath  the  calcareous  strata. 

The  annexed  cut  will  give  the  reader  an  idea  of  the  configuration  of 
the  surface  now  alluded  to,  such  as  may  be  seen  in  passing  from  London 
to  Cheltenham,  or  in  other  parallel  lines,  from  east  to  west,  in  the  southern 
part  of  England.  It  has  been  necessary,  however,  in  this  drawing,  greatly 


Fig.  367. 

Middle 
Oolite.  Oolite.  Oolite.  Chalk,  clay. 


Lower  Middle  Upper  London 


Lias.  Oxford  Clay.  Kim.  clay.       Gault. 

to  exaggerate  the  inclination  of  the  beds,  and  the  height  of  the  several 
formations,  as  compared  to  their  horizontal  extent.  It  will  be  remarked, 
that  the  lines  of  cliff,  or  escarpment,  face  towards  the  west  in  the  great 
calcareous  eminences  formed  by  the  Chalk  and  the  Upper,  Middle,  and 
Lower  Oolites  ;  and  at  the  base  of  which  we  have  respectively  the  Gault, 
Kimmeridge  clay,  Oxford  clay,  and  Lias.  This  last  forms,  generally,  a 
broad  vale  at  the  foot  of  the  escarpment  of  inferior  oolite,  but  where  it 
acquires  considerable  thickness,  and  contains  solid  beds  of  marl-stone,  it 
occupies  the  lower  part  of  the  escarpment. 

The  external  outline  of  the  country  which  the  geologist  observes  in 
travelling  eastward  from  Paris  to  Metz  is  precisely  analogous,  and  is 
caused  by  a  similar  succession  of  rocks  intervening  between  the  tertiary 
strata  and  the  Lias ;  with  this  difference,  however,  that  the  escarpments 
of  Chalk,  Upper,  Middle,  and  Lower  Oolites  face  towards  the  east  instead 
of  the  west. 


JH.  XX.] 


UPPER  PURBECK. 


379 


The  Chalk  crops  out  from  beneath  the  tertiary  sands  and  clays  of  the 
Paris  basin,  near  Epernay,  and  the  Gault  from  beneath  the  Chalk  and 
Upper  Greensand  at  Clermont-en-Argonne  ;  and  passing  from  this  place 
by  Verdun  and  Etain  to  Metz,  we  find  two  limestone  ranges,  with  inter- 
vening vales  of  clay,  precisely  resembling  those  of  southern  and  central 
England,  until  we  reach  the  great  plain  of  Lias  at  the  base  of  the  Inferior 
Oolite  at  Metz. 

It  is  evident,  therefore,  that  the  denuding  causes  have  acted  similarly 
over  an  area  several  hundred  miles  in  diameter,  sweeping  away  the  softer 
clays  more  extensively  than  the  limestones,  and  undermining  these  last  so 
as  to  cause  them  to  form  steep  cliffs  wherever  the  harder  calcareous  rock 
was  based  upon  a  more  yielding  and  destructible  clay. 

UPPER    OOLITE. 

Purbeck  beds  (a,  Tab.  p.  377). — These  strata,  which  we  class  as  the 
uppermost  member  of  the  Oolite,  are  of  limited  geographical  extent  in 
Europe,  as  already  stated,  but  they  acquire  importance,  when  we  consider 
the  succession  of  three  distinct  sets  of  fossil  remains  which  they  contain. 
Such  repeated  changes  in  organic  life  must  have  reference  to  the  history 
of  a  vast  lapse  of  ages.  The  Purbeck  beds  are  finely  exposed  to  view  in 
Durdlestone  Bay,  near  Swanage,  Dorsetshire,  and  at  Lulworth  Cove  and 
the  neighboring  bays  between  Weymouth  and  Swanage.  At  Meup's 
Bay,  in  particular,  Professor  E.  Forbes  examined  minutely  in  1850  the 
organic  remains  of  this  group,  displayed  in  a  continuous,  sea-cliff  section  ; 
and  he  added  largely  to  the  information  previously  supplied  in  the  works 
of  Messrs.  Webster,  Fitton,  De  la  Beche,  Buckland,  and  Mantell.  It  ap- 
pears from  these  researches  that  the  Upper,  Middle,  and  Lower  Purbecks 
are  each  marked  by  peculiar  species  of  organic  remains,  these  again  being 
different,  so  far  as  a  comparison  has  yet  been  instituted,  from  the  fossils  of 
the  overlying  Hastings  Sands  and  Weald  Clay.* 

Upper  Purbeclc. — The  highest  of  the  three  divisions  is  purely  fresh- 
water, the  strata,  .about  50  feet  in  thickness,  containing  shells  of  the 
genera  Paludina,  Physa,  Limnceus,  Planorbis,  Valvata,  Cyclas,  and 
Unio,  with  Cyprides  and  fish.  All  the  species  seem  peculiar,  and  among 
these  the  Cyprides  are  very  abundant  and  characteristic.  (See  figs. 
368,  a,  6,  c.) 

Fig.  868. 


Cyprides  from  the  Upper  Purbecks. 
a.  Cypris  gibbom,  E.  Forbes.  &.  Cypris  tuberculata,  E.Forbes,  c.  Cyprte  leffuminetta,  KForbea. 

*  "  On  the  Dorsetshire  Purbecks,"  by  Prof.  E.  Forbes,  Brit.  Assoc.  Edinb.  1850. 


380 


MIDDLE  PURBECK. 


[On.  XX. 


The  stone  called  "  Purbeck  marble,"  formerly  much  used  in  ornamental 
architecture  in  the  old  English  cathedrals  of  the  southern  counties,  is  ex- 
clusively procured  from  this  division. 

Middle  Purbeck. — Next  in  succession  is  the  Middle  Purbeck,  about  30 
feet  thick,  the  uppermost  part  of  which  consists  of  freshwater  limestone, 
with  cyprides,  turtles,  and  fish,  of  different  species  from  those  in  the  pre- 
ceding strata.  Below  the  limestone  are  brackish-water  beds  full  of 
Cyrena,  and  traversed  by  bands  abounding  in  Corbula  and  Melania. 
These  are  based  on  a  purely  marine  deposit,  with  Pecten,  Modiola, 
Avicula,  Thracia,  all  undescribed  shells.  Below  this,  again,  come  lime- 
stones and  shales,  partly  of  brackish  and  partly  of  freshwater  origin,  in 
which  many  fish,  especially  species  of  Lepidotus  and  Microdon  radiatus, 
are  found,  and  a  crocodilian  reptile  named  Macrorhyncus.  Among  the 
mollusks,  a  remarkable  ribbed  Melania,  of  the  section  Chilina,  occurs. 

Immediately  below  is  the  great  and  conspicuous  stratum,  12  feet  thick, 
long  familiar  to  geologists  under  the  local  name  of  "  Cinder-bed,"  formed 
of  a  vast  accumulation  of  shells  of  Ostrea  distorta  (fig.  369).  In  the 
uppermost  part  of  this  bed  Professor  Forbes  discovered  the  first  echino- 
derm  (fig.  370)  as  yet  known  in  the  Purbeck  series,  a  species  of  Ilemici- 
daris,  a  genus  characteristic  of  the  Oolitic  period,  and  scarcely,  if  at  all, 
distinguishable  from  a  previously  known  oolitic  species.  It  was  accom- 

Fig.  370. 


Ostrea  distorta. 
Cinder-bed,  Middle  Purbeck. 


Hemioidaris  Purbeckensis,  E.  Forbes. 
Middle  Purbeck. 


panied  by  a  species  of  Perna.    Below  the  Cinder-bed  freshwater  strata 
are  again  seen,  filled  in  many  places  with  species  of  Cypris  (fig.  371, 


Fig.  3T1. 


Cyprides  from  the  Middle  Purbecks. 

a.  Cypris  striato-punctata,  E.  Forbes.      b.  Cypris  fascioulata,  E.  Forbea 
c.  Cypris  granulata,  Sow. 

a,  b,    c),   and   with    Valvata,  Paludina,  Planorbis,  Limnceus,  Physa 
(fig.  372),  and  Cyclas,  all  different  from  any  occurring  higher  in  the 


CH.  XX.]  FOSSILS  OF  THE  MIDDLE  PURBECK.  33^ 

series.  It  will  be  seen  that  Cypris  fasciculata  (fig.  371,  6)  has  tuber- 
cles at  the  end  only  of  each  valve,  a  character  by  which  it  can  be 
immediately  recognized.  In  fact,  these  minute 
crustaceans,  almost  as  frequent  in  some  of  the 
shales  as  plates  of  mica  in  a  micaceous  sand- 
stone, enable  geologists  at  once  to  identify  the 
Middle  Purbeck  in  places  far  from  the  Dorset- 
shire cliffs,  as,  for  example,  in  the  Vale  of 
Wardour,  in  Wiltshire.  Thick  siliceous  beds 
of  chert  occur  in  the  Middle  Purbeck  filled 

. ,T  ,,  ,  .  ,  f    ^  Physa  JBristovii,  E.  Forbes. 

with  mollusca   and    cyprides   of   the   genera  Middle  Puibeck. 

already  enumerated,  in   a  beautiful   state   of 

preservation,  often  converted  into  chalcedony.  Among  these  Pro- 
fessor Forbes  met  with  gyrogonites  (the  spore-vessels  of  Charce), 
plants  never  until  1851  discovered  in  rocks  older  than  Eocene. 

Fossil  Mammalia  of  the  Middle  Purbeck. — In  the  fourth  edition  of 
this  work  (1852),  after  alluding  to  the  discovery  of  numerous  insects 
and  air-breathing  mollusca  in  the  "Purbeck,"  I  remarked  that, 
although  no  mammalia  had  then  been  found,  "  it  was  too  soon  to  infer 
their  non-existence  on  mere  negative  evidence."  Only  two  years 
after  this  remark  was  in  print,  Mr.  W.  R.  Brodie  found  in  the  Middle 
Purbeck,  about  twenty  feet  below  the  "  Cinder  "  above  alluded  to,  in 
Durdlestone  Bay,  portions  of  several  small  jaws  with  teeth,  which 
Professor  Owen,  after  clearing  away  the  matrix,  recognized  as  belong- 
ing to  a  small  mammifer  of  the  insectivorous  class.  The  teeth  with 
pointed  cusps  resemble  in  some  degree  those  of  the  Cape  Mole 
(Chrysochlora  aurea) ;  but  the  number  of  the  molar  teeth  (at  least  ten 
in  each  rarnus  of  the  lower  jaw)  accords  better  with  some  of  the  ex- 
tinct mammalia  of  the  Stonesfield  Oolite  (see  below,  p.  406).  This 
newly-found  quadruped,  therefore,  seems  to  have  been  more  closely 
allied  in  its  dentition  to  the  Amphitherium  (or  Thylacotherium)  than 
to  any  existing  insectivorous  type.  The  angular  process  of  the  jaw, 
as  in  Amphitherium,  is  not  bent  inwards,  an  osteological  peculiarity 
confined  to  the  marsupial  tribes,  and  Professor  Owen  therefore  at  first 
referred  the  Spalacotherium  to  the  placental  or  ordinary  monodelphous 
mammalia. 

Four  years  later  (in  1856)  the  remains  of  twelve  or  more  species 
of  warm-blooded  quadrupeds  were  exhumed  by  Mr.  S.  H.  Beckles, 
F.R.S.,  from  the  same  thin  bed  of  marl  near  tlie  base  of  the  Middle 
Purbeck.  In  this  marly  stratum  many  reptiles,  several  insects,  and 
some  freshwater  shells  of  the  genera  Paludina,  Planorbis,  and  Cyclas 
were  found. 

Mr.  Beckles  had  determined  thoroughly  to  explore  the  thin  layer 
of  calcareous  mud  from  which  in  the  suburbs  of  Swanage  the  bones 
of  the  Spalacotherium  had  already  been  obtained,  and  in  three  weeks 
he  brought  to  light  from  an  area  forty  feet  long  and  ten  wide,  and 
from  a  layer  the  average  thickness  of  which  was  only  five  inches, 


382  MAMMALIA  OF  MIDDLE  PURBECK.  [On.  XX. 

portions  of  the  skeletons  of  six  new  species  of  mammalia,  as  inter- 
preted by  Dr.  Falconer,  who  first  examined  them.  Before  the  begin- 
ning of  the  year  1857  the  number  of  species  recognized  by  the  eminent 
zoologist  last  mentioned  amounted  to  seven  or  eight,  exclusive  of  twc 
which  had  already  been  found  by  Mr.  Brodie  and  named  by  Professor 
Owen.  Before  these  interesting  inquiries  were  brought  to  a  close,  the 
joint  labors  of  Professor  Owen  and  Dr.  Falconer  had  made  it  clear 
that  twelve  or  more  species  of  mammalia  characterized  this  portion 
of  the  Middle  Purbeck,  most  of  them  insectivorous  or  predaceous, 
varying  in  size  from  that  of  a  mole  to  that  of  the  common  polecat, 
Mustela  putorius.  While  the  majority  had  the  character  of  insec- 
tivorous marsupials,  Dr.  Falconer  selected  one  as  differing  widely  from 
the  rest,  and  pointed  out  that  in  certain  characters  it  was  allied  to  the 
living  Kangaroo-rat,  or  Hypsiprymnus,  ten  species  of  which  now 
inhabit  the  prairies  and  scrub-jungle  of  Australia,  feeding  on  plants 
and  gnawing  scratched-up  roots.  A  striking  peculiarity  of  their 
dentition,  one  in  which  they  differ  from  all  other  quadrupeds,  consists 
in  their  having  a  single  large  pre-molar,  the  enamel  of  which  is 
furrowed  with  vertical  grooves,  usually  seven  in  number  (see  /,  fig. 
373,  where  the  pre-molar  of  the  recent  Hypsiprymnus  Graimardi  is 
represented). 

The  largest  pre-molar  in  the  fossil  genus  exhibits  in  like  manner 
seven  parallel  grooves,  producing  by  their  termination  a  similar  serrated 
edge  in  the  crown ;  but  their  direction  is  diagonal — a  distinction,  says 
Dr.  Falconer,  which  is  "  trivial,  not  typical." 

As  these  oblique  furrows  form  so  marked  a  character  of  the  majority 
of  the  teeth,  Dr.  Falconer  has  proposed  for  the  fossil  the  generic  name 
of  Plagiaulax.  The  shape  and  relative  size  of  the  incisor  a,  figs.  373 
and  374,  exhibit  a  no  less  striking  similarity  to  Hypsiprymnus. 
Nevertheless,  the  more  sudden  upward  curve  of  this  incisor,  especially 
in  the  larger  species,  as  well  as  the  number  and  characters  of  the  other 
teeth,  and  the  shortening,  compression,  and  depth  of  the  jaw,  taken 
together  with  the  backward  projection  of  the  condyle  (d,  fig.  373), 
indicate  a  great  deviation  in  the  form  of  Plagiaulax  from  that  of  the 
living  kangaroo-rats. 

Our  knowledge  is  at  present  confined  to  two  fossil  specimens  of 
lower  jaws,*  evidently  referable  to  two  distinct  species,  extremely 
unequal  in  size  and-  otherwise  distinguishable.  The  largest,  P. 
Becklesii  (fig.  373),  was  about  as  big  as  the  English  squirrel  or  the 
flying  phalanger  of  Australia  (Petaurus  Australis,  Waterhouse). 
The  skeleton  of  this  phalanger  (named  P.  macrurus,  No.  1849,  Mu- 
seum of  College  of  Surgeons)  measures  fifteen  inches  in  length, 
exclusive  of  the  tail,  which  is  more  than  eleven  inches  long.  The 

*  Three  additional  specimens  of  P.  Becklesii  have  since  been  found,  some  with 
the  two  back  molars  entire.  They  confirm  Dr.  Falconer's  conclusion  previously 
expressed  in  regard  to  the  affinity  of  Plagiaulax  and  Microlestes. 


CH.  XX.] 


MAMMALIA  OF  MIDDLE  PURBECK. 


383 


smaller  fossil  (P.  minor,  fig.  374),  having  only  half  the  linear  dimen- 
sions of  the  other,  was  probably  only  1-1 2th  of  its  bulk.     It  is  of 


Fig.  873. 


— - 


Plagiaulax  JBecklesii,  Falconer. 

These  two  figures  represent  the  same  right  ramus  of  the  lower  jaw  seen  on  the  opposite  sur- 
faces of  a  split  stone,  the  two  taken  together  affording  data  for  a  complete  restoration  of  the 
jaw. 

Upper  figure  (outer  side). 

a,  5,  ef.  Eight  ramus  of  lower  jaw  magnified  two  diameters,    a,  b.  Outer  side.    &,  o',  d,  ef.  Im- 
pression of  inner  side. 
#.  Incisor. 

Z>,  c.  Line  of  vertical  fracture  behind  the  pre-molars. 
d'.  Impression  of  the  condyle  in  the  matrix. 
ef.  Impression  of  top  of  coronoid  process. 

/.  Section  of  the  anterior  piece  of  the  jaw  at  the  fracture  5,  c,— SB,  inner  surface ;  y,  outer. 
The  notch  at  the  top  is  formed  by  one  of  the  sockets  of  the  double-fanged  true 
molar. 

g.  Section  of  the  hinder  piece  near  &,  c  ;  SB,  inner ;  y,  outer  surface. 
0'.  Broken-off  inflected  fold  of  inner  margin  buried  in  the  matrix. 
m.  Sockets  of  two  molars. 
p,  m.  Three  pre-molars,  the  third  and  last  divided  by  a  crack. 

Lower  figure  (inner  side). 

a/,  d.  Same  lower  jaw  on  the  opposite  slab  of  stone ;  Z>,  d,  e,  inner  side ;  5,  a',  h,  cast  and 

impression  of  outer  side. 
a/.  Outline  of  the  incisor  restored. 
6,  c.  Line  of  vertical  fracture. 

d.  Condyle. 

e.  Coronoid. 

h.  Impression  on  the  matrix  of  the  three  pre-molars. 
i.  Empty  sockets  of  the  two  true  molars. 
n.  Orifice  of  dentary  canal. 

0.  Indication  of  the  raised  and  inflected  fold  of  the  posterior  inner  margin. 

Jc.  Third  or  largest  pre-molar,  magnified  5£  diameters,  showing  the  7  diagonal  grooves. 

1.  Corresponding  pre-molar  in  the  recent  Australian  Hypsiprymnus  Gaimardi,  showing 

the  7  vertical  grooves,  magnified  3£  diameters. 


peculiar  geological  interest,  because,  as  shown  by  Dr.  Falconer,  its 
two  back  molars  bear  a  decided  resemblance  to  those  of  the  Triassic 
Microlestes  (6,  c,  fig.  375),  the  most  ancient  of  known  mammalia,  of 


384: 


HERBIVOROUS  MARSUPIALS 


[On.  XX. 


which  an  account  will  be  given  in  Chapter  XXII.  When  Dr.  Falconer, 
in  1857,  pronounced  the  Plagiaulax  to  be  marsupial  and  herbivorous, 
he  also  regarded  it  as  having  the  form  of  a  rodent ;  but  he  did  not 
overlook  that  in  some  of  its  characters,  especially  in  the  coronoid, 
it  resembled  certain  predaceous  marsupials  more  than  those  of  the 
herbivorous  class.  Professor  Owen  attaches  greater  importance  to 
these  characters,  and  he  has  declared  his  opinion  that  the  Plagiaulax 
was  carnivorous,  or  that  it  fed  on  small  insectivorous  mammalia  and 
lizards.*  Dr.  Falconer  objects  that  the  inference  as  to  the  preda- 
ceous habits  of  Plagiaulax  Beclclesii,  drawn  from  the  upward  curve 
of  the  incisor  (a,  fig.  373,  p.  383),  is  neutralized  by  the  more  hori- 
zontal position  of  the  same  incisor  in  the  smaller  species  (a,  fig.  374), 

Fig.  374. 


Plagiaulax  minor,  Falc. 
(Magnified  4  diameters.) 

All  the  teeth  in  this  specimen  are  in,  place  and  well  preserved.    The  hinder  part  of  the  jaw- 
bone, with  the  ascending  ramus  and  posterior  angle,  are  broken  away. 

a,  6.  Eight  ramus  of  lower  jaw,  with  all  the  teeth  magnified  4  diameters. 
a.  Incisor  with  point  brokon  off.     a'.  Impression  of  same,  showing  that  the  'inner  side 

near  the  apex  was  hollowed  out  in  a  longitudinal  direction. 
&.  Offset  of  coronoid,  the  rest  of  which  is  wanting. 
«*.  The  two  true  molars. 
p,  m.  The  four  pre-molars. 

c.  The  first  molar,  magnified  8  diameters. 

Upper  figure,  the  crown. 

d.  Second  molar,  crown  and  side  view. 

«.  Straight  line  indicating  the  length  of  the  jaw.  natural  size. 


Lower  figure,  side  view. 


to  say  nothing  of  the  fact  that  in  the  living  vegetable-feeding  Koala 
(Phascolarctus  cinereus)  the  incisor  is  also  projected  forwards  with  a 
slight  upward  inclination,  as  in  P.  BecUesii.\  The  same  anatomist 
also  insists,  and  apparently  with  no  small  force  of  reasoning,  on  the 
analogy  of  the  pre-molar  of  Plagiaulax  (&,  fig.  373,  p.  383),  with  that 
of  the  kangaroo-rat  (Z,  ibid).  The  reader  will  see  that  the  grooves  in 
Plagiaulax  are  close  set,  perfectly  parallel,  and  that  they  also  corre- 
spond in  number  with  those  of  the  living  hypsiprymnus ;  and  if  he  will 
compare  them,  as  I  have  done,  with  the  sinuous  and  bifurcating  fur- 
rows on  the  pre-molar  of  the  fossil  Thylacoleo,  to  which  Professor 

*  Owen's  Palseontology,  p.  353. 

f  Falconer,  Geol.  Quart.  Journ.,  vol.  xviii.  p.  357. 


CH.  XX.]  IN  MIDDLE  PURBECK.  3g5 

Owen  has  likened  them,  he  will,  I  think,  be  as  much  at  a  loss  as  Dr. 
Falconer  to  recognize  any  resemblance  between  them. 

All  the  fossil  bones  of  mammalia  discovered  before  the  year  185Y, 
in  rocks  older  than  the  tertiary,  had  consisted  exclusively  of  single 
branches  of  lower  jaws,  and  it  is  a  singular  fact  that  Mr.  Beckles 
should  have  sent  to  London  in  that  year  the  first  known  example  of 
the  upper  portion  of  the  skull  of  a  secondary  mammal  consisting,  as 
Dr.  Falconer  pointed  out  to  me  at  the  time,  of  the  two  frontal  and  the 
two  parietal  bones  in  a  good  state  of  preservation,  with  the  sagittal 
crest  well  marked,  and  the  occipital  also  with  its  crest.  Although  the 
lateral  and  basal  portions  of  this  cranium  were  wanting,  enough  re- 
mained to  show  that  it  agreed  with  the  ordinary  type  of  living  warm- 
blooded quadrupeds. 

In  the  same  slab  with  this  cranium  occurred  the  entire  side  of  the 
lower  jaw  of  another  quadruped,  to  which  Professor  Owen  gave  the 
generic  name  of  Triconodon.  It  contains  eight  molars,  a  large  and 
prominent  canine,  and  one  broad  and  thick  incisior.  This  creature 
must  have  been  nearly  as  large  as  the  common  hedgehog. 

Several  other  jaws  with  similar  tricuspid  teeth  of  larger  dimensions, 
found  by  Mr.  Beckles,  indicate  the  existence  of  another  species  of 
Triconodon  of  a  more  elongated  form,  and  about  one-third  larger  in 
size.  Its  marsupial  character  was  inferred  by  Dr.  Falconer  from  the 
number  of  the  true  molars,  the  strong  inflected  angular  process,  the 
broad  salient  everted  rim  of  the  ridge  which  is  decurrent  on  the  outer 
side  from  the  condyle  along  the  inferior  margin,  and  the  marked 
development  of  the  milo-hyoid  groove.  He  also  observed  that  these 
two  species  of  Triconodon  were  more  like  small  ferine  animals  than 
mere  insectivorous  marsupials,  and  that  they  probably  fed  on  prey  less 
minute  than  insects.  This  opinion  he  deduced  from  the  cutting  char- 
acter of  their  teeth,  and  their  comparatively  formidable  canines, 
together  with  the  form  of  the  ascending  ramus. 

Professor  Owen  has  proposed  the  name  of  Galestes  for  the  largest 
of  the  mammalia  discovered  in  1858  in  Purbeck,  equalling  the  pole- 
cat (Mustela  putorius)  in  size.  It  is  supposed  to  have  been  predaceous 
and  marsupial.  Its  generic  character  is  derived  from  a  peculiar  modi- 
fication in  the  form  of  one  of  the  pre-molars,  which  has  a  single  exter- 
nal vertical  groove. 

When  Mr.  Beckles  had  found  the  remains  of  twenty-eight  distinct 
individuals  of  Purbeck  mammalia,  and  Mr.  Brodie  seven  other  speci- 
mens, they  all  consisted  of  lower  jaws,  and  only  five  of  them  had  upper 
jaws  in  connection ;  and  the  ten  other  specimens  of  oolitic  mammalia 
belonging  to  four  species  discovered  at  Stonesfield  were  in  like  manner 
all  represented  by  lower  jaws.  That  between  forty  or  fifty  species  or 
sides  of  lower  jaws  with  teeth  should  have  been  found  in  oolitic  strata, 
and  with  them  only  five  upper  maxillaries,  together  with,  one  portion  of  a 
separate  cranium,  will  naturally  excite  surprise.  There  were  no  ex- 
amples in  Purbeck  of  an  entire  skeleton,  nor  of  any  considerable  num- 
25 


386  MAMMALIA  OF  MIDDLE  PURBECK.  [On.  XX. 

her  of  bones  in  juxtaposition.  In  several  portions  of  the  matrix  there 
were  detached  bones,  often  much  decomposed,  and  fragments  of  others 
apparently  mammalian ;  but,  if  all  of  them  were  restored,  they  would 
scarcely  suffice  to  complete  the  five  skeletons  to  which  the  five  upper 
maxillaries  above  alluded  to  belonged.  As  the  average  number  of 
pieces  in  each  mammalian  skeleton  is  about  250,  there  must  be  many 
thousands  of  missing  bones ;  and  when  we  endeavour  to  account  for 
their  absence,  we  are  almost  tempted  to  indulge  in  speculations  like 
those  once  suggested  to  me  by  Dr.  Buckland,  when  he  tried  to  solve 
the  enigma  in  reference  to  Stonesfield : — "  The  corpses,"  he  said,  "  of 
drowned  animals,  when  they  float  in  a  river,  distended  by  gases  during 
putrefaction,  have  often  their  lower  jaw  hanging  loose,  and  sometimes 
it  has  dropped  off"..  The  rest  of  the  body  may  then  be  drifted  else- 
where, and  sometimes  may  be  swallowed  entire  by  a  predaceous  rep- 
tile or  fish,  such  as  an  ichthyosaur  or  a  shark." 

We  may  also  suppose  that  when  fish  or  other  aquatic  animals  attack 
a  decaying  carcase,  whether  it  be  floating  or  has  sunk  to  the  bot- 
tom, they  will  first  devour  those  parts  which  are  covered  with  flesh. 
A  lower  jaw,  consisting  of  little  else  than  bones  and  teeth,  will  be 
neglected,  and  becoming  detached,  may  be  drifted  away  by  a  current 
of  moderate  velocity,  and  buried  apart  from  the  other  bones  in  sand 
or  mud. 

As  all  the  above-mentioned  Purbeck  mammalia,  belonging  to  eight 
or  nine  genera  and  to  about  fourteen  species  of  insectivorous,  preda- 
ceous and  herbivorous  marsupials,  have  been  obtained  from  an  area  less 
than  500  square  yards  in  extent,  and  from  a  single  stratum  not  more 
than  a  few  inches  thick,  we  may  safely  conclude  that  the  whole  lived 
together  in  the  same  region,  and  in  all  likelihood  they  constituted  a 
mere  fraction  of  the  mammalia  which  inhabited  the  lands  drained  by 
one  river  and  its  tributaries.  They  afford  the  first  positive  proof  as 
yet  obtained  of  the  coexistence  of  a  varied  fauna  of  the  highest  class 
of  vertebrata  with  that  ample  development  of  reptile  life  which  marks 
all  the  periods  from  the  Trias  to  the  Lower  Cretaceous  inclusive,  and 
with  a  gymnospermous  flora,  or  that  state  of  the -vegetable  kingdom 
when  cycads  and  conifers  predominated  over  all  kinds  of  plants,  ex- 
cept the  ferns,  so  far  at  least  as  our  present  imperfect  knowledge  of 
fossil  botany  entitles  us  to  speak. 

The  annexed  table  will  enable  the  reader  to  see  at  a  glance  how 
conspicuous  a  part,  numerically  considered,  the  mammalian  species 
of  the  Middle  Purbeck  now  play  when  compared  with  those  of  other 
formations  more  ancient  than  the  Paris  gypsum,  and  at  the  same  time 
it  will  help  him  to  appreciate  the  enormous  hiatus  in  the  history  of 
fossil  mammalia,  which  at  present  occurs  between  the  Purbeck  and 
Eocene  periods. 


CH.  XX.]         MAMMALIA  ANTERIOR  TO  PARIS  GYPSUM. 


387 


Number  and  Distribution  of  all  the  known  Species  of  Fossil  Mam- 
malia from  Strata  older  than  the  Paris  Gypsum,  or  than  the 
Bembridge  Series  of  the  Isle  of  Wight. 


f  Headon  Series   and    Beds    between  the ) 

Paris  Gypsum  and  the  Gres  de  Beau-  V 

champ,     -  ) 

Barton  Clay  and  Sables  de  Beauchamp, 


10  English. 
4  French. 


TERTIARY.     •( 


SECONDARY. 


Bagshot    Beds,    Calcaire    Grossier,    and  ) 
Upper  Soissonnais  of  Cuisse-Lamotte,     j" 

{16  French. 
1  English. 
3  U.  States.* 

London  Clay,  including  the  Kyson  Sand, 

7     All  English. 

Plastic  Clay  and  Lignite, 

.  •>       /> 

Qj    7  French. 
y  |    2  EngUsh. 

Sables  de  Bracheux, 

i  f:'    • 

1     French. 

Thanet  Sands  and  Lower  Landenian  of  ) 

•  A 

Belgium,  - 

;:••      f 

0 

"  Maestricht  Chalk, 

- 

0 

White  Chalk,        '        :        - 

0 

Chalk  Marl,          ••*-%. 

_ 

0 

Upper  Greensand, 

. 

0 

Gault, 

0 

Lower  Greensand, 

„ 

0 

Weald  Clay,  &c., 

. 

0 

Hastings  Sand, 

. 

0 

Upper  Purbeck  Oolite, 

. 

0 

Middle  Purbeck  Oolite, 
Lower  Purbeck  Oolite, 

• 

14  Swanage. 
0 

Portland  Oolite, 

. 

0 

Kimmeridge  Clay,     - 

"  ~~ 

0 

Coral  Rag,   -            -        •  <;4  } 

„ 

0 

Oxford  Clay,        •/'•>•       •  -   • 

,,  '^.  • 

0 

Great  Oolite, 

_ 

4  Stonesfield. 

Inferior  Oolite,         -           '* 

::'*i  -•     '.  " 

0 

Lias,           ;  £:          •         '.<*-' 
Upper  Trias,             -        -.  »  '  ' 

"  r.  *  . 

0  rWurtemberg. 
4  •<  Somersetsh. 

Middle,        -            -        v  -, 

•  "^  * 

0  (  N.  Carolina. 

[  Lower, 

vf. 

0 

{Permian,      ... 

. 

0 

Carboniferous, 

. 

0 

Silurian, 

. 

0 

Cambrian,    ... 

- 

0 

PRIMARY. 


In  drawing  up  the  above  table  I  have  been  assisted  by  Professor  Owen  in  refer- 
ence to  the  British,  and  by  MM.  Lartet  and  Hebert  in  reference  to  the  fossil  mam- 
malia of  the  French  Eocene  strata.  There  are,  besides,  several  undescribed  species 
in  the  collection  of  the  two  last-mentioned  palaeontologists,  or  in  museums  known 
to  them  ;  and,  in  regard  to  one  or  two  of  the  Eocene  continental  localities  out  of 
the  Paris  basin,  the  age  of  the  deposits  is  too  little  known  to  allow  us  to  include 
their  fossils  in  the  table. 

The  Sables  de  Bracheux,  enumerated  in  the  Tertiary  division  of  the  table,  sup- 
posed  by  Mr.  Prestwich  to  be  somewhat  newer  than  the  Thanet  Sands,  and  by  M. 
Hebert  to  be  of  about  that  age,  have  yielded  at  La  Fere  the  Arctocyon  (Palceocyori) 
primcevus,  the  oldest  known  tertiary  mammal. 


*  I  allude  to  several  Zeuglodons  found  in  Alabama,  and  referred  by  some  zoolo- 
gists to  three  species. 


388  MAMMALIA  FROM  THE  PURBECK  OOLITE.  [Cn.  XX. 

It  is  worthy  of  notice,  that  in  the  Hastings  Sands  there  are  certain 
layers  of  clay  and  sandstone  in  which  numerous  footprints  of  quadru- 
peds have  been  found  by  Mr.  Beetles,  and  traced  by  him  in  the  same 
set  of  rocks  through  Sussex  and  the  Isle  of  Wight.  They  appear  to 
belong  to  three  or  four  species  of  reptiles,  and  no  one  of  them  to  any 
warm-blooded  quadruped.  They  ought,  therefore,  to  serve  as  a  warn- 
ing to  us,  when  we  fail  in  like  manner  to  detect  mammalian  foot- 
prints in  older  rocks  (such  as  the  New  Red  Sandstone),  to  refrain 
from  inferring  that  quadrupeds,  other  than  reptilian,  did  not  exist  or 
preexist. 

But  the  most  instructive  lesson  read  to  us  by  the  Purbeck  strata 
consists  in  this :  They  are  all,  with  the  exception  of  a  few  interca- 
lated brackish  and  marine  layers,  of  freshwater  origin ;  they  are  160 
feet  in  thickness,  have  been  well  searched  by  skilful  collectors,  and  by 
the  late  Edward  Forbes  in  particular,  who  studied  them  for  months 
consecutively.  They  hate  been  numbered,  and  the  contents  of  each 
stratum  recorded  separately,  by  the  officers  of  the  Government  Sur- 
vey of  Great  Britain.  They  have  been  divided  into  three  distinct 
groups  by  Forbes,  each  characterized  by  the  same  genera  of  pul- 
moniferous  mollusca  and  cyprides,  but  these  genera  being  represented 
in  each  group  by  different  species;  they  have  yielded  insects  of 
many  orders,  and  the  fruits  of  several  plants ;  and  lastly,  they  con- 
tain "  dirt  beds,"  or  old  terrestrial  surfaces  and  soils  at  different  levels, 
in  some  of  which  erect  trunks  and  stumps  of  cycads  and  conifers, 
with  their  roots  still  attached  to  them,  are  preserved.  Yet  when  the 
geologist  inquires  if  any  land-animals  of  a  higher  grade  than  reptiles 
lived  during  any  one  of  these  three  periods,  the  rocks  are  all  silent, 
save  one  thin  layer  a  few  inches  in  thickness  ;  and  this  single  page  of 
the  earth's  history  has  suddenly  revealed  to  us  in  a  few  weeks  the 
memorials  of  so  many  species  of  fossil  mammalia,  that  they  already 
outnumber  those  of  many  a  subdivision  of  the  tertiary  series,  and  far 
surpass  those  of  all  the  other  secondary  rocks  put  together  ! 

Next  anterior  in  age  to  the  Purbeck  mammalia  are  those  of  the 
Lower  Oolite  at  Stonesfield,  to  be  mentioned  at  page  407.  These  are 
all  very  small,  comprising  four  species,  three  of  which  are  certainly 
marsupial,  and  the  other  possibly  placental,  but  so  unlike  any  living 
type  that  some  doubts  are  entertained  as  to  whether  it  may  not  have 
been  marsupial.  Still  older  than  the  above  are  some  fossil  quadru- 
peds, also  of  small  size,  found  in  the  Upper  Trias  of  Stuttgardt,  in 
Germany,  and  more  lately  by  Messrs.  Charles  Moore  and  W.  Boyd 
Dawkins,  in  beds  of  corresponding  age  in  Somersetshire,  which  are 
also  of  a  very  low  grade,  like  the  living  Myrmecobius  of  Australia. 

If  the  three  localities  where  the  most  ancient  mammalia  have  been 
found — Purbeck,  Stonesfield,  and  Stuttgardt — had  belonged  all  of 
them  to  formations  of  the  same  age,  we  might  well  have  imagined  so 
limited  an  area  to  have  been  peopled  exclusively  with  pouched  quad- 
rupeds, just  as  Australia  now  is,  while  other  parts  of  the  globe  were 


CH.  XX.]  LOWER  PURBECK.  339 

inhabited  by  placentals,  for  Australia  now  supports  one  hundred  and 
sixty  species  of  marsupials,  while  the  rest  of  the  continents  and 
islands  are  tenanted  by  about  seventeen  hundred  species  of  mamma- 
lia, of  which  only  forty-six  are  marsupial,  namely,  the  opossums  of 
North  and  South  America.  But  the  great  difference  of  age  of  the 
strata  in  each  of  these  three  localities  seems  to  indicate  the  pre- 
dominance throughout  a  vast  lapse  of  time  (from  the  era  of  the 
Upper  Trias  to  that  of  the  Purbeck  beds)  of  a  low  grade  of  quadru- 
peds;  and  this  persistency  of  similar  generic  and  ordinal  types  in 
Europe  while  the  species  were  changing,  and  while  the  fish,  reptiles, 
and  mollusca  were  undergoing  vast  modifications,  would  naturally 
lead  us  to  suspect  that  there  must  also  have  been  a  vast  extension  in 
space  of  the  same  marsupial  forms  during  that  portion  of  the  sec- 
ondary epoch  which  has  been  termed  "  the  age  of  reptiles."  Such  an 
inference  as  to  the  wide  geographical  range  of  the  marsupials  of  the 
olden  time  has  been  confirmed  by  the  discovery  in  the  Trias  of  North 
America  of  three  lower  jaws  of  a  quadruped  allied  to  Myrmecobius. 
It  was  found  by  the  late  Dr.  Emmons  in  beds  probably  coeval  with 
the  "  Keuper  "  of  Europe.  The  predominance  in  earlier  ages  of  these 
mammalia  of  a  low  grade,  and  the  absence  at  present  of  species  of 
higher  organization,  is  certainly  in  favor  of  the  theory  of  progressive 
development. 

Beneath  the  freshwater  strata  to  which  the  mammaliferous  marl 
belongs  is  a  thin  band  of  greenish  shales,  with  marine  shells  and  im- 
pressions of  leaves,  like  those  of  a  large  Zostera,  forming  the  base  of 
the  Middle  Purbeck. 

Lower  Purbeck. — Beneath  the  thin  marine  band  last  mentioned, 
purely  freshwater  marls  occur,  containing  species  of  Cypris  (fig.  375, 
a,  6),  Valvata,  and  Limncea,  dif- 
ferent from  those  of  the  Middle  Fig.  875. 
Purbeck.    This  is  the  beginning 
of  the  inferior  division,  which 
is  about  80  feet  thick.     Below 
the  marls  are  seen,  at  Meup's 
Bay,  more  than  30  feet  of  brack- 
ish-water strata,  abounding  in  a 
species  of  Serpula,  allied  to,  if 
not  identical  with    Serbia  co- 

acervites,  found  in  beds  of  the  E.  Forbes.  E.  Forbes. 

same   a^e   in  Hanover.     There 

O 

are  also  shells  of  the  genus  Rissoa  (of  the  subgenus  Hydrobia),  and  a 
little  Cardium  of  the  subgenus  Protocardium,  in  these  marine  beds, 
together  with  Cypris.  Some  of  the  cypris-bearing  shales  are  strangely 
contorted  and  broken  up,  at  the  west  end  of  the  Isle  of  Purbeck. 
The  great  dirt-bed  or  vegetable  soil  containing  the  roots  and  stools  of 
Cycadece,  which  I  shall  presently  describe,  underlies  these  marls,  and 
tests  upon  the  lowest  freshwater  limestone,  a  rock  about  8  feet  thick, 


390 


FOSSIL  FORESTS  IN  ISLE  OF  PORTLAND 


[On.  XX. 


Fig.  376. 


containing  Cydas,  Valvata,  and  Limncea,  of  the  same  species  as  those 
of  the  uppermost  part  of  the  Lower  Purbeck,  or  above  the  dirt-bed. 

The  freshwater  limestone  in  its 
turn  rests  upon  the  top  beds 
of  the  Portland  stone,  which, 
although  it  contains  purely  ma- 
rine remains,  often  consists  of  a 
rock  quite  homogeneous  in  min- 
eral character  with  the  Lowest 
Purbeck  limestone.* 

The  most  remarkable  of  all 
the  varied  succession  of  beds 
enumerated  in  the  above  list,  is 
that  called  by  the  quarrymen 
"the  dirt,"  or  "black  dirt," 

which  was  evidently  an  ancient  vegetable  soil.  It  is  from  12  to  18 
inches  thick,  is  of  a  dark  brown  or  black  color,  and  contains  a  large 
proportion  of  earthy  lignite.  Through  it  are  dispersed  rounded  frag- 
ments of  stone,  from  3  to  9  inches  in  diameter,  in  such  numbers  that 
it  almost  deserves  the  name  of  gravel.  Many  silicified  trunks  of 
coniferous  trees,  and  the  remains  of  plants  allied  to  Zamia  and  Cycas, 
are  buried  in  this  dirt-bed  (see  figure  of  fossil  species,  fig.  376,  and 
of  living  Zamia,  fig.  377). 

Fig.  377. 


Cycadeoidea  (MantelUd)  megalophylla, 
Buckland. 


Zamia  vpiralis.    Southern  Australia. 

These  plants  must  have  become  fossil  on  the  spots  where  they 
grew.  The  stumps  of  the  trees  stand  erect  for  a  height  of  from  one 
to  three  feet,  and  even  in  one  instance  to  six  feet,  with  their  roots 
attached  to  the  soil  at  about  the  same  distances  from  one  another  as 
the  trees  in  a  modern  forest.f  The  carbonaceous  matter  is  most 
abundant  immediately  around  the  stumps,  and  round  the  remains  of 
fossil  Cycadece.% 

*  Weston,  Geol.  Quart.  Journ.,  vol.  viii.  p.  117. 

f  Mr.  Webster  first  noticed  the  erect  position  of  the  trees,  and  described  the  Dirt-bed. 

j  Fitton,  Geol.  Trans.,  Second  Series,  vol.  iv.  pp.  220,  221. 


CH.  XX.] 


AND  LULWORTH  COVE. 


391 


Besides  the  upright  stumps  above  mentioned,  the  dirt-bed  contains 
the  stems  of  silicified  trees  laid  prostrate.  These  are  partly  sunk 
into  the  black  earth,  and  partly  enveloped  by  a  calcareous  slate 
which  covers  the  dirt-bed.  The  fragments  of  the  prostrate  trees  are 
rarely  more  than  3  or  4  feet  in  length  ;  but  by  joining  many  of  them 
together,  trunks  have  been  restored,  having  a  length  from  the  root  to 
the  branches  of  from  20  to  23  feet,  the  stems  being  undivided  for  17 
or  20  feet,  and  then  forked.  The  diameter  of  these  near  the  root  is 
about  one  foot.  Root-shaped  cavities  were  observed  by  Professor 
Henslow  to  descend  from  the  bottom  of  the  dirt-bed  into  the  subja- 
cent freshwater  stone,  which,  though  now  solid,  must  have  been  in  a 
soft  and  penetrable  state  when  the  trees  grew.* 


Freshwater  calcareous  slate. 


Dirt-bed  and  ancient  forest. 

Lowest  freshwater  beds  of  the  Lower 
Purbeck. 

Portland  stone,  marine. 


Section  in  Isle  of  Portland,  Dorset.    (Buckland  and  De  la  Beche.) 

The  thin  layers  of  calcareous  slate  (fig.  378)  were  evidently  de- 
posited tranquilly,  and  would  have  been  horizontal  but  for  the  pro- 
trusion of  the  stumps  of  the  trees,  around  the  top  of  each  of  which 
they  form  hemispherical  concretions. 

The  dirt-bed  is  by  no  means  confined  to  the  island  of  Portland, 
where  it  has  been  most  carefully  studied,  but  is  seen  in  the  same 
relative  position  in  the  cliffs  east  of  Lulworth  Cove,  in  Dorsetshire, 


Fig.  379. 


Freshwater  calcareous  slate. 
Dirt-bed,  with  stools  of  trees. 


Freshwater. 


Portland  stone,  marine. 


Section  in  cliff  east  of  Lulworth  Cove. ,  (Buckland  and  De  la  Beche.) 

where,  as  the  strata  have  been  disturbed,  and  are  now  inclined  at  an 
angle  of  45°,  the  stumps  of  the  trees  are  also  inclined  at  the  same 

*  Buckland  and  De  la  Beche,  Geol.  Trans.,  Second  Series,  vol.  iv.  p.  16.  Prof. 
Forbes  has  ascertained  that  the  subjacent  rock  is  a  freshwater  limestone,  and  not  a 
portion  of  the  Portland  oolite,  as  was  previously  imagined. 


392 


CHANGES  OF  MEDIUM— PURBECK  BEDS. 


[Cm  XX. 


angle  in  an  opposite  direction — a  beautiful  illustration  of  a  change 
in  the  position  of  beds  originally  horizontal  (see  fig.  379).  Traces 
of  the  dirt-bed  have  also  been  observed  by  Mr.  Fisher,  at  Ridgway  ;  by 
Dr.  Buckland,  about  two  miles  north  of  Thame,  in  Oxfordshire ;  and 
by  Dr.  Fitton,  in  the  cliffs  in  the  Boulonnois,  on  the  French  coast : 
but,  as  might  be  expected,  this  freshwater  deposit  is  of  limited  extent 
when  compared  to  most  marine  formations. 

From  the  facts  above  described  we  may  infer,  first,  that  those  beds 
of  the  Upper  Oolite,  called  "  the  Portland,"  which  are  full  of  marine 
shells,  were  overspread  with  fluviatile  mud,  which  became  dry  land, 
and  covered  by  a  forest,  throughout  a  portion  of  the  space  now  occu- 
pied by  the  south  of  England,  the  climate  being  such  as  to  admit  the 
growth  of  the  Zamia  and  Cycas.  2dly.  This  land  at  length  sank  down 
and  was  submerged  with  its  forests  beneath  a  body  of  fresh  water, 
from  which  sediment  was  thrown  down  enveloping  fluviatile  shells. 
3dly.  The  regular  and  uniform  preservation  of  this  thin  bed  of  black 
earth  over  a  distance  of  many  miles,  shows  that  the  change  from  dry 
land  to  the  state  of  a  freshwater  lake  or  estuary,  was  not  accompanied 
by  any  violent  denudation,  or  rush  of  water,  since  the  loose  black 
earth,  together  with  the  trees  which  lay  prostrate  on  its  surface,  must 
inevitably  have  been  swept  away  had  any  such  violent  catastrophe 
taken  place. 

The  dirt-bed  has  been  described  above  in  its  most  simple  form,  but 
in  some  sections  the  appearances  are  more  complicated.  The  forest 
of  the  dirt-bed  was  not  everywhere  the  first  vegetation  which  grew  in 
this  region.  Two  other  beds  of  carbonaceous  clay,  one  of  them  con- 
taining Cycadece,  in  an  upright  position,  have  been  found  below  it,  and 
one  above  it,  which  implies  other  oscillations  in  the  level  of  the  same 
ground,  and  its  alternate  occupation  by  land  and  water  more  than 


once. 


Table  showing  the  changes  of  Medium  in  which  the  strata  were 
formed,  from  the  Portland  Stone  up  to  the  Lower  Greensand  in- 
clusive, in  the  southeast  of  England  (beginning  with  the  lowest). 


Portland  Stone. 


Lower  Purbeck. 


1.  Marine 

2.  Freshwater 
Land 

Freshwater 
Land 

Freshwater 
Land  (Dirt-bed) 
Freshwater 
Land 
Brackish 
Freshwater 


The  annexed  tabular  view  will  enable  the  reader  to  take  in  at  a 
glance  the  successive  changes  from  sea  to  river,  and  from  river  to  sea, 


3.  Marine 

Freshwater 

Marine 

Brackish 

-  Middle  Purbeck. 

Marine 

Brackish 

Freshwater 

4.  Freshwater           Upper  Purbeck. 

5.  Freshwater       } 

Brackish           v  Hastings  Sands. 

Freshwater       ) 

6.  Freshwater           Wealden  day. 

7.  Marine                 Lower  Greensand. 

CH.  XX.]  PUKBECK  BEDS.  393 

or  from  these  again  to  a  state  of  land,  which  have  occurred  in  this 
part  of  England,  between  the  Oolitic  and  Cretaceous  periods.  That 
there  have  been  at  least  four  changes  in  the  species  of  testacea  during 
the  deposition  of  the  Wealden  and  Purbeck  beds,  seems  to  follow  from 
the  observations  recently  made  by  Professor  Forbes ;  so  that,  should 
we  hereafter  find  the  signs  of  many  more  alternate  occupations  of  the 
same  area  by  different  elements,  it  is  no  more  than  we  might  expect. 
Even  during  a  small  part  of  a  zoological  period,  not  sufficient  to  allow 
time  for  many  species  to  die  out,  we  find  that  the  same  area  has  been 
laid  dry,  and  then  submerged,  and  then  again  laid  dry,  as  in  the 
Deltas  of  the  Po  and  Ganges,  the  history  of  which  has  been  brought 
to  light  by  Artesian  borings.*  We  also  know  that  similar  revolutions 
have  occurred  within  the  present  century  (1819)  in  the  delta  of  the 
Indus  in  Cutch,f  where  land  has  been  laid  permanently  under  the 
waters  both  of  the  river  and  sea,  without  its  soil  or  shrubs  having  been 
swept  away.  Even  independently  of  any  vertical  movements  of  the 
ground,  we  see  in  the  principal  deltas,  such  as  that  of  the  Mississippi, 
that  the  sea  extends  its  salt  waters  annually  for  many  months  over 
considerable  spaces  which,  at  other  seasons,  are  occupied  by  the  river 
during  its  inundations. 

It  will  be  observed  that  the  division  of  the  Purbecks  into  upper, 
middle,  and  lower  has  been  made  by  Professor  Forbes  strictly  on  the 
principle  of  the  entire  distinctness  of  the  species  of  organic  remains 
which  they  include.  The  lines  of  demarcation  are  not  lines  of  dis- 
turbance, nor  indicated  by  any  striking  physical  characters  or  mineral 
changes.  The  features  which  attract  the  eye  in  the  Purbecks,  such 
as  the  dirt-beds,  the  dislocated  strata  at  Lulworth,  and  the  Cinder- 
bed,  do  not  indicate  any  breaks  in  the  distribution  of  organized  beings. 
"  The  causes  which  led  to  a  complete  change  of  life  three  times  during 
the  deposition  of  the  freshwater  and  brackish  strata  must,"  says  this 
naturalist,  "  be  sought  for,  not  simply  in  either  a  rapid  or  a  sudden 
change  of  their  area  into  land  or  sea,  but  in  the  great  lapse  of  time 
which  intervened  between  the  epochs  of  deposition  at  certain  periods 
during  their  formation." 

Each  dirt-bed  may,  no  doubt,  be  the  memorial  of  many  thousand 
years  or  centuries,  because  we  find  that  2  or  3  feet  of  vegetable  soil 
is  the  only  monument  which  many  a  tropical  forest  has  left  of  its 
existence  ever  since  the  ground  on  which  it  now  stands  was  first  cov- 
ered with  its  shade.  Yet,  even  if  we  imagine  the  fossil  soils  of  the 
Lower  Purbeck  to  represent  as  many  ages,  we  need  not  expect  on  that 
account  to  find  them  constituting  the  lines  of  separation  between  suc- 
cessive strata  characterized  by  different  zoological  types.  The  pres- 
ervation of  a  layer  of  vegetable  soil,  when  in  the  act  of  being  sub- 
merged, must  be  regarded  as  a  rare  exception  to  a  general  rule.  It  is 
of  so  perishable  a  nature,  that  it  must  usually  be  carried  away  by  the 

*  See  Principles  of  Geol,  9th  ed.,  pp.  255,  275.  \  ****•>  P-  460' 


394 


FOSSILS  OF  THE  PORTLAND  STONE. 


[Ca  XX. 


denuding  waves  or  currents  of  the  sea,  or  by  a  river ;  and  many  Pur- 
beck  dirt-beds  were  probably  formed  in  succession  and  annihilated, 
besides  those  few  which  now  remain. 

The  plants  of  the  Purbeck  beds,  so  far  as  our 
knowledge  extends  at  present,  consists  chiefly  of 
Ferns,  Coniferse  (fig.  380),  and  Cycadese  (fig.  376), 
without  any  angiosperms ;  the  whole  more  allied 
to  the  Oolitic  than  to  the  Cretaceous  vegetation. 
The  vertebrate  and  invertebrate  animals  indicate, 
like  the  plants,  a  somewhat  nearer  relationship  to 
the  Oolitic  than  to  the  Cretaceous  period.  Mr. 
cone  of  a  pine  from  the  Brodie  has  found  the  remains  of  beetles  and  sev- 
isieofPurbeck.  (Fitton.)  eraj  insects  of  the  homopterous  and  trichopterous 
orders,  some  of  which  now  live  on  plants,  while 
others  are  of  such  forms  as  hover  over  the  surface  of  our  present 
rivers. 

Portland  Oolite  and  Sand  (6,  Tab.,  p.  3*75). — The  Portland  oolite 
has  already  been  mentioned  as  forming  in  Dorsetshire  the  founda- 
tion on  which  the  freshwater  limestone  of  the  Lower  Purbeck  reposes 
(see  p.  389).  It  supplies  the  well-known  building-stone  of  which  St. 
Paul's  and  so  many  of  the  principal  edifices  of  London  are  construct- 
ed. This  upper  member  rests  on  a  dense  bed  of  sand,  called  the 
Portland  sand,  containing  for  the  most  part  similar  marine  fossils, 
below  which  is  the  Kimmeridge  clay.  In  England  these  Upper 
Oolite  formations  are  almost  wholly  confined  to  the  southern  coun- 
ties. Corals  are  rare  in  them,  although  one  species  is  found  plenti- 
fully at  Tisbury,  Wiltshire,  in  the  Portland  sand,  converted  into  flint 
and  chert,  the  original  calcareous  matter  being  replaced  by  silex 
(fig.  381). 

Fig.  881. 


Fig.  382. 


laastrcea  oblonga,  M.  Edw.  and  J.  Haime. 

As  seen  on  a  polished  slab  of  chert  from 

the  Portland  Sand,  Tisbury. 


Trigonia  gibbosa,    i  nat.  size. 

a.  The  hinge. 
Portland  Stone,  Tisbury. 


The  Kimmeridge  clay  consists,  in  great  part,  of  a  bituminous  shale, 
sometimes  forming  an  impure  coal,  several  hundred  feet  in  thickness 
In  some  places  in  Wiltshire  it  much  resembles  peat ;  and  the  bitu- 


CH.  XX.] 


FOSSILS  OF  THE  PORTLAND  STONE. 


395 


minous  matter  may  have  been,  in  part  at  least,  derived  from  the  de- 
composition of  vegetables.     But  as  impressions  of  plants  are  rare  in 


Fig.  3=!3. 


Fig.  384. 


Gardiwin  dissimile,    J  nat,  size. 
Portland  Stone. 


Ostrea  expanse. 
Portland  Sand. 


these  shales,  which  contain  ammonites,  oysters,  and  other  marine  shells, 
the  bitumen  may  perhaps  be  of  animal  origin. 

Among  the  characteristic  fossils  may  be  mentioned  Cardium  stria- 
tulum  (fig.  385)  and  Ostrea  deltoidea  (fig.  386),  the  latter  found  in 
the  Kimmeridge  clay  throughout  England  and  the  north  of  France, 
and  also  in  Scotland,  near  Brora.  The  Gryphcea  virgula  (fig.  387), 


Fig.  385. 


Fig.  386. 


Fig.  88T. 


Cardium  striatulum. 
Kimmeridge  clay,  Hartwell. 


Ostrea  deltoidea.  GrypJuaa  (Exogyra)  tir- 

Kimmeridge  clay,    i  nat.  size.     gula.    Kimmeridge  clay. 


Fig.  888. 


also  met  with  in  the  same  clay  near  Oxford,  is  so  abundant  in  the 
Upper  Oolite  of  parts  of  France  as  to  have  caused  the  deposit  to  be 
termed  "  marnes  a  gryphees  virgules."  Near  Clermont  in  Argonne, 
a  few  leagues  from  St.  Menehould,  where  these  indurated  marls  crop 
out  from  beneath  the  gault,  I  have  seen  them,  on  decomposing,  leave 
the  surface  of  every  ploughed  field  literally  strewed  over  with  this  fos- 
sil oyster.  The  Trigonellites  latus  (Aptychus,  of 
some  authors)  (fig.  388)  is  also  widely  dispersed 
through  this  clay.  The  real  nature  of  the  shell,  of 
which  there  are  many  species  in  oolitic  rocks,  is 
still  a  matter  of  conjecture.  Some  are  of  opinion 
that  the  two  plates  formed  the  gizzard  of  a 
cephalopod;  for  the  living  Nautilus  has  a  gizzard 
with  horny  folds,  and  the  Bulla  is  well  known  to  Kimmeridge  clay, 
possess  one  formed  of  calcareous  plates. 

The  celebrated  lithographic  stone  of  Solenhofen,  in  Bavaria,  be- 
longs to  one  of  the  upper  divisions  of  the  oolite,  and  affords  a  re- 


396  PTERODACTYL  AND  ARCH^IOPTERYX.  [On.  XX. 

markable  example  of  the  variety  of  fossils  which  may  be  preserved 
under  favorable    circumstances,   and  what    delicate   impressions   of 

the  tender  parts  of  certain  animals  and 
plants  may  be  retained  where  the  sediment 
is  of  extreme  fineness.  Although  the  num- 
ber of  testacea  in  this  slate  is  small,  and  the 
plants  few,  and  those  all  marine,  Count 
Miinster  had  determined  no  less  than  237 
species  of  fossils  when  I  saw  his  collection 
in  1833;  and  among  them  no  less  than 
seven  species  of  flying  lizards  or  pterodac- 
tyls (see  fig.  389),  six  saurians,  three  tor- 
toises, sixty  species  of  fish,  forty-six  of 
Crustacea,  and  twenty-six  of  insects.  These 
insects,  among  which  is  a  libellula,  or  dra- 
Skeieton  of  Pterodactyl^  gon-fly,  must  have  been  blown  out  to  sea, 

craseirostms.  *  ' 

Oolite  of  Pappenheim,  near  probably  from  the  same  land  to  which  the 
Soienhofen.  flying  lizards,  and  other  contemporaneous 

reptiles,  resorted. 

In  the  same  slate  of  Soienhofen  a  fine  example  was  met  with  in 
1862  of  the  skeleton  of  a  bird  almost  entire,  with  the  exception  of  the 
head,  and  retaining  even  its  feathers.  This  valuable  specimen  is  now 
in  the  British  Museum,  and  has  been  called  by  Professor  Owen 
Archceopteryx  macrura.  According  to  his  interpretation,  it  is  a  true 
bird,  and  not  intermediate,  as  was  at  first  imagined,  between  a  bird  and 
reptile.  It  was  about  the  size  of  a  rook.  It  differs  remarkably  from 
all  known  birds  in  having  two  free  claws  belonging  to  the  win^,  and 
in  the  structure  of  its  tail ;  for  in  almost  all  living  representatives  of 
the  class  Aves,  the  tail  feathers  are  attached  to  a  coccygian  bone,  con- 
sisting of  several  vertebrae  united  together,  whereas  in  the  Archseop- 
teryx  the  tail  is  composed  of  twenty  vertebrae,  each  of  which  supports 
a  pair  of  quill  feathers  so  perfect  that  the  vanes  as  well  as  the  shaft 
are  preserved.  The  first  five  only  of  the  vertebras  as  seen  in  A  have 
transverse  processes,  the  fifteen  remaining  ones  become  gradually  long- 
er and  more  tapering.  The  feathers  diverge  outward  from  them  at  an 
angle  of  45° ;  but  this  departure  from  the  true  ornithic  type  occurs, 
says  Professor  Owen,  in  that  part  of  the  skeleton  which  is  most  subject 
to  variation. 

Thus  there  are  short  and  long-tailed  species  of  bats,  rodents,  and 
pterodactyles,  with  great  variation  in  the  number  of  their  caudal  verte- 
bras ;  he  also  observes  that  although  in  living  birds  a  short  bony  tail, 
and  generally  accompanied  by  a  coalescence  of  the  terminal  vertebrae 
to  form  the  ploughshare  bone/E,  is  a  constant  character,  yet  all  birds 
in  their  embryonic  state  exhibit  the  vertebrae  distinct  and  separate,  so 
that  the  tail  of  the  Archaeopteryx  exhibits  a  retention  of  structure 
which  is  u  embryonal  and  transitory  in  the  modern  representatives  of 
the  class,  and  consequently  a  closer  adhesion  to  the  general  vertebrate 


CH.  XX.] 


ARCILEOPTERYX  OF  SOLENHOFEN. 


397 


type."     In  the  young  ostrich  from  eighteen  to  twenty  caudal  vertebra 
may  be  counted,  seven  or  eight  of  which  are  annexed  to  the  sacrum, 


Fig.  890. 


Tail  of  Archaopteryx  macrura,  Owen,  and  Feather  of  A.  UthograpMa,  Meyer,  from  the  slate 
of  Solenhofen ;  and  tail  of  living  bird  for  comparison. 

A.  Series  of  caudal  vertebrae  (with  impressions  of  the  tail-feathers  preserved  in  situ)  of  Ar- 

chceopteryx  macrura,  Owen.  |  nat.  size.  Drawn  from  the  specimen  in  the  British 
Museum  (ventral  aspect). 

B.  Two  of  the  caudal  vertebrae,  nat.  size,  showing  their  shape  and  the  absence  of  transverse 

processes. 

C.  Single  feather,  called  Archceopteryx  liihographica  by  Von  Meyer.    Natural  size. 

This  feather,  upon  which  the  genus  was  established  in  1861,  was  discovered  at  Solen- 
hofen. See  "  Jahrbuch  fur  Mineralogie,"  1861,  p.  561. 

D.  Tail  of  recent  vulture  (Gyps  JSengalensis),  showing  the  points  of  attachment  for  the  prin- 

cipal tail-feathers  (dorsal  view,  £  nat.  size). 

E.  Profile  of  caudal  vertebrae  of  same,  to  show  the  broad  terminal  joint,  or  "ploughshare" 

bone,  /,  of  the  tail,  the  same  as  that  seen  foreshortened  at/D,  so  largely  developed  in 
nearly  all  living  birds.  £  nat.  size. 

N.  B.— The  figures  1  to  6  indicate  the  correspondence  between  the  vertebrae  in  the  two 
views  D  and  E. 

/E  and/D  indicate  the  position  of  the  terminal  joint 

The  dotted  lines  E,  e,  e,  show  the  direction  of  the  quill  feathers  of  the  tail  when  seen 
in  profile. 

The  ploughshare  bone  can  be  elevated  at  pleasure  (as  seen  at  /  E),  to  meet  the  ex- 
tended beak  of  the  bird  when  seeking  the  coccigian  oil-gland  (which  is  placed  upon  this 
terminal  joint)  to  lubricate  its  feathers  while  preening.  Only  the  "primaries"  or  great 
tail  feathers  are  represented  in  fig.  D ;  the  bases  of  these  and  the  rest  of  tho  vertebra? 
are  clothed  in  secondary  feathers  and  down. 

while  two  or  three  are  welded  together  to  form  the  slender  terminal 
bone,  which  in  this  and  other  running  birds  (cursores)  is  not  plough- 
share-shaped. 

It  has  been  already  stated  that  no  species  of  British  fossil,  whether 
of  the  vertebrata  or  invertebrata,  are  common  to  the  Oolite  and  Chalk, 
or,  to  speak  more  strictly,  are  common  to  the  marine  beds  of  these 
two  groups  which  stand  nearest  to  each  other,  namely,  the  Portland 
limestone  and  the  Atherfield  beds ;  but  while  there  is  this  great  break 


398  CORAL-RAG.  [Cn.  XX. 

in  an  upward  direction,  there  is  no  similar  discordance  as  we  proceed 
downwards,  and  pass  from  one  to  another  of  the  several  members  of 
the  Jurassic  group,  the  Upper,  Middle,  and  Lower  Oolite,  and  the 
Lias.  Thus,  for  example,  I  find  on  consulting  Mr.  Etheridge's  tables 
of  British  Fossils,*  that  of  sixty  species  of  all  classes  that  lived  in  the 
period  of  the  Kimmeridge  clay,  twenty,  or  about  33  per  cent.,  pass 
down  into  the  Coral-Rag ;  or,  if  we  confine  our  attention  exclusively 
to  the  mollusca,  of  thirty-three  species  in  the  Kimmeridge  clay,  eight, 
or  24  per  cent.,  are  common  to  the  Coral-Rag. 

MIDDLE    OOLITE. 

Coral-Rag. — One  of  the  limestones  of  the  Middle  Oolite  has  been 
called  the  "Coral-Rag,"  because  it  consists,  in  part,  of  continuous 
beds  of  petrified  corals,  for  the  most  part  retaining  the  position  in 
which  they  grew  at  the  bottom  of  the  sea.  In  their  forms  they  more 
frequently  resemble  the  reef-building  poliparia  of  the  Pacific  than 
do  the  corals  of  any  other  member  of  the  Oolite.  They  belong 
chiefly  to  the  genera  Thecosmilia  (fig.  391),  Protosseis,  and  Tham- 
nastrcea,  and  sometimes  form  masses  of  coral  15  feet  thick.  In  the 
annexed  figure  of  a  Thamnastrcea  (fig.  392),  from  this  formation,  it 

Fig.  89L 


Fig.  892. 


Thecosmilia  annularis,  Milne  Edw.  and  J.  Haime.  Thamnastrcea. 

Coral-rag,  Steeple  Ashton.  Coral-rag,  Steeple  Ashton. 

will  be  seen  that  the  cup-shaped  cavities  are  deepest  on  the  right- 
hand  side,  and  that  they  grow  more  and  more  shallow,  until  those 
on  the  left  side  are  nearly  filled  up.  The  last-mentioned  stars  are 
supposed  to  represent  a  perfected  condition,  and  the  others  an  imma- 
ture state.  These  coralline  strata  extend  through  the  calcareous  hills 
of  the  N.W.  of  Berkshire,  and  north  of  Wilts,  and  again  recur  in 
Yorkshire,  near  Scarborough.  The  Ostrea  gregarea  (fig.  393)  is  very 
characteristic  of  the  formation  in  England  and  on  the  Continent. 

*  Compiled  for  a  work  entitled  "  Stratigraphical  Arrangement  of  British  Fos- 
sils," now  preparing  for  publication  by  Mr.  Etheridge. 


CH.  XX.] 


CORALS  OF  THE  OOLITE. 


399 


One  of  the  limestones  of  the  Jura,  referred  to  the  age  of  the 
English  coral-rag,  has  been  called  "Nerinaean  limestone"  (Calcaire 
a  Nerinees)  by  M.  Thirria ;  Nerincea  being  an  extinct  genus  of  uni- 
valve shells,  much  resembling  the  Cerithium  in  external  form.  The 
annexed  section  (fig.  394)  shows  the  curious  form  of  the  hollow  part 
of  each  whorl,  and  also  the  perforation  which  passes  up  the  middle 


Fig.  394. 


Fig.  395. 


Fig.  393. 


Ostrea  gregarea. 
Coral-rag,  Steeple  Ashton. 


Nerincea  Meroglyphica. 
Coral-rag. 


Nerinaa  GoodJiallii,  Fitton. 
Coral-rag,  "Weymouth.  }  nat.  size. 


of  the  columella.  N.  Goodhallii  (fig.  395)  is  another  English  spe- 
cies of  the  same  genus,  from  a  formation  which  seems  to  form  a 
passage  from  the  Kimmeridge  clay  to  the  coral-rag.* 

A  division  of  the  oolite  in  the  Alps,  regarded  by  most  geologists 
as  coeval  with  the  English  coral-rag,  has  been  often  named  "  Cal- 
caire a  Dicerates,"  or  "  Diceras  limestone,"  from  its  containing  abun- 
dantly a  bivalve  shell  (see  fig.  396)  of  a  genus  allied  to  the  Chama. 


Fig.  897. 


Fig.  396. 


Cast  ef  JHc&ras  arietina. 
Coral-rag,  France. 


Oidaris  coronate. 
Coral-rag. 


Oxford  Clay. — The  coralline  limestone,  or  "  coral-rag,"  above  de- 
scribed, and  the  accompanying  sandy  beds,  called  "  calcareous  grits," 
of  the  Middle  Oolite,  rest  on  a  thick  bed  of  clay,  called  the  "  Oxford 


*  Fitton,  Geol.  Trans.,  Second  Series,  rol.  iv.  pi.  23,  fig.  12. 


400 


KELLOWAY  ROCK. 


[On.  XX. 


clay,"  sometimes  not  less  than  500  feet  thick.  In  this  there  are  no 
corals,  but  great  abundance  of  cephalopoda,  of  the  genera  Ammonite 
|ind  Belemnite.  (See  figs.  398,  399.)  In  some  of  the  finely  lami- 


Fig. 


Belmwites  Tiaslatus.    Oxford  clay. 

nated  clays  ammonites  are  very  perfect,  although  somewhat  com- 
pressed, and  are  frequently  found  with  the  lateral  lobe  expanded  on 
each  side  of  the  opening  of  the  mouth  into  a  single  horn-like  projec- 
tion (see  fig.  399).  These  were  discovered  in  the  cuttings  of  the 
Great  Western  Railway,  near  Chippenham,  in  1841,  and  have  been 
described  by  Mr.  Pratt  (An.  Nat.  Hist.,  Nov.  1841). 

Fig.  899. 


Ammonites  (Jason,  Eeinecke.    Syn.  A.  Elisabethce,  Pratt). 
Oxford  clay,  Christian  Malford,  Wiltshire. 

Similar  elongated  processes  have  been  also  observed  to  extend  from 
the  shells  of  some  belemnites  discovered  by  Dr.  Mantell,  in  the  same 
clay  (see  fig.  400),  who,  by  the  aid  of  this  and  other  specimens,  has 
been  able  to  throw  much  light  on  the  structure  of  this  and  other  sin- 
gular extinct  forms  of  cuttle-fish.* 

Kelloway  Rock. — The  arenaceous  limestone  which  passes  under  this 
name  is  generally  grouped  as  a  member  of  the  Oxford  clay,  in  which 
it  forms,  in  the  south-west  of  England,  lenticular  masses,  8  or  10  feet 
thick,  containing  at  Kelloway,  in  Wiltshire,  numerous  casts  of  am- 
monites and  other  shells.  But  in  Yorkshire  this  calcareo-arenaceous 
formation  thickens  to  about  30  feet,  and  constitutes  the  lower  part  of 

*  See  Phil.  Trans.,  1850,  p.  393 ;  also  fluxley,  Memoirs  of  Geol.  Survey,  1864. 


CH.  XX.] 


LOWER  OOLITE. 


401 


the  Middle  Oolite,  extending  inland  from 
Scarborough  in  a  southerly  direction.  The 
number  of  mollusca  which  it  contains  is, 
according  to  Mr.  Etheridge,  106,  of  which 
only  twenty-three,  or  22J  per  cent.,  are 
common  to  the  Oxford  clay  proper.  Of 
the  twenty  Cephalopoda,  eight  (namely, 
one  of  the  Sepia  family,  six  species  of 
ammonite,  and  the  Ancyloceras  Callovi- 
ense)  are  common  to  the  Oxford  Clay,  giv- 
ing a  proportion  of  40  per  cent. 

If,  on  the  other  hand,  we  compare  the 
fossils  of  all  kinds  in  the  Kelloway  rock, 
amounting  to  151  species,  with  the  fossils 
of  the  underlying  Lower  Oolite,  we  find 
that  seventy-four  pass  down  into  the  older 
rocks,  or  about  49  per  cent. ;  or  if  we  con- 
fine our  attention  to  the  mollusca  alone  of 
the  Kelloway  considered  as  the  base  of  the 
Middle  Oolite,  and  compare  them  with 
those  of  the  Cornbrash,  or  the  top  mem- 
ber of  the  Lower  Oolite,  we  find  106  spe- 
cies in  the  Kelloway,  and  123  in  the  Corn- 
brash,  and  22  species  common  to  the  two, 
implying  a  community  of  21  per  cent,  be- 
tween the  two  formations. 


Fig.  347. 


LOWER    OOLITE. 

Cornbrash  and  Forest  Marble.  —  The 
upper  division  of  this  series,  which  is  more 
extensive  than  the  preceding  or  Middle 
Oolite,  is  called  in  England  the  Cornbrash. 
It  consists  of  clays  and  calcareous  sand- 
stones, which  pass  downwards  into  the 
Forest  Marble,  an  argillaceous  limestone, 
abounding  in  marine  fossils.  In  some 
places,  as  at  Bradford,  this  limestone  is 
replaced  by  a  mass  of  clay.  The  sand- 
stones of  the  Forest  Marble  of  Wiltshire 
are  often  ripple-marked  and  filled  with 
fragments  of  broken  shells  and  pieces  of 
drift-wood,  having  evidently  been  formed 
on  a  coast.  Rippled  slabs  of  fissile  oolite 
are  used  for  roofing,  and  have  been  traced 
over  a  broad  band  of  country  from  Brad- 
26 


Belemnites  Puzosianus, 
B.  Owenii,  Pierce. 

Oxford  Clay,  Christian  Malford. 

rt,  a.  Projecting  processes  of  the 
shell  or  phragmocone. 

&,  c.  Broken  exterior  of  a  coni- 
cal shell  called  the  phrag- 
mocone, which  is  cham- 
bered within,  or  composed 
of  a  series  of  shallow  con- 
cave cells  pierced  by  a 
siphnncle. 

c,  d.  The  guard  or  osselet,  which 
is  commonly  called  the 
belemnite. 


402 


BRADFORD  ENCRINITES. 


[On.  XX. 


ford  in  Wilts,  to  Tetbury  in  Gloucestershire.  These  calcareous  tile- 
stones  are  separated  from  each  other  by  thin  seams  of  clay,  which 
have  been  deposited  upon  them,  and  have  taken  their  form,  preserv- 
ing the  undulating  ridges  and  furrows  of  the  sand  in  such  complete 
integrity,  that  the  impressions  of  small  footsteps,  apparently  of  crus- 
taceans, which  walked  over  the  soft  wet  sands,  are  still  visible.  In 
the  same  stone  the  claws  of  crabs,  fragments  of  echini,  and  other 
signs  of  a  neighboring  beach,  are  observed.* 

Great  Oolite. — Although  the  name  of  coral-rag  has  been  appropri- 
ated, as  we  have  seen,  to  a  member  of  the  Upper  Oolite  before  de- 
scribed, some  portions  of  the  Lower  Oolite  are  equally  entitled  in 
many  places  to  be  called  coralline  limestones.  Thus  the  Great  Oolite 
near  Bath  contains  various  corals,  among  which  the  Eunomia  radiata 
(fig.  401)  is  very  conspicuous,  single  individuals  forming  masses  sev- 


Ewnomia  radiata,  Lamouroux.    (CalamopJiyllia,  Milne  Edw.) 

a.  Section  transverse  to  the  tubes. 

ft.  Vertical  section,  showing  the  radiation  of  the  tubes. 

c.  Portion  of  interior  of  tubes  magnified,  showing  striated  surface. 

eral  feet  in  diameter ;  and  having  probably  required,  like  the  large 
existing  brain-coral  (Meandrina)  of  the  tropics,  many  centuries  before 
their  growth  was  completed. 

Different  species  of  crinoids,  or  stone-lilies,  are  also  common  in  the 
same  rocks  with  corals ;  and,  like  them,  must  have  enjoyed  a  firm 
bottom,  where  their  root,  or  base  of  attachment,  remained  undis- 
turbed for  years  (c,  fig.  402).  Such  fossils,  therefore,  are  almost  con- 
fined to  the  limestones ;  but  an  exception  occurs  at  Bradford,  near 
Bath,  where  they  are  enveloped  in  clay.  In  this  case,  however,  it 
appears  that  the  solid  upper  surface  of  the  "  Great  Oolite  "  had  sup- 
ported, for  a  time,  a  thick  submarine  forest  of  these  beautiful  zoo- 
phytes, until  the  clear  and  still  water  was  invaded  by  a  current 
charged  with  mud,  which  threw  down  the  stone-lilies,  and  broke  most 
of  their  stems  short  off  near  the  point  of  attachment.  The  stumps 
still  remain  in  their  original  position ;  but  the  numerous  articulations, 
once  composing  the  stem,  arms,  and  bodji  of  the  encrinite,  were  scat- 

*  P.  Scrope,  Geol.  Proceed.,  March,  1831. 


CH.  XX.] 


BRADFORD  ENCRINITES. 


403 


tered  at  random  through,  the  argillaceous  deposit  in  which  some  now 
lie  prostrate.  These  appearances  are  represented  in  the  section  6,  fig. 
402,  where  the  darker  strata  represent  the  Bradford  clay,  which  some 


Fig.  402. 


Apiocnnites  rotundus,  or  Pear  Encrinite ;  Miller.    Fossil  at  Bradford,  "Wilts. 
a.  Stem  of  Apiocrinites,  and  one  of  the  articulations,  natural  size. 

&.  Section  at  Bradford  of  Great  Oolite  and  overlying  clay,  containing  the  fossil  encrinites.    See 
text. 

c.  Threo  perfect  individuals  of  Apiocrinites,  represented  as  they  grow  on  the  surface  of  the 

Great  Oolite. 

d.  Body  of  the  ApiocHnites  rotundus. 

geologists  class  with  the  Forest  Marble,  others  with  the  Great  Oolite. 
The  upper  surface  of  the  calcareous  stone  below  is  completely  en- 
crusted over  with  a  continuous  pavement,  formed  by  the  stony  roots 
or  attachments  of  the  Crinoidea ;  and  besides  this  evidence  of  the 
length  of  time  they  had  lived  on  the  spot,  we  find  great  numbers  of 
single  joints,  or  circular  plates  of  the  stem  and  body  of  the  encrinite, 
covered  over  with  serpulce.  Now  these  serpulce  could  only  have 

Fig.  408. 


a.  Single  plate  or  articulation  of  an  Encrinite  overgrown  with  aerpulce  and  ~bryozoa.    Natural 

size.    Bradford  clay. 
&.  Portion  of  the  same  magnified,  showing  the  bryozoan  Diastopora  diluviana  covering  one 

of  the  serpulce. 

begun  to  grow  after  the  death  of  some  of  the  stone-lilies,  parts  of 
whose  skeletons  had  been  strewed  over  the  floor  of  the  ocean  before 
the  irruption  of  argillaceous  mud.  In  some  instances  we  find  that, 


404  BRADFORD  ENCRINITES.  [Cn.  XX. 

after  the  parasitic  serpulce  were  full  grown,  they  had  become  incrusted 
over  with  a  bryozoan,  called  Diastopora  diluviana  ;  and  many  gener- 
ations of  these  molluscoids  had  succeeded  each  other  in  the  pure 
water  before  they  became  fossil. 

We  may,  therefore,  perceive  distinctly  that,  as  the  pines  and  cyca- 
deous  plants  of  the  ancient  "  dirt-bed,"  or  fossil  forest,  of  the  Lower 
Purbeck  were  killed  by  submergence  under  fresh  water,  and  soon 
buried  beneath  muddy  sediment,  so  an  invasion  of  argillaceous  matter 
put  a  sudden  stop  to  the  growth  of  the  Bradford  Encrinites  and  led  to 
their  preservation  in  marine  strata.* 

Such  differences  in  the  fossils  as  distinguish  the  calcareous  and 
argillaceous  deposits  from  each  other,  would  be  described  by  natu- 
ralists as  arising  out  of  a  difference  in  the  stations  of  species ;  but 
besides  these,  there  are  variations  in  the  fossils  of  the  higher,  middle, 
and  lower  part  of  the  oolitic  series,  which  must  be  ascribed  to  that 
great  law  of  change  in  organic  life  by  which  distinct  assemblages  of 
species  have  been  adapted,  at  successive  geological  periods,  to  the 
varying  conditions  of  the  habitable  surface.  In  a  single  district  it  is 
difficult  to  decide  how  far  the  limitation  of  species  to  certain  minor 
formations  has  been  due  to  the  local  influence  of  stations,  or  how  far 
it  has  been  caused  by  time  or  the  creative  and  destroying  law  above 
alluded  to.  But  we  recognize  the  reality  of  the  last-mentioned  influ- 
ence, when  we  contrast  the  whole  oolitic  series  of  England  with  that 
of  parts  of  the  Jura,  Alps,  and  other  distant  regions,  where  there  is 
scarcely  any  lithological  resemblance ;  and  yet  some  of  the  same  fossils 
remain  peculiar  in  each  country  to  the  Upper,  Middle,  and  Lower 
Oolite  formations  respectively.  Mr.  Thurmann  has  shown  how  remark- 
ably this  fact  holds  true  in  the  Bernese  Jura,  although  the  argillaceous 
divisions,  so  conspicuous  in  England,  are  feebly  represented  there,  and 
some  entirely  wanting. 

The  Bradford  clay,  above  alluded  to,  is  sometimes  60  feet  thick,  but 
in  many  places  it  is  wanting ;  and  in  others,  where  there  are  no  lime- 
stones, it  cannot  easily  be  separated  from  the  clays  of  the  overlying 
"  forest  marble  "  and  underlying  "  fuller's  earth." 

The  calcareous  portion  of  the  Great  Oolite  consists  of  several  shelly 
limestones,  one  of  which,  called  the  Bath  Oolite,  is  much  celebrated 
as  a  building-stone.  In  parts  of  Gloucestershire,  especially  near  Min- 
chinhampton,  the  Great  Oolite,  says  Mr.  Lycett,  "  must  have  been  de- 
posited in  a  shallow  sea,  where  strong  currents  prevailed,  for  there  are 
frequent  changes  in  the  mineral  character  of  the  deposit,  and  some  beds 
exhibit  false  stratification.  In  others,  heaps  of  broken  shells  are  min- 
gled with  pebbles  of  rocks  foreign  to  the  neighborhood,  and  with  frag- 
ments of  abraded  madrepores,  dicotyledonous  wood,  and  crabs'  claws. 
The  shelly  strata,  also,  have  occasionally  suffered  denudation,  and  the 

*  For  a  fuller  account  of  these  Encrinites,  see  Buckland's  Bridgewater  Treatise, 
vol.  i.  p.  429. 


On.  XX.] 


STONESFIELD  SLATE. 


405 


removed  portions  have  been  replaced  by  clay."  *  In  such  shallow- 
water  beds  shells  of  the  genera  Patella,  Nerita,  Rimula,  and  Cylindrites 
are  common  (see  figs.  406  to  409) ;  while  cephalopods  are  rare,  and,  in- 


Fig.  405. 


Fig.  404. 


Fig.  406. 


Terebratula  digona. 
Nat.  size.    Bradford  clay. 


Fig.  407. 


Purpuroidea  nodulata. 

J  nat.  size.    Great  Oolite, 

Minchinhampton. 


Fig.  408. 


Oylindrites  acv&us,  Sow. 
Syn.  ActcBon  acutus. 

Great  Oolite, 
Minchinhampton. 

Fig.  409. 


Patella  rugosa,  Sow. 
Great  Oolite. 


ITerita  costulata,  Desh.    fiimula  (Emarginula)  clath- 
Great  Oolite.  rota,  Sow.    Great  Oolite. 


stead  of  ammonites  and  belemnites,  numerous  genera  of  carnivorous 
trachelipods  appear.  Out  of  142  species  of  univalves  obtained  from 
the  Minchinhampton  beds,  Mr.  Lycett  found  no  less  than  41  to  be 
carnivorous.  They  belong  principally  to  the  genera  Buccinum,  Pleuro- 
toma,  Rostellaria,  Murex,  Purpuroidea  (fig.  405),  and  Fusus,  and  ex- 
hibit a  proportion  of  zoophagous  species  not  very  different  from  that 
which  obtains  in  warm  seas  of  the  Recent  period.  These  zoological 
results  are  curious  and  unexpected,  since  it  was  imagined  that  we  might 
look  in  vain  for  the  carnivorous  trachelipods  in  rocks  of  such  high  anti- 
quity as  the  Great  Oolite,  and  it  was  a  received  doctrine  that  they  did 
not  begin  to  appear  in  considerable  numbers  till  the  Eocene  period, 
when  those  two  great  families  of  cephalopoda,  the  ammonites  and  belem- 
nites, had  become  extinct. 

Stonesfield  slate. — The  slate  of  Stonesfield  has  been  shown  by  Mr. 
Lonsdale  to  lie  at  the  base  of  the  Great  Oolite.f  It  is  a  slightly  oolitic 
shelly  limestone,  forming  large  lenticular  masses  imbedded  in  sand, 
only  6  feet  thick,  but  very  rich  in  organic  remains.  It  contains  some 
pebbles  of  a  rock  very  similar  to  itself,  and  which  may  be  portions  of 
the  deposit,  broken  up  on  a  shore  at  low  water  or  during  storms,  and 
redeposited.  The  remains  of  belemnites,  trigonise,  and  other  marine 


*  Lycett,  Geol.  Journ.,  vol.  iv.  p.  188. 
f  Proceedings  Geol.  Soc.,  vol.  i.  p.  414. 


406 


MAMMALIA  OF  GREAT  OOLITE. 


[On.  XX. 


Fig.  410. 


Elytron  of 
BupreaUa  f 
Stonesfleld. 


shells,  with  fragments  of  wood,  are  common,  and  impressions  of  ferns, 
cycadese,  and  other  plants.  Several  insects,  also,  and,  among  the  rest, 
the  wing-covers  of  beetles,  are  perfectly  preserved  (see  fig. 
410),  some  of  them  approaching  nearly  to  the  genus  Bupres- 
tis*  The  remains,  also,  of  many  genera  of  reptiles,  such  as 
Pleiosaur,  Crocodile,  and  Pterodactyl,  have  been  discover- 
ed in  the  same  limestone. 

But  the  remarkable  fossils  for  which  the  Stonesfield 
slate  is  most  celebrated  are  those  referred  to  the  mam- 
miferous  class.  The  student  should  be  reminded  that  in 
all  the  rocks  described  in  the  preceding  chapters  as  older 
than  the  Eocene,  no  bones  of  any  land-quadruped,  or  of 
any  cetacean,  had  been  discovered  until  the  Spalacothe- 
rium  of  the  Purbeck  beds  came  to  light  in  1854  (see 
above,  p.  381).  Yet  we  have  seen  that  terrestrial  plants  were  not 
rare  in  the  lower  cretaceous  formation,  and  that  in  the  Wealden  there 
was  evidence  of  freshwater  sediment  on  a  large  scale,  containing  various 
plants,  and  even  ancient  vegetable  soils.  We  had  also  in  the  same 
Wealden  many  land-reptiles  and  winged  insects,  which  render  the  ab- 
sence of  terrestrial  quadrupeds  the  more  striking.  The  want,  however, 
of  any  bones  of  whales,  seals,  dolphins,  and  other  aquatic  mammalia, 
whether  in  the  chalk  or  in  the  upper  or  middle  oolite,  is  certainly 
still  more  remarkable.  Formerly,  indeed,  a  bone  from  the  Great  Oolite 
of  Enstone,  near  Woodstock,  in  Oxfordshire,  was  cited,  on  the  author- 
ity of  Cuvier,  as  referable  to  this  class.  Dr.  Buckland,  who  stated 
this  in  his  Bridgewater  Treatise,f  had  the  kindness  to  send  me  the 
supposed  ulna  of  a  whale,  that  Prof.  Owen  might  examine  into  its 
claims  to  be  considered  as  cetacean.  It  is  the  opinion  of  that  eminent 
comparative  anatomist  that  it  cannot  have  belonged  to  the  cetacea, 
because  the  fore-arm  in  these  marine  mammalia  is  invariably  much 

Fig.  4U. 


Bone  of  a  Beptile,  formerly  supposed  to  be  the  ulna  of  a  Cetacean ;  from  the  Great  Oolite 
of  Enstone,  near  "Woodstock. 

*  See  Buckland's  Bridgewater  Treatise ;  and  Brodie's  Fossil  Insects,  where  it  is 
suggested  that  these  elytra  may  belong  to  Prionus. 
f  Vol.  i.  p.  115. 


CH.  XX.]  MAMMALIA  OF  STONESFIELD  OOLITE.  407 

flatter,  and  devoid  of  all  muscular  depressions  and  ridges,  one  of 
which  is  so  prominent  in  the  middle  of  this  bone,  represented  in  the 
preceding  cut  (fig.  411).  In  saurians,  on  the  contrary,  such  ridges  exist 
for  the  attachment  of  muscles ;  and  to  some  animal  of  that  class  the 
bone  is  probably  referable. 

These  observations  are  made  to  prepare  the  reader  to  appreciate 
more  justly  the  interest  felt  by  every  geologist  in  the  discovery  in  the 
Stonesfield  slate  of  no  less  than  ten  specimens  of  lower  jaws  of  mam- 
miferous  quadrupeds,  belonging  to  four  different  species  and  to  three 
distinct  genera,  for  which  the  names  of  Amphitherium,  Phascolotherium, 
and  Stereo gnathus,  have  been  adopted.  When  Cuvier  was  first  shown 
one  of  these  fossils  in  1818  (namely,  the  Amphitherium),  he  pro- 
nounced it  to  belong  to  a  small  ferine  mammal,  with  a  jaw  much  re- 
sembling that  of  an  opossum,  but  differing  from  all  known  ferine 
genera  in  the  great  number  of  the  molar  teeth,  of  which  it  had  at 
least  ten  in  a  row.  Since  that  period  a  much  more  perfect  specimen 
of  the  same  fossil,  obtained  by  Dr.  Buckland  (see  fig.  412),  has  been 
examined  by  Professor  Owen,  who  finds  that  the  jaw  contained  on  the 
whole  twelve  molar  teeth,  with  the  socket  of  a  small  canine,  and  three 
small  incisors,  which  are  in  situ,  altogether  amounting  to  sixteen  teeth 
on  each  side  of  the  lower  jaw. 

The  only  question  which  could  be  raised  respecting  the  nature  of 
these  fossils  was,  whether  they  belonged  to  a  mammifer,  a  reptile,  or 
a  fish.  Now  on  this  head  the  osteologist  observes  that  each  of  the  half 
jaws  in  question  is  composed  of  but  one  single  piece,  and  not  of  two 
or  more  separate  bones,  as  in  fishes  and  most  reptiles,  or  of  two  bones 
united  by  a  suture,  as  in  some  few  species  belonging  to  those  classes. 

Fig.  412. 
Natural  size. 


Amphitherium  Prevostii,  Cuv.  sp.  Stonesfield  Slate.  Syn.  Thylacotherium  Prevostii,  Valenc. 
a.  Coronoid  process.       &.  Condyle.       c.  Angle  of  jaw.       d.  Double-fanged  molars. 

The  condyle,  moreover  (6,  fig.  412),  or  Fis-  413< 

articular  surface,  by  which  the  lower  jaw 
unites  with  the  upper,  is  convex  in  the 
Stonesfield  specimens,  and  not  concave  as 
in  fishes  and  reptiles.  The  coronoid  pro-  Amphitherium  Broderipii,  Owen. 

Cess  (a,  fig.  412)  is  well  developed,  whereas       Natural  size.    Stonesfield  slate. 

it  is  wanting,  or  very  small,  in  the  inferior 

classes  of  vertebrata.     Lastly,  the  molar  teeth  in  the  Amphitherium 


408 


MAMMALIA  OF  STONESFIELD  OOLITE. 


[On.  XX. 


and  Phascolotherium  have  complicated  crowns  and  two  roots  (see  d, 
fig.  412),  instead  of  being  simple  and  with  single  fangs.* 

The  only  question,  therefore,  which  could  fairly  admit  of  contro- 
versy was  limited  to  this  point,  whether  the  fossil  mammalia  found  in 
the  Lower  Oolite  of  Oxfordshire  ought  to  be  referred  to  the  marsupial 
quadrupeds,  or  to  the  ordinary  placental  series.  Cuvier  had  long  ago 
pointed  out  a  peculiarity  in  the  form  of  the  angular  process  (c,  figs. 
41 Y  and  418)  of  the  lower  jaw,  as  a  character  of  the  genus  Didelphys  ; 


Fig.  414. 


Tupaia  Tana. 
Eight  ramus  of  lower  jaw. 

Natural  size. 

A  recent  insectivorous  placental 
mammal,  from  Sumatra. 


Fig.  418. 


Part  of  lower  jaw  of  Tupaia  Tana  ; 

twice  natural  size. 
Fig.  415.    End  view  seen  from  behind, 

showing  the  very  slight  inflection  of 

the  angle  at  c. 
Fig.  416.    Side  view  of  same. 


Part  of  lower  jaw  of  Didelphys  Asarce  ; 
recent,  Brazil.    Natural  size. 

Fig.  417.  End  view  seen  from  behind,  show- 
ing the  inflection  of  the  angle  of  the  jaw, 
c,d, 

Fig.  418.    Side  view  of  same. 


and  Professor  Owen  has  since  confirmed  the  doctrine  of  its  generality 
in  the  entire  marsupial  series.  In  all  these  pouched  quadrupeds  this 
process  is  turned  inwards,  as  at  c  d,  fig.  41V,  in  the  Brazilian  opossum, 
whereas  in  the  placental  series,  as  at  c,  figs.  415  and  416,  there  is  an 
almost  entire  absence  of  such  inflection.  The  Tupaia  Tana  of  Sumatra 
has  been  selected  by  my  friend  Mr.  Waterhouse  for  this  illustration, 
because  the  jaws  of  that  small  insectivorous  quadruped  bear  a  great 
resemblance  to  those  of  the  Stonesfield  Amphitherium.  By  clearing 
away  the  matrix  from  the  specimen  of  Amphitherium  Prevostii  above 
represented  (fig.  412),  Professor  Owen  ascertained  that  the  angular 
process  (c)  bent  inwards  in  a  slighter  degree  than  in  any  of  the  known 
marsupialia ;  in  short,  the  inflection  does  not  exceed  that  of  the  mole 
or  hedgehog.  This  fact  made  him  doubt  whether  the  Amphitherium 
might  not  be  an  insectivorous  placental,  although  it  offered  some 


*  I  have  given  a  figure  in  the  Principles  of  Geology,  chapter  ix.,  of  another 
Stonesfield  specimen  of  Amphitherium  Prevostii,  in  which  the  sockets  and  roots 
of  the  teeth  are  finely  exposed. 


CH.  XX.]          STONESFIELD  MAMMALIA— STEREOGNATHUS.  4Q9 

points  of  approximation  in  its  osteology  to  the  marsupials,  especially 
to  the  Myrmecobius,  a  small  insectivorous  quadruped  of  Australia, 
which  has  nine  molars  on  each  side  of  the  lower  jaw,  besides  a  canine 
and  three  incisors.* 

Another  species  of  Amphitherium  has  been  found  at  Stonesfield 
(fig.  413,  p.  407),  which  differs  from  the  former  (fig.  412)  principally 
in  being  larger. 

The  second  mammiferous  genus  discovered  in  the  same  slates  was 
named  originally  by  Mr.  Broderip  Didelphys  Bucklandi  (see  fig.  419), 

Fig.  419. 


Phascolotherium  JBucklandi,  Broderip,  sp. 
a.  Natural  size.  &.  Molar  of  same,  magnified. 

and  has  since  been  called  Phascolotherium  by  Owen.  It  manifests  a 
much  stronger  likeness  to  the  marsupials  in  the  general  form  of  the 
jaw,  and  in  the  extent  and  position  of  its  inflected  angle,  while  the 
agreement  with  the  living  genus  Didelphys  in  the  number  of  the  pre- 
molar  and  molar  teeth  is  complete.! 

In  1854  the  remains  of  another  mammifer,  small  in  size,  but  larger 
than  any  of  those  previously  known,  was  announced  by  Mr.  Charles- 
worth  to  the  British  Association  as  having  been  obtained  many  years 
before  from  the  Stonesfield  slate  by  the  Rev.  J.  P.  Dennis.  This  fossil, 
to  which  the  generic  name  of  Stereognathus  was  given,  consisted,  as 
is  usually  the  case  in  these  old  rocks  (see  above,  p.  385),  of  part  of  a 
lower  jaw,  in  which  were  implanted  three  double-fanged  teeth,  differ- 
ing in  structure  from  those  of  all  other  known  recent  or  extinct  mam- 
mals. According  to  Professor  Owen,  the  molar  of  Pliolophus,  a  small 
extinct  herbivorous  genus  of  the  London  clay,  makes  the  nearest  ap- 
proach to  it.  The  form  and  structure  of  the  teeth  in  Stereognathus 
seemed  to  imply  that  this  quadruped  possessed  a  higher  organization 
than  any  other  secondary  mammal  yet  discovered,  but  the  doubts 
entertained  respecting  its  true  affinities  afford  a  somewhat  disappoint- 
ing illustration  of  the  limited  extent  to  which  Cuvier's  law  of  cor- 
rellation  or  the  coexistence  of  animal  structures  is  available  in  palae- 
ontology. Given  a  lower  jawbone  with  three  perfect  molar  teeth, 
having  two  or  more  fangs  each  implanted  in  separate  sockets,  to  find 
the  rest  of  the  organization,  or  at  least  to  determine  the  family  and 
sub-class  to  which  the  animal  belonged — such  being  the  problem, 
Professor  Owen  tells  us  that  he  believes  that  Stereognathus  was  hoofed, 
herbivorous,  and  placental,  but  he  adds,  that  for  anything  that  physio- 

*  A  figure  of  this  recent  Myrmecobius  will  be  found  in  the  Principles,  chap.  ix. 
f  Owen's  British  Fossil  Mammals,  p.  62. 


410  FOSSIL  PLANTS  OF  GREAT  OOLITE.  [On.  XX. 

logical  science  can  prove  to  the  contrary,  it  may  have  been  unguicu- 
late,  insectivorous,  and  marsupial !  * 

Professor  Owen  has  remarked  that,  as  the  marsupial  genera,  to 
which  the  Phascolotherium  is  most  nearly  allied,  are  now  confined 
to  New  South  Wales  and  Van  Dieman's  Land,  so  also  is  it  in  the 
Australian  seas  that  we  find  the  Cestracion,  a  cartilaginous  fish  which 
has  a  bony  palate,  allied  to  those  called  Acrodus  (see  fig.  453,  p.  421) 
and  Strophodus,  so  common  in  the  Oolite  and  Lias.  In  the  same 
Australian  seas,  also,  near  the  shore,  we  find  the  living  Trigonia,  a 
genus  of  mollusca  so  frequently  met  with  in  'the  Stonesfield  slate. 
So,  also,  the  Araucarian  pines  are  now  abundant,  together  with  ferns, 
in  Australia  and  its  islands,  as  they  were  in  Europe  in  the  Oolitic 
period  (see  fig.  421).  Endogens  of  the  most  perfect  structure  are  met 
with  in  oolitic  rocks,  as,  for  example,  the  Podocarya  of  Buckland, 
a  fruit  allied  to  the  Pandanus,  found  in  the  Inferior  Oolite  (see 
fig.  420). 

Fig.  421. 


Fig.  420. 


Portion  of  a  fossil  fruit  of  Podocarya, 
magnified.  (Buckland's  Bridgew. 
Treat,  pi.  63.)  Inferior  Oolite, 
Charmouth,  Dorset. 

Cone  of  fossil  Araucaria.    Inferior  Oolite.    Bruton, 

Somersetshire.    £  diam.  of  original. 
In  the  collection  of  the  British  Museum. 

The  Stonesfield  slate,  in  its  range  from  Oxfordshire  to  the  northeast 
is  represented  by  flaggy  and  fissile  sandstones,  as  at  Collyweston  in 
Northamptonshire,  where,  according  to  the  researches  of  Messrs.  Ibbet- 
son  and  Morris,f  it  contains  many  shells,  such  as  Trigonia  angulata, 
also  found  at  Stonesfield.  But  the  Northamptonshire  strata  of  this 
age  assume  a  more  marine  character,  or  appear  at  least  to  have  been 
formed  farther  from  land.  They  enclose,  however,  some  fossil  ferns, 
such  as  Pecopteris  polypodioides,  of  species  common  to  the  oolites  of 
the  Yorkshire  coast,  where  rocks  of  this  age  put  on  all  the  aspect  of  a 
true  coal-field ;  thin  seams  of  coal  having  actually  been  worked  in  them 
for  more  than  a  century. 

*  Owen's  Paleontology,  2d  ed.,  p.  348. 

f  Ibbetson  and  Morris,  Keport  of  Brit.  Ass.,  1847,  p.  131 ;  and  Morris,  Geol. 
Journ.,  ix.  p.  334. 


CH.  XX.] 


FOSSIL  PLANTS  OF  GREAT   OOLITE. 


411 


In  the  northwest  of  Yorkshire,  the  formation  alluded  to  consists  of 
an  upper  and  a  lower  carbonaceous  shale,  abounding  in  impressions 
of  plants,  divided  by  a  limestone  considered  by  many  geologists  as 
the  representative  of  the  Great  Oolite ;  but  the  scarcity  of  marine 
fossils  makes  all  comparisons  with  the  subdivisions  adopted  in  the 
south  extremely  difficult.  A  rich  harvest  of  fossil  ferns  has  been 
obtained  from  the  upper  carbonaceous  shales  and  sandstones  at 
Gristhorpe,  near  Scarborough  (see  figs.  422,  423).  The  lower 

Fig.  422. 


Pterophyllum  comptum.    Syn.  Gycadites  comptus. 
Upper  Sandstone  and  Shale,  Gristhorpe,  near  Scarborough, 

Fig.  423. 


Hemitelitea  Brownii,  Goepp.    Syn.  Phlebopterie  contigua,  Lind.  &  Hutt. 
Upper  Carbonaceous  strata,  Lower  Oolite,  Gristhorpe,  Yorkshire. 

shales  are  well  exposed  in  the  sea-cliffs  at  Whitby,  and  are  chiefly 
characterized  by  ferns  and  cycadese.  They  contain,  also,  a  species 
of  calamnite,  and  a  fossil  called  Equisetum  columnare,  which  main- 
'tains  an  upright  position  in  sandstone  strata,  over  a  wide  area. 
Shells  of  Estheria  and  Unio,  collected  by  Mr.  Bean  from  these  York- 
shire coal-bearing  beds,  point  to  the  estuary  or  fluviatile  origin  of  the 
deposit. 

At  Brora  in  Sutherlandshire,  a  coal  formation,  probably  coeval  with 
the  above,  or  belonging  to  some  of  the  lower  divisions  of  the  Oolitic 
period,  has  been  mined  extensively  for  a  century  or  more.  It  affords 
the  thickest  stratum  of  pure  vegetable  matter  hitherto  detected  in  any. 
secondary  rock  in  England.  One  seam  of  coal  of  good  quality  has 
been  worked  3|-  feet  thick,  and  there  are  several  feet  more  of  pyritous 
coal  resting  upon  it. 


412 


FOSSILS  OF  INFERIOR  OOLITE. 


[Cn. 


Fig.  424  Fuller's  Earth  (h,  Tab.,  p.  377).— Between 

the  Great  and  Inferior  Oolite,  near  Bath,  an 
argillaceous  deposit,  called  "  the  fuller's  earth," 
occurs ;  but  it  is  wanting  in  the  north  of  Eng- 
land. It  abounds  in  the  small  oyster  presented 
in  fig.  424.  The  number  of  mollusca  known  in 
this  deposit  is  only  22,  viz.  17  lamellibranchiate 
bivalves,  4  Brachiopods,  and  1  Cephalopod  (Belemnites  giganteus). 

Inferior  Oolite. — This  formation  consists  of  a  calcareous  freestone, 
usually  of  small  thickness,  which  sometimes  rests  upon,  or  is  replaced 
by,  yellow  sands,  called  the  sands  of  the  Inferior  Oolite.  These  last, 


Of>trea  acummata, 
Fullers  Earth. 


Fig.  425. 


Fig.  426. 


Fig.  42T. 


Terebratula  fimbria.    Ehynchonella  spinosa.    a.  Pholadomyafidicula.  %  nat  size.  Inf.  O«l. 
Inferior  Oolite.  Inferior  Oolite.  5.  Heart-shaped  anterior  termination  of  same. 


Fig.  428. 


Fig.  429. 


Pleurotomaria  granulata.      Pleurotomaria  ornata,  Sow.  sp. 
Ferruginous  Oolite.    Normandy.  Inferior  Oolite. 

Inferior  Oolite,  England. 

Fig.  481. 


Collyrites  ringent. 
Inf.  Ool..  Somersetshire. 


Ammonites  Hwnphresianm,  Sow.    Inferior  Oolite. 


CH.  XX.]  OOLITIC  STRATA.  413 

in  their  turn,  repose  upon  the  lias  in  the  south  and  west  of  England. 
Among  the  characteristic  shells  of  the  Inferior  Oolite,  I  may  instance 
Terebratula  fimbria  (fig.  425),  Rhynchonella  spinosa  (fig.  426),  and 
Pho ladomya  fidicula  (fig.  427).  The  extinct  genus  Pleurotomaria  is 
also  a  form  very  common  in  this  division  as  well  as  in  the  Oolitic  sys- 
tem generally.  It  resembles  the  Trochus  in  form,  but  is  marked  by  a 
deep  cleft  (a,  fig.  428  and  429)  on  one  side  of  the  mouth.  The  Col- 
ly rites  ringens  (fig.  430)  is  an  Echinoderm  common  to  the  Inferior 
Oolite  of  England  and  France,  as  are  the  two  Ammonites  of  which 
representations  are  here  given  (figs.  431,  432). 

Fig.  432.  Fig.  48& 


Ammonites  Braikenridgii,  Sow.  Ostrea  MarsMi.    \  nat.  size. 

Oolite,  Scarborough.  Middle  and  Lower  Oolite,  or  ranging 

Inf.  Ool.,  Dundry  ;  Calvados ;  &c.  from  Coral  Bay  to  Cornbrash. 


Palceontological  relations  of  the  Oolitic  strata. — Observations  have 
already  been  made,  p.  345,  on  the  distinctness  of  organic  remains  of 
the  Oolitic  and  Cretaceous  strata,  and  at  pp.  398  and  401  of  the 
proportion  of  species  common  to  the  Upper  and  Middle,  and  to  the 
Middle  and  Lower  Oolite.  Between  the  latter  and  the  Lias  there  is  a 
somewhat  greater  break,  for  out  of  120  mollusca  of  the  Upper  Lias  13 
species  only  pass  up  into  the  Inferior  Oolite.  Professor"  Ramsay  has  call- 
ed our  attention  to  an  important  generalization  not  yet  alluded  to,  name- 
ly, that  there  are  at  present  wider  breaks  between  some  of  our  minor  sub- 
divisions, and  especially  between  the  Inferior  and  the  Great  Oolite,  palae- 
ontologically  considered,  than  between  what  we  generally  regard  as 
divisions  of  a  higher  order,  such  as  the  Lower,  Middle,  and  Upper 
Oolites.  Thus,  for  example,  there  are,  according  to  Mr.  Etheridge's 
tables,  518  species  of  mollusca  known  in  the  Great  Oolite  and  370  in 
the  Inferior,  and  of  these  only  93,  or  about  12  per  cent.,  are  common 
to  the  two ;  and,  what  is  very  remarkable,  of  39  species  of  Cephalopoda 
known  in  the  Inferior  Oolite,  only  one  passes  upwards  into  the  Great 
Oolite,  namely,  Belemnites  giganteus,  and  it  has  been  questioned  by 
some  palaeontologists  whether  even  this  Belemnite  has  really  been 
found  in  the  Upper  of  the  two  formations.  This  distinctness  of  the 
Cephalopoda  is  the  more  striking,  because  both  the  Great  and  Inferior 
Oolites  are  calcareous  formations,  and  we  cannot,  therefore,  account 
for  the  difference  of  species  by  any  marked  dissimilarity  in  the  nature 
of  the  sea-bottom.  As  to  the  intervening  Fuller's  Earth,  it  affords  us 


414:  PAL^ONTOLOGICAL  RELATIONS.  [On.  XX. 

"but  little  information  in  regard  to  the  condition  of  marine  life,  hav- 
ing yielded  at  present  only  22  mollusca,  as  before  mentioned  (p.  412). 
While,  therefore,  the  break  between  two  great  members  of  the  Lower 
Oolite  is  expressed  by  saying  that  the  proportion  of  species  in  common 
only  amounts  to  12  per  cent.,  we  have  seen  that  there  is  a  connection 
of  24  per  cent,  between  the  Upper  and  Middle,  and  21  per  cent,  be- 
tween the  Middle  and  Lower  Oolite ;  in  other  words,  there  is  twice  as 
great  a  connection  between  our  larger  divisions  as  between  two  separate 
members  of  one  of  them. 

In  illustration  of  shells  having  a  great  vertical  range,  it  may  be 
stated  that  in  England  4  species,  and  4  only,  are  known  to  pass  up 
from  the  Lower  to  the  Upper  Oolite,  namely,  Rhynchonella  obsoleta, 
Lithodomus  inclusus,  Pholadomya  ovalis,  and  Trigonia  elongata. 

Of   all   the  Jurassic   Ammonites   of  Great 
Fig.  484  Britain,  A.  Macrocephalus,  Schloth,  which  is 

common  to  the  Great  Oolite  and  Oxford  Clay, 
has  the  widest  range. 

That  most  of  the  sudden  changes  of  species 
were  due  to   migration,  may  be  inferred,  as 
Prof.  Ramsay  remarks,  from  the  fact  that,  after 
disappearing  from  an  intermediate  formation, 
Ammonite*  macrocephaiw,    ttey  often  reappear  in  a  higher  one.     But  the 
Schloth.   A  nat  size.         phenomena,  on  the  whole,  indicate  a  constant 

Great  Oolite  and  Oxford         •,    .  /.          ..    .   , .  .  , 

Clay-  dying  out  ot  preexisting  species  and  a  coming 

in  of  new  ones.  We  have  every  reason  to  con- 
clude that  the  gaps  which  occur,  both  between  the  larger  and  smaller 
sections  of  the  English  Oolites,  imply  intervals  of  time,  elsewhere 
represented  by  fossiliferous  strata,  although  no  deposit  may  have 
taken  place  in  the  British  area.  This  conclusion  is  warranted  by  the 
partial  extent  of  many  of  the  minor  and  some  of  the  larger  .divisions 
even  in  England.  "  Thus,  the  Inferior  Oolite,"  says  Prof.  Ramsay, 
"  attains  its  maximum  development  near  Cheltenham,  where  it  can 
be  subdivided  into  at  least  three  parts.  Passing  north,  the  two  lower 
divisions,  each  more  or  less  characterized  by  its  own  fossils,  disappear, 
and  the  rag-stone,  northeast  of  Cheltenham,  lies  directly  upon  the 
Lias,  apparently  as  conformably  as  if  it  formed  its  true  and  immediate 
successor.  In  Dorsetshire,  on  the  coast,  the  series  is  again  perfect, 
though  thin.  Near  Chipping  Norton,  in  Oxfordshire,  the  Inferior 
Oolite  disappears  altogether,  and  the  Great  Oolite,  having  first  over- 
lapped the  Fuller's  Earth,  passes  across  the  Inferior  Oolite,  and  in  its 
turn  seems  to  lie  on  the  Upper  Lias  with  a  regularity  as  perfect  as  if 
no  formation  anywhere  in  the  neighborhood  came  between  them.  In 
Yorkshire  the  changed  type  of  the  Inferior  Oolite,  the  prevalence  of 
sands,  land-plants,  and  beds  of  coal,  leave  no  doubt  of  the  presence 
of  terrestrial  surfaces  on  which  the  plants  grew,  and  all  these  phe- 
nomena lead  to  the  conclusion  that  various  and  considerable  oscilla- 
tions of  level  took  place  in  the  British  area  during  the  deposition  of 


CH.  XXL]  MINERAL   CHARACTER  OF  THE  LIAS. 

the  strata,  both  of  the  Inferior  Oolite  and  of  the  formations  that 
immediately  succeed  it."  * 

Mr.  Howell  has  pointed  out  that  in  Bedfordshire  the  Cornbrash 
and  Kelloway  rocks  are  sometimes  both  absent,  and  the  Oxford  clay 
rests  conformably  on  the  Great  Oolite,  showing,  like  the  examples 
before  cited,  that  conformity  is  no  proof  of  direct  sequence,  and 
aiding  us  more  and  more  to  conceive  that  the  changes  in  the  organic 
world  may  in  reality  have  been  gradual  and  uninterrupted,  although 
the  fragmentary  character  of  the  records  handed  down  to  us  might 
lead  us  to  infer,  unless  we  were  constantly  on  our  guard  against 
being  deceived,  that  there  had  been  many  general  and  sudden  breaks 
in  the  recording  process,  and  abrupt  transitions  from  one  set  of 
organic  types  to  another. 


CHAPTER  XXI. 

JURASSIC  GROUP,  continued — LIAS. 

Mineral  character  of  Lias — Numerous  successive  Zones  in  the  Lias,  marked  by  dis- 
tinct fossils,  without  unconformity  in  the  stratification,  or  change  in  the  mineral 
character  of  the  deposits — Name  of  Gryphite  limestone — Fossil  shells  and  fish — 
Radiata — Ichthyodorulites — Reptiles  of  the  Lias — Ichthyosaur  and  Plesiosaur — 
Marine  Reptile  of  the  Galapagos  Islands — Sudden  destruction  and  burial  of  fos- 
sil animals  in  Lias — Fluvio-marine  beds  in  Gloucestershire,  and  insect  limestone 
— Fossil  plants — Origin  of  the  Oolite  and  Lias,  and  of  alternating  calcareous  and 
argillaceous  formations. 

LIAS. — The  English  provincial  name  of  Lias  has  been  very  gen- 
erally adopted  for  a  formation  of  argillaceous  limestone,  marl,  and 
clay,  which  forms  the  base  of  the  Oolite,  and  is  classed  by  many 
geologists  as  part  of  that  group.  They  pass,  indeed,  into  each  other 
in  some  places,  as  near  Bath,  a  sandy  marl  called  the  marlstone  of 
the  Lias  being  interposed,  and  partaking  of  the  mineral  characters 
of  the  lias  and  the  inferior  oolite.  These  last-mentioned  divisions 
have  also  some  fossils  in  common,  such  as  the  Avicula  incequivalvis 
(fig.  435).  Nevertheless  the  Lias  may  be  traced  throughout  a  great 
part  of  Europe  as  a  separate  and  independent  group,  of  consider- 
able thickness,  varying  from  500  to  1000  feet,  containing  many 
peculiar  fossils,  and  having  a  very  uniform  lithological  aspect. 
Although  usually  conformable  to  the  oolite,  it  is  sometimes,  as  in 
the  Jura,  unconformable.  In  the  environs  of  Lons-le-Saulnier,  for 
instance,  in  the  department  of  Jura,  the  strata  of  Lias  are  inclined 

*  Geol.  Quart.  Journ.,  vol.  xx.  p.  56.     1864. 


416  SUCCESSIVE  ZONES  OF  LIAS.  [Cn.  XXI 

at  an  angle  of  about  45°,  while  the  incumbent  oolitic  marls  are  hori- 
zontal. 

Fig.  436. 


Fig.  435. 


Avicula  incequivalms,  Sow.  Amcula  cygnipes,  Phil. 

Lower  Oolite,  and  Lias.  Lias,  Gloucestershire  and  Yorkshire. 

The  peculiar  aspect  which  is  most  characteristic  of  the  Lias  in 
England,  France,  and  Germany,  is  an  alternation  of  thin  beds  of 
blue  or  gray  limestone,  having  a  surface  which  becomes  light-brown 
when  weathered,  these  beds  being  separated  by  dark-colored,  narrow 
argillaceous  partings,  so  that  the  quarries  of  this  rock,  at  a  distance, 
assume  a  striped  and  riband-like  aspect.* 

The  Lias  has  been  divided  in  England  into  three  formations,  the 
Upper,  Middle,  and  Lower.  The  Upper  Lias  consists  first  of  sands, 
which  were  formerly  regarded  as  the  base  of  the  Oolite,  but  which, 
according  to  Dr.  Wright,  are  by  their  fossils  more  properly  refer- 
able to  the  Lias ;  secondly,  of  clay  shale  and  thin  beds  of  limestone. 
The  Middle  Lias,  or  marlstone  series,  has  been  divided  into  three 
zones ;  and  the  Lower  Lias,  according  to  the  labors  of  Quenstedt, 
Oppel,  Strickland,  Wright,  and  others,  into  six  zones,  each  marked 
by  its  own  group  of  fossils.  This  Lower  Lias  averages  from  600  to 
900  feet  in  thickness. 

From  Devon  and  Dorsetshire  to  Yorkshire  all  these  divisions,  ob- 
serves Professor  Kamsay,  are  constant ;  and  from  bottom  to  top  we 
cannot  assert  that  anywhere  there  is  actual  unconformity  between  any 
two  subdivisions,  whether  of  the  larger  or  smaller  kind.  In  the  whole 
of  the  English  Lias,  there  are  about  243  genera,  and  467  known  spe- 
cies.f  The  whole  series  has  been  divided  by  zones  characterized  by 
particular  ammonites;  for  while  other  families  of  shells  pass  from 
one  division  to  another  in  numbers  varying  from  about  20  to  50  per 
cent.,  these  cephalopods  are  almost  always  limited  to  single  zones,  as 
Quenstedt  and  Oppel  have  shown  for  Germany,  and  Dr.  Wright  for 
England.  J 

As  no  actual  unconformity  is  known  from  the  bottom  of  the  Lower 
to  the  top  of  the  Upper  Lias,  and  as  there  is  a  marked  uniformity  in 
the  mineral  character  of  almost  all  the  strata,  it  is  somewhat  difficult 

*  Conyb.  and  Phil.,  p.  261. 

f  Ramsay,  Geol.  Quart.  Journ.,  vol.  xx.  p.  60.     1864. 

i  Dr.  Wright,  ibid.,  vol.  xvi.  p.  10.     1859. 


CH.  XXI.]  NAME  OF   "  GRYPHITE  LIMESTONE."  41  f 

to  account  even  for  such  partial  breaks  as  have  been  alluded  to  in  the 
succession  of  species,  if  we  reject  the  hypothesis  that  the  old  species 
were  in  each  case  destroyed  at  the  close  of  the  deposition  of  the 
rocks  containing  them,  and  replaced  by  the  creation  of  new  forms 
when  the  succeeding  formation  began.  I  agree  with  Professor  Ram- 
say in  not  accepting  this  hypothesis.  No  doubt  some  of  the  old 
species  occasionally  died  out,  and  left  no  representatives  in  Europe  or 
elsewhere ;  others  were  locally  exterminated  in  the  struggle  for  life 
by  species,  which  invaded  their  ancient  domain,  or  by  varieties  better 
fitted  for  a  new  state  of  things.  Pauses  also  of  vast  duration  may 
have  occurred  in  the  deposition  of  strata,  allowing  time  for  the  modi- 
fication of  organic  life  throughout  the  globe,  slowly  brought  about  by 
variation  as  well  as  by  extinction. 

In  some  parts  of  France,  near  the  Vosgcs  Mountains,  and  in  Lux- 
embourg, M.  E.  de  Beaumont  has  shown  that  the  lias  containing 
Gryphcea  arcuata,  Plagiostoma  giganteum  (see  fig.  437),  and  other 
characteristic  fossils,  becomes  arenaceous ;  and  around  the  Hartz,  in 
Westphalia  and  Bavaria,  the  inferior  parts  of  the  lias  are  sandy,  and 
sometimes  afford  a  building-stone. 

The  name  of  Gryphite  limestone  has  sometimes  been  applied  to 
the  lias,  in  consequence  of  the  great  number  of  shells  which  it  con- 
tains of  a  species,  of  oyster,  or  Gryphcea  (fig.  438,  see  also  fig.  387, 
p.  395).  A  large  heavy  shell  called  Hippopodium  (fig.  439),  allied  to 

Fig.  437. 

Fig.  488. 


GrypTuea  incwrva,  Sow. 
(G.  arcuata,  Lam.) 

Lias. 


Plagiostoma  (Lima)  giganteum.  Sow. 
Inf.  Ool.  and  Lias. 

Cypricardia,  is  also  characteristic  of  the  lower  lias  shales.  The  Lias 
formation  is  also  remarkable  for  being  the  newest  of  the  secondary 
rocks  in  which  brachiopoda  of  the  genera  Spirifer  and  Leptcena  (figs. 
440,  441)  occur:  no  less  than  nine  species  of  Spirifers  are  enumer- 
ated by  Mr.  Davidson  as  belonging  to  the  Lias.  These  pallio- 
branchlate  mollusca  predominate  greatly  in  strata  older  than  the 
Trias ;  but,  so  far  as  we  yet  know,  they  did  not  survive  the  Liassic 
epoch.  The  marine  beds  of  the  Lias  also  abound  in  cephalopoda 
27 


4:18 


FOSSILS  OF  THE  LIAS. 


[On.  XXI. 


of  the  genera  Belemnites,  Nautilus,  and  Ammonites  (see  figs.  442, 
443,  444). 


Fig.  489. 


ffippopodiwn  ponderoswn,  Sow. 
i  diam.    Lias,  Cheltenham. 


Fig.  442. 


Nautitua  truncatw,  Lias. 
Fig.  444. 


440. 


Spirifer  WalcotU,  Sow. 
Lower  Lias. 


Fig.  441. 


Leptcena  Moorei,  Dav. 
Upper  Lias,  Ilminster. 


Fig.  443. 


Ammonites  Nodotianus  f 
A.  striatulw,  Sow.    Lias. 


Ammonites  T)ifron8,  Brug. 
A  Walcotii,  Sow. 
Upper  Lias  shales. 


CH.  XXI.] 


FOSSILS  OF  THE  LIAS. 


419 


Fig.  446. 


Pig.  445. 


Ammonites  striatulus,  Sow. 
j  nat.  size.    Upper  Lias. 


Ammonites  margaritatus,  Montf. 
Syn.  A  Stolcesii,  Sow.    Middle  Lias. 


Among  the  Crinoids  or  Stone-lilies  of  the  Lias,  the  Pentacrinites 
are  conspicuous.  (See  fig.  449.)  Of  Ophioderma  Egertoni  (fig. 
450),  referable  to  the  Ophiuridce  of  Muller,  perfect  specimens  have 
been  met  with  in  the  Middle  Lias  beds  of  Dorset  and  Yorkshire. 

Allusion  has  already  been  made,  p.  416,  to  numerous  zones  in  the 
Lias  characterized  by  distinct  Ammonites.  Two  of  these  occur  near 
the  base  of  the  Lower  Lias,  having  a  united  thickness,  varying  from 
40  to  80  feet.  The  upper  and  larger  of  these  is  characterized,  espe- 
cially in  the  southwest  of  England,  by  Ammonites  BucTclandi,  and  the 
lower  by  Ammonites  Planorbis  (figs.  447,  448).* 


Pig.  44T. 


Fig.  448. 


Ammonites  Bucklandi,  Sow. 
"          bisulcatw,  Brug. 
£  diam.  of  original. 
a.  Side  view. 

&.  Front  view,  showing  mouth  and  bisulcated  keel. 

Characteristic  of  the  lower  part  of  the  Lias  of 

England  and  the  Continent 


A.  Planorbis,  Sow. 

£  diam.  of  original. 

From  the  base  of  the  Lower  Lias 

of  England  and  the  Continent. 


These  two  shells  have  a  wide  range  on  the  Continent  of  Europe, 
occurring  in  beds  which  occupy  similar  positions  in  the  Liassic  series. 

The  Extracrinus  Briar eus  (removed  by  Major  Austin  from  Penta- 
crinus  on  account  of  generic  differences)  occurs  in  tangled  masses, 
forming  thin  beds  of  considerable  extent,  in  the  Lower  Lias  of  Dor- 
set, Gloucestershire,  and  Yorkshire.  The  remains  are  often  highly 
charged  with  pyrites.  This  Crinoid,  with  its  innumerable  tentacular 


*  Quart.  Journ.,  vol.  xvi.  p.  376. 


420 


FOSSILS  OF  THE  LIAS. 


[On.  XXI. 


arms,  appears  to  have  been  frequently  attached  to  the  driftwood  of 
the  liassic  sea,  in  the  same  manner  as  Barnacles  float  about  at  the 


Tig.  450. 


Extracrinus  Bridreus  =  Pentaorin/ns 

Sriareus.    i  nat.  size. 

(Body,  arms,  and  part  of  stem.) 

Lias,  Lyme  Eegis. 


Ophioderma  Egertoni,  E.  Forbes. 
Middle  Lias,  Seatown,  Dorset. 


present  day.  There  is  another  species  of  Extracrinus  and  several  of 
Pentacrinus  in  the  lias  ;  and  the  latter  genus  is  found  in  nearly  all  the 
formations  from  the  lias  to  the  London  clay  inclusive.  It  is  repre- 
sented in  the  present  seas  by  the  delicate  and  rare  Pentacrinus  Caput- 
medusce  of  the  Antilles,  which,  with  Comatula,  are  the  only  surviving 
members  of  the  great  and  ancient  family  of  the  Crinoids,  so  widely 
represented  throughout  the  older  formations  by  the  genera  Taxocrinus, 
Actinocrinus,  Cyathocrinus,  Encrinus,  Apiocrinus,  and  many  others. 

Fig.  451. 


Scales  of  Lepidotus  gigas,  Agass. 
a.  Two  of  the  scales,  detached. 


The  fossil  fish  resemble  generically  those  of  the  oolite,  belonging 
all,  according  to  M.  Agassiz,  to  extinct  genera,  and  differing  for  the 
most  part  from  the  ichthyolites  of  the  Cretaceous  period.  Among 


CH.  XXI.] 


FOSSILS  OF  THE  LIAS. 


421 


them  is  a  species  of  Lepidotus  (L.  gigas,  Agass.),  fig.  451,  which  is 
found  in  the  lias  of  England,  France,  and  Germany.*  This  genus 
was  before  mentioned  (p.  349)  as  occurring  in  the  Wealden,  and  is 
supposed  to  have  frequented  both  rivers  and  coasts.  Another  genus 
of  Ganoids  (or  fish  with  hard,  shining,  and  enamelled  scales),  called 
(see  fig.  452),  is  almost  exclusively  Liassic.  The  teeth 

Fig.  452. 


Leachii. 


a.  ^Echmodus.    Eestored  outline.  c.  Scales  of  Dapedius 

monilifer. 


of  a  species  of  Acrodus,  also,  are  very  abundant  in  the  lias  (fig. 
453). 

Fig.  458. 


Acrodus  nobilis,  Agass.  (tooth) ;  commonly  called  "fossil  leech." 
Lias,  Lyme  Kegis  and  Germany. 

But  the  remains  of  fish  which  have  excited  more  attention  than 
any  others  are  those  large  bony  spines  called  ichthyodorulites  (a,  fig. 

Fig.  454. 


Hybodus  reticulatus^  Agass.    Lias,  Lyme  Begis. 
a.  Part  of  fin,  commonly  called  Ichthyodorulite.  &.  Tooth. 

454),  which  were  once  supposed  by  some  naturalists  to  be  jaws,  and 
by  others  weapons,  resembling  those  of  the  living  Balistes  and  Silu- 

*  Agassiz,  Poissons  Fossiles,  vol.  ii.  tab.  28,  29. 


422  SAURIANS  OF  THE  LIAS.  [On.  XXI. 

rus  ;  but  which  M.  Agassiz  has  shown  to  be  neither  the  one  nor  the 
other.  The  spines,  in  the  genera  last  mentioned,  articulate  with  the 
backbone,  whereas  there  are  no  signs  of  any  such  articulation  in  the 
ichthyodorulites.  These  last  appear  to  have  been  bony  spines  which 
formed  the  anterior  part  of  the  dorsal  fin,  like  that  of  the  living  Ces- 
tracion  and  Chimcem  (see  er,  fig.  455).  In  both  of  these  genera,  the 

Fig.  455. 


Chimcera  monstrosa* 
a.  Spine  forming  anterior  part  of  dorsal  fin. 

posterior  concave  face  is  armed  with  small  spines,  as  in  that  of  the 
fossil  Ifybodus  (fig.  454),  a  placoid  fish  of  the  shark  family  found 
fossil  at  Lyme  Regis.  Such  spines  are  simply  imbedded  in  the  flesh, 
and  attached  to  strong  muscles.  "  They  serve,"  says  Dr.  Buckland, 
"  as  in  the  Chimcera  (fig.  455),  to  raise  and  depress  the  fin,  their 
action  resembling  that  of  a  movable  mast,  raising  and  lowering 
backwards  the  sail  of  a  barge."  f 

JReptiles  of  the  Lias. — It  is  not,  however,  the  fossil  fish  which  form 
the  most  striking  feature  in  the  organic  remains  of  the  Lias ;  but  the 
Enaliosaurian  reptiles,  which  are  extraordinary  for  their  number,  size, 
and  structure.  Among  the  most  singular  of  these  are  several  species 
of  Ichthyosaurus  and  Plesiosaurus  (figs.  456,  457).  The  genus  Ich- 
thyosaurus, or  fish-lizard,  is  not  confined  to  this  formation,  but  has 
been  found  in  strata  as  high  as  the  white  chalk  of  England,  and  as 
low  as  the  trias  of  Germany,  a  formation  which  immediately  succeeds 
the  lias  in  the  descending  order.J  It  is  evident  from  their  fish-like 
vertebrae,  their  paddles,  resembling  those  of  a  porpoise  or  whale,  the 
length  of  their  tail,  and  other  parts  of  their  structure,  that  the  habits 
of  the  Ichthyosaurs  were  aquatic.  Their  jaws  and  teeth  show  that 
they  were  carnivorous ;  and  the  half-digested  remains  of  fishes  and 
reptiles,  found  within  their  skeletons,  indicate  the  precise  nature  of 
their  food.§ 

A  specimen  of  the  hinder  fin  or  paddle  of  Ichthyosaurus  communis 
was  discovered  in  1840  at  Barrow-on-Soar,  by  Sir  P.  Egerton,  which 
distinctly  exhibits  on  its  posterior  margin  the  remains  of  cartila- 

*  Agassiz,  Poissons  Fossiles,  vol.  iii.,  tab.  0,  fig.  1. 

f  Bridgewater  Treatise,  p.  290. 

\  Ibid.,  p.  168.  §  Ibid.,  p.  1ST. 


CH.  XXI.] 


SAURIANS  OF  THE  LIAS. 


423 


Fig.  458. 


Posterior  part  of  hind  fin  or  paddle  of  Ichthyosaurus  communis. 


424  SAURIANS  OF  THE  LIAS.  [Cn.  XXI. 

ginous  rays  that  bifurcate  as  they  approach  the  edge,  like  those  in  the 
fin  of  a  fish.  (See  a,  fig  458.)  It  had  previously  been  supposed,  says 
Prof.  Owen,  that  the  locomotive  organs  of  the  Ichthyosaurus  were 
enveloped,  while  living,  in  a  smooth  integument,  like  that  of  the  turtle 
and  porpoise,  which  has  no  other  support  than  is  afforded  by  the  bones 
and  ligaments  within ;  but  it  now  appears  that  the  fin  was  much  larger, 
expanding  far  beyond  its  osseous  framework,  and  deviating  widely  in 
its  fish-like  rays  from  the  ordinary  reptilian  type.  In  fig.  458  the 
posterior  bones,  or  digital  ossicles  of  the  paddle,  are  seen  near  b ;  and 
beyond  these  is  the  dark  carbonized  integument  of  the  terminal  half 
of  the  fin,  the  outline  of  which  is  beautifully  defined.*  Prof.  Owen 
believes  that,  besides  the  fore-paddles,  these  short  and  stiff-necked 
saurians  were  furnished  with  a  tail-fin  without  radiating  bones,  and 
purely  tegumentary,  expanding  in  a  vertical  direction ;  an  organ  of 
motion  which  enabled  them  to  turn  their  heads  rapidly.f 

Mr.  Conybeare  was  enabled,  in  1824,  after  examining  many  skele- 
tons nearly  perfect,  to  give  an  ideal  restoration  of  the  osteology  of 
this  genus,  and  of  that  of  the  Plesiosaurus.^  (See  figs.  456,  457.) 
The  latter  animal  had  an  extremely  long  neck  and  small  head,  with 
teeth  like  those  of  the  crocodile,  and  paddles  analogous  to  those  of 
the  Ichthyosaurus,  but  larger.  It  is  supposed  to  have  lived  in  shal- 
low seas  and  estuaries,  and  to  have  breathed  air  like  the  Ichthyo- 
saur  and  our  modern  cetacea.§  Some  of  the  reptiles  above  men- 
tioned were  of  formidable  dimensions.  One  specimen  of  Ichthyo- 
saurus platyodon,  from  the  lias  at  Lyme,  now  in  the  British  Museum, 
must  have  belonged  to  an  animal  more  than  24  feet  in  length ;  and 
there  are  species  of  Plesiosaurus  which  measure  from  18  to  20  feet  in 
length.  The  form  of  the  Ichthyosaurus  may  have  fitted  it  to  cut 
through  the  waves  like  the  porpoise ;  but  it  is  supposed  that  the  Plesio- 
saurus, at  least  the  long-necked  species  (fig.  457),  was  better  suited  to 
fish  in  shallow  creeks  and  bays  defended  from  heavy  breakers. 

In  many  specimens  both  of  Ichthyosaur  and  Plesiosaur  the  bones 
of  the  head,  neck,  and  tail  are  in  their  natural  position,  while  those 
of  the  rest  of  the  skeleton  are  detached  and  in  confusion.  Mr.  Stutch- 
bury  has  suggested  that  their  bodies  after  death  became  inflated  with 
gases,  and  while  the  abdominal  viscera  were  decomposing,  the  bones, 
though  disunited,  were  retained  within  the  tough  dermal  covering  as 
in  a  bag,  until  the  whole,  becoming  water-logged,  sank  to  the  bottom.  || 
As  they  belonged  to  individuals  of  all  ages  they  are  supposed,  by  Dr. 
Buckland,  to  have  experienced  a  violent  death ;  and  the  same  con- 
clusion might  also  be  drawn  from  their  having  escaped  the  attacks 

*  Geol.  Soc.  Transact,  Second  Series,  vol.  vi.  p.  199,  pi.  xx. 
f  Ibid.,  Second  Series,  vol.  v.  p.  511. 
\  Ibid.,  Second  Series,  vol.  i.  p.  49. 

§  Conybeare  and  De  la  Beche,  Geol.  Trans.,  First  Series,  vol.  v.  p.  659 ;  and 
Buckland,  Bridgew.  Treat.,  p.  203. 
1  Quart.  Geol.  Journ.,  vol.  ii.  p.  411. 


CH.  XXI.]  SAURIANS  OF  THE  LIAS.  425 

of  their  own  predacebus  race,  or  of  fishes  found  fossil  in  the  same 
beds. 

For  the  last  twenty  years,  anatomists  have  agreed. that  these  ex- 
tinct saurians  must  have  inhabited  the  sea :  and  it  was  urged  that  as 
there  are  now  chelonians,  like  the  tortoise,  living  in  fresh  water,  and 
others,  as  the  turtle,  frequenting  the  ocean,  so  there  may  have  been 
formerly  some  saurians  proper  to  salt,  others  to  freshwater.  The  com- 
mon crocodile  of  the  Ganges  is  well  known  to  frequent  equally  that 
river  and  the  brackish  and  salt  water  near  its  mouth ;  and  crocodiles 
are  said  in  like  manner  to  be  abundant  both  in  the  rivers  of  the  Isla 
de  Pinos  (or  Isle  of  Pines),  south  of  Cuba,  and  in  the  open  sea  round 
the  coast.  More  recently  a  saurian  has  been  discovered  of  aquatic 
habits  and  exclusively  marine.  This  creature  was  found  in  the  Galapa- 
gos Islands,  during  the  visit  of  H.M.S.  "Beagle"  to  that  archipelago, 
in  1835,  and  its  habits  were  then  observed  by  Mr.  Darwin.  The 
islands  alluded  to  are  situated  under  the  equator,  nearly  600  miles  to 
the  westward  of  the  coast  of  South  America.  They  are  volcanic; 
some  of  them  being  3000  or  4000  feet  high ;  and  one  of  them,  Albe- 
marle  Island,  75  miles  long.  The  climate  is  mild ;  very  little  rain  falls; 
and  in  the  whole  archipelago  there  is  only  one  rill  of  fresh  water  that 
reaches  the  coast.  The  soil  is  for  the  most  part  dry  and  harsh,  and 
the  vegetation  scanty.  The  birds,  reptiles,  plants,  and  insects  are,  with 
very  few  exceptions,  of  species  found  nowhere  else  in  the  world,  although 
all  partake,  in  their  general  form,  of  a  South  American  type.  Of  the 
mammalia,  says  Mr.  Darwin,  one  species  alone  appears  to  be  indigenous, 
namely,  a  large  and  peculiar  kind  of  mouse  ;  but  the  number  of  lizards, 
tortoises,  and  snakes  is  so  great,  that  it  may  be  called  a  land  of  reptiles. 
The  variety,  indeed,  of  species  is  small ;  but  the  individuals  of  each 
are  in  wonderful  abundance.  There  is  a  turtle,  a  large  tortoise 
(Testudo  Indicus),  four  lizards,  and  about  the  same  number  of  snakes, 
but  no  frogs  or  toads.  Two  of  the  lizards  belong  to  the  family  Iguanidce 
of  Bell,  and  to  a  peculiar  genus  (Amblyrhynchus)  established  by 
that  naturalist,  and  so  named  from  their  obtusely  truncated  head  and 

Fig.  459. 


AmUyrhynchus  cridtatus,  Bell.    Length  varying  from  3  to  4  feet.    The  only  existing  marine 

lizard  now  known, 
a.  Tooth,  natural  size  and  magnified. 


426  SUDDEN  DESTRUCTION  OF  SAURIANS.  [On.  XXI. 

short  snout.*  Of  these  lizards  one  is  terrestrial  in  its  habits,  and 
burrows  in  the  ground,  swarming  everywhere  on  the  land,  having  a 
round  tail,  and  a  mouth  somewhat  resembling  in  form  that  of  a  tortoise. 
The  other  is  aquatic,  and  has  its  tail  flattened  laterally  for  swimming 
(see  fig.  459).  "  This  marine  saurian,"  says  Mr.  Darwin,  "  is  extremely 
common  on  all  the  islands  throughout  the  Archipelago.  It  lives 
exclusively  on  the  rocky  sea-beaches,  and  I  never  saw  one  even  ten 
yards  in  shore.  The  usual  length  is  about  a  yard,  but  there  are  some 
even  4  feet  long.  It  is  of  a  dirty  black  color,  sluggish  in  its  move- 
ments on  the  land  ;  but,  when  in  the  water,  it  swims  with  perfect  ease 
and  quickness  by  a  serpentine  movement  of  its  body  and  flattened 
tail,  the  legs  during  this  time  being  motionless,  and  closely  collapsed 
on  its  sides.  Their  limbs  and  strong  claws  are  admirably  adapted  for 
crawling  over  the  rugged  and  fissured  masses  of  lava  which  everywhere 
form  the  coast.  In  such  situations,  a  group  of  six  or  seven  of  these 
hideous  reptiles  may  oftentimes  be  seen  on  the  black  rocks,  a  few  feet 
above  the  surf,  basking  in  the  sun,  with  outstretched  legs.  Their  stom- 
achs, on  being  opened,  were  found  to  be  largely  distended  with  minced 
sea-weed,  of  a  king  which  grows  at  the  bottom  of  the  sea  at  some 
little  distance  from  the  coast.  To  obtain  this  the  lizards  o;o  out  to 

o 

sea  in  shoals.  One  of  these  animals  was  sunk  in  salt  water  from  the 
ship,  with  a  heavy  weight  attached  to  it,  and  on  being  drawn  up  again 
after  an  hour  it  was  quite  active  and  unharmed.  It  is  not  yet  known 
by  the  inhabitants  where  this  animal  lays  its  eggs  ;  a  singular  fact, 
considering  its  abundance,  and  that  the  natives  are  well  acquainted 
with  the  eggs  of  the  terrestrial  Amblyrhynchus,  which  is  also  her- 
bivorous." f 

In  those  deposits  now  forming  by  the  sediment  washed  away  from 
the  wasting  shores  of  the  Galapagos  Islands,  the  remains  of  saurians, 
both  of  the  land  and  sea,  as  well  as  of  chelonians  and  fish,  may  be 
mingled  with  marine  shells,  without  any  bones  of  land  quadrupeds  or 
batrachian  reptiles  ;  yet  even  here  we  should  expect  the  remains  of 
marine  mammalia  to  be  imbedded  in  the  strata,  for  there  are  seals, 
besides  several  kinds  of  cetacea,  on  the  Galapagian  shores  ;  and,  in  this 
respect,  the  parallel  between  the  modern  fauna,  above  described,  and 
the  ancient  one  of  the  lias  would  not  hold  good. 

Sudden  destruction  of  Saurians.  —  It  has  been  remarked,  and  truly, 
that  many  of  the  fish  and  saurians,  found  fossil  in  the  lias,  must 
have  met  with  sudden  death  and  immediate  burial;  and  that  the 
destructive  operation,  whatever  may  have  been  its  nature,  was  often 
repeated. 

"  Sometimes,"  says  Dr.  Bucklaud,  "  scarcely  a  single  bone  or  scale 
has  been  removed  from  the  place  it  occupied  during  life  ;  which  could 
not  have  happened  had  the  uncovered  bodies  of  these  saurians  been 


f  ,  amblys,  blunt  ;  pi)^x°^  rhynchus,  snout. 
f  Darwin's  Journal,  chap.  xix. 


CH.  XXL]  SUDDEN  DESTRUCTION  OF  SAURIANS.  4% 7 

left,  even  for  a  few  hours,  exposed  to  putrefaction,  and  to  the  attacks 
of  fishes  and  other  smaller  animals  at  the  bottom  of  the  sea."  *  Not 
only  are  the  skeletons  of  the  Ichthyosaurs  entire,  but  sometimes  the  con- 
tents of  their  stomachs  still  remain  between  their  ribs,  as  before  remark- 
ed, so  that  we  can  discover  the  particular  species  of  fish  on  which  they 
lived,  and  the  form  of  their  excrements.  Not  unfrequently  there  are 
layers  of  these  coprolites,  at  different  depths  in  the  lias,  at  a  distance 
from  any  entire  skeletons  of  the  marine  lizards  from  which  they  were 
derived ;  "  as  if,"  says  Sir  H.  de  la  Beche,  "  the  muddy  bottom  of  the 
sea  received  small  sudden  accessions  of  matter  from  time  to  time, 
covering  up  the  coprolites  and  other  exuviae  which  had  accumulated 
during  the  intervals."  f  It  is  further  stated  that,  at  Lyme  Regis,  those 
surfaces  only  of  the  coprolites  which  lay  uppermost  at  the  bottom  of 
the  sea  have  suffered  partial  decay,  from  the  action  of  water  before 
they  were  covered  and  protected  by  the  muddy  sediment  that  has 
afterwards  permanently  enveloped  them.J 

Numerous  specimens  of  the  Calamary  or  pen-and-ink  fish  (Geoteuthis 
Bollensis,  Schuble  sp.)  have  also  been  met  with  in  the  lias  at  Lyme, 
with  the  ink-bags  still  distended,  containing  the  ink  in  a  dried  state, 
chiefly  composed  of  carbon,  and  but  slightly  impregnated  with  car- 
bonate of  lime.  These  cephalopoda,  therefore,  must,  like  the  saurians, 
have  been  soon  buried  in  sediment ;  for,  if  long  exposed  after  death, 
the  membrane  containing  the  ink  would  have  decayed.§ 

As  we  know  that  river-fish  are  sometimes  stifled,  even  in  their 
own  element,  by  muddy  water  during  floods,  it  cannot  be  doubted 
that  the  periodical  discharge  of  large  bodies  of  turbid  fresh  water 
into  the  sea  may  be  still  more  fatal  to  marine  tribes.  In  the  "  Prin- 
ciples of  Geology "  I  have  shown  that  large  quantities  of  mud  and 
drowned  animals  have  been  swept  down  into  the  sea  by  rivers  during 
earthquakes,  as  in  Java  in  1699  ;  and  that  indescribable  multitudes  of 
dead  fishes  have  been  seen  floating  on  the  sea  after  a  discharge  of 
noxious  vapors  during  similar  convulsions.  ||  But  in  the  intervals  be- 
tween such  catastrophes,  strata  may  have  accumulated  slowly  in  the 
sea  of  the  lias,  some  being  formed  chiefly  of  one  description  of  shell, 
such  as  ammonites,  others  of  gryphites. 

From  the  above  remarks  the  reader  will  infer  that  the  lias  is  for  the 
most  part  a  marine  deposit.  Some  members,  however,  of  the  series, 
especially  in  the  lowest  part  of  it,  have  an  estuary  character,  and  must 
have  been  formed  within  the  influence  of  rivers.  In  Gloucestershire, 
where  the  lias  of  the  West  of  England  is  well  developed,  it  is  divisible 
into  an  upper  mass  of  sand  and  shale  with  a  base  of  marlstone,  and  a 
lower  series  of  shales  with  underlying  limestones  and  shales.  We 
learn  from  the  researches  of  the  Rev.  P.  B.  Brodie,^[  that  in  the  inferior 

*  Bridgew.  Treat.,  p.  125.  f  Geological  Researches,  p.  334. 

$  Buckland,  Bridgew.  Treat.,  p.  307.  §  Buckland,  Bridgew.  Treat.,  p.  307. 

I  See  Principles,  Index,  Lancerote,  Graham  Island,  Calabria. 

TT  A  History  of  Fossil  Insects,  &c.,  1846.     London. 


428  FOSSIL  PLANTS—  LIAS.  [On.  XXL 

of  these  two  divisions  numerous  remains  of  insects  and  plants  have 
been  detected  in  several  places,  mingled  with  marine  shells.  One  band, 
rarely  exceeding  a  foot  in  thickness,  has  been  named  the  "  insect  lime- 
stone." It  passes  upwards  into  a  shale  containing  Cypris  and  Esiheria,^ 
and  is  charged  with  the  wing-cases  of  several  genera  of  coleoptera,  and 

with  some  nearly  entire  beetles,  of 
which  the  eye's  are  preserved.  The 
nervures  of  the  wings  of  neuropterous 
insects  (fig.  460)  are  beautifully  perfect 
in  this  bed.  Ferns,  with  cycads  and 
leaves  of  monocotyledonous  plants, 
and  some  apparently  brackish  and 


freshwater  shells'  accompany  theinsects 

B.  Brodie.)  in  several  places,  while  in  others  ma- 

rine  shells    predominate,   the    fossils 

varying  apparently  as  we  examine  the  bed  nearer  or  further  from  the 
ancient  land,  or  the  source  whence  the  freshwater  was  derived.  There 
are  two,  or  even  three,  bands  of  "  insect  limestone  "  in  several  sections, 
and  they  have  been  ascertained  by  Mr.  Brodie  to  retain  the  same 
lithological  and  zoological  characters  when  traced  from  the  centre  of 
Warwickshire  to  the  borders  of  the  southern  part  of  Wales.  After 
studying  300  specimens  of  these  insects  from  the  lias,  Mr.  Westwood 
declares  that  they  comprise  both  wood-eating  and  herb-devouring 
beetles,  of  the  Linnean  genera  JEJlater,  Carabus,  &c.,  besides  grass- 
hoppers (Gfryllus),  and  detached  wings  of  dragon-flies  and  mayflies, 
or  insects  referable  to  the  Linnean  genera,  Libellula,  Ephemera,  Jfemero- 
bius,  and  Panorpa,  in  all  belonging  to  no  less  than  twenty-four  families. 
The  size  of  the  species  is  usually  small,  and  such  as  taken  alone 
would  imply  a  temperate  climate  ;  but  many  of  the  associated  organic 
remains  of  other  classes  must  lead  to  a  different  conclusion. 

Fossil  plants.  —  Among  the  vegetable  remains  of  the  Lias,  several 
species  of  Zamia  have  been  found  at 
461-  Lyme  Regis,  and  the  remains  of  conifer- 

ous plants  at  Whitby.  Fragments  of 
wood  are  common,  and  often  convert- 
ed into  limestone.  That  some  of  this 
wood,  though  now  petrified,  was  soft 
when  it  first  lay  at  the  bottom  of  the  sea? 
is  shown  by  a  specimen  now  in  the  mu- 

seum of  the  Geological  Society  (see  fig.  461),  which  has  the  form  of 
an  ammonite  indented  on  its  surface. 

M.  Ad.  Brongniart  enumerates  47  liassic  acrogens,  most  of  them 
ferns;  and  50  gymnosperms,  of  which  39  are  cycads  and  11  coni- 
fers. Among  the  cycads  the  predominance  of  Zamites,  and  among 
the  ferns  the  numerous  genera  with  leaves  having  reticulated  veins 
(as  in  fig.  423,  p.  411),  are  mentioned  as  botanical  characteristics  of 


CH.  XXL]  ORIGIN  OF  THE  OOLITE  AND  LIAS.  429 

this  era,*  The  absence  as  yet  from  the  Lias  and  Oolite  of  all  signs 
of  dicotyledonous  angiosperms  is  worthy  of  notice.  The  leaves  of 
such  plants  are  frequent  in  tertiary  strata,  and  occur  in  the  Cretaceous, 
though  less  plentifully  (see  above,  p.  335).  The  angiosperms  seem, 
therefore,  to  have  been  at  the  least  comparatively  rare  in  these  older 
secondary  periods,  when  more  space  was  occupied  by  the  Cycads  and 
Conifers. 

Origin  of  the  Oolite  and  Lias. — If  we  now  endeavor  to  restore,  in 
imagination,  the  ancient  condition  of  the  European  area  at  the  period 
of  the  Oolite  and  Lias,  we  must  conceive  a  sea  in  which  the  growth 
of  coral-reefs  and  shelly  limestones,  after  proceeding  without  interrup- 
tion for  ages,  was  liable  to  be  stopped  suddenly  by  the  deposition  of 
clayey  sediment.  Then,  again,  the  argillaceous  matter,  devoid  of  corals, 
was  deposited  for  ages,  and  attained  a  thickness  of  hundreds  of  feet, 
until  another  period  arrived  when  the  same  space  was  again  occupied 
by  calcareous  sand,  or  solid  rocks  of  shell  and  coral,  to  be  again  suc- 
ceeded by  the  recurrence  of  another  period  of  argillaceous  deposition. 
Mr.  Conybeare  has  remarked  of  the  entire  group  of  Oolite  and  Lias, 
that  it  consists  of  repeated  alternations  of  clay,  sandstone,  and  limestone, 
following  each  other  in  the  same  order.  Thus  the  clays  of  the  lias  are 
followed  by  the  sands  of  the  inferior  oolite,  and  those  again  by  shelly 
and  coralline  limestone  (Bath  oolite,  &c.) ;  so,  in  the  middle  oolite, 
the  Oxford  clay  is  followed  by  calcareous  grit  and  coral-rag ;  lastly,  in 
the  upper  oolite,  the  Kimmeridge  clay  is  followed  by  the  Portland 
sand  and  limestone.f  The  clay  beds,  however,  as  Sir  H.  De  la  Beche 
remarks,  can  be  followed  over  larger  areas  than  the  sands  or  sand- 
stones.]; It  should  also  be  remembered  that  while  the  oolitic  system 
becomes  arenaceous  and  resembles  a  coal-field  in  Yorkshire, 'it  assumes 
in  the  Alps  an  almost  purely  calcareous  form,  the  sands  and  clays 
being  omitted ;  and  even  in  the  intervening  tracts  it  is  more  compli- 
cated and  variable  than  appears  in  ordinary  descriptions.  Neverthe- 
less, some  of  the  clays  and  intervening  limestones  do  retain,  in  reality, 
a  pretty  uniform  character  for  distances  of  from  400  to  600  miles  from 
east  to  west  and  north  to  south. 

According  to  M.  Thirria,  the  entire  oolitic  group  in  the  Depart- 
ment of  the  Haute  Saone,  in  France,  may  be  equal  in  thickness  to 
that  of  England ;  but  the  importance  of  the  argillaceous  divisions  is 
in  the  inverse  ratio  to  that  which  they  exhibit  in  England,  where  they 
are  about  equal  to  twice  the  thickness  of  the  limestones,  whereas,  in 
the  part  of  France  alluded  to,  they  reach  only  about  a  third  of  that 
thickness.§  In  the  Jura  the  clays  are  still  thinner  and  in  the  Alps 
they  thin  out  and  almost  vanish. 


*  Tableau  des  V6g.  Foss.,  1849,  p.  105. 

f  Con.  and  Phil.,  p.  166. 

J  Geol.  Researches,  p.  337. 

§  Burat's  D'Aubuisson,  torn.  iii.  p.  456. 


430  ORIGIN  OF  THE  OOLITE  AND  LIAS.  [On.  XXI. 

In  order  to  account  for  such  a  succession  of  events,  we  may  imag- 
ine, first,  the  bed  of  the  ocean  to  be  the  receptacle  for  ages  of  fine 
argillaceous  sediment,  brought  by  oceanic  currents,  which  may  have 
communicated  with  rivers,  or  with  part  of  the  sea  near  a  wasting 
coast.  This  mud  ceases,  at  length,  to  be  conveyed  to  the  same  region, 
either  because  the  laud  which  had  previously  suffered  denudation  is 
depressed  and  submerged,  or  because  the  current  is  deflected  in  another 
direction  by  the  altered  shape  of  the  bed  of  the  ocean  and  neighbor- 
ing dry  land.  By  such  changes  the  water  becomes  once  more  clear 
and  fit  for  the  growth  of  stony  zoophytes.  Calcareous  sand  is  then 
formed  from  comminuted  shell  and  coral,  or,  in  some  cases,  arenaceous 
matter  replaces  the  clay ;  because  it  commonly  happens  that  the  finer 
sediment,  being  first  drifted  farthest  from  coasts,  is  subsequently  over- 
spread by  coarse  sand,  after  the  sea  has  grown  shallower,  or  when 
the  land  increasing  in  extent,  whether  by  upheaval  or  by  sediment 
filling  up  parts  of  the  sea,  has  approached  nearer  to  the  spots  occupied 
by  fine  mud. 

In  order  to  account  for  another  great  formation,  like  the  Oxford 
clay,  again  covering  one  of  coral  limestone,  we  must  suppose  a  sink- 
ing down  like  that  which  is  now  taking  place  in  some  existing 
regions  of  coral  between  Australia  and  South  America.  The  oc- 
currence of  subsidences,  on  so  vast  a  scale,  may  have  caused  the  bed 
of  the  ocean  and  the  adjoining  land,  throughout  great  parts  of  the 
European  area,  to  assume  a  shape  favorable  to  the  deposition  of  another 
set  of  clayey  strata ;  and  this  change  may  have  been  succeeded  by  a 
series  of  events  analogous  to  that  already  explained,  and  these  again 
by  a  third  series  in  similar  order.  Both  the  ascending  and  descend- 
ing movements  may  have  been  extremely  slow,  like  those  now  going 
on  in  the  Pacific ;  and  the  growth  of  every  stratum  of  coral,  a  few  feet 
of  thickness,  may  have  required  centuries  for  its  completion,  during 
which  certain  species  of  organic  beings  disappeared  from  the  earth, 
and  others  were  introduced  in  their  place ;  so  that,  in  each  set  of  strata, 
from  the  Lias  to  the  Upper  Oolite,  some  peculiar  and  characteristic 
fossils  were  imbedded. 


CH.  XXII.]  NEW  RED  SANDSTONE.  4.31 


CHAPTER  XXII. 

TRIAS    OR    NEW   RED    SANDSTONE    GROUP. 

Distinction  between  New  and  Old  Red  Sandstone — Between  Upper  and  Lower  New 
Red — The  Trias  and  its  three  divisions — Most  largely  developed  in  Germany — 
Recognition  of  a  Marine  equivalent  of  the  Upper  Trias  in  the  Austrian  Alps — 
True  position  of  the  St.  Cassian  and  Hallstadt  Beds — 800  new  species  of  triassic 
Mollusca  and  Radiata — Links  thus  supplied  for  connecting  the  Palaeozoic  and 
Neozoic  faunas — Keuper  and  its  fossils — Muschelkalk  and  fossils — Fossil  plants 
of  the  Bunter — Triassic  group  in  England — Bone-bed  of  Axmouth  and  Aust — 
Red  Sandstone  of  Warwickshire  and  Cheshire — Footsteps  of  Ckeirotherium  in 
England  and  Germany — Osteology  of  the  Labyrinthodon — Whether  this  Batra- 
chian  was  identical  with  Cheirotherium — Dolomitic  Conglomerate  of  Bristol — 
Origin  of  Red  Sandstone  and  Rock-salt — Hypothesis  of  saline  volcanic  exhala- 
tions— Theory  of  the  precipitation  of  salt  from  inland  lakes  or  lagoons — Saltness 
of  the  Red  Sea — Triassic  coal-field  of  Eastern  Virginia,  near  Richmond — New 
Red  Sandstone  in  the  United  States — Fossil  footprints  of  birds  and  reptiles  in  the 
valley  of  the  Connecticut — Antiquity  of  the  Red  Sandstone  containing  them — 
Triassie  mammifer  of  North  Carolina. 

BETWEEN  the  Lias  and  the  Coal  (or  Carboniferous  group)  there  is 
interposed,  in  the  midland  and  western  counties  of  England,  a  great 
series  of  red  loams,  shales,  and  sandstones,  to  which  the  name  of  the 
"  New  Red  Sandstone  formation "  was  first  given,  to  distinguish  it 
from  other  shales  and  sandstones  called  the  "  Old  Red  "  (c,  fig.  462), 
often  identical  in  mineral  character,  which  lie  immediately  beneath 
the  coal  (6). 

Fig.  462. 


c.  Old  Eed  Sandstone.  5.  Coal.  a.  New  Eed  Sandstone. 

The  name  of  "  Red  Marl "  has  been  incorrectly  applied  to  the  red 
clays  of  this  formation,  as  before  explained  (p.  13),  for  they  are  re- 
markably free  from  calcareous  matter.  The  absence,  indeed,  of  car- 
bonate of  lime,  as  well  as  the  scarcity  of  organic  remains,  together 
with  the  bright  red  color  of  most  of  the  rocks  of  this  group,  causes  a 
strong  contrast  between  it  and  the  Jurassic  formations  before  described. 

Before  the  distinctness  of  the  fossil  remains  characterizing  the 
upper  and  lower  part  of  the  English  New  Red  had  been  clearly  recog- 


432  KEUPER  AND  MUSCHELKALK  FORMATIONS.       [Cn.  XXII. 

nized,  it  was  found  convenient  to  have  a  common  name  for  all  the 
strata  intermediate  in  position  between  the  Lias  and  Coal ;  and  the 
term  "Poikilitic"  was  proposed  by  Messrs.  Conybeare  and  Buck- 
land,*  from  rroiKikos,  poikilos,  variegated,  some  of  the  most  charac- 
teristic strata  of  this  group  having  been  called  variegated  by  Werner, 
from  their  exhibiting  spots  and  streaks  of  light-blue,  green,  and  buff 
color,  in  a  red  base. 

A  single  term,  thus  comprehending  both  Upper  and  Lower  New 
Red,  or  the  Triassic  and  Permian  groups  of  modern  classification, 
may  still  be  useful  in  describing  districts  where  we  have  to  speak  of 
masses  of  red  sandstone  and  shale,  referable,  in  part,  to  both  these 
eras,  but  which,  in  the  absence  of  fossils,  it  is  impossible  to  divide. 

Trias  or  Upper  New  Red  Sandstone  Group. — As  the  group  of 
strata  now  to  be  considered  is  more  fully  developed  in  Germany  than 
in  England  or  France,  it  will  be  well  to  consider  in  the  first  place  the 
manner  in  which  it  presents  itself  in  that  country.  It  has  been  called 
the  Trias  by  German  writers,  or  the  Triple  Group,  because  it  is  sepa- 
rable into  three  distinct  formations,  called  the  "Keuper,"  the 
"  Muschelkalk,"  and  the  "  Bunter-sandstein." 

NOMENCLATURE  OP  TRIAS. 

German.  French.  English. 

Keuper,  -       Marnes  irisees,    - 

Muschelkalk,    -        :  >;i.     j  M^£*'    ™    Calcdre  |  wanting  in  England. 

mdstone  and 
conglomerate. 


Bunter-sandstein,         -        Ores  bigarre,     ^  r        -     |  Sandstone  and  quartzos€ 


Upper  Trias,  or  Keuper.  —  It  has  been  already  stated,  p.  419,  that 
near  the  base  of  the  Lower  Lias  are  certain  zones  of  strata,  distin- 
guished by  the  abundance  of  peculiar  species  of  ammonite,  in  one  of 
which  A.  BucJclandi,  and  in  another  still  lower  A.  PlanorUs  abound. 
In  Northwestern  Germany,  as  in  England,  beneath  these  ammonitifer- 
ous  zones,  there  occurs  a  remarkable  bone  breccia,  a  marine  forma- 
tion, the  shells  of  which  are  distinct  from  those  of  the  Lias.  It  is 
filled  with  the  remains  of  fishes  and  reptiles,  almost  all  the  genera  of 
which,  and  some  even  of  the  species,  agree  with  those  of  the  subja- 
cent Trias.  This  breccia  has  accordingly  been  considered  by  Profes- 
sor Quenstedt  and  other  German  geologists  of  high  authority,  as  the 
newest  or  uppermost  part  of  the  Trias.  Professor  Plieninger  found 
in  it,  in  1847,  the  molar  tooth  of  a  small  Triassic  Mammifer,  called 
by  him  Microlestes  antiquus.  He  inferred  its  true  nature  from  its 
double  fangs,  and  from  the  form  and  number  of  the  protuberances  or 
cusps  on  the  flat  crown  ;  and  considering  it  as  predaceous,  probably 
insectivorous,  he  called  it  Microlestes,  from  /u/cpof  ,  little,  and 


Buckland,  Bridgew.  Treat.,  vol.  ii.  p.  38. 


CH.  XXII.] 


OLDEST   KNOWN  FOSSIL  MAMMIFER. 


433 


a  beast  of  prey.  Soon  afterwards  he  found  a  second  tooth,  also  at 
the  same  locality,  Diegerloch,  about  two  miles  to  the  southeast  of 
Stuttgart.  Some  of  its  cusps  are  broken,  but  there  seem  to  have 
been  six  of  them  originally.  From  its  agreement  in  general  charac- 
ter, it  was  supposed  by  Professor  Plieninger  to  belong  to  the  same 
animal ;  but  as  it  is  four  times  as  big,  it  may  perhaps  have  been  the 
tooth  of  another  allied  species.  This  molar  is  attached  to  the  matrix 
consisting  of  sandstone,  whereas  the  tooth  (fig.  463)  is  isolated.  Sev- 

Hg.  468. 


Microlestes  antiqmis,  Plieninger.    Molar  tooth,  magnified.    Upper  Trias,  Diegerloch, 

near  Stuttgart,  Wiirtemberg. 

a.  View  of  inner  side  ?  &.  Same,  outer  side  ? 

c.  Same  in  profile.  d.  Crown  of  same. 


Fig.  464. 


Fig.  465. 


Microlestes  antiquus,  Plien. 
View  of  same  molar  as  fig.  463.    From  a  drawing  by 

Hermann  Yon  Meyer. 

a.  View  of  inner  side  ?        &.  Crown  of  same. 
c.  Crown  of  the  same,  magnified. 


Molar  of  Microlestes  ?  Plien. 
4  times  as  large  as  the  fig. 
463.  From  the  Trias  of 
Diegerloch,  Stuttgart. 


cral  fragments  of  bone,  differing  in  structure  from  that  of  the  asso- 
ciated saurians  and  fish,  and  believed  to  be  mammalian,  were  imbed- 
ded near  them  in  the  same  rock.  No  anatomist  had  been  able  to 
give  any  feasible  conjecture  as  to  the  affinities  of  this  minute  quadru- 
ped until  Dr.  Falconer,  in  1857,  recognized  an  unmistakable  resem- 
blance between  its  teeth  and  the  two  back  molars  of  his  new  genus 
Plagiaulax  (see  above,  fig.  373,  p.  383),  from  the  Purbeck  strata. 
This  would  lead  us  to  the  conclusion  that  Microlestes  was  marsupial 
and  plant-eating. 

In  Wiirtemberg  there  are  two  bone-beds,  namely,  that  containing 
the  Microlestes,  which  has  just  been  described,  which  constitutes,  as 
we  have  seen,  the  uppermost  member  of  the  Trias,  and  another  of 
still  greater  extent,  and  still  more  rich  in  the  remains  of  fish  and 
reptiles,  which  is  of  older  date,  intervening  between  the  Keuper  and 
Muschelkalk. 

The  genera  Saurichthys,  Hybodus,  and  Gyrolepis,  are  found  in 
both  these  breccias,  and  one  of  the  species,  Saurichthys  Mongeoti,  is 
common  to  both  bone-beds,  as  is  also  a  remarkable  reptile  called 
28 


4:34  ST.   CASSIAN  AND  HALLSTADT  BEDS.  [Cn.  XXII. 

Nothosaurus  mirabilis.  The  saurian  called  Belodon  by  H.  Yon 
Meyer,  of  the  Thecodont  family,  is  another  Triassic  form,  associated 
at  Diegerloch  with  Microlestes. 

Beneath  this  bone-breccia  follows  the  regular  series  of  strata  called 
Keuper,  which  in  Wurtemberg  is  about  1000  feet  thick.  It  is  divided 
by  Alberti  into  sandstone,  gypsum,  and  carbonaceous  slate  clay.* 
Remains  of  reptiles  called  Nothosaurus  and  Phytosaurus  have  been 

found  in  it  with  Labyrinthodon ;  the 
detached  teeth,  also,  of  placoid  fish  and 
of  rays,  and  of  the  genera  Saurichthys 
and  Gyrolepis  (figs.  481,  482,  p.  442). 

The  plants  of  the  Keuper  are  generic- 
ally  very  analogous  to  those  of  the  lias 
and  oolite,  consisting  of  ferns,  equiseta- 
ceous  plants,  cycads,  and  conifers,  with 
a  few  doubtful  monocotyledons.  A  few 
Equisetites  columnar**  (Syn.  Eqwi-  species  such  as  Equisetites  columnaris, 

setum  columnare.)     Fragment  of     are     COmmon     to    this     group    and     the 
stem,  and  a  small  portion  of  same 
magnified.    Keuper.  oolite. 

St.  Cassian  and  Hallstadt  Beds. — The 

sandstones  and  clay  of  the  Keuper  resemble  the  deposits  of  estu- 
aries and  a  shallow  sea  near  the  land,  and  afford,  in  the  N.  W.  of 
Germany,  as  in  France  and  England,  but  a  scanty  representation  of 
the  marine  life  of  that  period.  We  might,  however,  have  anticipated, 
from  its  rich  reptilian  fauna,  that  the  contemporaneous  inhabitants  of 
the  sea  of  the  Keuper.  period  would  be  very  numerous,  should  we 
ever  have  an  opportunity  of  bringing  their  remains  to  light.  This,  it 
is  believed,  has  at  length  been  accomplished,  by  the  position  now 
assigned  to  certain  Alpine  rocks  called  the  "  St.  Cassian  beds,"  the 
true  place  of  which  in  the  series  was  until  lately  a  subject  of  much 
doubt  and  discussion.  For  valuable  researches  relating  to  these  for- 
mations, we  are  indebted  to  many  eminent  geologists,  especially  to 
MM.  Yon  Buch,  E.  de  Beaumont,  Murchison,  Sedgwick,  and  Klip- 
stein,  and  in  Switzerland  to  MM.  Escher  and  Merian,  and  more  lately 
in  Austria  to  MM.  Yon  Hauer,  Suess,  Homes,  and  Giimbel.  It  has 
been  proved  that  the  Hallstadt  beds  on  the  Northern  flanks  of  the 
Austrian  Alps  correspond  in  age  with  the  St.  Cassian  beds  on  their 
southern  declivity,  and  the  Austrian  geologists  hence  satisfied  them- 
selves that  the  Hallstadt  formation  is  referable  to  the  period  of  the 
Upper  Trias.  Assuming  this  conclusion  to  be  correct,  we  become 
acquainted  suddenly  and  unexpectedly  with  a  rich  marine  fauna  be- 
longing to  a  period  previously  believed  to  be  very  barren  of  organic 
remains,  because  in  England,  France,  and  Northern  Germany  the 
Upper  Trias  is  chiefly  represented  by  beds  of  fresh  or  brackish-water 
origin.  Mr.  Edward  Suess,  of  Yienna,  to  whom  we  are  indebted  for 

*  Monog.  des  Bunten  Sandsteins. 


CH.  XXII.]      INFRA-LIASSIC  STRATA  OF  AUSTRIAN  -ALPS. 


435 


several  memoirs  on  the  rocks  in  question,  has  favored  me  with  the 
following  summary  of  the  order  of  succession  of  the  Hallstadt  beds 
in  the  Austrian  Alps,  which  I  had  an  opportunity,  when  travelling  in 
the  autumn  of  1856,  of  verifying  in  company  with  Mr.  Giimbel,  of 
Munich. 

The  uppermost  strata  first  enumerated  immediately  underlie  the 
Lower  Lias  of  the  Swabian  Jura.  This  lias  is  represented  near 
Vienna  by  a  brown  limestone,  containing  Ammonites  Bucklandi,  A. 
Conybearii,  &c. 


Strata  below  the  Lias  in  the  Austrian  Alps,  in  Descending  Order. 


1.  Koessen  beds. 

(Synonyms,  Upper  St. 
Cassian  beds  of  Escher 
and  Merian.) 


2.  Dachstein  beds. 


Hallstadt  beds 
(or  St.  Cassian). 


4.  A.  Guttenstein  beds. 
B.  Werfen  beds,   base 

of  Upper  Trias  ? 
Lower  Trias   of   some 


Gray  and  black  limestone,  with  calcareous  marls  hav- 
ing a  thickness  of  about  50  feet.  Among  the 
fossils,  Brachiopoda  very  numerous ;  some  few 
species  common  to  the  genuine  Lias ;  many  pecu- 
liar. Avicula  contorta,  Pecten  Valoniensis,  Car- 
dium  JRhceticum,  Avicula  incequivalvis,  Spirifer 
Munsteri,  Dav.  Strata  containing  the  above  fos- 
sils alternate  with  the  Dachstein  beds,  lying  next 
below. 

White  or  grayish  limestone,  often  in  beds  3  or  4  feet 
thick.  Total  thickness  of  the  formation  above 
2000  feet.  Upper  part  fossiliferous,  with  some 
strata  composed  of  corals.  (Liihodendron.)  Lower 
portion  without  fossils.  Among  the  characteristic 
shells  are  Hemicardium  Wulferii,  Megalodon  tri- 
queter,  and  other  large  bivalves. 

Red,  pink,  or  white  marble,  from  800  to  1000  feet  in 
thickness,  containing  more  than  800  species  of  ma- 
rine fossils,  for  the  most  part  mollusca.  Many  spe- 
cies of  Orthoceras.  True  Ammonites,  besides 
Ceratites  and  Goniatites,  Belemnites  (rare),  Por- 
cellia,  Pleurotomaria,  Trochus,  Monotis  salinaria, 
&c. 

A.  Black  and  gray  limestone 
150  feet  thick,  alternating 
with  the  underlying  Wer- 
fen beds. 

B.  Red  and  green  shale  and 
sandstone,  with  Salt  and 
Gypsum. 


Among  the  fossils  are 
Ceratites  cassiamts, 
Myadtes  fassaen- 
sis,  Naticella  cos- 
tata,  &c. 


In  regard  to  the  age  of  the  rocks  above  mentioned,  the  Koessen 
and  Dachstein  beds  have  been  referred  by  some  to  the  Lias,  by  others 
to  the  Trias,  while  many  have  considered  them  to  be  of  intermediate 
date.  But  Mr.  Suess  has  shown  that  the  Koessen  beds  correspond  to 
the  upper  bone-bed  of  Swabia,  in  which  the  Microlestes  was  found 
(see  p.  432),  and  the  same  geologist  remarks  that  some  of  the  fossils 
of  the  beds  1  and  2  are  identical  with  the  Irish  "  Portrush  beds  "  of 
General  Portlock,  described  in  his  Report  on  Londonderry.  The 
Koessen  beds  have  been  traced  for  100  geographical  miles  from  near 
Geneva  to  the  environs  of  Vienna. 

The  German  geologists  are  now  generally  agreed,  as  already  stated, 
that  the  Hallstadt  and  St.  Cassian  beds  are  of  the  age  of  the  lower 


436 


ST.   CASSIAN  BEDS,  UPPER  TRIASSIC. 


[On.  XXIL 


part  of  the  Keuper  or  Upper  Trias ;  but  whether  the  Werfen  sand- 
stone, No.  4,  should  form  part  of  the  same  series,  or,  as  Von  Hauer 
inclines  to  believe,  should  be  classed  as  the  equivalent  of  "  the  Bun- 
ter  or  Lower  Trias,"  is  still  undetermined.  The  absence  of  well- 
characterized  Muschelkalk  fossils  in  the  Austrian  Alps  renders  this 
point  very  difficult  to  decide.  Rich  deposits  of  salt,  associated  with 
the  Werfen  beds,  have  inclined  some  geologists  to  presume  that  they 
belong  to  the  Upper  Trias.  Should  they  be  classed  as  "  Bunter,"  the 
Guttenstein  limestone  would  then  correspond  in  position  with  the 
Muschelkalk,  but  no  Muschelkalk  fossils  have  ever  been  met  with  in 
it  or  in  the  Werfen. 

Among  the  800  species  of  fossils  of  the  Hallstadt  and  St.  Cassian 
beds,  many  are  still  undescribed ;  some  are  of  new  and  peculiar 
genera,  as  Scoliostoma,  fig.  467,  Platystoma,  fig.  468,  among  the 
Gasteropoda ;  and  Koninckia,  fig.  46&,  among  the  Brachiopoda. 


Fig.  467. 


Fig.  468. 


Scoliostoma,  St.  Cassian. 


Platystoma  Suessii, 

Hoernes. 
From  Hallstadt. 


Fig.  469. 


KonincMa  Leorihardi,  Wissmann. 
a.  Dorsal  view,  natural  size. 
5.  Yentral  view,  part  of  the  converse  ventral  valve  removed  to  show  the  interior  of 

dorsal  valve  and  its  vascular  impressions.     One  of  the  spiral  processes  is  seen 

through  the  translucent  shell. 

c.  Section  of  both  valves. 

d.  Interior  of  dorsal  valve,  with  spiral  processes  restored.    (Sucss.) 

The  following  table  of  genera  of  marine  shells  from  the  Hallstadt 
and  St.  Cassian  beds,  drawn  up  on  the  joint  authority  of  MM.  Suess 
and  Woodward,  shows  how  many  connecting  links  between  the  fauna 
of  primary  and  secondary  rocks  are  supplied  by  the  St.  Cassian  and 
Hallstadt  beds. 


CH.  XXII.]  ST.   CASSIAN  BEDS,  UPPER  TRIASSIC.  437 

Genera  of  Fossil  Mollusca  in  the  St.  Cassian  and  Hallstadt  Beds. 

Common  to  Older  Kocks.       Characteristic  Triassic  Genera.       Common  to  Newer  Eoefc& 


Cyrtoceras. 

Orthoceras. 

Goniatites. 
*Loxonema. 
*Holopella. 

Murchisonia. 

Euomphalus. 

Porcellia, 
*Megalodon. 

Cyrtia. 


Ceratites. 
Scoliostoma  (or 
Cochlearia). 
Naticella. 
Platystoma. 
Isoarca. 
Pleurophorus. 
Myophoria. 
Monotis. 
Koninckia. 


Ammonites. 
*Belemnites, 
*Neringea. 

Opis. 

Cardita. 

Trigonia. 

Myoconchus. 

Ostrea.     1  sp. 

Plicatula. 

Thecidium. 


The  genera  marked  by  an  asterisk  are  given  on  the  authority  of  Mr.  Suess,  the 
rest  on  that  of  Mr.  Woodward  from  fossils  of  the  St.  Cassian  rocks  in  the  British 
Museum. 

The  first  column  marks  the  last  appearance  of  several  genera  which 
are  characteristic  of  Palaeozoic  strata.  The  second  shows  those  genera 
which  are  characteristic  of  the  Upper  Trias,  either  as  peculiar  to  it  or 
as  reaching  their  maximum  of  development  at  this  era.  The  third 
column  marks  the  first  appearance  'of  genera  destined  to  become  more 
abundant  in  later  ages. 

As  the  Orthoceras  had  never  been  met  with  in  the  marine  Mus- 
chelkalk, much  surprise  was  naturally  felt  that  7  or  8  species  of  the 
genus  should  appear  in  the  JIallstadt  beds,  assuming  these  last  to  be- 
long to  the  Upper  Trias.  Among  these  species  are  some  of  large  di- 
mensions, associated  with  large  Ammonites  with  foliated  lobes,  a  form 
never  seen  before  so  low  in  the  series,  while  the  Orthoceras  had  never 
been  seen  so  high.  But  the  latter  genus  has  also  been  met  with  in 
the  Adnet,  or  lias  strata  of  Austria,  as  I  was  assured  in  1856  by  several 
eminent  geologists  of  Germany. 

Professor  Kamsay  has  lately  made  a  careful  analysis  of  the  lists  giv- 
en by  Bronn  of  104  genera  and  774  species  of  fossils,  derived  from  the 
St.  Cassian  beds,  of  all  classes  of  the  animal  kingdom,  nearly  the  whole 
of  them  invertebrata ;  and  he  has  also  made  an  analysis  of  another  list 
of  79  genera  and  427  species  of  fossils  from  the  same  beds,  drawn  up 
by  a  skilful  naturalist,  the  late  Count  Munster.  The  results  arrived  at 
in  both  cases  agree  very  closely,  proving  that  somewhat  less  that  one- 
third  of  the  St.  Cassian  fossils  have  a  primary  or  palaeozoic,  and  two- 
thirds  of  them  a  secondary  or  mesozoic  character.  There  would  be 
nothing  wonderful  or  anomalous  in  such  a  result,  were  it  not  that  the 
fossils  of  the  Muschelkalk,  which  arc  supposed  to  be  older  than  the 
St.  Cassian  beds,  contain  a  comparatively  small  proportion  of  primary 
types,  so  that  a  palaeontologist  would  naturally  presume,  says  Professor 
Ramsay,  that  the  St.  Cassian  beds  were  a  stage  nearer  in  time  than  is 
the  Muschelkalk  to  the  Permian  period.  Bronn,  accordingly,  in  draw- 
ing up  his  catalogue,  placed  the  St.  Cassian  beds  in  that  position,  or 
as  intermediate  between  the  Bunter-sandstein  and  the  Upper  Per- 
mian, or  Zeckstein.  It  must,  I  think,  be  admitted  that,  were  we  not 


4.38  MUSCHELKALK  AND  FOSSILS.  [Cn.  XXII. 

controlled  by  the  decided  opinion  as  to  the  order  of  superposition  to 
which  the  most  able  living  surveyors  of  the  Austrian  Alps  have  come, 
we  should  naturally  take  for  granted,  when  presented  with  such  a  sec- 
tion as  that  given  at  p.  435,  that  the  Muschelkalk,  if  it  happened  to 
be  present  at  Hallstadt,  would  have  overlaid  the  bed  No.  3,  instead  of 
having  to  be  intercalated  between  Nos.  3  and  4,  or  even  placed  below 
No.  4. 

Whatever  ambiguity  may  still  remain  in  many  minds  respecting  the 
precise  chronological  relations  of  the  St.  Cassian  beds,  no  one  ques- 
tions that  they  are  Triassic,  and  they  have  entirely  dissipated  the  no- 
tion formerly  entertained  as  to  the  marine  fauna  of  the  whole  Triassic 
era  having  been  poverty-stricken.  The  St.  Cassian  fauna,  moreover, 
leads  us  to  expect  that,  should  we  hereafter  have  an  opportunity  of 
studying  the  marine  fossils  of  the  lowest  division  of  the  Bunter  sand- 
stone, the  present  break  between  the  Palaeozoic  and  Neozoic  forms  will 
almost  entirely  disappear. 

Muschelkalk. 

The  next  member  of  the  Trias  in  Germany,  the  Muschelkalk, 
which  underlies  the  Keuper  before  described,  consists  chiefly  of  a 
compact  grayish  limestone,  but  includes  beds  of  dolomite  in  many 
places,  together  with  gypsum  and  rock  salt.  This  limestone,  a  forma- 
tion wholly  unrepresented  in  England,  abounds  in  fossil  shells,  as  the 
name  implies.  Among  the  Cephalopoda  there  are  no  belemnites,  and 
no  ammonites  with  foliated  sutures,  as  in  the  lias  and  oolite  as  well 
as  in  the  Hallstadt  beds  ;  but  we  find  instead  a  genus  allied  to  the 
Ammonite,  called  Ceratites  by  De  Hann,  in  which  the  descending 
lobes  (see  a,  6,  c,  fig.  470)  terminate  in  a  few  small  denticulations  point- 


Fig.  470. 


O&ratiles  nodosus.    Muschelkalk. 

a.  Side  view,  5.  Front  view. 

c.  Partially  denticulated  outline  of  the  septa  diving  the  chambers. 

ing  inwards,  the  saddles  being  plane.  Among  the  bivalve  shells,  the 
Posidonia  minuta,  Goldf.  (Estheria  minuta,  Bronn),  (see  fig.  471),  is 
abundant,  ranging  through  the  Keuper,  Muschelkalk,  and  Bunter- 


CH.  XXII.] 


MUSCHELKALK  AND  FOSSILS. 


439 


sandstein ;  and  Avicula  socialis  (fig.  472),  having  a  similar  range,  is 
found  in  great  numbers  in  the  Muschelkalk  of  Germany,  France,  and 
Poland. 


Fig.  471. 


Fig.  472. 


Estheria  (Posidonia)  mi- 
nuta,  Goldf.  (Posido- 
nomya  minuta,  Bronn.) 


a.  Avicula  sociaUs.  5.  Side  view  of  same. 

Characteristic  of  the  Muschelkalk. 


The  abundance  of  the  heads  and  stems  of  lily  encrinites,  Encrinm 
liliiformis  (fig.   473),   (or  Encrinites  moniliformis),  shows  the  slow 
manner  in  which  some  beds  of  this  limestone  have 
Fig.  473.  keen   forme(i    in    ciear    sea-water.      The    star- fish 

called  Aspidura  loricata  (fig.  474)  is  as  yet  pecu- 
liar to  the  Muschelkalk.     In  the  same  formation  are 

Fig.  474. 


Enerinus  liliiformis,  Schlott.    Syn.  E.  moniliform/is. 

Body,  arms,  and  part  of  stem. 

a.  Section  of  stem. 

Muschelkalk. 


Aspidura  loricata, 
a.  Upper  side. 
Z>.  Lower  side. 
Muschelkalk. 


Fig.  475. 


Fig.  476. 


Palatal  teeth  of  Placodus  gigas. 
Muschelkalk. 


a.  Voltsia  Jieterophylla.    (Syn.  Voltzia 

brevifolia.) 
5.  Portion  of  same  magnified  to  show 

fructification.    Sulzbad. 
Bunter-sandstein 


440  BUNTER-SANDSTEIN.  [Cn.  XXII 

found  the  skull  and  teeth  of  a  reptile  of  the  genus  Placodus  (see  fig. 
475),  which  was  referred  originally  by  Count  Miinster,  and  afterwards 
by  Agassiz,  to  the  class  of  fishes.  But  more  perfect  specimens  ena- 
bled Professor  Owen,  in  1858,  to  show  that  this  fossil  animal  was  a 
Saurian  reptile,  which  probably  fed  on  shell-bearing  mollusks,  and 
used  its  short  and  flat  teeth,  so  thickly  coated  with  enamel,  for 
pounding  and  crushing  the  shells.* 

Bunter-sandstein. 

The  Bunter-sandstein  consists  of  various-colored  sandstones,  dolo- 
mites, and  red  clays,  with  some  beds,  especially  in  the  Hartz,  of  cal- 
careous pisolite  or  roe-stone,  the  whole  sometimes  attaining  a  thick- 
ness of  more  than  1000  feet.  The  sandstone  of  the  Vosges,  accord- 
ing to  Von  Meyer,  is  proved,  by  the  presence  of  Labyrinthodon  and 
other  fossils,  to  belong  to  this  lowest  member  of  the  Triassic  group. 
At  Sulzbad  (or  Soultz-les-bains),  near  Strasburg,  on  the  flanks  of  the 
Vosges,  many  plants  have  been  obtained  from  the  "  Bunter,"  espe- 
cially conifers  of  the  extinct  genus  Voltzia,  peculiar  to  this  period,  in 
which  even  the  fructification  has  been  preserved.  (See  fig.  476.) 

Out  of  thirty  species  of  ferns,  cycads,  conifers,  and  other  plants, 
enumerated  by  M.  Ad.  Brongniart,  in  1849,  as  coming  from  the 
"  Gres  bigarre,"  or  Bunter,  not  one  is  common  to  the  Keuper.f  This 
difference,  however,  may  arise,  partly  from  the  fact  that  the  flora  of 
the  "  Bunter  "  has  been  almost  entirely  derived  from  one  district  (the 
neighborhood  of  Strasburg),  and  its  peculiarities  may  be  local. 

The  footprints  of  a  reptile  (Labyrinthodon)  have  been  observed  on 
the  clays  of  this  member  of  the  Trias,  near  Hildburghausen,  in  Sax- 
ony, impressed  on  the  upper  surface  of  the  beds,  and  standing  out  as 
casts  in  relief  from  the  under  sides  of  incumbent  slabs  of  sandstone. 
To  these  I  shall  again  allude  in  the  sequel ;  they  attest,  as  well  as  the 
accompanying  ripple-marks,  and  the  tracks  which  traverse  the  clays, 
the  gradual  deposition  of  the  beds  of  this  formation  in  shallow  water, 
and  sometimes  between  high  and  low  water. 

Triassic  Group  in  England. 

The  Trias  or  New  Red  series  of  England  is  subdivided  by  Pro- 
fessor Ramsay  in  the  following  manner : 

(  Koessen  or  Penarth  beds  (Avicula  contorta  zone). 
Keuper  -j  New  Red  Marl,  with  streaks  of  Sandstone. 
(  White  and  Brown  Sandstone  and  Marl. 

{Upper  Variegated  Sandstone. 
Conglomerate  or  Pebble  beds. 
Lower  Variegated  Marble. 

*  Owen,  Phil.  Trans.,  1868,  p.  169. 

f  Tableau  des  Genres  de  Veg.  Foss.,  Diet.  Univ.,  1849. 


OH.  XXII.]  TRIASSIC  GROUP  IN  ENGLAND. 

Different  members  of  the  above  group  rest  in  England,  in  some 
region  or  other,  on  almost  every  principal  member  of  the  palaeozoic 
series,  on  Cambrian,  Silurian,  Devonian,  Carboniferous,  and  Permian 
rocks,  and  there  is  evidence  everywhere  of  disturbance,  contortion, 
partial  upheaval  into  land,  and  vast  denudations  which  the  older 
rocks  underwent  before  and  during  the  deposition  of  the  successive 
strata  of  the  New  Red  Sandstone  group.  It  was  stated  (p.  419)  that 
the  Lower  Lias  in  the  southwest  of  England  contained  near  its  base 
strata  characterized  by  Ammonites  planorbis,  below  which  beds  with 
many  reptilian  remains  sometimes  occur. 

Still  lower,  on  the  boundary  line  between  the  Lias  and  Trias,  cer- 
tain cream-colored  limestones,  called  White  Lias  by  Smith,  are  found 
usually,  but  not  always,  without  fossils.  These  white  beds  have  late- 
ly been  referred  by  Mr.  Chas.  Moore  to  what  he  calls  the  Rhsetic  beds,* 
because  largely  developed  in  the  Rhaetian  Alps,  and  which  are  the 
same  as  the  Koessen  beds  of  Germany,  No.  1,  p.  435.  The  marine 
organic  remains  observed  in  them  near  Frome,  in  Somersetshire,  show 
that  they  appertain  to  the  highest  member  of  the  Upper  Trias,  in 
which  occur  the  sandstones  and  shales  with  Avicula  contorta  (fig.  479), 
together  with  other  fossil  shells  belonging  to  the  same  zone  in  Ger- 
many, France,  and  Lombardy.  Among  the  most  abundant  of  the 
shells  in  all  these  countries  is  the  above-mentioned  Avicula  (fig.  479), 
and  with  it  Cardium  rhceticum  (fig.  477)  and  Pecten  Valoniensis 
(tig.  478). 

Fig.  478. 


Fig.  477. 

Fig.  479. 


.     Cardium  rhceticum.            Pecten   Valoniensis,   Dfr.  Avicula  contorta.    Portlock. 

Kat.   size.     Uppermost             £   nat-    Bize-     Portrush,  Portrush,      Ireland,      &c. 

Trias.                            Ireland,  &c.    Uppermost  Nat.      size.       Uppermost 

Trias.  Trias. 

The  principal  member  of  this  group  has  been  called  by  Dr.  Wright 
the  Avicula  contorta  bed,f  as  this  shell  is  very  abundant,  and  has  a 
wide  range  in  Europe.  General  Portlock  first  described  the  forma- 
tion as  it  occurs  at  Portrush,  in  Antrim,  where  the  Avicula  contorta 
is  accompanied  by  Pecten  Valoniensis,  as  in  Germany.  The  beds 
under  consideration,  although  of  moderate  thickness,  are  already  rich 
in  synonyms,  as,  besides  the  German  names  mentioned  at  page  435 

*  Moore,  Rhjetic  Beds,  Quart.  Geol.  Journ.,  1861,  vol.  xvii. 

f  Dr.  Wright,  on  Lias  and  Bone-bed,  Quart.  Geol.  Journ.,  1860,  vol.  xvi. 


442  FOSSIL  TEETH  IN  NEW  RED  SANDSTONE.         [Cn.  XXII. 

and  the  Bone-bed  series  of  many  geologists,  as  well  as  the  Khsetic  beds 
of  Mr.  C.  Moore,  it  has  lately  been  named  the  Penarth  beds  by  the 
Government  surveyors  of  Great  Britain,  from  Penarth,  near  Cardiff, 
in  Glamorganshire,  where  these  strata  are  finely  exhibited  in  the 
sea-cliffs. 

The  best-known  member  of  the  group,  a  thin  band  or  bone-breccia, 
is  conspicuous  among  the  black  shales  in  the  neighborhood  of  Axmouth, 
in  Devonshire,  and  in  the  cliffs  of  Westbury-on-Severn,  as  well  as  at 
Aust  and  other  places  on  the  borders  of  the  British  Channel.  It 
abounds  in  the  remains  of  saurians  and  fish,  and  was  formerly  classed 
as  the  lowest  bed  of  the  Lias ;  but  Sir  P.  Egerton  first  pointed  out,  in 
1841,  that  it  should  be  referred  to  the  Upper  New  Red  Sandstone, 
because  it  contained  an  assemblage  of  fossil  fish  which  are  either 
peculiar  to  this  stratum,  or  belong  to  species  well  known  in  the  Mus- 
chelkalk  of  Germany.  These  fish  belong  to  the  genera  Acrodus, 
ffybodus,  Gyrolepis,  and  Saurichthys. 

Among  those  common  to  the  English  bone-bed  and  the  Muschelkalk 
of  Germany  are  JTybodus  plicatilis  (fig.  480),  Saurichthys  apicalis  (fig. 
481),  Gyrolepis  tenuistriatus  (fig.  482),  and  G,  Albertii.  Remains  of 
saurians,  Plesiosaurus  among  others,  have  also  been  found  in  the  bone- 
bed,  and  plates  of  an  Encrinus. 

Fig.  481.  Fig.  482. 

Fig.  480. 


Hylodus  plicatilis.    Teeth.    Bone-bed, 
Aust  and  Axmouth. 

Saurichthys  apicalis.  Gyrolepis  tenuistriatus. 
Tooth ;  nat.  size,  and  Scale ;  nat.  size  and 
magnified.  Axmouth.  magnified.  Axmouth. 

In  certain  gray  indurated  marls  below  the  bone-bed,  Mr.  Dawkins 
found,  at  Watchett,  on  the  coast  of  Somersetshire,  in  1863,  a  two-fanged 
molar  tooth  of  a  fossil  mammifer  of  the  Microlestes  family.  Mr.  Chas. 
Moore  had  previously  discovered  -twenty-seven  teeth  of  mammalia  of  the 
same  family  near  Frome,  in  Somersetshire,  in  the  contents  of  a  vertical 
fissure  traversing  a  mass  of  carboniferous  limestone.  The  top  of  this 
fissure  must  have,  communicated  with  the  bed  of  the  Triassic  sea,  and 
probably  at  a  point  not  far  from  the  ancient  shore  on  which  the  small 
marsupials  of  that  era  abounded. 

The  strata  of  red  and  green  marl,  which  follow  the  bone-bed  in  the 
descending  order  at  Axmouth  and  Aust,  are  destitute  of  organic  remains : 
as  is  the  case,  for  the  most  part,  in  the  corresponding  beds  in  almost 
every  part  of  England.  But  fossils  have  been  found  at  a  few  localities 
in  sandstones  of  this  formation,  in  Worcestershire  and  Warwickshire, 


CH.  XXII.]      FOSSIL  FOOTSTEPS  IN  NEW  RED  SANDSTONE.  443 

and  among  them  the  bivalve  shell  called  Posidonia  minuta,  Goldf., 
before  mentioned  (fig.  471,  p.  439). 

The  member  of  the  English  "  New  Red  "  containing  this  shell,  in 
those  parts  of  England,  is,  according  to  Sir  Roderick  Murchison  and 
Mr.  Strickland,  600  feet  thick,  and  consists  chiefly  of  red  marl  or  slate, 
with  a  band  of  sandstone.  Ichthyodoralites,  or  spines  of  Hybodus, 
teeth  of  fishes,  and  footprints  of  reptiles  were  observed  by  the  same 
geologists  in  these  strata ;  *  and  the  remains  of  a  saurian,  called  Khyn- 
chosaurus,  have  been  found  in  this  portion  of  the  Trias  at  Grinsell,  near 
Shrewsbury. 

In  Cheshire  and  Lancashire  the  gypseous  and  saliferous  red  shales 
and  clays  of  the  Trias  are  between  1000  and  1500  feet  thick.  In 
some  places  lenticular  masses  of  rock-salt  are  interpolated  between 
the  argillaceous  beds,  the  origin  of  which  will  be  spoken  of  in  the 
sequel. 

The  lower  division  or  English  representative  of  the  "  Bunter"  attains 
a  thickness  of  600  feet  in  the  counties  last  mentioned.  Besides  red 
and  green  shales  and  red  sandstones,  it  comprises  much  soft  white 
quartzose  sandstone  in  which  the  trunks  of  silicified  trees  have  been 
met  with  at  Allesley  Hill,  near  Coventry.  Several  of  them  were  a  foot 
and  a  half  in  diameter,  and  some  yards  in  length,  decidedly  of  conifer- 
ous wood,  and  showing  rings  of  annual  growth.f  Impressions,  also, 
of  the  footsteps  of  animals  have  been  detected  in  Lancashire  and  Che- 
shire in  this  formation.  Some  of  the  most  remarkable  occur  a  few 
miles  from  Liverpool,  in  the  whitish  quartzose  sandstone  of  Storton 
Hill,  on  the  west  side  of  the  Mersey.  They  bear  a  close  resem- 
blance to  tracks  first  observed  in  a  member  of  the  Upper  New  Red 
Sandstone,  at  the  village  of  Hesseberg,  near 
Hildburghausen,  in  Saxony,  to  which  I  have  Fig-  483. 

already  alluded.      For  many   years   these 
footprints  have  been   referred  to   a  large 
unknown  quadruped,  provisionally  named 
Cheirotherium  by  Professor  Kaup,  because 
the  marks  both  of  the  fore  and  hind  feet 
resembled  impressions  made  by  a  human 
hand.     (See  fig.  483.)     The  footmarks  at 
Hesseberg  are  partly  concave,  and  partly  in 
relief;  the  former,  or  the  depressions,  are 
seen  upon  the  upper  surface  of  the  sand-      Single  footstep  of  Oheirothe. 
stone  slabs,  but  those  in  relief  are  only  upon        num.    Bunter-sandstein, 
the  lower   surfaces,  being  in  fact  natural        ^™r'™ 
casts,  formed  in  the  subjacent  footprints  as 
in  moulds.     The  larger  impressions,  which  seem  to  be  those  of  the 


*  Geol.  Trans.,  Second  Series,  vol.  v.  p.  318,  &c. 

f  Buckland,  Proc.  Geol.  Soc.,  vol.  ii.  p.  ^439 ;  and  Murchison  and  Strickland, 
Geol.  Trans.,  Second  Series,  vol.  v.  p.  34 Y. 


444:  FOSSIL  REMAINS.  [Cn.  XXII. 

hind  foot,  are  generally  8  inches  in  length,  and  5  in  width,  and  one 
was  12  inches  long.     Near  each  large  footstep,  and  at  a  regular  dis- 

Fig.  481. 


Line  of  footsteps  on  slab  of  sandstone.    Hildburghausen,  in  Saxony. 

tance  (about  an  inch  and  a  half),  before  it,  a  similar  print  of  a  fore 
foot,  4  inches  long  and  3  inches  wide,  occurs.  The  footsteps  follow 
each  other  in  pairs,  each  pair  in  the  same  line,  at  intervals  of  14  inches 
from  pair  to  pair.  The  large  as  well  as  the  small  steps  show  the  great 
toes  alternately  on  the  right  and  left  side ;  each  step  makes  the  print 
of  five  toes,  the  first  or  great  toe  being  bent  inwards  like  a  thumb. 
Though  the  fore  and  hind  foot  differ  so  much  in  size,  they  are  nearly 
similar  in  form. 

The  similar  footmarks  afterwards  observed  in  a  rock  of  correspond- 
ing age  at  Storuton  Hill  were  imprinted  on  five  thin  beds  of  clay,  super- 
imposed one  upon  the  other  in  the  same  quarry,  and  separated  by  beds 
of  sandstone.  On  the  lower  surface  of  the  sandstone  strata,  the  solid 
casts  of  each  impression  are  salient,  in  high  relief,  and  afford  models 
of  the  feet,  toes,  and  claws  of  the  animals  which  trod  on  the  clay.  On 
the  same  surfaces  Mr.  J.  Cunningham  discovered  (1839)  distinct  casts 
of  rain-drop  markings. 

As  neither  in  Germany  nor  in  England  any  bones  or  teeth  had  been 
met  with  in  the  same  identical  strata  as  the  footsteps,  anatomists  in- 
dulged, for  several  years,  in  various  conjectures  respecting  the  myste- 
rious animals  from  which  they  might  have  been  derived.  Professor 
Kaup  suggested  that  the  unknown  quadruped  might  have  been  allied 
to  the  Marsupialia  ;  for  in  the  kangaroo  the  first  toe  of  the  fore  foot 
is  in  a  similar  manner  set  obliquely  to  the  others,  like  a  thumb,  and  the 
disproportion  between  the  fore  and  hind  feet  is  also  very  great.  But 
M.  Link  conceived  that  some  of  the  four  species  of  animals  of  which 
the  tracks  had  been  found  in  Saxony  might  have  been  gigantic  Batra- 
chians ;  and  Dr.  Buckland  designated  some  of  the  footsteps  as  those 
of  a  small  web-footed  animal,  probably  crocodilian. 

In  the  course  of  these  discussions  several  naturalists  of  Liverpool, 
in  their  report  on  the  Storton  quarries,  declared  their  opinion  that 
each  of  the  thin  seams  of  clay  in  which  the  sandstone  casts  were 
moulded  had  formed  successively  a  surface  above  water,  over  which 
the  Cheirotherium  and  other  animals  walked,  leaving  impressions  of 
their  footsteps,  and  that  each  layer  had  been  afterwards  submerged  by 
a  sinking  down  of  the  surface,  so  that  a  new  beach  was  formed  at  low 
water  above  the  former,  on  which  other  tracks  were  then  made.  The 
repeated  occurrence  of  ripple-marks  at  various  heights  and  depths  in 
red  sandstone  of  Cheshire  had  been  explained  in  the  same  manner.  It 


On.  XXII.]  FOSSIL  REMAINS  OF  LABYRINTHODOK 


445 


Fig.  485. 


was  also  remarked  that  impressions  of  such  depth  and  clearness  could 
only  have  been  made  by  animals  walking  on  the  land,  as  their  weight 
would  have  been  insufficient  to  make  them  sink  so  deeply  in  yielding 
clay  under  water.  They  must,  therefore,  have  been  air-breathers. 

When  the  inquiry  had  been  brought  to  this  point,  the  reptilian  re- 
mains discovered  in  the  Trias,  both  of  Germany  and  England,  were  care- 
fully examined  by  Prof.  Owen.  He  found,  after  a  microscopic  investiga- 
tion of  the  teeth  from  the  German  sandstone  called  Keuper,  and  from 
the  sandstone  of  Warwick  and  Leamington  (fig.  485),  that  neither  of 
them  could  be  referred  to  true  saurians,  although  they  had  been  named 
Mastodonsaurus  and  Phytosaurus  by  Jager.  It 
appeared  that  they  were  of  the  Batrachian  order, 
and  of  gigantic  dimensions  in  comparison  with  any 
representatives  of  that  order  now  living.  Both 
the  Continental  and  English  fossil  teeth  exhibited 
a  most  complicated  texture,  differing  from  that 
previously  observed  in  any  reptile,  whether  recent  th 
or  extinct,  but  most  nearly  analogous  to  the  Ich- 
thyosaurus. A  section  of  one  of  these  teeth  ex- 
hibits a  series  of  irregular  folds,  resembling  the 
labyrinthic  windings  of  the  surface  of  the  brain ;  and  from  this 
character  Prof.  Owen  has  proposed  the  name  Ldbyrinthodon  for  the 
new  genus.  The  annexed  representation  (fig.  486)  of  part  of  one  is 

Fig.  486. 


of  LabyrintTic- 
don;  nat.  size.  "War- 
wick sandstone. 


Transverse  section  of  tooth  of  Labyrinthodon  Jaegeri,  Owen  (Mastodonsaurus  Jaegeri, 

Meyer) ;  nat.  size,  and  a  segment  magnified. 
a.  Pulp  cavity,  from  which  the  processes  of  pulp  and  dentine  radiate. 

given  from  his  "  Odontography,"  plate  64  A.  The  entire  length  of 
this  tooth  is  supposed  to  have  been  about  three  inches  and  a  half,  and 
the  breadth  at  the  base  one  inch  and  a  half. 


446  FOSSIL  REMAINS  OF  LABYRINTHODON.  [Cn.  XXII. 

When  Prof.  Owen  had  satisfied  himself,  from  an  inspection  of  the 
cranium,  jaws,  and  teeth,  that  a  gigantic  Batrachian  had  existed  at 
the  period  of  the  Trias  or  Upper  New  Red  Sandstone,  he  soon  found, 
from  the  examination  of  various  bones  derived  from  the  same  forma- 
tion, that  he  could  define  three  species  of  Labyrinthodon,  and  that  in 
this  genus  the  hind  extremities  were  much  larger  than  the  anterior 
ones.  This  circumstance,  coupled  with  the  fact  of  the  Labyrinthodon 
having  existed  at  the  period  when  the  Cheirotherium  footsteps  were 
made,  was  the  first  step  towards  the  identification  of  those  tracks  with 
the  newly-discovered  Batrachian.  It  was  at  the  same  time  observed 
that  the  footmarks  of  Cheirotherium  were  more  like  those  of  toads 
than  of  any  other  living  animal ;  and,  lastly,  that  the  size  of  the  three 
species  of  Labyrinthodon  corresponded  with  the  size  of  three  different 
kinds  of  footprints  which  had  already  been  supposed  to  belong  to 
three  distinct  Cheirotheria.  It  was  moreover  inferred,  with  confidence, 
that  the  Labyrinthodon  was  an  air-breathing  reptile  from  the  structure 
of  the  nasal  cavity,  in  which  the  posterior  outlets  were  at  the  back 
part  of  the  mouth,  instead  of  being  directly  under  the  anterior  or  ex- 
ternal nostrils.  It  must  have  respired  air  after  the  manner  of  saurians, 
and  may  therefore  have  imprinted  on  the  shore  those  footsteps,  which, 
as  we  have  seen,  could  not  have  originated  from  an  animal  walking 
under  water. 

But  the  structure  of  the  foot  is  still  wanting,  and  a  more  connected 
and  complete  skeleton  is  required  for  demonstration  ;  for  the  circum- 
stantial evidence  above  stated  is  not  strong  enough  to  produce  in  the 
minds  of  some  eminent  anatomists  the  conviction  that  the  Cheirotherium 
and  Labyrinthodon  are  one  and  the  same. 

Dolomitic  Conglomerate  of  JBristol. — Near  Bristol,  in  Somersetshire, 
and  in  other  countries  bordering  the  Severn,  are  certain  strata  which 
rest  unconformably  upon  the  coal-measures,  and  consist  of  a  conglom- 
erate called  "  dolomitic,"  because  the  pebbles  of  older  rocks  contained 
in  it  are  cemented  together  by  a  red  or  yellow  base  of  dolomite.  This 
conglomerate  or  breccia  occurs  in  patches  over  the  downs  near  Bristol, 
and  upon  the  flanks  of  the  hills,  filling  up  hollows  and  irregularities  in 
the  Old  Red  Sandstone,  Millstone  Grit,  and  Mountain  Limestone. 
The  imbedded  fragments  are  both  rounded  and  angular,  and  some  of 
them  of  vast  size,  especially  those  of  millstone  grit,  weighing  nearly  a 
ton.  It  is  principally  composed,  at  every  spot  of  the  debris,  of  those 
rocks  on  which  it  immediately  rests.  At  one  point  we  find  pieces  of 
coal-shale,  in  another  of  mountain  limestone,  recognizable  by  its 
peculiar  shells  and  zoophytes.  Fractured  bones,  also,  and  teeth  of 
saurians  of  contemporaneous  origin,  are  dispersed  through  some  parts 
of  the  breccia. 

These  saurians  are  distinguished  by  having  the  teeth  implanted 
deeply  in  the  jaw-bone,  and  in  distinct  sockets,  instead  of  being  solder- 
ed, as  in  frogs,  to  a  simple  alveolar  parapet.  In  the  dolomitic  con- 
glomerate near  Bristol  the  remains  of  species  of  two  genera  have  been 


CH.  XXII.]  ORIGIN  OF  RED  SANDSTONE.  447 

found,  called  Thecodontosaurus  and  Palceosaurus  by  Dr.  Riley  and  Mr. 
Stutchbury ;  *  the  teeth  of  which  are  conical,  compressed,  and  with 
finely  serrated  edges  (figs.  487  and  488). 

Teeth  of  Saurians.    Dolomitic  conglomerate ;  Kedland,  near  Bristol. 
Fig.  487.  Fig.  488. 


Teeth  of  Pakeosaurus  111      lift    Teeth  of  Theeodonlosaiirus ; 

platyodon;  nat.  size.  3  times  magnified. 


Messrs.  Conybeare  and  Buckland  refen'ed  the  strata  containing  these 
saurians  to  the  period  of  the  magnesian  limestone,  or  the  lowest  part 
of  their  Poikilitic  series,  and  for  a  long  time  these  reptiles  ranked  as 
the  most  ancient  representatives  of  their  class  which  had  been  found 
in  any  British  rocks ;  but  Sir  H.  De  la  Beche  afterwards  pointed  out 
that,  in  consequence  of  the  isolated  position  of  the  breccia  containing 
the  fossils  in  question,  it  was  very  difficult  to  determine  to  what  pre- 
cise part  of  the  Poikilitic  series  they  belonged.f  More  lately,  our 
Government  surveyors  have  satisfied  themselves  that  the  breccia  is  of 
Triassic  date,  probably  referable  to  the  base  of  the  Keuper. 

Origin  of  Red  Sandstone  and  Rock  Salt. 

We  have  seen  that,  in  various  parts  of  the  world,  red  and  mottled 
clays  and  sandstones,  of  several  distinct  geological  epochs,  are  found 
associated  with  salt,  gypsum,  magnesian  limestone,  or  with  one  or  all 
of  these  substances.  There  is,  therefore,  in  all  likelihood,  a  general 
cause  for  such  a  coincidence.  Nevertheless,  we  must  not  forget  that 
there  are  dense  masses  of  red  and  variegated  sandstones  and  clays,  thou- 
sands of  feet  in  thickness,  and  of  vast  horizontal  extent,  wholly  devoid 
of  saliferous  or  gypseous  matter.  There  are  also  deposits  of  gypsum 
and  of  muriate  of  soda,  as  in  the  blue  clay  formation  of  Sicily,  without 
any  accompanying  red  sandstone  or  red  clay. 

To  account  for  deposits  of  red  nmd  and  red  sand,  we  have  simply 
to  suppose  the  disintegration  of  ordinary  crystalline  or  metamorphic 
schists.  Thus,  in  the  eastern  Grampians  of  Scotland,  in  the  north  of 
Forfarshire,  for  example,  the  mountains  of  gneiss,  mica-schist,  and  clay- 
slate  are  overspread  with  alluvium,  derived  from  the  disintegration  of 
those  rocks ;  and  the  mass  of  detritus  is  stained  by  oxide  of  iron,  of 
precisely  the  same  color  as  the  Old  Red  Sandstone  of  the  adjoining 
lowlands.  Now  this  alluvium  merely  requires  to  be  swept  down  to  the 

*  Geol.  Trans.,  Second  Series,  vol.  v.  p.  349,  pi.  29,  figs.  2  and  5. 
f  Memoirs  of  Geol.  Survey  of  Great  Britain,  vol.  i.  p.  268. 


448  ORIGIN  OF  ROCK  SALT.  [On.  XXII. 

sea,  or  into  a  lake,  to  form  strata  of  red  sandstone  and  red  marl,  pre- 
cisely like  the  mass  of  the  "  Old  Red "  or  "  New  Eed "  systems  of 
England,  or  those  tertiary  deposits  of  Auvergne  (see  p.  224),  before 
described,  which  are  in  lithological  characters  quite  undistinguishable. 
The  pebbles  of  gneiss  in  the  Eocene  red  sandstone  of  Auvergne  point 
clearly  to  the  rocks  from  which  it  has  been  derived.  The  red  coloring 
matter  may,  as  in  the  Grampians,  have  been  furnished  by  the  decom- 
position of  hornblende  or  mica,  which  contain  oxide  of  iron  in  large 
quantity. 

It  is  a  general  fact,  and  one  not  yet  accounted  for,  that  scarcely  any 
fossil  remains  are  preserved  in  stratified  rocks  in  which  this  oxide  of 
iron  abounds ;  and  when  we  find  fossils  in  the  New  or  Old  Red  Sand- 
stone in  England,  it  is  in  the  gray,  and  usually  calcareous  beds,  that 
they  occur. 

The  gypsum  and  saline  matter,  occasionally  interstratified  with  such 
red  clays  and  sandstones  of  various  ages,  primary,  secondary,  and  ter- 
tiary, have  been  thought  by  some  geologists  to  be  of  volcanic  origin. 
Submarine  and  subaerial  exhalations  often  occur  in  regions  of  earth- 
quakes and  volcanoes  far  from  points  of  actual  eruption,  and  charged 
with  sulphur,  sulphuric  salts,  and  with  common  salt  or  muriate  of  soda. 
In  a  word,  such  "  solfataras  "  are  vents  by  which  all  the  products  which 
issue  in  a  state  of  sublimation  from  the  craters  of  active  volcanoes  ob- 
tain a  passage  from  the  interior  of  the  earth  to  the  surface.  That,  such 
gaseous  emanations  and  mineral  springs,  impregnated  with  the  ingre- 
dients before  enumerated,  and  often  intensely  heated,  continue  to  flow 
out  unaltered  in  composition  and  temperature  for  ages,  is  well  known. 
But  before  we  can  decide  on  their  real  instrumentality  in  producing  in 
the  course  of  ages  beds  of  gypsum,  salt,  and  dolomite,  we  require  to 
know  more  respecting  the  chemical  changes  actually  in  progress  in  seas 
where  volcanic  agency  is  at  work. 

The  origin  of  rock  salt,  however,  is  a  problem  of  so  much  interest 
in  theoretical  geology  as  to  demand  the  discussion  of  another  hypoth- 
esis advanced  on  the  subject ;  namely,  that  which  attributes  the  pre- 
cipitation of  the  salt  to  evaporation,  whether  of  inland  lakes  or  of 
lagoons  communicating  with  the  ocean. 

At  Northwich,  in  Cheshire,  in  the  Upper  Trias  or  Keuper,  two  beds 
of  salt,  in  great  part  unmixed  with  earthy  matter,  attain  the  extra- 
ordinary thickness  of  90  and  even  100  feet.  The  upper  surface  of  the 
highest  bed  is  very  uneven,  forming  cones  and  irregular  figures.  Be- 
tween the  two  masses  there  intervenes  a  bed  of  indurated  clay,  trav- 
ersed with  veins  of  salt.  The  highest  bed  thins  off  towards  the  south- 
west, losing  1 5  feet  in  thickness  in  the  course  of  a  mile.*  The  horizon- 
tal extent  of  these  particular  masses  in  Cheshire  and  Lancashire  is  not 
exactly  known ;  but  the  area,  containing  saliferous  clays  and  sand- 
stones, is  supposed  to  exceed  150  miles  in  diameter,  while  the  total 

*  Ormerod,  Quart.  Geol.  Journ.,  1848,  vol.  iv.  p.  277. 


CH.  XXII.]  RUNN    OF  CUTCH.  449 

thickness  of  the  trias  in  the  same  region  is  estimated  by  Mr.  Ormerod 
at  more  than  1700  feet.  Ripple-marked  sandstones,  and  the  footprints 
of  animals,  before  described,  are  observed  at  so  many  levels  that  we 
may  safely  assume  the  whole  area  to  have  undergone  a  slow  and  grad- 
ual depression  during  the  formation  of  the  Bed  Sandstone.  The 
evidence  of  such  a  movement,  wholly  independent  of  the  presence  of 
salt  itself,  is  very  important  in  reference  to  the  theory  under  considera- 
tion. 

In  the  "  Principles  of  Geology  "  (chap,  xxvii.),  I  published  a  map, 
furnished  to  me  by  the  late  Sir  Alexander  Burnes,  of  that  singular  flat 
region  called  the  Runn  of  Cutch,  near  the  delta  of  the  Indus,  which  is 
7000  square  miles  in  area,  or  equal  in  extent  to  about  one-fourth  of 
Ireland.  It  is  neither  land  nor  sea,  but  is  dry  during  a  part  of  every 
year,  and  again  covered  by  salt  water  during  the  monsoons.  Some 
parts  of  it  are  liable,  after  long  intervals,  to  be  overflowed  by  river- 
water.  Its  surface  supports  no  grass,  but  is  encrusted  over,  here  and 
there,  by  a  layer  of  salt,  about  an  inch  in  depth,  caused  by  the  evapora- 
tion of  sea-water.  Certain  tracts  have  been  converted  into  dry  land 
by  upheaval  during  earthquakes  since  the  commencement  of  the  pres- 
ent century,  and,  in  other  directions,  the  boundaries  of  the  Runn  have 
been  enlarged  by  subsidence.  That  successive  layers  of  salt  might  be 
thrown  down,  one  upon  the  other,  over  thousands  of  square  miles,  in 
such  a  region,  is  undeniable.  The  supply  of  brine  from  the  ocean  would 
be  as  inexhaustible  as  the  supply  of  heat  from  the  sun  to  cause  evapora- 
tion. The  only  assumption  required  to  enable  us  to  explain  a  great 
thickness  of  salt  in  such  an  area  is,  the  continuance,  for  an  indefinite 
period,  of  a  subsiding  movement,  the  country  preserving  all  the  time 
a  general  approach  to  horizontally.  Pure  salt  could  only  be  formed 
in  the  central  parts  of  basins,  where  no  sand  could  be  drifted  by  the 
wind,  or  sediment  be  brought  by  currents.  Should  the  sinking  of 
the  ground  be  accelerated,  so  as  to  let  in  the  sea  freely,  and  deepen 
the  water,  a  temporary  suspension  of  the  precipitation  of  salt  would 
be  the  only  result.  On  the  other  hand,  if  the  area  should  dry  up, 
ripple-marked  sands  and  the  footprints  of  animals  might  be  formed, 
where  salt  had  previously  accumulated.  According  to  this  view,  the 
thickness  of  the  salt,  as  well  as  of  the  accompanying  beds  of  mud  and 
sand,  becomes  a  mere  question  of  time,  or  requires  simply  a  repetition 
of  similar  operations. 

Mr.  Hugh  Miller,  in  an  able  discussion  of  this  question,  refers  to  Dr. 
Frederick  Parrot's  account,  in  his  journey  to  Ararat  (1836),  of  the  salt 
lakes  of  Asia.  In  several  of  these  lakes  west  of  the  river  Manech, 
"  the  water,  during  the  hottest  season  of  the  year,  is  covered  on  its 
surface  with  a  crust  of  salt  nearly  an  inch  thick,  which  is  collected  with 
shovels  into  boats.  The  crystallization  of  the  salt  is  effected  by  rapid 
evaporation  from  the  sun's  heat  and  the  supersaturation  of  the  water 
with  muriate  of  soda ;  the  lake  being  so  shallow  that  the  little  boats 
trail  on  the  bottom  and  leave  a  furrow  behind  them,  so  that  the  lake 
29 


450  SALTNESS  OF  THE  RED  SEA.  [On.  XXIL 

must  be  regarded  as  a  wide  pan  of  enormous  superficial  extent,  in 
which  the  brine  can  easily  reach  the  degree  of  concentration  required." 

Another  traveller,  Major  Harris,  in  his  "Highlands  of  Ethiopia," 
describes  a  salt  lake,  called  the  Bahr  Assal,  near  the  Abyssinian  fron- 
tier, which  once  formed  the  prolongation  of  the  Gulf  of  Tadjara,  but 
was  afterwards  cut  off  from  the  gulf  by  a  broad  bar  of  lava  or  of  land 
upraised  by  an  earthquake.  "  Fed  by  no  rivers,  and  exposed  in  a 
burning  climate  to  the  unmitigated  rays  of  the  sun,  it  has  shmnk  into 
an  elliptical  basin,  seven  miles  in  its  transverse  axis,  half  filled  with 
smooth  water  of  the  deepest  caerulean  hue,  and  half  with  a  solid  sheet 
of  glittering  snow-white  salt,  the  offspring  of  evaporation."  "  If,"  says 
Mr.  Hugh  Miller,  "  we  suppose,  instead  of  a  barrier  of  lava,  that  sand- 
bars were  raised  by  the  surf  on  a  flat  arenaceous  coast  during  a  slow 
and  equable  sinking  of  the  surface,  the  waters  of  the  outer  gulf  might 
occasionally  topple  over  the  bar,  and  supply  fresh  brine  when  the  first 
stock  had  been  exhausted  by  evaporation."  * 

We  may  add  that  the  permanent  impregnation  of  the  waters  of  a 
large  shallow  basin  with  salt,  beyond  the  proportion  which  is  usual  in 
the  ocean,  would  cause  it  to  be  uninhabitable  by  mollusks  or  fish,  as 
is  the  case  in  the  Dead  Sea,  and  the  muriate  of  soda  might  remain  in  ex- 
cess, even  if  it  were  occasionally  replenished  by  irruptions  of  the  sea. 
Should  the  saline  deposit  be  eventually  submerged,  it  might,  as  we  have 
seen  from  the  example  of  the  Runn  of  Cutch,  be  covered  by  a  fresh- 
water formation  containing  fluviatile  organic  remains ;  and  in  this  way 
the  apparent  anomaly  of  beds  of  sea-salt  and  clays  devoid  of  marine 
fossils,  alternating  with  others  of  freshwater  origin,'  may  be  explained. 

Dr.  G.  Buist,  in  a  communication  to  the  Bombay  Geographical 
Society  (vol.  ix.),  has  asked  how  it  happens  that  the  Red  Sea  should 
not  exceed  the  open  ocean  in  saltness  by  more  than  -^th  per  cent. 
The  Red  Sea  receives  no  supply  of  water  from  any  quarter  save  through 
the  Straits  of  Babelmandeb ;  and  there  is  not  a  single  river  or  rivulet 
flowing  into  it  from  a  circuit  of  4000  miles  of  shore.  The  countries 
around  are  all  excessively  sterile  and  arid,  and  composed,  for  the  most 
part,  of  burning  deserts.  From  the  ascertained  evaporation  in  the  sea 
itself,  Dr.  Buist  computes  that  nearly  8  feet  of  pure  water  must  be 
carried  off  from  the  whole  of  its  surface  annually,  this  being  probably 
equivalent  to  T^th  part  of  its  whole  volume.  The  Red  Sea,  therefore, 
ought  to  have  1  per  cent,  ajided  annually  to  its  saline  contents ;  and 
as  these  constitute  4  per  cent,  by  weight,  or  2  J  per  cent,  in  volume  of 
its  entire  mass,  it  ought,  assuming  the  average  depth  to  be  800  feet, 
which  is  supposed  to  be  far  beyond  the  truth,  to  have  been  converted 
into  one  solid  salt  formation  in  less  than  3000  years.f  Does  the  Red 
Sea  receive  a  supply  of  water  from  the  ocean,  through  the  narrow 
Straits  of  Babelmandeb,  sufficient  to  balance  the  loss  by  evaporation  ? 

*  Hugh  Miller,  First  Impressions  of  England,  1847,  pp.  183,  214. 
f  Buist.  Trans,  of  Bombay  Geograph.  Soc.,  1850,  vol.  ix.  p.  38. 


CH.  XXII.]  TRIAS  OF  THE  UNITED  STATES. 

And  is  there  an  undercurrent  of  heavier  saline  water  annually  flowing 
outwards  ?  If  not,  in  what  manner  is  the  excess  of  salt  disposed 
of?  An  investigation  of  this  subject  by  our  nautical  surveyors  may 
perhaps  aid  the  geologist  in  framing  a  true  theory  of  the  origin  of 
rock-salt. 

Trias  of  the  United  States. 

Coal-field  of  Richmond,  Virginia. — There  are  large  tracts  on  the 
globe,  as  in  Russia  and  the  Atlantic  border  of  the  United  States,  where 
all  the  members  of  the  oolitic  series  are  unrepresented.  In  the  State 
of  Virginia,  at  the  distance  of  about  13  miles  eastward  of  Richmond, 
the  capital  of  that  State,  there  is  a  regular  coal-field  occurring  in  a  de- 
pression of  the  granite  rocks  (see  section,  fig.  489).  It  extends  26 


Section  showing  the  geological  position  of  the  James  Kiver,  or  East  Virginian  Coal-field. 
A.  Granite,  gneiss,  &c.  B.  Coal-measures. 

C.  Tertiary  strata.  D.  Drift  or  ancient  alluvium. 

miles  from  north  to  south,  and  from  4  to  12  from  east  to  west.  Pro- 
fessor W.  B.  Rogers  formerly  referred  these  strata  to  the  lower  part 
of  the  Jurassic  group ;  and  this  opinion  I  adopted  in  former  editions 
of  this  work,  after  collecting  a  large  number  of  fossil  plants,  fish,  and 
shells,  and  examining  the  coal-field  throughout  its  whole  area.  The 
plants  consist  chiefly  of  zamites,  calamites,  equiseta,  and  ferns.  The 
equiseta  are  very  commonly  met  with  in  a  vertical  position  more  or 
less  compressed  perpendicularly.  It  is  clear  that  they  grew  in  the 
places  where  they  are  now  buried  in  strata  of  hardened  sand  and  mud. 
I  found  them  maintaining  their  erect  attitude,  at  points  many  miles 
distant  from  others,  in  beds  both  above  and  between  the  seams  of  coal. 
In  order  to  explain  this  fact  we  must  suppose  such  shales  and  sand 
stones  to  have  been  gradually  accumulated  during  the  slow  and  repeat- 
ed subsidence  of  the  whole  region. 

It  is  worthy  of  remark  that  the  Equisetum  columnare  of  these  Vir- 
ginian rocks  appears  to  be  undistinguishable  from  the  species  found  in 
the  oolitic  sandstones  near  Whitby  in  Yorkshire,  where  it  also  is  met 
with  in  an  upright  position.  One  of  the  Virginian  fossil  ferns,  Pecopteris 
Whitbyensis,  is  also  a  species  which  has  been  considered  as  common  to 
the  Yorkshire  oolites,  although  Professor  Heer  doubts  its  identity.* 

*  See  description  of  the  coal-field  by  the  Author,  and  of  the  plants  by  C.  J.  F. 
Bunbury,  Esq.,  Quart.  Geol.  Journ.,  vol.  iii.  p.  281. 


4.52  TRIAS  OF  THE  UNITED  STATES.  [On.  XXII 

But  trie  plants  upon  the  whole  are  considered  by  Professor  Heer  to 
have  the  nearest  affinity  to  those  of  the  European  Keuper.  When 
Sir  Charles  Bunbury  compared  them  in  1847  to  the  fossil  plants  of 
"Neueweld  near  Basle,  and  of  other  plant-bearing  rocks  near  Baireuth, 
he  supposed,  as  linger  had  done  before  him,  that  those  localities  were 
Liassic,  whereas  geologists  afterwards  determined  them  to  be  of  Upper 
Triassic  date. 

The  fossil  fish  are  Ganoids,  some  of  them  of  the  genus  Catopterus, 
others  belonging  to  the  Liassic  genus  Tetragonolepis  (jffchmodus),  see 
fig.  452  p.  421.  Fossil  rnollusca  are  very  rare,  as  usually  in  all  coal- 
bearing  deposits,  but  two  species  of  Entomostraca  called  Estheria  are 
in  such  profusion  in  some  shaly  beds  as  to  divide  them  like  the  plates 
of  mica  in  micaceous  shales  (see  fig.  490). 

Fig.  490. 


a.  Estheria  ovata.  6.  Young  of  same. 

Oolitic  coal-shale,  Eichmond,  Virginia. 

These  Virginian  coal-measures  are  composed  of  grits,  sandstones, 
and  shales,  exactly  resembling  those  of  older  or  primary  date  in  America 
and  Europe,  and  they  rival  or  even  surpass  the  latter  in  the  richness 
and  thickness  of  the  coal-seams.  One  of  these,  the  main  seam,  is  in 
some  places  from  30  to  40  feet  thick,  composed  of  pure  bituminous 
coal.  On  descending  a  shaft  800  feet  deep,  in  the  Blackheath  mines 
in  Chesterfield  County,  I  found  myself  in  a  chamber  more  than  40  feet 
high,  caused  by  the  removal  of  this  coal.  Timber  props  of  great 
strength  supported  the  roof,  but  they  were  seen  to  bend  under  the 
incumbent  weight.  The  coal  is  like  the  finest  kinds  shipped  at  New- 
castle, and  when  analysed  yields  the  same  proportions  of  carbon  and 
hydrogen — a  fact  worthy  of  notice  when  we  consider  that  this  fuel  has 
been  derived  from  an  assemblage  of  plants  very  distinct  specifically, 
and  in  part  generically  from  those  which  have  contributed  to  the  for- 
mation of  the  ancient  or  palaeozoic  coal. 

New  Red  Sandstone  of  the  Valley  of  the  Connecticut  River. — In  a 
depression  of  the  granitic  or  hypogene  rocks  in  the  States  of  Massa- 
chusetts and  Connecticut,  strata  of  red  sandstone,  shale,  and  con- 
glomerate are  found,  occupying  an  area  more  than  150  miles  in  length 
from  north  to  south,  and  about  5  to  10  miles  in  breadth,  the  beds 
dipping  to  tho  eastward  at  angles  varying  from  5  to  50  degrees.  The 


On.  XXII.]  TRIAS  OF  THE  UNITED  STATES.  453 

extreme  inclination  of  50  degrees  is  rare,  and  only  observed  in  tlie 
neighborhood  of  masses  of  trap  which  have  been  intruded  into  the  red 
sandstone  while  it  was  forming,  or  before  the  newer  parts  of  the  deposit 
had  been  completed.  Having  examined  this  series  of  rocks  in  many 
places,  I  feel  satisfied  that  they  were  formed  in  shallow  water,  and  for 
the  most  part  near  the  shore,  and  that  some  of  the  beds  were  from 
time  to  time  raised  above  the  level  of  the  water,  and  laid  dry,  while  a 
newer  series,  composed  of  similar  sediment,  was  forming.  The  red 
flags  of  thin-bedded  sandstone  are  often  ripple-marked,  and  exhibit  on 
their  under-sides  casts  of  cracks  formed  in  the  underlying  red  and 
green  shales.  These  last  must  have  shrunk  by  drying  before  the  sand 
was  spread  over  them.  On  some  shales  of  the  finest  texture  impres- 
sions of  rain-drops  may  be  seen,  and  casts  of  them  in  the  incumbent 
argillaceous  sandstones.  Having  observed  similar  markings  produced 
by  showers,  of  which  the  precise  date  was  known,  on  the  recent  red 
mud  of  the  Bay  of  Fundy,  and  casts  in  relief  of  the  same  on  layers  of 
dried  mud  thrown  down  by  subsequent  tides,*  I  feel  no  doubt  in  regard 
to  the  origin  of  some  of  the  ancient  Connecticut  impressions.  I  have 
also  seen  on  the  mud-flats  of  the  Bay  of  Fundy  the  footmarks  of  birds 
(Tringa  minuta),  which  daily  run  along  the  borders  of  that  estuary 
at  low  water  and  which  I  have  described  in  my  travels,  f  Similar 
layers  of  red  mud,  now  hardened  and  compressed  into  shale,  are  laid 
open  on  the  banks  of  the  Connecticut,  and  retain  faithfully  the  im- 
pressions and  casts  of  the  feet  of  numerous  birds  and  reptiles  which 
walked  over  them  at  the  time  when  they  were  deposited,  probably  in 
the  Triassic  period. 

According  to  Professor  Hitchcock,  the  footprints  of  no  less  than 
thirty-two  species  of  bipeds,  and  twelve  of  quadrupeds,  have  been 
already  detected  in  these  rocks.  Thirty  of  these  are  believed  to  be 
those  of  birds,  four  of  lizards,  two  of  chelonians,  and  six  of  batrachians. 
The  tracks  have  been  found  in  more  than  twenty  places,  scattered 
through  an  extent  of  nearly  80  miles  from  north  to  south,  and  they 
are  repeated  through  a  succession  of  beds  attaining  at  some  points  a 
thickness  of  more  than  1000  feet,  which  may  have  been  thousands  of 
years  in  forming.;]; 

As  considerable  skepticism  is  naturally  entertained  in  regard  to 
the  nature  of  the  evidence  derived  from  footprints,  it  may  be  well  to 
enumerate  some  facts  respecting  them  on  which  the  faith  of  the 
geologist  may  rest.  When  I  visited  the  United  States  in  1842,  more 
than  2000  impressions  had  been  observed  by  Professor  Hitchcock,  in 
the  district  alluded  to,  and  all  of  them  were  indented  on  the  upper 
surface  of  the  layers,  while  the  corresponding  casts,  standing  out  in 
relief,  were  always  on  the  lower  surfaces  or  planes  of  the  strata.  If 

*  Principles  of  Geology,  9th  ed.,  p.  203. 
•j-  Travels  in  N.  America,  vol.  ii.  p.  168. 
j  Hitchcock,  Mem.  of  Amer.  Acad.,  New  Series,  vol.  Hi.  p.  129 ;  1848. 


4.54  FOSSIL  FOOTPRINTS.  [Cn.  XXII. 

we  follow  a  single  line  of  marks  we  find  them  uniform  in  size,  and 
nearly  uniform  in  distance  from  each  other,  the  toes  of  two  successive 
footprints  turning  alternately  right  and  left  (see  fig.  491).  Such 


Fig.  491. 


Footprints  of  a  bird.    Turner's  Falls,  Valley  of  the  Connecticut.    (See  Dr.  Deane, 
Mem.  of  Amer.  Acad.,  vol.  iv.  1849.) 

single  lines  indicate  a  biped ;  and  there  is  generally  such  a  deviation 
from  a  straight  line  in  any  three  successive  prints,  as  we  remark  in  the 
tracks  left  by  birds.  There  is  also  a  striking  relation  between  the 
distance  separating  two  footprints  in  one  series,  and  the  size  of  the 
impressions ;  in  other  words,  an  obvious  proportion  between  the 
length  of  the  stride  and  the  dimension  of  the  creature  which  walked 
over  the  mud.  If  the  marks  are  small,  they  may  be  half  an  inch 
asunder ;  if  gigantic,  as,  for  example,  where  the  toes  are  20 
inches  long,  they  are  occasionally  4  feet  and  a  half  apart.  The 
bipedal  impressions  are  for  the  most  part  trifid,  and  show  the  same 
number  of  joints  as  exist  in  the  feet  of  living  tridactylous  birds. 
Now,  such  birds  have  three  phalangeal  bones  for  the  inner  toe,  four 
for  the  middle,  and  five  for  the  outer  one  (see  fig.  491) ;  but  the  im- 
pression of  the  terminal  joint  is  that  of  the  nail  only.  The  fossil 
footprints  exhibit  regularly,  where  the  joints  are  seen,  the  same  num- 
ber ;  and  we  see  in  each  continuous  line  of  tracks  the  three-jointed 
and  five-jointed  toes  placed  alternately  outwards,  first  on  the  one  side 
and  then  on  the  other.  In  some  specimens,  besides  impressions  of 
the  three  toes  in  front,  the  rudiment  is  seen  of  the  fourth  toe  behind. 
It  is  not  often  that  the  matrix  has  been  fine  enough  to  retain  impres- 
sions of  the  integument  or  skin  of  the  foot ;  but  in  one  fine  specimen 
found  at  Turner's  Falls  on  the  Connecticut,  by  Dr.  Deane,  these 
markings  are  well  preserved,  and  have  been  recognized  by  Professor 
Owen  as  resembling  the  skin  of  the  ostrich,  and  not  that  of  reptiles.* 
Much  care  is  required  to  ascertain  the  precise  layer  of  a  laminated 
rock  on  which  an  animal  has  walked,  because  the  impression  usually 
extends  downwards  through  several  laminae ;  and  if  the  upper  layer 
originally  trodden  upon  is  wanting,  the  mark  of  one  or  more  joints, 
or  even  in  some  cases  an  entire  toe,  which  sank  less  deep  into  the  soft 
ground,  may  disappear,  and  yet  the  remainder  of  the  footprint  be 
well  defined. 

*  This  specimen  was  in  the  late  Dr.  Mantell's  museum,  and  indicated  a  bird  of  a 
size  intermediate  between  the  small  and  the  largest  of  the  Connecticut  species. 


CH.  XXIL]  FOSSIL  FOOTPRINTS.  4.55 

The  size  of  several  of  the  fossil  impressions  of  the  Connecticut  red 
sandstone  so  far  exceeds  that  of  any  living  ostrich,  that  naturalists  at 
first  were  extremely  adverse  to  the  opinion  of  their  having  been  made 
by  birds,  until  the  bones  and  almost  entire  skeleton  of  the  Dinornis 
and  of  other  feathered  giants  of  New  Zealand  were  discovered. 
Their  dimensions  have  at  least  destroyed  the  force  of  this  particular 
objection.  The  magnitude  of  the  impressions  of  the  feet  of  a  heavy 
animal,  which  has  walked  on  soft  mud,  increases  for  some  distance 
below  the  surface  originally  trodden  upon.  In  order,  therefore,  to 
guard  against  exaggeration,  the  casts  rather  than  the  mould  are  relied 
on.  These  casts  show  that  some  of  the  fossil  bipeds  had  feet  four 
times  as  large  as  the  ostrich,  but  not  perhaps  much  larger  than  the 
Dinornis. 

The  eggs  of  another  gigantic  bird,  called  ^Epiornis,  which  has 
probably  been  exterminated  by  man,  have  recently  been  discovered 
in  an  alluvial  deposit  in  Madagascar.  The  egg  has  six  times  the 
capacity  of  that  of  the  ostrich ;  but,  judging  from  the  large  size  of 
the  egg  of  the  Apteryx,  Professor  Owen  does  not  believe  that  the 
^Epiornis  exceeded,  if  indeed  it  equalled,  the  Dinornis  in  stature. . 

Among  the  supposed  bipedal  tracks,  a  single  distinct  animal  only  has 
been  observed  of  feet  in  which  there  are  four  toes  directed  forwards. 
In  "this  case  a  series  of  four  footprints  is  seen,  each  22  inches  long  and 
12  wide,  with  joints  much  resembling  those  in  the  toes  of  birds.  Pro- 
fessor Agassiz  has  suggested  that  it  might  have  belonged  to  a  gigantic 
bipedal  batrachian.  Other  naturalists  have  called  our  attention  to  the 
fact,  that  some  quadrupeds,  when  walking,  place  the  hind  foot  so  pre- 
cisely on  the  same  spot  just  quitted  by  the  fore  foot,  as  to  produce  a 
single  line  of  imprints,  like  those  of  a  biped;  and  Mr.  Waterhouse 
Hawkins  has  remarked  that  certain  species  of  frogs  and  lizards  in  Aus- 
tralia have  the  two  outer  toes  so  slightly  developed  and  so  much  raised 
that  they  might  leave  tridactylous  footprints  on  mud  and  sand. 
Another  osteologist,  Dr.  Leidy,  in  the  United  States,  observed  to  me 
that  the  pterodactyl  was  a  biped  reptile  approaching  the  bird  so  nearly 
in  the  structure  and  shape  of  its  wing-bones  and  tibia3,  that  some  of 
these  last,  obtained  from  the  Chalk  and  Wealden  in  England,  had  been 
mistaken  by  the  highest  authorities  for  true  birds'  bones.  May  not 
the  foot,  therefore,  of  a  pterodactyl  have  equally  resembled  that  of  a 
bird  ?  Be  this  as  it  may,  the  greater  number  of  the  American  impres- 
sions agree  so  precisely  in  form  and  size  with  the  footmarks  of  known 
living  birds,  especially  with  those  of  waders,  that  we  shall  act  most  in 
accordance  with  known  analogies  by  referring  most  of  them  at  present 
to  feathered,  rather  than  to  featherless  bipeds. 

*  No  bones  have  as  yet  been  met  with,  whether  of  pterodactyl  or  bird, 
in  the  rocks  of  the  Connecticut,  but  there  are  numerous  coprolites ; 
and  an  ingenious  argument  has  been  derived  by  Dr.  Dana  from  the- 
analysis  of  these  bodies,  and  the  proportion  they  contain  of  uric  acid, 
phosphate  of  lime,  carbonate  of  lime,  and  organic  matter,  to  show 


456  ANTIQUITY  OF  THE  [Cn.  XXII. 

that,  like  guano,  they  are  the  droppings  of  birds  rather  than  of 
reptiles. 

Some  of  the  quadrupedal  footprints  which  accompany  those  of  birds 
are  analogous  to  European  Cheirotheria,  and  with  a  similar  dispropor- 
tion between  the  hind  and  fore  feet.  Others  resemble  that  remarkable 
reptile,  the  Rhynchosaurus  of  the  English  Trias,  a  creature  having  some 
relation  in  its  osteology  both  to  chelonians  and  birds.  Other  imprints, 
again,  are  like  those  of  turtles. 

Mr.  Darwin,  in  his  "  Journal  of  a  Voyage  in  the  Beagle,"  informs  us 
that  the  "  South  American  ostriches,  although  they  live  on  vegetable 
matter,  such  as  roots  and  grass,  are  repeatedly  seen  at  Bahia  Blanca 
(lat.  39°  S.),  on  the  coast  of  Buenos  Ay  res,  coming  down  at  low  water 
to  the  extensive  mud-banks  which  are  then  dry,  for  the  sake,  as  the 
Guachos  say,  of  feeding  on  small  fish."  They  readily  take  to  the  water, 
and  have  been  seen  at  the  Bay  of  San  Bias,  and  at  Port  Valdez,  in 
Patagonia,  swimming  from  island  to  island.*  It  is  therefore  evident, 
that  in  our  times  a  South  American  mud-bank  might  be  trodden 
simultaneously  by  ostriches,  alligators,  tortoises,  and  frogs ;  and  the 
impressions  left,  in  the  nineteenth  century,  by  the  feet  of  these  various 
tribes  of  animals,  would  not  differ  from  each  other  more  entirely  than 
do  those  attributed  to  birds,  saurians,  chelonians,  and  batrachians  in 
the  rocks  of  the  Connecticut. 

To  determine  the  exact  age  of  the  red  sandstone  and  shale  contain- 
ing these  ancient  footprints  in  the  United  States,  is  not  possible  at 
present.  No  fossil  shells  have  yet  been  found  in  the  deposit,  nor  plants 
in  a  determinable  state.  The  fossil  fish  are  numerous  and  very  perfect ; 
but  they  are  of  a  peculiar  type,  which  was  originally  referred  to  the 
genus  Palceoniscus,  but  has  since,  with  propriety,  been  ascribed,  by 
Sir  Philip  Egerton,  to  a  new  genus.  To  this  he  has  given  the  name 
of  Ischypterus,  from  the  great  size  and  strength  of  the  fulcral  rays  of 
the  dorsal  fin  (from  la^vc;,  strength,  and  Trrepbf,  a  fin).  They  differ 
from  Palceoniscus,  as  Mr.  Redfield  first  pointed  out,  by  having  the 
vertebral  column  prolonged  to  a  more  limited  extent  into  the  upper 
lobe  of  the  tail,  or,  in  the  language  of  M.  Agassiz,  they  are  less  hetero- 
cercal.  The  teeth  also,  according  to  Sir  P.  Egerton,  who,  in  1 844, 
examined  for  me  a  fine  series  of  specimens  which  I  procured  at  Durham, 
Connecticut,  differ  from  tliose  of  Palceoniscus  in  being  strong  and  conical. 

That  the  sandstones  containing  these  fish  are  of  older  date  than  the 
coal-bearing  strata  near  Richmond  in  Virginia,  which  have  been  shown 
(p.  451)  to  be  about  the  age  of  the  European  Keuper,  is  probable. 
The  high  antiquity  of  the  Connecticut  beds  cannot  be  proved  by  direct 
superposition,  but  may  be  presumed  from  the  general  structure  of  the 
country.  That  structure  proves  them  to  be  newer  than  the  movements 
to  which  the  Appalachian  or  Alleghany  chain  owes  its  flexures,  and 
this  chain  includes  the  ancient  or  palaeozoic  coal-formation  among  its 

*  Journal  of  Voyage  of  Beagle,  &c.,  2d  edit,  p.  89 ;  1845. 


CH.  XXIL]  CONNECTICUT  BEDS.  45Y 

contorted  rocks.  The  unconformable  position  of  this  New  Red  with 
ornithichnites  on  the  edges  of  the  inclined  primary  or  palaeozoic  rocks 
of  the  Appalachians  is  seen  at  4  of  the  section,  fig.  552  p.  497.  The 
absence  of  fish  with  decidedly  heterocercal  tails  may  afford  an  argu- 
ment against  the  Permian  age  of  the  formation ;  and  the  opinion  that 
the  red  sandstone  is  triassic  seems,  on  the  whole,  the  best  that  we  can 
embrace  in  the  present  state  of  our  knowledge. 

In  North  Carolina,  the  late  Professor  Emmons  has  described  the 
strata  of  the  Chatham  coal-field,  which  correspond  in  age  to  those 
near  Richmond  in  Virginia.  In  beds  underlying  them  he  has  met 
with  three  jaws  of  a  small  insectivorous  mammal,  which  he  has  called 
Dromatherium  sylvestre,  closely  allied  to  Spalacotherium.  Its  nearest 
living  analogue,  says  Professor  Owen,  "  is  found  in  Myrmecobius ;  for 
each  ramus  of  the  lower  jaw  contained  ten  small  molars  in  a  continu- 
ous series,  one  canine,  and  three  conical  incisors — the  latter  being 
divided  by  short  intervals."  There  is  every  reason  to  believe  that 
this  fossil  quadruped  is  at  least  as  ancient  as  the  Microlestes  of  the 
European  Trias  above  described ;  and  the  fact,  as  I  have  already  re- 
marked (p.  389),  is  highly  important,  as  proving  that  a  certain  low 
grade  of  marsupials  had  not  only  a  wide  range  in  time  from  the  Trias 
to  the  Purbeck  or  uppermost  oolitic  strata  of  Europe,  but  had  also  a 
wide  range  in  space,  namely,  from  Europe  to  North  America,  in  an 
east  and  west  direction,  and,  in  regard  to  latitude,  from  Stonesfield, 
in  52°  N.,  to  that  of  North  Carolina,  35°  N. 


458  DIVISION  OF  THE  PERMIAN  GROUP.  On.  XXIH.] 


CHAPTER  XXIIL 

PERMIAN    OR   MAGNESIAN   LIMESTONE    GROUP. 

Fossils  of  Magnesian  Limestone  and  Lower  New  Red  distinct  from  the  Triassic — 
Term  "  Permian " — English  and  German  equivalents — Marine  shells  and  corals 
of  English  Magnesian  Limestone — Palseoniscus  and  other  fish  of  the  marl-slate — 
Zechstein  and  Rothliegendes  of  Thuringia — Permian  Flora — Its  generic  affinity 
to  the  Carboniferous — Psaronites  or  tree-ferns. 

WHEN  the  use  of  the  term  "  Poikilitic  "  was  explained  in  the  last 
chapter,  I  stated,  that  in  some  parts  of  England  it  is  scarcely  possible 
to  separate  the  red  marls  and  sandstones  so  called  (originally  named 
"  the  New  Red  ")  into  two  distinct  geological  systems.  Nevertheless, 
the  progress  of  investigation,  and  a  careful  comparison  of  English 
rocks  between  the  lias  and  the  coal  with  those  occupying  a  similar 
geological  position  in  Germany  and  Russia,  have  enabled  geologists 
to  divide  the  Poikilitic  formation;  and  have  even  shown  that  the 
lowermost  of  the  two  divisions  is  more  closely  connected,  by  its  fossil 
remains,  with  the  carboniferous  group  than  with  the  trias.  If,  there- 
fore, we  are  to  draw  a  line  between  the  secondary  and  primary  fossilif- 
erous  strata,  as  between  the  tertiary  and  secondary,  it  must  run  through 
the  middle  of  what  was  once  called  the  "  New  Red,"  or  Poikilitic  group. 
The  inferior  half  of  this  group  will  rank  as  Primary  or  Palaeozoic,  while 
its  upper  member  will  form  the  base  .of  the  Secondary  or  Mesozoic 
series.  For  the  lower,  or  Magnesian  Limestone  division  of  English 
geologists,  Sir  R.  Murchison  proposed,  in  1841,  the  name  of  Permian, 
from  Perm,  a  Russian  government  where  these  strata  are  more  exten- 
sively developed  than  elsewhere,  occupying  an  area  twice  the  size  of 
France,  and  containing  an  abundant  and  varied  suite  of  fossils. 

Professor  King,  in  his  valuable  monograph  *  of  the  Permian  fossils 
of  England,  has  given  a  table  of  the  following  six  members  of  the 
Permian  system  of  the  north  of  England,  with  what  he  conceives  to 
be  the  corresponding  formations  in  Thuringia : 

North  of  England.  Thuringia. 

1.  Crystalline  or  concretionary,  and          1.  Stinkstein. 

non-crystalline  limestone. 

2.  Brecciated  and  pseudo-brecciated          2.  Rauchwacke. 

limestone.  .    j 

3.  Fossiliferous  limestone.  3.  Dolomite,  or  Upper  Zechstein. 

4.  Compact  limestone.  4.  Zechstein,  or  Lower  Zechstein. 

6.  Marl-slate.  5.  Mergel-schiefer,  or  Kupferschiefer. 

6.  Inferior    sandstones    of    various          6.  Rothliegendes. 
colors. 

*  PalaBontographical  Society,  1850,  London. 


CH.  XXIH.]  PERMIAN  LIMESTONES.  459 

I  shall  proceed,  therefore,  to  treat  briefly  of  these  subdivisions,  be- 
ginning with  the  highest,  and  referring  the  reader,  for  a  fuller  descrip- 
tion of  the  lithological  character  of  the  whole  group,  as  it  occurs  in 
the  north  of  England,  to  a  valuable  memoir  by  Professor  Sedgwick, 
published  in  1835.* 

Crystalline  or  Concretionary  Limestone  (No.  1). — This  formation  is 
seen  upon  the  coast  of  Durham  and  Yorkshire,  between  the  Wear 
and  the  Tees.  Among  its  characteristic  fossils  are  Schizodus  Schlo- 
theimi  (fig.  492)  and  Mytilus  septifer  (fig.  494). 


Fig.  492.  Fig.  493.  Fig.  494. 


ScMzodua  ScJilofheimi,  Geinitz.  The  hinge  of  Schizodus         Mytilus  septifer,  King. 

Crystalline  Limestone,  Permian.  truncatus,  King.  Syn.  Modiola  acuminata. 

Permian.  James  Sow. 

Permian  crystalline  lime- 
stone. 

These  shells  occur  at  Hartlepool  and  Sunderland,  where  the  rock 
assumes  an  oolitic  and  botryoidal  character.  Some  of  the  beds  in  this 
division  are  ripple-marked ;  and  Mr.  l£ing  imagines  that  the  absence 
of  corals  and  the  character  of  the  shells  indicate  shallow  water.  In 
some  parts  of  the  coast  of  Durham,  where  the  rock  is  not  crystalline, 
it  contains  as  much  as  44  per  cent,  of  carbonate  of  magnesia,  mixed 
with  carbonate  of  lime.  In  other  places — for  it  is  extremely  variable 
in  structure — it  consists  chiefly  of  carbonate  of  lime,  and  has  con- 
creted into  globular  and  hemispherical  masses,  varying  from  the  size 
of  a  marble  to  that  of  a  cannon-ball,  and  radiating  from  the  centre. 
Occasionally  earthy  and  pulverulent  beds  pass  into  compact  limestone 
or  hard  granular  dolomite.  The  stratification  is  very  irregular,  in 
some  places  well  defined,  in  others  obliterated  by  the  concretionary 
action  which  has  rearranged  the  materials  of  the  rocks  subsequently 
to  their  original  deposition.  Examples  of  this  are  seen  at  Pontefract 
and  Bipon  in  Yorkshire. 

The  brecciated  limestone  (No.  2)  contains  no  fragments  of  foreign 
rocks,  but  seems  composed  of  the  breaking-up  of  the  Permian  lime- 
stone itself,  about  the  time  of  its  consolidation.  Some  of  the  angu- 
lar masses  in  Tynemouth  Cliff  are  2  feet  in  diameter.  This  breccia 
is  considered  by  Professor  Sedgwick  as  one  of  the  forms  of  the  pre- 
ceding limestone,  No.  1,  rather  than  as  regularly  underlying  it.  The 
fragments  are  angular  and  never  water-worn,  and  appear  to  have  been 
recemented  on  the  spot  where  they  were  formed.  It  is,  therefore, 
suggested  that  they  may  have  been  due  to  those  internal  movements 
of  the  mass  which  produced  the  concretionary  structure ;  but  the 

*  Trans.  Geol.  Soc.  Lond.,  Second  Series,  vol.  iii.  p.  37. 


460 


PERMIAN   COMPACT  LIMESTONES. 


[CH.  xxm. 


subject  is  very  obscure,  and  after  studying  the  phenomenon  in  the 
Marston  Rocks,  on  the  coast  of  Durham,  I  found  it  impossible  to 
form  any  positive  opinion  on  the  subject.  The  well-known  brecciated 
limestones  of  the  Pyrenees  appeared  to  me  to  present  the  nearest 
analogy,  but  on  a  much  smaller  scale. 

The  fossiliferous  limestone  (No.  3)  is  regarded  by  Mr.  King  as  a 
deep-water  formation,  from  the  numerous  delicate  bryozoa  which  it 
includes.  One  of  these,  Fenestella  retiformis  (fig.  495),  is  a  very 


a.  Fenestella  retiformis,  Schlot.  sp. 
8yn.  GorgoniainfundibuUformi8,GfO\dS.\  Retepora  flustracea,  Phillips. 

6.  Part  of  the  same  highly  magnified. 
Magnesian  Limestone,  Hnmbleton  Hill,  near  Sunderland.* 

variable  species,  and  has  received  many  different  names.  It  some- 
times attains  a  large  size,  measuring  8  inches  in  width.  The  same 
zoophyte,  or  rather  mollusk,  with  several  other  British  species,  is  also 
found  abundantly  in  the  Permian  of  Germany. 

Shells  of  the  genera  Productus  (fig.  496)  and  Strophalosia  (the 
latter  of  allied  form  with  teeth  in  the  hinge),  which  do  not  occur  in 


Fig.  496. 


Kg.  497. 


Fig.  498. 


Productw  horridus,  Sowerby 

(including  P.  calmw,  Sow.) 
Sunderland  and  Durham,  in  Mag- 
nesian Limestone ;   Zechstein 
and  Kupferschiefer,  Germany. 


lAngula  Crednerii. 

(Geinitz.) 

Magnesian. 

Limestone ; 

Marl-slate  Durham ; 

Zechstein,  Thuringia. 


Spirifer  undulatus, 

Sow.  Min.  Con. 
Syn.  Triog&notreta  undulata, 

King's  Monogr. 
Magnesian  Limestone. 


strata  newer  than  the  Permian,  are  abundant  in  this  division  of  the 
series  in  the  ordinary  yellow  magnesian  limestone.  They  are  accom- 
panied by  certain  species  of  Spirifer  (fig.  498),  Lingula  Crednerii 
(fig.  497),  and  other  brachiopoda  of  the  true  primary  or  palaeozoic 


King's  Monograph,  pi.  2. 


CH.  XXIIL]          FOSSIL  FISH  OF  PERMIAN  MARL-SLATE. 


461 


type.  Some  of  this  same  tribe  of  shells,  such  as  Athyris  Roissyt, 
allied  to  Terebratula,  are  specifically  the  same  as  fossils  of  the  car- 
boniferous rocks.  Avicula,  Area,  and  Schizodus  (see  above,  fig.  492), 
and  other  lamellibranchiate  bibalves,  are  abundant,  but  spiral  uni- 
valves are  very  rare. 

The  compact  limestone  (No.  4)  also  contains  organic  remains,  espe- 
cially bryozoa,  and  is  intimately  connected  with  the  preceding.  Be- 
neath it  lies  the  marl-slate  (No.  5),  which  consists  of  hard,  calcareous 
shales,  marl-slate,  and  thin-bedded  limestones.  At  East  ThicMey,  in 
Durham,  where  it  is  thirty  feet  thick,  this  slate  has  yielded  many  fine 
specimens  of  fossil  fish  of  the  genera  Palceoniscus,  Pygopterus,  Ccela- 
canthus,  and  Platysomus,  genera  which  are  all  found  in  the  coal- 
measures  of  the  Carboniferous  epoch,  and  which  therefore,  says  Mr. 
King,  probably  lived  at  no  great  distance  from  the  shore.  But  the 
Permian  species  are  peculiar,  and,  for  the  most  part,  identical  with 
those  found  in  the  marl-slate  or  copper-slate  of  Thuringia. 

Fig.  499. 


Ecstored  outline  of  a  fish  of  the  genus  Palceoniscus,  Agass. 
Palceothrissum,  Blainville. 

The  Palceoniscus  above  mentioned  belongs  to  that  division  of  fishes 
which  M.  Agassiz  has  called  "  Heterocercal,"  which  have  their  tails 
unequally  bilobate,  like  the  recent  shark  and  sturgeon,  and  the  verte- 
bral column  running  along  the  upper  caudal  lobe.  (See  fig.  500.) 


Fig.  500. 


Fig.  501. 


Shad.    (Clupea.    Herring  tribe.) 
Homoc&rcal. 


The  "  Homocercal "  fish,  which  comprise  almost  all  the  9000  species 
at  present  known  in  the  living  creation,  have  the  tail-fin  either  single 
or  equally  divided ;  and  the  vertebral  column  stops  short,  and  is  not 
prolonged  into  either  lobe.  (See  fig.  501.) 

Now  it  is  a  singular  fact,  first  pointed  out  by  Agassiz,  that  the 
heterocercal  form,  which  is  confined  to  a  small  number  of  genera  in 
the  existing  creation,  is  universal  in  the  magnesian  limestone,  and 


462 


MAGNESIAN  LIMESTONE. 


[On.  XXIII. 


all  the  more  ancient  formations.  It  characterizes  the  earlier  periods 
of  the  earth's  history,  whereas  in  the  secondary  strata,  or  those  newer 
than  the  Permian,  the  homocercal  tail  predominates. 

A  full  description  has  been  given  by  Sir  Philip  Egerton  of  the 
species  of  fish  characteristic  of  the  marl-slate,  in  Prof.  King's  mono- 
graph before  referred  to,  where  figures  of  the  ichthyo'lites,  which  are 
very  entire  and  well  preserved,  will  be  found.  Even  a  single  scale  is 
usually  so  characteristically  marked  as  to  indicate  the  genus,  and 
sometimes  even  the  particular  species.  They  are  often  scattered 
through  the  beds  singly,  and  may  be  useful  to  a  geologist  in  deter- 
mining the  age  of  the  rock. 


Fig.  502. 


Scales  of  fish.    Magnesian  Limestone. 
Fig.  503.  Fig.  504. 


Fig.  505. 


Fig.  502.  Palceoniscua  comptus,  Agassiz.    Scale,  magnified.    Marl-slate. 

Fig.  50a  PaloBoniscus  elegans,  Sedg.    Under  surface  of  scale,  magnified.    Marl-slate. 

Fig.  504.  Palceoniscus  glaphyrus,  Ag.    Under  surface  of  scale,  magnified.    Marl-elate. 

Fig.  505.  Ccelacanihus  granulatus,  Ag.    Granulated  surface  of  scale,  magnified.   Marl-slate. 


Fig.  506. 


Fig.  507. 


Pygopterm  mandibularis,  Ag.    Marl-slate. 
a.  Outside  of  scale,  magnified. 
&.  Under  surface  of  same. 


Acrolepis  Sedgwickii,  Ag. 

Outside  of  scale,  magnified. 

Marl-slate. 


The  inferior  sandstones  (No.  6,  Tab.,  p.  458),  which  lie  beneath  the 
marl-slate,  consist  of  sandstone  and  sand,  separating  the  magnesian 
limestone  from  the  coal,  in  Yorkshire  and  Durham.  In  some  in- 
stances, red  marl  and  gypsum  have  been  found  associated  with  these 
beds.  They  have  been  classed  with  the  magnesian  limestone  by  Pro- 
fessor Sedgwick,  as  being  nearly  coextensive  with  it  in  geographical 
range,  though  their  relations  are  very  obscure.  In  some  regions  we 
find  it  stated  that  the  imbedded  plants  are  all  specifically  identical 
with  those  of  the  carboniferous  series ;  and,  if  so,  they  probably  be- 
long to  that  epoch;  for  the  true  Permian  flora  appears,  from  the 
researches  of  MM.  Murchison  and  de  Verneuil  in  Russia,  and  of  MM. 
Geinitz  and  Von  Gutbier  in  Saxony,  to  be,  with  few  exceptions,  dis- 
tinct from  that  of  the  coal  (see  p.  463). 


CH.  XXIIL]  PERMIAN  FLORA.  4.33 

According  to  Sir  R.  Murchison,*  the  Permian  rocks  are  composed, 
in  Russia,  of  white  limestone,  with  gypsum  and  white  salt :  and  of 
red  and  green  grits,  occasionally  with  copper-ore ;  also  magnesian 
limestones,  marlstones,  and  conglomerates. 

The  country  of  Mansfield,  in  Thuringia,  may  be  called  the  classic 
ground  of  the  Lower  New  Red,  or  Magnesian  Limestone,  or  Permian 
formation,  on  the  Continent.  It  consists  there  principally  of,  first, 
the  Zechstein,  corresponding  to  the  upper  portion  of  our  English 
series ;  and,  secondly,  the  marl-slate,  with  fish  of  species  identical 
with  thjose  of  the  bed  so  called  in  Durham.  This  slaty  marlstone  is 
richly  impregnated  with  copper-pyrites,  for  which  it  is  extensively 
worked.  Magnesian  limestone,  gypsum,  and  rock-salt  occur  among 
the  superior  strata  of  this  group.  At  its  base  lies  the  Rothliegendes, 
supposed  to  correspond  with  the  Inferior  or  Lower  New  Red  Sand- 
stone, which  occupies  a  similar  place  in  England  between  the  marl- 
slate  and  coal.  Its  local  name  of  "  Rothliegendes,"  red-Iyer,  or 
"  Roth-todt-liegendes,"  red-dead-Iyer,  was  given  by  the  workmen  in 
the  German  mines  from  its  red  color,  and  because  the  copper  has 
died  out  when  they  reach  this  rock,  which  is  not  metalliferous.  It  is, 
in  fact,  a  great  deposit  of  red  sandstone  and  conglomerate,  with 
associated  porphyry,  basaltic  trap,  and  amygdaloid. 

In  the  "  Kupferschiefer,"  or  marl-slate,  a  highly  organized  reptile 
allied  to  the  living  monitor,  was  found  in  1709,  which  has  been 
named  Protorosaurus,  and  it  remained  for  a  century  and  a  quarter 
the  oldest  known  fossil  reptile,  when,  at  length,  in  1844,  the  Arche- 
gosaurus  was  discovered  in  the  coal  of  Saarbruch,  near  Treves. 

Permian  Flora. — We  learn  from  the  investigations  of  Colonel  Yon 
Gutbier,  that  in  the  Permian  rocks  of  Saxony  no  less  than  60  species 
of  fossil  plants  have  been  met  with,  40  of  which  have  not  yet  been 
found  elsewhere.  Two  or  three  of  these,  as  Calamites  gigas,  Sphe- 

Fig.  508. 


Walchia  piniformis,  Sternb.    Permian,  Saxony.    (Gutbier,  Die  Versteinenmgen  des 

permiachen  Systemes  in  Sachsen,  vol.  ii.  pi.  x.) 
a.  Branch.  &.  Twig  of  the  same.  c.  Leaf,  magnified. 

*  Russia  and  the  Ural  Mountains,  1845  ;  and  Siluria,  chap.  xii.  1854. 


464 


PERMIAN  FLORA. 


[On.  XXIII. 


Fig.  510. 


nopteris  erosa,  and  S.  lobata,  are  also  met  with  in  the  government  of 
Perm  in  Russia.     Seven  others,  and  among  them  Neuropteris  Loshii, 
Pecopteris  arborescens,  and  P.  similis,  with  several  species  of  Walchia 
(see    fig.    508),  a   genus    of    Conifers,    called    Lyco- 
Fig.  509.        podites  by  some  authors,  are  common   to   the   coal- 
measures. 

Among  the   genera   also    enumerated    by   Colonel 
Gutbier   are  the   fruit  called    Cardiocarpon   (see  fig. 
509),  Asterophyllites,  and  Annularia,  so  characteristic 
of   the    Carboniferous   period  ;    also    Lepidodendron, 
. '  which  is  common  to  the  Permian  of  Saxony,  Thurin- 
Saxony.  gia>  an(j  Russia,  although  not  abundant.     Noeggera- 
thia  (see  fig.  510),  supposed  by  A.  Brongniart  to  be 
allied  to  Cycas,  is  another  link  between  the  Permian  and  Carbonif- 
erous vegetation.     Coniferse,  of  the  Araucarian  division,  also  occur ; 
but  these  are  likewise  met  with  both  in  older 
and  newer  rocks.     The  plants  called  Sigillaria 
and  Stigmaria,  so  marked  a  feature  in  the  Car- 
boniferous period,  are  as  yet  wanting. 

-  Among  the  remarkable  fossils  of  the  roth- 
liegendes,  or  lowest  part  of  the  Permian  in 
Saxony  and  Bohemia,  are  the  silicified  trunks 
of  tree-ferns  called  generically  Psaronius. 
Their  bark  was  surrounded  by  a  dense  mass 
of  air-roots,  which  often  constituted  a  great 
addition  to  the  original  stem,  so  as  to  double 
or  quadruple  its  diameter.  The  same  remark 
holds  good  in  regard  to  certain  living  extra- 
tropical  arborescent  ferns,  particularly  those  of 
New  Zealand. 

Psaronites  are  also  found  in  the  uppermost 
coal  of  Autun  in  France,  and  in  the  upper  coal- 
measures  of  the  State  of  Ohio  in  the  United 
States,  but  specifically  different  from  those  of 
the  rothliegendes.  They  serve  to  connect  the 

Foeggerathia  cuneifolia.  .         jf  J 

A<L  Brongniart.*        Permian  flora  with  the  more  modern  portion 

of  the  preceding  or  carboniferous  group.    Upon 

the  whole,  it  is  evident  that  the  Permian  plants  approach  much  nearer 

to  the  carboniferous  flora  than  to  the  triassic  ;  and  the  same  may  be 

said  of  the  Permian  fauna. 


*  Murchison's  Russia,  vol.  ii.  pi.  A,  fig.  8. 


Oa.  XXIV.]  THE  CARBONIFEROUS  GROUP. 


CHAPTER  XXIV. 

THE  COAL,  OR  CARBONIFEROUS  GROUP. 

Carboniferous  strata  in  the  southwest  of  England — Superposition  of  Coal-measures 
to  Mountain  Limestone — Departure  from  this  type  in  North  of  England  and 
Scotland — Carboniferous  series  in  Ireland — Section  in  South  Wales — Under-clays 
with  Stigmaria — Carboniferous  Flora — Ferns,  Lepidodendra,  Equisetacese,  Cala- 
mites,  Asterophyllites,  Sigillariae,  Stigmarise — Coniferae — Sternbergia — Trigono- 
carpon — Grade  of  Coniferse  in  the  Vegetable  Kingdom — Absence  of  Angiosperms 
— Coal,  how  formed — Erect  fossil  trees — Parkfield  Colliery — St.  Etienne  Coal- 
field— Oblique  trees  or  snags — Fossil  forests  in  Nova  Scotia — Rain-prints — Purity 
of  the  Coal  explained — Tune  required  for  the  accumulation  of  the  Coal-measures 
— Brackish-water  and  marine  strata — Crustaceans  of  the  Coal — Origin  of  Clay- 
iron-stone. 

THE  next  group  which  we  meet  with  in  the  descending  order  is  the 
Carboniferous,  commonly  called  "  The  Coal ; "  because  it  contains 
many  beds  of  that  mineral,  in  a  more  or  less  pure  state,  interstratified 
with  sandstones,  shales,  and  limestones.  The  coal  itself,  even  in  Great 
Britain  and  Belgium,  where  it  is  most  abundant,  constitutes  but  an 
insignificant  portion  of  the  whole  mass.  In  the  north  of  England, 
for  example,  the  thickness  of  the  coal-bearing  strata  has  been  esti- 
mated by  Professor  Phillips  at  3000  feet,  while  the  various  coal-seams, 
20  or  30  in  number,  do  not  in  the  aggregate  exceed  60  feet. 

The  carboniferous  formation  assumes  various  characters  in  different 
parts  even  of  the  British  Islands.  It  usually  comprises  two  very  dis- 
tinct members :  1st,  that  usually  called  the  Coal-measures,  of  mixed 
freshwater,  terrestrial,  and  marine  origin,  often  including  seams  of 
coal ;  2dly,  that  named  in  England  the  Mountain  or  Carboniferous 
Limestone,  of  purely  marine  origin,  and  containing  corals,  shells,  and 
encrinites. 

In  the  southwestern  part  of  our  island,  in  Somersetshire  and  South 
Wales,  the  three  divisions  usually  spoken  of  by  English  geologists 
are: 


1.  Coal-measures. 


2.  Millstone-grit. 

3.  Mountain  or 

Carboniferous 
Limestone. 
30 


Strata  of  shale,  sandstone,  and  grit,  with  occasional  seams 

of  coal  from  600  to  12,000  feet  thick. 
A  coarse  quartzose  sandstone  passing  into  a  conglomerate, 

sometimes  used  for  millstones,  with  beds  of  shale ;  usually 

devoid  of  coal ;  occasionally  above  600  feet  thick. 
A  calcareous  rock   containing    marine  shells   and   corals  ; 

devoid    of   coal ;    thickness    variable,   sometimes    1500 

feet. 


466  COAL-MEASUKES.  [Cn.  XXTV. 

The  millstone-grit  may  be  considered  as  one  of  the  coal-sandstones 
of  coarser  texture  than  usual,  with  some  accompanying  shales,  in 
which  coal-plants  are  occasionally  found.  In  the  north  of  England 
some  bands  of  limestone,  with  pectens,  oysters,  and  other  marine 
shells,  occur  in  this  grit,  just  as  in  the  regular  coal-measures,  and  even 
a  few  seams  of  coal.  I  shall  treat,  therefore,  of  the  whole  group  as 
consisting  of  two  divisions  only,  the  Coal-measures  and  the  Mountain 
Limestone.  The  latter  is  found  in  the  southern  British  coal-fields,  at 
the  base  of  the  system,  or  immediately  in  contact  with  the  subjacent 
Old  Red  Sandstone  ;  but  as  we  proceed  northwards  to  Yorkshire  and 
Northumberland  it  begins  to  alternate  with  true  coal-measures,  the 
two  deposits  forming  together  a  series  of  strata  about  1000  feet  in 
thickness.  To  this  mixed  formation  succeeds  the  great  mass  of 
genuine  mountain  limestone.*  Farther  north,  in  the  Fifeshire  coal- 
field in  Scotland,  we  observe  a  still  wider  departure  from  the  type  of 
the  south  of  England,  or  a  more  complete  intercalation  of  dense 
masses  of  marine  limestones  with  sandstones  and  shales  containing 
coal. 

In  Ireland  a  series  of  shales  and  slates,  constituting  the  base  of  the 
Mountain  Limestone,  attain  so  great  a  thickness,  often  upwards  of 
1000  feet,  as  to  be  classed  as  a  separate  division.  Under  these  slates 
is  a  Yellow  Sandstone,  also  considered  as  carboniferous  from  its  ma- 
rine fossils,  although  passing  into  the  underlying  Devonian.  A  simi- 
lar sandstone  of  much  less  thickness  occurs  in  the  same  position  in 
Gloucestershire  and  South  Wales. 

The  following  are  the  subdivisions  adopted  in  the  geological  map 
of  Ireland,  constructed  by  Sir  Richard  Griffiths  : 

Thickness  in  Feet. 

1.  Coal-measures,  Upper  and  Lower,        -  •„      1000  to  2200 

2.  Millstone-grit,  -  -         350  to  1800 

3.  Mountain  limestone,   Upper,   Middle  (or  Calp),  and 

Lower,         -  -      1200  to  6400 

4.  Carboniferous  slate,      -  '-        700  to  1200 

5.  Yellow  sandstone  (of  Mayo,  &c.)  with  shales  and  lime- 

stone,         -  -  -  ...        400  to  2000 


COAL-MEASURES. 

In  South  Wales  the  coal-measures  have  been  ascertained  by  actual 
measurement  to  attain  the  extraordinary  thickness  of  12,000  feet; 
the  beds  throughout,  with  the  exception  of  the  coal  itself,  appearing 
to  have  been  formed  in  water  of  moderate  depth,  during  a  slow,  but 
perhaps  intermittent,  depression  of  the  ground,  in  a  region  to  which 
rivers  were  bringing  a  never-failing  supply  of  muddy  sediment  and 
sand.  The  same  area  was  sometimes  covered  with  vast  forests,  such 

*  Sedgwick,  Geol.  Trans.,  Second  Series,  vol.  iv. ;  and  Phillips,  Geol.  of  York- 
shire, Part  2. 


CH.  XXIV.]  COAL-MEASURES. 

as  we  see  in  the  deltas  of  great  rivers  in  warm  climates,  which  are 
liable  to  be  submerged  beneath  fresh  or  salt  water  should  the  ground 
sink  vertically  a  few  feet. 

In  one  section  near  Swansea,  in  South  Wales,  where  the  total 
thickness  of  strata  is  3246  feet,  we  learn  from  Sir  H.  De  la  Beche 
that  there  are  ten  principal  masses  of  sandstone.  One  of  these  is 
500  feet  thick,  and  the  whole  of  them  make  together  a  thickness  of 
2125  feet.  They  are  separated  by  masses  of  shale,  varying  in  thick- 
ness from  10  to  50  feet.  The  intercalated  coal-beds,  sixteen  in  num- 
ber, are  generally  from  1  to  5  feet  thick,  one  of  them,  which  has  two 
or  three  layers  of  clay  interposed,  attaining  9  feet.*  At  other  points 
in  the  same  coal-field  the  shales  predominate  over  the  sandstones. 
The  horizontal  extent  of  some  seams  of  coal  is  much  greater  than 
that  of  others,  but  they  all  present  one  characteristic  feature,  in  hav- 
ing, each  of  them,  what  is  called  its  underclay.  These  underclays, 
coextensive  with  every  layer  of  coal,  consist  of  arenaceous  shale, 
sometimes  called  fire-stone,  because  it  can  be  made  into  bricks  which 
stand  the  fire  of  a  furnace.  They  vary  in  thickness  from  6  inches  to 
more  than  10  feet ;  and  Sir  William  Logan  first  announced  to  the 
scientific  world  in  1841  that  they  were  regarded  by  the  colliers  in 
South  Wales  as  an  essential  accompaniment  of  each  of  the  one  hun- 
dred seams  of  coal  met  with  in  their  coal-field.  They  are  said  to 
form  the  floor  on  which  the  coal  rests ;  and  some  of  them  have  a 
slight  admixture  of  carbonaceous  matter,  while  others  are  quite  black- 
ened by  it. 

All  of  them,  as  Sir  William  Logan  pointed  out,  are  characterized 
by  enclosing  a  peculiar  species  of  fossil  vegetable  called  Stigmaria,  to 
the  exclusion  of  other  plants.  It  was  also  observed  that,  while  in  the 
overlying  shales  or  "roof"  of  the  coal,  ferns  and  trunks  of  trees 
abound  without  any  Stigmarice,  and  are  flattened  and  compressed, 
those  singular  plants  of  the  underclay  very  often  retain  their  natural 
forms,  branching  freely,  and  sending  out  their  slender  leaf-like  root- 
lets, formerly  thought  to  be  leaves,  through  the  mud  in  all  directions. 
Several  species  of  Stigmaria  had  long  been  known  to  botanists,  and 
described  by  them,  before  their  position  under  each  seam  of  coal  was 
pointed  out,  and  before  their  true  nature  as  the  roots  of  trees  was 
recognizecl.  It  was  conjectured  that  they  might  be  aquatic,  perhaps 
floating  plants,  which  sometimes  extended  their  branches  and  leaves 
freely  in  fluid  mud,  and  which  were  finally  enveloped  in  the  same 
mud. 

CARBONIFEROUS    FLORA. 

These  statements  will  suffice  to  convince  the  reader  that  we  cannot 
arrive  at  a  satisfactory  theory  of  the  origin  of  coal  until  we  under- 

*  Memoirs  of  Geol.  Survey,  vol.  i.  p.  195. 


468 


CARBONIFEROUS  FLORA. 


[On.  XXIV 


stand  the  true  nature  of  Stigmaria  ;  and  in  order  to  explain  what  is 
now  known  of  this  plant,  and  of  others  which  have  contributed  by 
their  decay  to  produce  coal,  it  will  be  necessary  to  offer  a  brief  pre- 
liminary sketch  of  the  whole  carboniferous  flora — an  assemblage  of 
fossil  plants  with  which  we  are  better  acquainted  than  with  any  other 
which  flourished  antecedently  to  the  Tertiary  epoch.  It  should  also 
be  marked  that  Goppert  has  ascertained  that  the  remains  of  every 
family  of  plants  scattered  through  the  coal-measures  are  sometimes 
met  with  in  the  pure  coal  itself — a  fact  which  adds  greatly  to  the 
geological  interest  attached  to  this  flora. 

Ferns. — The  number  of  species  of  carboniferous  plants  hitherto 
described  amounts,  according  to  M.  Ad.  Brongniart,  to  about  500. 
These  may  perhaps  be  a  fragment  only  of  the  entire  flora,  but  they 
are  enough  to  show  that  the  state  of  the  vegetable  world  was  then 
extremely  different  from  that  now  prevailing.  We  are  struck  at  the 
first  glance  with  the  similarity  of  many  of  the  ferns  to  those  now 
living,  and  the  dissimilarity  of  almost  all  the  other  fossils  except  the 
Coniferae.  Among  the  ferns,  as  in  the  case  of  Pecopteris  for  example 
(fig.  511),  it  is  not  always  easy  to  decide  whether  they  should  be  re- 


Fig.  511. 


Fig.  512. 


Pecopt&ri*  loncUUca. 
(Foss.  Flo.,  153.) 


&.  Sphenopteris  crenata. 
5.  Part  of  the  same,  magnified. 
(Foss.  Flo.,  101.) 


ferred  to  different  genera  from  those  established  for  the  classification 
of  living  species ;  whereas,  in  regard  to  most  of  the  other  contempo- 
rary tribes,  with  the  exception  of  the  fir  tribe,  it  is  often  difficult  to 
guess  the  family,  or  even  the  class,  to  which  they  belong.  The  ferns 


CH.  XXIV.] 


FERNS  OF  CARBONIFEROUS  PERIOD. 


of  the  Carboniferous  period  are  generally 
without  organs  of  fructification,  but  in 
some  specimens  these  are  well  preserved. 
In  the  general  absence  of  such  characters, 
they  have  been  divided  into  genera  distin- 
guished chiefly  by  the  branching  of  the 
fronds,  and  the  way  in  which  the  veins  of 
the  leaves  are  disposed.  The  larger  por- 
tion are  supposed  to  have  been  of  the  size 
of  ordinary  European  ferns,  but  some  were 
decidedly  arborescent,  especially  the  group 
called  Caulopteris  by  Lindley,  and  the 
Psaronius  of  the  upper  or  newest  coal- 
measures,  before  alluded  to  (p.  464). 

All  the  recent  tree-ferns  belong  to  one 
tribe  (Polypodiaeece),  and  to  a  small  num- 
ber only  of  genera  in  that  tribe,  in  which  the  surface  of  the  trunk  is 
marked  with  scars,  or  cicatrices,  left  after  the  fall  of  the  fronds. 
These  scars  resemble  those  of  Caulopteris  (see  fig.  513).  No  less 
than  250  ferns  have  already  been  obtained  from  the  coal-strata ;  and 
even  if  we  make  some  reduction  on  the  ground  of  varieties  which 

Fig.  515. 


Living  tree-ferna  of  different  genera.    (Ad.  Brong.) 
Fig.  514.    Tree-fern  from  Isle  of  Bourbon. 
Fig.  515.    Cyathea  glauca,  Mauritius. 
Fig.  516.    Tree-fern  from  Brazil. 

have  been  mistaken,  in  the  absence  of  their  fructification,  for  species, 
still  the  result  is  singular,  because  the  whole  of  Europe  affords  at 
present  no  more  than  sixty  indigenous  species. 

Lepidodendron. — About  40  species  of  fossil  plants  of  the  Coal  have 


4:70 


FERNS— LEPIDODENDRON. 


[On.  XXIV 


been  referred  to  this  genus.  They  consist  of  cylindrical  stems  or 
trunks,  covered  with  leaf-scars.  In  their  mode  of  branching,  they 
are  always  dichotomous  (see  fig.  518).  They  are  considered  by 
Brongniart  and  Hooker  to  belong  to  the  Lycopodiacece,  plants  of  this 
family  bearing  cones,  with  similar  sporangia  and  spores  (fig.  521). 
Most  of  them  grew  to  the  size  of  large  trees.  The  figs.  517-519 


Fig.  51T. 


Fig.  518. 


Lepidodendron  Sterribergii.    Coal-measures,  near  Newcastle. 
Fig.  517.    Branching  trunk,  49  feet  long,  supposed  to  have  belonged  to  L.  Sterribergii. 

(Foss.  Flo.,  203.) 

Fig.  5ia    Branching  stem  with  bark  and  leaves  of  L.  Sterribergii.    (Foss.  Flo.,  4.) 
Fig.  519.    Portion  of  same  nearer  the  root ;  natural  size.    (Ibid.) 

represent  a  fossil  Lepidodendron,  49  feet  long,  found  in  Jarrow  Col- 
liery, near  Newcastle,  lying  in  shale  parallel  to  the  planes  of  stratifica- 
tion. Fragments  of  others,  found  in  the  same  shale,  indicate,  by  the 
size  of  the  rhomboidal  scars  which  cover  them,  a  still  greater  magni- 
tude. The  living  club-mosses,  of  which  there  are  about  200  species, 
are  most  abundant  in  tropical  climates.  They  usually  creep  on  the 
ground,  but  some  stand  erect,  as  the  Lycopodium  densum  from  New 
Zealand  (fig.  520),  which  attains  a  height  of  3  feet. 


Fig. 


a.  Lycopodiwn  densum  ;  banks  of  K.  Thames,  New  Zealand. 
&.  Branch,  natural  size.  c.  Part  of  same,  magnified. 


CH.  XXIV.] 


EQUISETACE.E— CALAMITES. 


471 


In  the  carboniferous  strata  of  Coalbrook  Dale,  and  in  many  other 
coal-fields,  elongated  cylindrical  bodies,  called  fossil  cones,  named 
Lepidostrobus  by  M.  Adolphe  Brongniart,  are  met  with.  (See  fig. 
521.)  They  often  form  the  nucleus  of  concretionary  balls  of  clay- 


Fig.  521. 


a.  Lepidostrobus  ornatus,  Brong.    Shropshire ;  half  natural  size. 

&.  Portion  of  a  section,  showing  the  large  sporangia  in  their  natural  position,  and  each 

supported  by  its  bract  or  scale. 
c.  Spores  in  these  sporangia,  highly  magnified.    (Hooker,  Mem.  Geol.  Survey,  vol.  ii. 

part  2,  p.  440.) 

ironstone,  and  are  well  preserved,  exhibiting  a  conical  axis,  around 
which  a  great  quantity  of  scales  were  compactly  imbricated.  The 
opinion  of  M.  Brongniart  is  now  generally  adopted,  that  the  Lepido- 
strobus is  the  fruit  of  Lepidodendr&n  ;  indeed,  it  is  not  uncommon  in 
Coalbrook  Dale  and  elsewhere  to  find  these  strobili  or  fruits  termi- 
nating the  tip  of  a  branch  of  a  well-characterized  Lepidodendron. 

Equisetacece. — To  this  family  belong  two  fossil  species  of  the  Coal, 
one  called  Equisetum  infundibuliforme  by  Brongniart,  and  found  also 
in  Nova  Scotia,  which  has  sheaths,  regularly  toothed,  ribbed,  and 
overlapping  like  those  on  the  young  fertile  stems  of  Equisetum  flu- 
viatile.  It  was  much  larger  than  any  living  "  Horsetail."  The  Equi- 
setum giganteum,  discovered  by  Humboldt  and  Bonpland  in  South 
America,  attained  a  height  of  about  5  feet,  the  stem  being  an  inch  in 
diameter ;  but  more  recently  Gardner  has  met  with  one  in  Brazil  15 
feet  high,  and  Meyen  gives  the  height  of  E.  Bogotense  in  Chili  as  15 
to  20  feet. 

Calamites. — The  fossil  plants  so  called  were  originally  classed  by 
most  botanists  as  cryptogamous,  being  regarded  as  gigantic  Equiseta  ; 


Fig.  522. 


Fig.  523. 


Calamites  cannceformis,  Schlot. 
(Foss.  Flo.,  79.)  Common  in 
English  coal. 


Fig.  524. 


Calamites  Sucowii,  Brong. ; 
natural  size.  Common  in 
coal  throughout  Europe. 


Radical  termination 
of  a  Calamite. 
Nova  Scotia. 


472 


CALAMITES. 


[Cn.  XXTV. 


for,  like  the  common  "horsetail,"  they  usually  exhibit  little  more 
than  hollow  jointed  stems,  furrowed  externally.  (See  figs.  522,  523, 
524.) 

Mr.  Salter  stated  to  me  many  years  ago  his  conviction  that  the 
calamite  as  frequently  represented  by  palaeontologists  was  in  an  in- 
verted position,  aod  that  the  conical  part  given  as  the  top  of  the  stem 
was  in  truth  the  root.  This  point  Dr.  Dawson  and  I  had  opportuni- 
ties of  testing  in  Nova  Scotia,  in  1853,  where  we  saw  many  erect 
calamites,  having  their  radical  termination  as  in  the  foregoing  figure 
(fig.  524).  The  scars,  from  which  whorls  of  vessels  have  proceeded, 
are  observed  at  the  upper,  not  the  lower,  end  of  each  joint  or  inter- 
node.*  The  specimen  (fig.  522),  therefore,  is  no  doubt  the  lower  end 
of  the  plant,  and  I  have  therefore  reversed  its  position  as  given  in  the 
work  of  Lindley  and  Hutton. 

M.  Adolphe  Brongniart,  following  up  the  discoveries  of  Germar 
and  Corda,  has  shown  in  his  "Genres  de  Vegetaux  Fossiles,"  1849, 
that  many  Calamites  cannot  belong  to  the  Equiseta,  nor  probably  to 
any  tribe  of  flowerless  plants.  JSe  conceives  that  they  are  more 
nearly  allied  to  the  Gymnospermous  Dicotyledons.  They  possessed 
a  central  pith,  surrounded  by  a  ligneous  cylinder,  which  was  divided 
by  regular  medullary  rays.  This  cylinder  was  surrounded  in  turn  by 
a  thick  bark.  Of  fossil  stems  having  this  structure  Brongniart 
formed  his  genus  Calamodendron,  which  includes  many  species  re- 

ferred by  Gotta,  Petzholdt,  and 
linger  to  the  genus  Calamitea. 
The  Calamodendron  is  described 
as  smooth  externally,  its  pith 
being  articulated  and  marked 
with  deep  external  vertical 
striae,  agreeing,  in  short,  with 
what  geologists  commonly  call 
a  Calamite.  Since  the  appear- 
ance of  Brongniart's  essay,  Mr. 
E.  W.  Binney  has  made  many 
important  discoveries  on  the 
same  subject;  and  Mr.  J.  S. 
Dawes  has  published  a  more 
complete  account  of  this  singu- 
lar fossilf  Their  views  have 
been  confirmed  by  Professor 
Williamson  of  Manchester,  who 

communicated     to     me     a 

specimen  figured  in  the  annexed 

Communicated  by  Profc  C.  Williamson.  cut   (fig.  525),  in   which  WC   866 


Fig.  525. 


Portion  of  a  Calamite,  near  the  base,  showing  the     has 


*  See  Dawson,  Geol.  Quart.  Journ.,  1854,  vol.  x.  p.  85. 
f  Quart  Journ.  Geol.  Soc.  Lond.,  1851,  voL  vii.  p.  196. 


OH.  XXIV.]  ASTEROPHYLLITES.  4.73 

an  internal  pith  answering  in  character  to  the  Calamodendron,  and 
yet  having  outside  of  it  another  jointed  cylinder  vertically  grooved 
on  its  outer  surface,  so  that  in  the  same  stem  we  have  one  calamite 
enveloping  another.  Yet  that  they  both  formed  part  of  the  same 
plant  is  proved  by  the  following  circumstances : — 1st.  Near  each 
articulation  of  the  pith  radiating  spokes  are  seen  to  proceed  and 
penetrate  the  ligneous  zone.  One  complete  whorl  or  circle  of  these 
radii  is  visible  in  the  foregoing  figure  near  the  bottom  of  the  hollow 
cavity,  whilst  another  and  superior  whorl  is  incomplete ;  several  radii, 
corresponding  to  the  first,  remaining,  while  the  rest  have  been  broken 
away,  their  place  being  shown  by  scars  which  they  have  left.  2dly. 
In  addition  to  these  whorls,  called  medullary  by  Professor  William- 
son, there  are  seen  in  other  specimens  a  set  of  true  or  ordinary  me- 
dullary rays.  3dly.  The  woody  zone,  penetrated  both  by  the  spoke- 
like  vessels  before  mentioned  and  by  the  medullary  rays,  is  usually 
reduced  to  brown  carbonaceous  matter,  preserving  merely  a  tendency 
to  break  in  longitudinal  slips,  but  in  some  specimens  its  fibrous  tissue 
is  retained,  and  resembles  that  of  Dadoxylon.  4thly.  Outside  of  this 
zone  again  is  another  cylinder,  supposed  to  have  been  originally  a 
thick  cellular  bark,  nearly  equal  to  one-third  of  the  whole  stem  in 
diameter,  grooved  and  jointed  externally  like  the  pith. 

In  conclusion,  I  may  remark  that  these  discoveries  make  it  more 
and  more  doubtful  to  what  family  the  greater  number  of  Calamites 
should  be  referred.  Their  internal  organization,  says  Professor 
Williamson,  was  very  peculiar ;  for  while  they  exhibit  remarkable 
affinities  with  gymnospermous  dicotyledons,  the  arrangement  of  their 
tissues  differs  widely  from  that  of  all  known  forms  of  gymnosperms. 

Asterophyllites. — The  graceful  plant  represented  in  the  annexed 
figure  is  supposed  by  M.  Brongniart  to  be  a  branch  of  the  Calamo- 
dendron, and  he  infers  from  its  pith  and  medullary  rays  that  it  was 

Fig.  526. 


Asterophyllites  foliosus.    (Foss.  Flo.,  25.)    Coal-measures,  Newcastle. 

dicotyledonous.     It  appears  to  have  been  allied,  by  the  nature  of  its 
tissue,  to  the  gymnogens,  and  to  Sigillaria.     But  under  the  head  of 


474: 


SIGILLARIA. 


[Cn.  XXIV. 


Asterophyllites  many  vegetable  fragments  have  been  grouped  which 
probably  belong  to  different  genera.  They  have,  in  short,  no  charac- 
ter in  common,  except  that  of  possessing  narrow,  verticillate,  one- 
ribbed  leaves.  Dr.  Dewberry,  of  Ohio,  has  discovered  in  the  coal  of 
that  country  fossil  stems  which  in  their  upper  part  bear  wedge-shaped 
leaves,  corresponding  to  Sphenophyllum,  while  below  the  leaves  are 
stalk-like  and  capillary,  and  would  have  been  called  Asterophyllites  if 
found  detached.  From  this  he  infers  that  Sphenophyllum  was  an 
aquatic  plant,  the  superior  and  floating  leaves  of  which  were  broad, 
and  possessed  a  compound  nervation,  while  the  inferior  or  submersed 
leaves  were  linear  and  one-ribbed.  "  This  supposition,"  he  adds,  "  is 
further  strengthened  by  the  extreme  length  and  tenuity  of  the  branches 
of  this  apparently  herbaceous  plant,  which  would  seem  to  have  re- 
quired the  support  of  a  denser  medium  than  air."  * 

Sigillaria. — A  large  portion  of  the  trees  of  the  Carboniferous  pe- 
riod belonged  to  this  genus,  of  which  about  thirty-five  species  are 
known.  The  structure,  both  internal  and  external,  was  very  pecu- 
liar, and,  with  reference  to  existing  types,  very  anomalous.  They 
were  formerly  referred,  by  M.  Ad.  Brongniart,  to  ferns,  which  they 
resemble  in  the  scalariform  texture  of  their  vessels,  and,  in  some  de- 
gree, in  the  form  of  the  cicatrices  left  by  the  base  of  the  leaf-stalks 
which  have  fallen  off  (see  fig.  527).  But 
with  these  points  of  analogy  to  cryptoga- 
mia,  they  combine  an  internal  organization 
much  resembling  that  of  cycads,  and  some 
of  them  are  ascertained  to  have  had  long 
linear  leaves,  quite  unlike  those  of  ferns. 
They  grew  to  a  great  height,  from  30  to 
60,  or  even  70  feet,  with  regular  cylindri- 
cal stems,  and  without  branches,  although 
some  species  were  dichotomous  towards 
the  top.  Their  fluted  trunks,  from  1  to  5 
feet  in  diameter,  appear  to  have  decayed 
more  rapidly  in  the  interior  than  exter- 
nally, so  that  they  became  hollow  when 
standing;  and  when  thrown  prostrate  on 
the  mud,  they  were  squeezed  down  and 
flattened.  Hence,  we  find  the  bark  of  the 
two  opposite  sides  (now  converted  into 

bright  shining  coal)  to  constitute  two  horizontal  layers,  one  upon  the 
other,  half  an  inch,  or  an  inch,  in  thickness.  These  same  trunks, 
when  they  are  placed  obliquely  or  vertically  to  the  planes  of  stratifi- 
cation, retain  their  original  rounded  form,  and  are  uncompressed,  the 
cylinder  of  bark  having  been  filled  with  sand,  which  now  affords  a 
cast  of  the  interior. 


Fig.  527. 


Sigillaria  Icevigata,  Brong. 


*  Annals  of  Science,  Cleveland,  Ohio,  1853,  p.  97. 


CH.  XXIV.] 


STIGMARIA. 


475 


Dr.  Hooker  still  inclines  to  the  belief  that  the  Sigillarice  may  have 
been  cryptogamous,  though  more  highly  developed  than  any  flowerless 
plants  now  living.  The  scalariform  structure  of  their  vessel  agrees  pre- 
cisely with  that  of  ferns. 

Stigmaria. — This  fossil,  the  importance  of  which  has  already  been 
pointed  out,  was  formerly  conjectured  to  be  an  aquatic  plant.  It  is 
now  ascertained  to  be  the  root  of  Sigillaria.  The  connection  of  the 
roots  with  the  stem,  previously  suspected,  on  botanical  grounds,  by 
Brongniart,  was  first  proved,  by  actual  contact,  in  the  Lancashire  coal- 
field, by  Mr.  Binney.  The  fact  has  lately  been  shown,  even  more  dis- 
tinctly, by  Mr.  Bichard  Brown,  in  his  description  of  the  Stigmarice 
occurring  in  the  underclays  of  the  coal-seams  of  the  Island  of  Cape 
Breton,  in  Nova  Scotia. 

In  a  specimen  of  one  of  these,  represented  in  the  annexed  figure 
(fig.  528),  the  spread  of  the  roots  was  sixteen  feet,  and  some  of  them 
sent  out  rootlets,  in  all  directions,  into  the  surrounding  clay. 

Fig.  528. 


Stigmaria  attached  to  a  trunk  of  Sigillaria.* 

In  the  sea-cliffs  of  the  South  Joggins  in  Nova  Scotia  I  examined 
several  erect  Sigillarice,  in  company  with  Dr.  Dawson,  and  we  found 
that  from  the  lower  extremities  of  the  trunk  they  sent  out  Stigmarice 
as  roots.  All  the  stools  of  the  fossil  trees  dug  out  by  us  divided  into 
four  parts,  and  these  again  bifurcated,  forming  eight  roots,  which  were 
also  dichotomous  when  traceable  far  enough. 

The  cylindrical  rootlets  formerly  regarded  as  leaves  are  now  shown 
by  more  perfect  specimens  to  have  been  originally  attached  to  the  root 
by  fitting  into  deep  cylindrical  pits.  In  the  fossil  there  is  rarely  any 
trace  of  the  form  of  these  cavities,  in  consequence  of  the  shrinkage  of 
the  surrounding  tissues.  Where  the  rootlets  are  removed  nothing 
remains  on  the  surface  of  the  Stigmaria  but  rows  of  rnammillated  tuber- 
cles (see  figs.  529,  530),  which  have  formed  the  base  of  each  rootlet. 
These  protuberances  may  possibly  indicate  the  place  of  a  joint  at  the 
lower  extremity  of  the  rootlet.  Rows  of  these  tubercles  are  arranged 
spirally  round  each  root,  which  have  always  a  medullary  axis  and 

*  The  trunk  in  this  case  is  referred  by  Mr.  Brown  to  Lepidodendron,  but  his 
illustrations  seem  to  show  the  usual  markings  assumed  by  Sigillaria  near  its  base. 


476 


CONLFERJE  OF  THE  COAL  PERIOD. 

Fig.  629. 


[On.  XXIV. 


Fig.  680. 


Surface  of  another  individual 
of  same  species,  showing  form 
of  tubercles.  (Foss.  Flo.,  34.) 


SUgmana  ficoides,  Brong.    }  nat.  size.    (Foss.  Flo.,  82). 


woody  system  much  resembling  that  of  Sigillaria,  the  structure  of  the 
vessels  being,  like  it,  scalarifonn. 

Conifers. — The  coniferous  trees  of  this  period  are  referred  to  five 
genera ;  the  woody  structure  of  some  of  them  showing  that  they  were 
allied  to  the  Araucarian  division  of  pines,  more  than  to  any  of  our 
common  European  firs.  Some  of  their  trunks  exceeded  44  feet  in 
height.  Many,  if  not  all  of  them,  seem  to  have  differed  from  living 
Coniferce  in  having  large  piths ;  for  Professor  Williamson  has  demon- 
strated the  fossil  of  the  coal-measures  called  Sterribergia  to  be  the  pith 
of  these  trees,  or  rather  the  cast  of  cavities  formed  by  the  shrinking 


Fig.  581.    Fragment  of  coniferous  wood,  Dadoxylon, 
Endlicher,  fractured  longitudinally ;  from  Coalbrook 
Dale.    W.C.Williamson.* 
a.  Bark, 
Z».  Woody  zone  or  fibre  (pleurenchyma). 

c.  Medulla  or  pith. 

d.  Cast  of  hollow  pith,  or  "  Sternbergia." 


Magnified  portion  of  fig.  531 ;  transverse  section. 
c.  Pith.  6,  &.  Woody  fibre.  e,  e.  Medullary  rays. 


*  Manchester  Philos.  Mem.,  vol.  ix.,  1851. 


CH.  XXIV.]  CONIFERS  OF  THE  COAL  PERIOD. 

or  partial  absorption  of  the  original  medullary  axis  (see  figs.  531  and 
532).  This  peculiar  type  of  pith  is  observed  in  living  plants  of  very 
different  families,  such  as  the  common  Walnut  and  the  White  Jas- 
mine, in  which  the  pith  becomes  so  reduced  as  simply  to  form  a  thin 
lining  of  the  medullary  cavity,  across  which  transverse  plates  of  pith 
extend  horizontally,  so  as  to  divide  the  cylindrical  hollow  into  discoid 
interspaces.  When  these  interspaces  have  been  filled  up  with  inorganic 
matter,  they  constitute  an  axis  to  which,  before  their  true  nature  was 
known,  the  provisional  name  of  Sterribergia  (c?,  d,  fig.  531)  was  given. 

In  the  above  specimen  the  structure  of  the  wood  (6,  figs.  531  and 
532)  is  coniferous,  and  the  fossil  is  referable  to  Endlicher's  fossil  genus 
Dadoxylon. 

The  fossil  named  Trigonocarpon  (figs.  553  and  554),  formerly  sup- 
posed to  be  the  fruit  of  a  palm,  may  now,  according  to  Dr.  Hooker,  be 
referred,  like  the  Sterribergia,  to  the  Coniferce.  Its  geological  im- 
portance is  great,  for  so  abundant  is  it  in  the  Coal-Measures,  that  in 
certain  localities  the  fruit  of  some  species  may  be  procured  by  the 
bushel ;  nor  is  there  any  part  of  the  formation  where  they  do  not 
occur,  except  the  underclays  and  limestone.  The  sandstone,  iron- 
stone, shales,  and  coal  itself,  all  contain  them.  Mr.  Binney  has  at 
length  found  in  the  clay-ironstone  at  Lancashire  several  specimens  dis- 
playing structure,  and  from  these,  says  Dr.  Hooker,  we  learn  that  the 
Trigonocarpon  belonged  to  that  large  section  of  existing  coniferous 
plants  which  bear  fleshy  solitary  fruits,  and  not  cones.  It  resembled 
very  closely  the  fruit  of  the  Chinese  genus  Salisburia,  one  of  the  Yew 
tribe,  or  Taxoid  conifers.  In  five  of  the  fossil  specimens  there  is  evi- 

Fig.  534. 
Fig.  538. 


Trigonocarpum  walwm,  Lindley  and  Hutton. 
Peel  Quarry,  Lancashire. 

Trigonocarpum  olivatform6>  Lindley, 
its  fleshy  envelope.  Felling  Col- 
liery, Newcastle. 

dence  of  four  distinct  integuments,  and  of  a  large  internal  cavity  filled 
with  carbonate  of  lime  and  magnesia,  and  probably  once  occupied  by 
the  albumen  and  embryo  of  the  seed.  The  general  form  of  the  fossil 
when  perfect  is  an  elongated  ovoid,  rather  larger  than  a  hazel-nut.  The 
exterior  integument  is  very  thick  and  cellular,  and  was  no  doubt  once 
fleshy  (see  fig.  534).  It  alone  is  produced  beyond  the  seed,  and  forms 
the  beak.  The  second  coat  was  thinner,  but  hard,  and  marked  by 


4:78  GRADE  OF  THE   CARBONIFEROUS  FLORA.        [On.  XXIV. 

three  ridges.  This  coat,  being  all  that  commonly  remains  in  a  fossil 
state,  has  suggested  the  name  of  Trigonocarpon.  Within  this  were 
the  third  and  fourth  coats,  both  of  which  are  very  delicate  mem- 
branes, and  may  possibly  have  been  two  plates  belonging  to  one  mem- 
brane. 

Grade  of  the  Carboniferous  Flora. — On  the  whole,  these  fruits,  says 
Dr.  Hooker,  are  referable  to  "  a  highly  developed  type,  exhibiting  ex- 
tensive modifications  of  elementary  organs  for  the  purpose  of  their 
adaptation  to  special  functions,  and  these  modifications  are  as  great, 
and  the  adaptations  as  special,  as  any  to  be  found  amongst  analogous 
fruits  in  the  existing  vegetable  world."  *  Professor  Williamson,  in 
his  paper  on  Sterribergia,  has  likewise  remarked  that  its  structure  was 
complex,  and  that  "  at  a  period  so  early  as  the  carboniferous  all  the 
now-existing  forms  of  vegetable  tissue  appear  to  have  been  created." 
These  observations  deserve  notice,  because  a  question  has  arisen, 
whether  the  Coniferce  hold  a  high  or  a  low  position  among  flowering 
plants — a  point  bearing  directly  on  the  theory  of  progressive  develop- 
ment. By  some  botanists  all  the  Gymnospermous  Dicotyledons  are 
regarded  as  inferior  in  grade  to  the  Angiosperms.  Others  hold,  with 
Dr.  Hooker,  that  the  Gymnosperms  are  not  inferior  in  rank,  having 
every  typical  character  of  the  dicotyledons  highly  developed.  Thus 
Coniferse  have  flowers,  and  are  propagated  by  seeds  which  are  developed 
through  the  mutual  action  of  the  stamens  and  ovules ;  they  have  dico- 
tyledonous and  polycotyledonous  embryos,  and  germinate  in  the  same 
manner  as  other  dicotyledons.  The  seed-vessel  (or  ovary)  is  not  closed, 
but  this  is  also  the  case  in  some  genera  of  angiosperms,  in  which 
the  ovary  is  open  before  or  after  impregnation,  so  that  this  character 
cannot  be  relied  on  as  constituting  a  fundamental  difference  in  struc- 
tural development.  The  Coniferse  are  exogenous,  and  have  the  same 
arrangement  of  pith,  wood,  bark,  and  medullary  rays  as  have  the  typical 
dicotyledonous  trees.  Whether  the  woody  fibre  with  discs  character- 
istic of  Coniferse  be  a  more  or  a  less  complex  tissue  than  the  spiral  ves- 
sels, is  a  controverted  point.  As  the  spiral  vessels  occur  in  the  young 
shoots,  and  are  lost  in  the  mature  growth  of  some  plants,  and  as  they 
appear  in  many  acrogens,  they  do  not  seem  to  mark  a  high  develop- 
ment. In  fine,  there  is  much  ambiguity  in  deciding  what  should  or 
should  not  be  called  high  or  low  in  vegetable  structure,  and  physi- 
ologists entertain  very  different  abstract  ideas  as  to  the  perfection  of 
certain  organs  and  their  relative  functional  importance,  even  where  the 
function  is  clearly  ascertained.  It  is  enough  for  the  geologist  to  know, 
that  fossil  Coniferse  abound  in  the  oldest  rocks,  yielding  a  considerable 
number  of  vegetable  remains,  and  that  plants  of  this  order  lay  claim, 
if  not  to  the  highest,  at  least  to  so  high  a  place  in  the  scale  of  vegeta- 
ble life,  as  to  preclude  us  from  characterizing  the  carboniferous  flora 
as  consisting  of  imperfectly  developed  plants. 

*  Proceedings  of  the  Royal  Society,  vol.  vii.,  March,  1854,  p.  28. 


CH.  XXIV.]  ANGIOSPERMS— COAL,  HOW  FORMED.  479 

Although  our  data  are  confessedly  too  defective  to  entitle  us  to 
generalize  respecting  the  entire  vegetable  creation  of  this  era,  yet  we 
may  affirm  that  so  far  as  it  is  known  it  differed  widely  from  any  flora 
now  existing.  The  comparative  rarity  of  Monocotyledons  and  of  Dico- 
tyledonous Angiosperms  seems  clear,  and  the  abundance  of  Ferns  and 
Lycopods  may  justify  Adolphe  Brongniart  in  calling  the  primary 
periods  the  age  of  Acrogens  *  ("  le  regne  des  Acrogens  ").  As  to  the 
SigillariaB  and  Calamites,  they  seem  to  have  been  distinct  from  all 
tribes  of  now-existing  plants.  That  the  abundance  of  ferns  implies  a 
moist  atmosphere,  is  admitted  by  all  botanists ;  but  no  safe  conclusion, 
says  Hooker,  can  be  drawn  from  the  Coniferae  alone,  as  they  are  found 
in  hot  and  dry  and  in  cold  and  dry  climates,  in  hot  and  moist  and  in 
cold  and  moist  regions.  In  New  Zealand  the  Coniferse  attain  their 
maximum  in  numbers,  constituting  -J^d  part  of  all  the  flowering  plants ; 
whereas  in  a  wide  district  around  the  Cape  of  Good  Hope  they  do  not 
form  1 6*0  Oth  of  the  phenogamic  flora.  Besides  the  conifers,  many 
species  of  ferns  flourish  in  New  Zealand,  some  of  them  arborescent, 
together  with  many  lycopodiums ;  so  that  a  forest  in  that  country  may 
make  a  nearer  approach  to  the  carboniferous  vegetation  than  any  other 
now  existing  on  the  globe. 

Angiosperms. — Some  of  the  grass-like  leaves  termed         Fig.  535. 
Poacites,  having  fine  longitudinal  striae,  are  conjec- 
tured to  belong  to  Monocotyledons ;   but  the  deter- 
mination is  doubtful,  as  some  of  them  may  be  the 
leaves  of  Lepidodendra,  others  the   stems  of  Ferns. 
The   curious    plants    called   Antholithes  by  Lindley 
have   usually  been    considered  to   be   flower-spikes, 
having  what   seems  a  calyx   and  linear  petals   (see 
fig.  535).      Dr.  Hooker   suggested  that  they  might 
be  tufts  of  young  leaves  like  those  of  the  larch,  but, 
after  seeing  the  most  perfect  specimens,  he  no  longer 
thought  them   oniferous,  but  resembling  rather  the 
spike  of  a  highly  organized  plant  in  full  flower,  such  Anthomhe&  Felling 
as  one  of  the  Bromeliaceae,  to  which  Professor  Lind-  Colliery,  Newcastle. 
ley  first  compared  them.     In  the  absence,  however,  of 
all  structure,  the  affinities  of  these  fossils  are  still  considered  very 
uncertain. 

Coal,  how  formed. — Erect  trees. — I  shall  now  consider  the  manner 
in  which  the  above-mentioned  plants  are  imbedded  in  the  strata,  and 
how  they  may  have  contributed  to  produce  coal.  Professor  Goppert, 
after  examining  the  fossil  vegetables  of  the  coal-fields  of  Germany, 
has  detected,  in  beds  of  pure  coal,  remains  of  plants  of  every  family 
hitherto  known  to  occur  fossil  in  the  carboniferous  rocks.  Many 
seams,  he  remarks,  are  rich  in  Sigillarice,  Lepidodendra,  and  Stig- 
marice,  the  latter  in  such  abundance  as  to  appear  to  form  the  bulk  of 

*  For  terminology  of  classification  of  plants,  see  above,  note,  p.  331 


480  FOSSIL  TREES  OF  COAL.  [On.  XXIY. 

the  coal.  In  some  places,  almost  all  the  plants  were  calamites,  in 
others  ferns.*  "  Some  of  the  plants  of  our  coal,"  says  Dr.  Buckland, 
"grew  on  the  identical  banks  of  sand,  silt,  and  mud  which,  being  now 
indurated  to  stone  and  shale,  form  the  strata  that  accompany  the  coal ; 
whilst  other  portions  of  these  plants  have  been  drifted  to  various  dis- 
tances from  the  swamps,  savannahs,  and  forests  that  gave  them  birth, 
particularly  those  that  are  dispersed  through  the  sandstones,  or  mixed 
with  fishes  in  the  shale  beds."  "  At  Balgray,  three  miles  north  of 
Glasgow,"  says  the  same  author,  "I  saw  in  the  year  1824,  as  there 
still  may  be  seen,  an  unequivocal  example  of  the  stumps  of  several  stems 
of  large  trees,  standing  close  together  in  their  native  place,  in  a  quarry 
of  sandstone  of  the  coal-formation."  f 

Between  the  years  1837  and  1840,  six  fossil  trees  were  discovered 
in  the  coal-fields  of  Lancashire,  where  it  is  intersected  by  the  Bolton 
railway.  They  were  all  in  a  vertical  position,  with  respect  to  the  plane 
of  the  bed  which  dips  about  15°  to  the  south.  The  distance  between 
the  first  and  the  last  was  more  than  100  feet,  and  the  roots  of  all  were 
imbedded  in  a  soft  argillaceous  shale.  In  the  same  plane  with  the 
roots  is  a  bed  of  coal,  eight  or  ten  inches  thick,  which  has  been  found 
to  extend  across  the  railway,  or  to  the  distance  of  at  least  ten  yards. 
Just  above  the  covering  of  the  roots,  yet  beneath  the  coal-seam,  so 
large  a  quantity  of  the  Lepidostrobus  variabilis  was  discovered  enclosed 
in  nodules  of  hard  clay,  that  more  than  a  bushel  was  collected  from  the 
small  openings  around  the  base  of  the  trees  (see  figure  of  this  genus, 
p.  471).  The  exterior  trunk  of  each  was  marked  by  a  coating  of  friable 
coal,  varying  from  one  quarter  to  three  quarters  of  an  inch  in  thick- 
ness ;  but  it  crumbled  away  on  removing  the  matrix.  The  dimensions 
of  one  of  the  trees  is  15^  feet  in  circumference  at  the  base,  7-J  feet  at 
the  top,  its  height  being  11  feet.  All  the  trees  have  large  spreading 
roots,  solid  and  strong,  sometimes  branching,  and  traced  to  a  distance 
of  several  feet,  and  presumed  to  extend  much  farther.  Mr.  Hawkshaw, 
who  has  described  these  fossils,  thinks  that,  although  they  were  hollow 
when  submerged,  they  may  have  consisted  originally  of  hard  wood 
throughout ;  for  solid  dicotyledonous  trees,  when  prostrated  in  tropical 
forests,  as  in  Venezuela,  on  the  shore  of  the  Caribbean  Sea,  were  ob- 
served by  him  to  be  destroyed  in  the  interior,  so  that  little  more  is 
left  than  an  outer  shell,  consisting  chiefly  of  the  bark.  This  decay, 
he  says,  goes  on  most  rapidly  in  low  and  flat  tracts,  in  which  there  is 
a  deep  rich  soil  and  excessive  moisture,  supporting  tall  forest  trees  and 
large  palms,  below  which  bamboos,  canes,  and  minor  palms  flourish  luxu- 
riantly. Such  tracts,  from  their  lowness,  would  be  most  easily  submerged, 
and  their  dense  vegetation  might  then  give  rise  to  a  seam  of  coal.J 

In  a  deep  valley  near  Capel-Coelbren,  branching  from  the  higher 


*  <Juart.  Geol.  Journ.,  vol.  v.,  Mem.,  p.  17. 

f  Anniv.  Address  to  Geol.  Soc.,  1840. 

j  Hawkshaw,  Geol.  Trans.,  Second  Series,  vol.  vi.  pp.  173,  177,  pi.  17. 


CH.  XilV.]  FOSSIL  TREES  OF  COAL.  481 

part  of  the  Swansea  valley,  four  stems  of  upright  Sigillarice  were  seen 
in  1838,  piercing  through  the  coal-measures  of  S.  Wales  ;  one  of  them 
was  2  feet  in  diameter,  and  one  13^  feet  high,  and  they  were  all  found 
to  terminate  downwards  in  a  bed  of  coal.  "  They  appear,"  says  Sir 
H.  De  la  Beche,  "  to  have  constituted  a  portion  of  a  subterranean 
forest  at  the  epoch  when  the  lower  carboniferous  strata  were  formed."  * 

In  a  colliery  near  Newcastle,  say  the  authors  of  the  Fossil  Flora,  a 
great  number  of  Sigillarice  were  placed  in  the  rock  as  if  they  had  re- 
tained the  position  in  which  they  grew.  Not  less  than  thirty,  some 
of  them  4  or  5  feet  in  diameter,  were  visible  within  an  area  of  50  yards 
square,  the  interior  being  sandstone,  and  the  bark  having  been  con- 
verted into  coal.  The  roots  of  one  individual  were  found  imbedded 
in  shale ;  and  the  trunk,  after  maintaining  a  perpendicular  course  and 
circular  form  for  the  height  of  about  ten  feet,  was  then  bent  over  so  as 
to  become  horizontal.  Here  it  was  distended  laterally,  and  flattened 
so  as  to  be  only  one  inch  thick,  the  flutings  being  comparatively  dis- 
tinct, f  Such  vertical  stems  are  familiar  to  our  miners,  under  the  name 
of  coal-pipes.  One  of  them,  72  feet  in  length,  was  discovered,  in  1829, 
near  Gosforth,  about  five  miles  from  Newcastle,  in  coal-grit,  the  strata 
of  which  it  penetrated.  The  exterior  of  the  trunk  was  marked  at  in- 
tervals with  knots,  indicating  the  points  at  which  branches  had  shot  off. 
The  wood  of  the  interior  had  been  converted  into  carbonate  of  lime ; 
and  its  structure  was  beautifully  shown  by  cutting  transverse  slices,  so 
thin  as  to  be  transparent.  (See  p.  40.) 

These  "  coal  pipes  "  are  much  dreaded  by  our  miners,  for  almost 
every  year  in  the  Bristol,  Newcastle,  and  other  coal-fields,  they  are  the 
cause  of  fatal  accidents.  Each  cylindrical  cast  of  a  tree,  formed  of 
solid  sandstone,  and  increasing  gradually  in  size  towards  the  base,  and 
being  without  branches,  has  its  whole  weight  thrown  downwards,  and 
receives  no  support  from  the  coating  of  friable  coal  which  has  replaced 
the  bark.  As  soon,  therefore,  as  the  cohesion  of  this  external  layer  is 
overcome,  the  heavy  column  falls  suddenly  in  a  perpendicular  or 
oblique  direction  from  the  roof  of  the  gallery  whence  coal  has  been 
extracted,  wounding  or  killing  the  workman  who  stands  below.  It  is 
strange  to  reflect  how  many  thousands  of  these  trees  fell  originally  in 
their  native  forests  in  obedience  to  the  law  of  gravity ;  and  how  the 
few  which  continued  to  stand  erect,  obeying,  after  myriads  of  ages,  the 
same  force,  are  cast  down  to  immolate  their  human  victims. 

It  has  been  remarked,  that  if,  instead  of  working  in  the  dark,  the 
miner  was  accustomed  to  remove  the  upper  covering  of  rock  from  each 
seam  of  coal,  and  to  expose  to  the  day  the  soils  on  which  ancient 
forests  grew,  the  evidence  of  their  former  growth  would  be  obvious. 
Thus  in  South  Staffordshire  a  seam  of  coal  was  laid  bare  in  the  year 
1844,  in  what  is  called  an  open  work  at  Parkfield  Colliery,  near 

*  Geol.  Report  on  Cornwall,  Devon,  and  Somerset,  p.  143. 
f  Lindley  and  Hutton,  Foss.  Flo.,  Part.  6,  p.  150. 
31 


482  PARKFIELD  COLLIERY.  [Cn.  XXIV. 

Wolverhampton.  lu  the  space  of  about  a  quarter  of  an  acre  the 
stumps  of  no  less  than  seventy-three  trees  with  their  roots  attached 
appeared,  as  shown  in  the  annexed  plan  (fig.  536),  some  of  them  more 


Ground-plan  of  a  fossil  forest,  Parkfield  Colliery,  near  Wolverhampton, 
showing  the  position  of  73  trees  in  a  quarter  of  an  acre.* 

than  8  feet  in  circumference.  The  trunks  broken  off  close  to  the  root, 
were  lying  prostrate  in  every  direction,  often  crossing  each  other. 
One  of  them  measured  15,  another  30  feet  in  length,  and  others  less. 
They  were  invariably  flattened  to  the  thickness  of  one  or  two  inches, 
and  converted  into  coal.  Their  roots  formed  part  of  a  stratum  of  coal 
10  inches  thick,  which  rested  on  a  layer  of  clay  2  inches  thick,  below 
which  was  a  second  forest,  resting  on  a  2-foot  seam  of  coal.  Five  feet 
below  this  again  was  a  third  forest  with  large  stumps  of  Lepidodendra, 
Calamites,  and  other  trees. 

In  the  account  given,  in  1821,  by  M.  Alex.  Brongniart  f  of  the  coal- 
mine of  Treuil,  at  St.  Etienne,  near  Lyons,  he  states  that  distinct 
horizontal  strata  of  micaceous  sandstone  are  traversed  by  vertical 
trunks  of  monocotyledonous  vegetables,  resembling  bamboos  or  large 
Equiseta  (fig.  537).  Since  the  consolidation  of  the  stone,  there  has 
been  here  and  there  a  sliding  movement,  which  has  broken  the  con- 
tinuity of  the  stems,  throwing  the  upper  parts  of  them  on  one  side,  so 
that  they  are  often  not  continuous  with  the  lower. 

From  these  appearances  it  was  inferred  that  we  have  here  the  monu- 
ments of  a  submerged  forest.  I  formerly  objected  to  this  conclusion, 
suggesting  that,  in  that  case,  all  the  roots  ought  to  have  been  found  at 
one  and  the  same  level,  and  not  scattered  irregularly  through  the  mass. 
I  also  imagined  that  the  soil  to  which  the  roots  were  attached  should 
have  been  different  from  the  sandstone  in  which  the  trunks  are  enclosed. 
Having,  however,  seen  calamites  near  Pictou,  in  Nova  Scotia,  buried 
at  various  heights  in  sandstone  and  in  similar  erect  attitudes,  I  have 

*  Messrs.  Becket  and  Ick,  Proceed.  Geol.  Soc.,  vol.  iv.  p.  287. 
f  Annales  des  Mines,  1821. 


CH.  XXIV.]       ERECT  POSITION  OF  FOSSIL  TREES— SNAGS. 

Fig.  537. 


483 


Section  showing  the  erect  position  of  fossil  trees  in  coal-sandstone  at 
St.  Etienne.    (Alex.  Brongniart.) 

now  little  doubt  that  M.  Brongniart's  view  was  correct.  These  plants 
seem  to  have  grown  on  a  sandy  soil,  liable  to  be  flooded  from  time  to 
time,  and  raised  by  new  accessions  of  sediment,  as  may  happen  in 
swamps  near  the  banks  of  a  large  river  in  its  delta.  Trees  which  delight 
in  marshy  grounds  are  not  injured  by  being  buried  several  feet  deep 
at  their  base ;  and  other  trees  are  continually  rising  up  from  new  soils, 
several  feet  above  the  level  of  the  original  foundation  of  the  morass. 
In  the  banks  of  the  Mississippi,  when  the  water  has  fallen,  I  have  seen 
sections  of  a  similar  deposit  in  which  portions  of  the  stumps  of  trees 
with  their  roots  in  situ  appeared  at  many  different  heights.* 

When  I  visited,  in  1843,  the 
quarries  of  Treuil  above  men- 
tioned, the  fossil  trees  seen  in 
fig.  537  were  removed,  but  I 
obtained  proofs  of  other  forests 
of  erect  trees  in  the  same  coal- 
field. 

Snags. — In  1830,  a  slanting 
trunk  was  exposed  in  Craigleith 
quarry,  near  Edinburgh,  the  total 
length  of  which  exceeded  60 

feet.        Its    diameter    at    the    top    Inclined  position  of  a  fossil  tree,  cutting  through 

Was  about  7  inches,  and  near  the       horizontal  beds  of  sandstone,  Craigleith  quarry, 

,          .       .  Edinburgh.    Angle  of  inclination  from  a  to  I 

base  it  measured   5  teet  in  its      27°. 


Fig.  588. 


*  Principles  of  Geology,  9th  ed.,  p.  268. 


484:  OBLIQUE  FOSSIL  TREES— FOSSIL  FORESTS.        [On.  XXIV. 

greater,  and  2  feet  in  its  lesser  width.  The  bark  was  converted  into 
a  thin  coating  of  the  purest  and  finest  coal,  forming  a  striking  con- 
trast in  color  with  the  white  quartzose  sandstone  in  which  it  lay. 
The  foregoing  cut  (fig.  538)  represents  a  portion  of  this  tree,  about 
15  feet  long,  which  I  saw  exposed  in  1830,  when  all  the  strata  had 
been  removed  from  one  side.  The  beds  which  remained  were  so 
unaltered  and  undisturbed  at  the  point  of  junction,  as  clearly  to 
show  that  they  had  been  tranquilly  deposited  round  the  tree,  and 
that  the  tree  had  not  subsequently  pierced  through  them  while  they 
were  yet  in  a  soft  state.  They  were  composed  chiefly  of  siliceous 
sandstone,  for  the  most  part  white;  and  divided  into  laminae  so 
thin,  that  from  six  to  fourteen  of  them  might  be  reckoned  in  the 
thickness  of  an  inch.  Some  of  these  thin  layers  were  dark,  and  con- 
tained coaly  matter ;  but  the  lowest  of  the  intersected  beds  were  cal- 
careous. The  tree  could  not  have  been  hollow  when  imbedded,  for 
the  interior  still  preserved  the  woody  texture  in  a  perfect  state,  the 
petrifying  matter  being,  for  the  most  part,  calcareous.*  It  is  also 
clear  that  the  lapidifying  matter  was  not  introduced  laterally  from 
the  strata  through  which  the  fossil  passes,  as  most  of  these  were 
not  calcareous.  It  is  well  known  that,  in  the  Mississippi  and  other 
great  American  rivers,  where  thousands  of  trees  float  annually  down 
the  streams,  some  sink  with  their  roots  downwards,  and  become 
fixed  in  the  mud.  Thus  placed  they  have  been  compared  to  a 
lance  in  rest;  and  so  often  do  they  pierce  through  the  bows  of 
vessels  which  run  against  them,  that  they  render  the  navigation  ex- 
tremely dangerous.  Mr.  Hugh  Miller  mentions  four  other  huge 
trunks  exposed  in  quarries  near  Edinburgh,  which  lay  diagonally 
across  the  strata  at  an  angle  of  about  30°,  with  their  lower  or 
heavier  portions  downwards,  the  roots  of  all,  save  one,  rubbed  off 
by  attrition.  One  of  these  was  60  and  another  70  feet  in  length, 
and  from  4  to  6  feet  in  diameter. 

The  number  of  years  for  which  the  trunks  of  trees,  when  con- 
stantly submerged,  can  resist  decomposition,  is  very  great ;  as  we 
might  suppose  from  the  durability  of  wood,  in  artificial  piles,  perma- 
nently covered  by  water.  Hence  these  fossil  snags  may  not  imply  a 
rapid  accumulation  of  beds  of  sand,  although  the  channel  of  a  river 
or  part  of  a  lagoon  is  often  filled  up  in  a  very  few  years. 

Nova  Scotia. — One  of  the  finest  examples  in  the  world  of  a  suc- 
cession of  fossil  forests  of  the  Carboniferous  period,  laid  open  to  view 
in  a  natural  section,  is  that  seen  in  the  lofty  cliffs  called  the  South 
Joggins,  bordering  the  Chignecto  Channel,  a  branch  of  the  Bay  of 
Fundy,  in  Nova  Scotia,  f 

In  the  annexed  section  (fig.  539),  which  I  examined  in  July,  1842, 


*  See  figures  of  texture,  Witham,  Foss.  Veget.,  pi.  3. 

f  See  Lyell's  Travels  in  N.  America,  vol.  ii.  p.  179 ;  and  Dawson,  Geol.  Journ., 
No.  37. 


CH.  XXIV.]        COAL— FOSSIL  FORESTS  IN  NOVA  SCOTIA. 


485 


H 
1 1 

?f 

I6 

Ii 

8- 


I 


the  beds  from  c  to  i  are  seen  all  dipping  the  same 
way,  their  average  inclination  being  at  an  angle 
of  24°  S.S.W.  The  vertical  height  of  the  cliffs  is 
from  150  to  200  feet;  and  between  d  and  #,  in 
which  space  I  observed  seventeen  trees  in  an  up- 
right position,  or,  to  speak  more  correctly,  at 
right  angles  to  the  planes  of  stratification,  I 
counted  nineteen  seams  of  coal,  varying  in  thick- 
ness from  2  inches  to  4  feet.  At  low  tide  a  fine 
horizontal  section  of  the  same  beds  is  exposed  to 
view  on  the  beach.  The  thickness  of  the  beds 
alluded  to,  between  d  and  <7,  is  about  2500  feet, 
the  erect  trees  consisting  chiefly  of  large  Sigil- 
larice,  occurring  at  ten  distinct  levels,  one  above 
the  other ;  but  Mr.  Logan,  who  afterwards  made  a 
more  detailed  survey  of  the  same  line  of  cliffs, 
found  erect  trees  at  seventeen  levels,  extending 
through  a  vertical  thickness  of  4515  feet  of 
strata ;  and  he  estimated  the  total  thickness  of 
the  carboniferous  formation,  with  and  without 
coal,  at  no  less  than  14,570  feet,  everywhere  de- 
void of  marine  organic  remains.*  The  usual 
height  of  the  buried  trees  seen  by  me  was  from 
6  to  8  feet ;  but  one  trunk  was  about  25  feet  high 
and  4  feet  in  diameter,  with  a  considerable  bulge 
at  the  base.  In  no  instance  could  I  detect  any 
trunk  intersecting  a  layer  of  coal,  however  thin ; 
and  most  of  the  trees  terminated  downwards  in 
seams  of  coal.  Some  few  only  were  based  in 
clay  and  shale ;  none  of  them,  except  calamites, 
in  sandstone.  The  erect  trees,  therefore,  appeared 
in  general  to  have  grown  on  beds  of  coal.  In  the 
underclays  Stigmaria  abounds. 

In  1852  Dr.  Dawson  and  the  author  made  a 
detailed  examination  of  one  portion  of  the  strata, 
1400  feet  thick,  where  the  coal-seams  are  most 
frequent,  and  found  evidence  of  root-bearing  soils 
at  sixty-eight  different  levels.  Like  the  seams  of 
coal  which  often  cover  them,  these  root-beds  or  old 
soils  are  at  present  the  most  destructible  masses  in 
the  whole  cliff,  the  sandstones  and  laminated  shales  being  harder  and 
more  capable  of  resisting  the  action  of  the  waves  and  the  weather. 
Originally  the  reverse  was  doubtless  true,  for  in  the  existing  delta  of 
the  Mississippi  those  clays  in  which  the  innumerable  roots  of  the  decidu- 
ous cypress  and  other  swamp  trees  ramify  in  all  directions,  are  seen  to 


conl. 

,  No 


1 

f 


*  Quart.  Geol.  Journ.,  vol.  ii.  p.  177. 


486 


COAL— FOSSIL  FORESTS 


[Cn.  XXIV 


withstand  far  more  effectually  the  undermining  power  of  the  river,  or  of 
the  sea  at  the  base  of  the  delta,  than  do  beds  of  loose  sand  or  layers  of 
mud  not  supporting  trees. 

This  fact  may  explain  why  seams  of  coal  have  so  often  escaped 
denudation,  and  remain  continuous  over  wide  areas,  since  the  tough 
roots,  now  turned  to  coal,  which  once  traversed  them,  would  enable 
them  to  resist  a  current  of  water,  whilst  other  members  of  the  coal- 
formation,  in  their  original  and  unconsolidated  state  of  sand  and  mud, 
would  be  readily  removed. 

In  regard  to  the  plants,  they  belonged  to  the  same  genera  and  most 
of  them  to  the  same  species,  as  those  met  with  in  the  distant  coral- 
fields  of  Europe.  In  the  sandstone,  which  filled  their  interiors,  I  fre- 
quently observed  fern-leaves,  and  sometimes  fragments  of  Stigmaria, 
which  had  evidently  entered  together  with  sediment  after  the  trunk 
had  decayed  and  become  hollow,  and  while  it  was  still  standing  under 
water.  Thus  the  tree,  a  b,  fig.  540,  the  same  which  is  represented  at 
a,  fig.  541,  or  in  the  bed  e  in  the  larger  section,  fig.  539,  is  a  hollow 


Fig.  540. 


Fossil  tree  at  right  angles  to  the  planes  of  stratification. 
Coal-measures,  Nova  Scotia. 


Fig.  541. 


Erect  fossil  trees.    Coal-measures,  Nova  Scotia. 

trunk  5  feet  8  inches  in  length,  traversing  various  strata,  and  cut  off 
at  the  top  by  a  layer  of  clay  2  feet  thick,  on  which  rests  a  seam  of 
coal  (b,  fig.  541)  1  foot  thick.  On  this  coal  again  stood  two  large 


OH.  XXIV.]  IN  NOVA  SCOTIA. 

trees  (c  and  c?),  while  at  a  greater  height  the  trees  /  and  g  rest  upon 
a  thin  seam  of  coal  (e),  and  above  them  is  an  underclay,  supporting  the 
4-feet  coal. 

If  we  now  return  to  the  tree  first  mentioned  (fig.  540),  we  find  the 
diameter  (a  b)  14  inches  at  the  top  and  16  inches  at  the  bottom,  the 
length  of  the  trunk  5  feet  8  inches.  The  strata  in  the  interior  consist- 

£3 

ed  of  a  series  entirely  different  from  those  on  the  outside.  The  lowest 
of  the  three  outer  beds  which  it  traversed  consisted  of  purplish  and 
blue  shale  (c,  fig.  540),  2  feet  thick,  above  which  was  sandstone  (d)  1 
foot  thick,  and,  above  this,  clay  (e)  2  feet  8  inches.  But  in  the  interior 
were  nine  distinct  layers  of  different  composition  :  at  the  bottom,  first, 
shale  4  inches,  then  sandstone  1  foot,  then  shale  4  inches,  then  sand- 
stone 4  inches,  then  shale  11  inches,  then  clay  (/)  with  nodules  of 
ironstone  2  inches,  then  pure  clay  2  feet,  then  sandstone  3  inches,  and, 
lastly,  clay  4  inches.  Owing  to  the  outward  slope  of  the  face  of  the 
cliff,  the  section  (fig.  540)  was  not  exactly  perpendicular  to  the  axis 
of  the  tree ;  and  hence,  probably,  the  apparent  sudden  termination  at 
the  base  without  a  stump  and  roots. 

In  this  example  the  layers  of  matter  in  the  inside  of  the  tree  are 
more  numerous  than  those  without ;  but  it  is  more  common  in  the 
coal-measures  of  all  countries  to  find  a  cylinder  of  pure  sandstone — 
the  cast  of  the  interior  of  a  tree — intersecting  a  great  many  alter- 
nating beds  of  shale  and  sandstone,  which  originally  enveloped  the 
trunk  as  it  stood  erect  in  the  water.  Such  a  want  of  correspondence 
in  the  materials  outside  and  inside,  is  just  what  we  might  expect 
if  we  reflect  on  the  difference  of  time  at  which  the  deposition 
of  sediment  will  take  place  in  the  two  cases;  the  imbedding  of 
the  tree  having  gone  on  for  many  years  before  its  decay  had  made 
much  progress. 

In  many  places  distinct  proof  is  seen  that  the  enveloping  strata  took 
years  to  accumulate,  for  some  of  the  sandstones  surrounding  erect 
sigillarian  trunks  support  at  different  levels  roots  and  stems  of  Calam- 
ites ;  the  Calamites  having  begun  to  grow  after  the  older  Sigillarice 
had  been  partially  buried. 

The  general  absence  of  structure  in  the  interior  of  the  large  fossil 
trees  of  the  Coal  implies  the  very  durable  nature  of  their  bark,  as  com- 
pared with  their  woody  portion.  The  same  difference  of  durability 
of  bark  and  wood  exists  in  modern  trees,  and  was  first  pointed  out  to 
me  by  Dr.  Dawson,  in  the  forests  of  Nova  Scotia,  where  the  Canoe 
Birch  (Betula  papyracea)  has  such  tough  bark  that  it  may  sometimes 
be  seen  in  the  swamps  looking  externally  sound  and  fresh,  although 
consisting  simply  of  a  hollow  cylinder  with  all  the  wood  decayed  and 
gone.  In  such  cases  the  submerged  portion  is  sometimes  found  filled 
with  mud. 

One  of  the  erect  fossil  trees  of  the  South  Joggins  has  been  shown 
by  Dr.  Dawson  to  have  Araucarian  structure,  so  that  some  Coniferce 
of  the  Coal  period  grew  in  the  same  swamps  as  Sigillarice,  just  as  now 


488  COAL— FOSSIL  FORESTS.  [Cn.  XXIV. 

the  deciduous  cypress  (Taxodium  distichum)  abounds  in  the  marshes 
of  Louisiana  even  to  the  edge  of  the  sea. 

When  the  carboniferous  forests  sank  below  high-water  mark,  a 
species  of  Spirorbis  or  Serpula  (fig.  545)  attached  itself  to  the  outside 
of  the  stumps  and  stems  of  the  erect  trees,  adhering  occasionally  even 
to  the  interior  of  the  bark — another  proof  that  the  process  of  envelop- 
ment was  very  gradual.  These  hollow  upright  trees,  covered  with 
innumerable  marine  annelids,  reminded  me  of  a  "  cane-brake,"  as  it  is 
commonly  called,  consisting  of  tall  reeds  of  Arundhwria  macrosperma, 
which  I  saw  in  1846,  at  the  Balize,  or  extremity  of  the  delta  of  the 
Mississippi.  Although  these  reeds  are  freshwater  plants,  they  were 
covered  with  barnacles,  having  been  killed  by  an  incursion  of  salt 
water  over  an  extent  of  many  acres,  where  the  sea  had  for  a  season 
usurped  a  space  previously  gained  from  it  by  the  river.  Yet  the  dead 
reeds,  in  spite  of  this  change,  remained  standing  in  the  soft  mud,  show- 
ing how  easily  the  Sigillarice,  hollow  as  they  were  but  supported  by 
strong  roots,  may  have  resisted  an  incursion  of  the  sea. 

The  high  tides  of  the  Bay  of  Fundy,  rising  more  than  60  feet,  are 
so  destructive  as  to  undermine  and  sweep  away  continually  the  whole 
face  of  the  cliffs,  and  thus  a  new  crop  of  erect  fossil  trees  is  brought 
into  view  every  three  or  four  years.  They  are  known  to  extend  over 
a  space  between  two  or  three  miles  from  north  to  south,  and  more 
than  twice  that  distance  from  east  to  west,  being  seen  in  the  banks  of 
streams  intersecting  the  coal-field. 

In  Cape  Breton,  Mr.  Richard  Brown  has  observed  in  the  Sydney 
coal-field  a  total  thickness  of  coal-measures,  without  including  the 
underlying  millstone-grit,  of  1843  feet,  dipping  at  aji  angle  of  80°. 
He  has  published  minute  details  of  the  whole  series,  showing  at  how 
many  different  levels  erect  trees  occur,  consisting  of  Sigillarice,  Le- 
pidodendron,  Calamites,  and  other  genera.  In  one  place  eight  erect 
trunks,  with  roots  and  rootlets  attached  to  them,  were  seen  at  the 
same  level,  within  a  horizontal  space  80  feet  in  length.  Beds  of  coal 
of  various  thickness  are  interstratified.  Taking  into  account  forty- 
one  clays,  filled  with  roots  of  Stigmaria  in  their  natural  position, 
and  eighteen  layers  of  upright  trees  at  other  levels,  there  is,  on  the 
whole,  clear  evidence  of  at  least  fifty-nine  fossil  forests,  ranged  one 
above  the  other,  in  this  coal-field,  in  the  above-mentioned  thickness  of 
strata.* 

The  fossil  shells  of  Cape  Breton  and  those  of  the  Nova  Scotia  sec- 
tion, consist  of  species  of  Unionidce,  or  an  allied  extinct  family.  None 
of  them  agree  with  any  shells  known  in  the  marine  carboniferous  lime- 
stones. In  some  strata  the  shells  of  an  annelid  allied  to  the  genus 
Spirorbis  (see  fig.  545)  seem  to  indicate  brackish  water ;  but  we  ought 
never  to  be  surprised  if,  in  pursuing  the  same  stratum,  we  should  come 
either  to  a  freshwater  or  a  purely  marine  deposit ;  for  this  will  depend 

*  Geol.  Quart.  Journ.,  vol.  ii.  p.  393  ;  and  vol.  vi.  p.  116. 


CH.  XXIV.] 


COAL— RAIN-PRINTS. 


489 


upon  our  taking  a  direction  higher  up  or  lower  down  the  ancient  river 
or  delta  deposit. 

In  the  strata  above  described,  the  association  of  clays  supporting 
upright  trees,  with  other  beds  containing  brackish-water  shells,  implies 
such  a  repeated  change  in  the  same  area,  from  land  to  sea  and  from 
sea  to  land,  that  here,  if  anywhere,  we  should  expect  to  meet  with 
evidence  of  the  fall  of  rain  on  ancient  sea-beaches.  Accordingly,  rain- 
prints  were  seen  by  Dr.  Dawson  and  myself  at  various  levels,  but  the 
most  perfect  hitherto  observed  were  discovered  by  Mr.  Brown  near 
Sydney  in  Cape  Breton.  They  consist  of  very  delicate  impressions 


Fig.  542. 


Fig.  543. 


Fig.  542.    Carboniferous  rain-prints  with  worm-tracks  (a,  &)  on  green  shale,  from 

Cape  Breton,  Nova  Scotia.    Natural  size. 
Fig.  543.    Casts  of  rain-prints  on  a  portion  of  the  same  slab,  fig.  542,  seen  on  the  under 

side  of  an  incumbent  layer  of  arenaceous  shale.    Natural  size. 

The  arrow  represents  the  supposed  direction  of  the  shower. 


Fig.  544. 


Casts  of  carboniferous  rain-prints  and  shrinkage-cracks  (a)  on  the  under  side  of  a  layer 
of  sandstone,  Cape  Breton,  Nova  Scotia.    Natural  size. 

of  rain-drops  on  greenish  slates,  with  several  worm-tracks  (#,  b,  fig. 
542),  such  as  usually  accompany  rain-marks  on  the  recent  mud  of  the 
Bay  of  Fundy,  and  other  modern  beaches. 


490  COAL— RAIN-PRINTS.  [On.  XXIV. 

The  casts  of  rain-prints  in  figs.  543  and  544,  project  from  the  under 
side  of  two  layers,  occurring  at  different  levels,  the  one  a  sandy  shale, 
resting  on  the  green  shale  (fig.  542),  the  other  a  sandstone  presenting  a 
similar  warty  or  blistered  surface,  on  which  are  also  observable  some 
small  ridges  as  at  a,  which  stand  out  in  relief,  and  afford  evidence  of 
cracks  formed  by  the  shrinkage  of  subjacent  clay,  on  which  rain  had 
fallen.  Many  of  the  associated  sandstones  are  ripple-marked. 

The  great  humidity  of  the  climate  of  the  Coal  period  had  been  pre- 
viously inferred  from  the  nature  of  its  vegetation  and  the  continuity 
of  its  forests  for  hundreds  of  miles  ;  but  it  is  satisfactory  to  have  at 
length  obtained  such  positive  proofs  of  showers  of  rain,  the  drops  of 
which  resembled  in  their  average  size  those  which  now  fall  from  the 
clouds.  From  such  data  we  may  presume  that  the  atmosphere  of  the 
Carboniferous  period  corresponded  in  density  with  that  now  investing 
the  globe,  and  that  different  currents  of  air  varied  then  as  now  in 
temperature,  so  as  to  give  rise,  by  their  mixture,  to  the  condensation 
of  aqueous  vapor. 

The  more  closely  the  strata  productive  of  coal  have  been  studied, 
the  greater  has  become  the  force  of  the  evidence  in  favor  of  their 
having  originated  in  the  manner  of  modern  deltas.  They  display  a 
vast  thickness  of  stratified  mud  and  fine  sand  without  pebbles,  and  in 
them  are  seen  countless  stems,  leaves-,  and  roots  of  terrestrial  plants, 
free  for  the  most  part  from  all  intermixture  of  marine  remains — cir- 
cumstances which  imply  the  persistency  in  the  same  region  of  a  vast 
body  of  fresh  water.  This  water  was  also  charged,  like  that  of  a  great 
river,  with  an  inexhaustible  supply  of  sediment,  which  seems  to  have 
been  transported  over  alluvial  plains  so  far  from  the  higher  grounds 
that  all  coarser  particles  and  gravel  were  left  behind.  Such  phenomena 
imply  the  drainage  and  denudation  of  a  continent  or  large  island,  hav- 
ing within  it  one  or  more  ranges  of  mountains.  The  partial  intercala- 
tion of  brackish-water  beds  at  certain  points  is  equally  consistent  with 
the  theory  of  a  delta,  the  lower  parts  of  which  are  always  exposed  to 
be  overflowed  by  the  sea,  even  where  no  oscillations  of  level  are  ex- 
perienced. 

The  purity  of  the  coal  itself,  or  the  absence  in  it  of  earthy  particles 
and  sand,  throughout  areas  of  vast  extent,  is  a  fact  which  appears  very 
difficult  to  explain  when  we  attribute  each  coal-seam  to  a  vegetation 
growing  in  swamps.  It  has  been  asked  how,  during  river  inundations 
capable  of  sweeping  away  the  leaves  of  ferns  and  the  stems  and  roots 
of  Sigillarice  and  other  trees,  could  the  waters  fail  to  transport  some 
fine  mud  into  the  swamps  ?  One  generation  after  another  of  tall  trees 
grew  with  their  roots  in  mud,  and  their  leaves  and  prostrate  trunks 
formed  layers  of  vegetable  matter,  which  was  afterwards  covered  with 
mud  since  turned  to  shale.  Yet  the  coal  itself,  or  altered  vegetable 
matter,  remained  all  the  while  unsoiled  by  earthy  particles.  This 
enigma,  however  perplexing  at  first  sight,  may,  I  think,  be  solved  by 
attending  to  what  is  now  taking  place  in  deltas.  The  dense  growth 


OH.  XXIV.]  PURITY  OF  THE  COAL.  491 

of  reeds  and  herbage  which  encompasses  the  margins  of  forest-covered 
swamps  in  the  valley  and  delta  of  the  Mississippi  is  such  that  the 
fluviatile  waters,  in  passing  through  them,  are  filtered  and  made  to 
clear  themselves  entirely  before  they  reach  the  areas  in  which  vegetable 
matter  may  accumulate  for  centuries,  forming  coal  if  the  climate  be 
favorable.  There  is  no  possibility  of  the  least  intermixture  of  earthy 
matter  in  such  cases.  Thus  in  the  large  submerged  tract  called  the 
"  Sunk  Country,"  near  New  Madrid,  forming  part  of  the  western  side 
of  the  valley  of  the  Mississippi,  erect  trees  have  been  standing  ever 
since  the  year  1811-'12,  killed  by  the  great  earthquake  of  that  date; 
lacustrine  and  swamp  plants  have  been  growing  there  in  the  shallows, 
and  several  rivers  have  annually  inundated  the  whole  space,  and  yet 
have  been  unable  to  carry  in  any  sediment  within  the  outer  boundaries 
of  the  morass,  so  dense  is  the  marginal  belt  of  reeds  and  brushwood. 
It  maybe  affirmed  that  generally  in  the  "cypress  swamps  "of  the 
Mississippi  no  sediment  mingles  with  the  vegetable  matter  accumulated 
there  from  the  decay  of  trees  and  semi-aquatic  plants.  As  a  singular 
proof  of  this  fact,  I  may  mention  that  whenever  any  part  of  a  swamp 
in  Louisiana  is  dried  up,  during  an  unusually  hot  season,  and  the  wood 
set  on  fire,  pits  are  burnt  into  the  ground  many  feet  deep,  or  as  far  down 
as  the  fire  can  descend,  without  meeting  with  water,  and  it  is  then  found 
that  scarcely  any  residuum  or  earthy  matter  is  left.*  At  the  bottom 
of  all  these  "  cypress  swamps  "  a  bed  of  clay  is  found,  with  roots  of  the 
tall  cypress  (Taxodium  distichum),  just  as  the  underclays  of  the  coal 
are  filled  with  Stigmaria. 

It  has  been  already  stated  that  the  carboniferous  strata  at  the  South 
Joggins,  in  Nova  Scotia,  are  nearly  three  miles  thick,  and  the  coal- 
measures  are  ascertained  to  be  of  vast  thickness  near  Pictou,  more  than 
100  miles  to  the  eastward.  If,  therefore,  we  speculate  on  the  prob- 
able volume  of  solid  matter  contained  in  the  Nova  Scotia  coal-fields, 
there  appears  little  danger  of  erring  on  the  side  of  excess  if  we  take  the 
average  thickness  of  the  beds  at  7500  feet,  or  about  half  that  ascer- 
tained to  exist  in  one  carefully-measured  section.  As  to  the  area  of 
the  coal-field,  it  includes  a  large  part  of  New  Brunswick  to  the  west, 
and  extends  north  to  Prince  Edward's  Island,  and  probably  to  the 
Magdalen  Isles.  When  we  add  the  Cape  Breton  beds,  and  the  con- 
necting strata,  which  must  have  been  denuded  or  are  still  concealed 
beneath  the  waters  of  the  Gulf  of  St.  Lawrence,  we  obtain  an  area 
comprising  about  36,000  square  miles.  This,  with  the  thickness  of 
7500  feet  before  assumed,  will  give  51,000  cubic  miles  of  solid  matter 
as  the  volume  of  the  carboniferous  rocks. 

According  to  the  latest  estimate  of  the  annual  discharge  of  water  by 
the  Mississippi,  and  the  proportion  of  sediment  held  in  suspension  in 
its  waters  at  different  seasons  of  the  year,  after  making  due  allowance 

*  Ly ell's  Second  Visit  to  the  U.  S.,  vol.  ii.  p.  245  ;  and  American  Jouni.  of  Sci- 
ence, Second  Series,  vol.  v.  p.  17. 


492  LOXG  PERIODS  OF  ACCUMULATION.  [Cn.  XXIV. 

for  tlie  sand  and  coarser  particles  pushed  along  the  bottom,  it  would 
take,  according  to  the  late  survey  of  Messrs.  Humphreys  and  Abbot, 
more  than  a  million  years  for  the  great  river  to  carry  down  from  the 
continent  to  the  gulf  an  amount  of  solid  matter  equal  to  that  of  the 
rocks  above  alluded  to.* 

The  Ganges,  according  to  the  data  supplied  to  mo  by  Mr.  Everest 
and  Captain  Strachey,  conveys  so  much  larger  a  volume  of  solid  matter 
annually  to  the  Bay  of  Bengal,  that  it  might  accomplish  a  similar  task 
in  375,000  years. 

As  the  lowest  of  the  carboniferous  strata  of  Nova  Scotia,  like  the 
middle  and  uppermost,  consist  of  shallow- water  beds,  the  whole  vertical 
subsidence  of  three  miles,  at  the  South  Joggins,  must  have  taken  place 
gradually.  Even  if  this  depression  was  brought  about  in  the  course 
of  375,000  years,  it  may  have  been  accomplished  at  the  average  rate 
of  4  feet  in  a  century,  resembling  that  now  experienced  in  certain 
countries,  where,  whether  the  movement  be  upward  or  downward,  it 
is  quite  insensible  to  the  inhabitants,  and  only  known  by  scientific 
inquiry.  If,  on  the  other  hand,  it  was  brought  about  in  rather  more 
than  a  million  of  years  according  to  the  other  standard  before  alluded 
to,  the  rate  would  be  little  more  than  a  foot  in  a  century.  The  same 
movement  taking  place  in  an  upward  direction  would  be  sufficient  to 
uplift  a  portion  of  the  earth's  crust  to  the  height  of  Mont  Blanc,  or  to 
a  vertical  elevation  of  three  miles  above  the  level  of  the  sea. 

The  delta  of  the  Ganges  presents  in  one  respect  a  striking  parallel 
to  the  Nova  Scotia  coal-field,  since  at  Calcutta,  at  the  depth  of  eight 
or  ten  feet  from  the  surface,  the  buried  stools  of  trees  with  their  roots 
attached  have  been  found  in  digging  tanks,  indicating  an  ancient  soil 
now  underground ;  and,  in  boring  on  the  same  site  for  an  Artesian 
well,  to  the  depth  of  481  feet,  other  signs  of  ancient  forest-covered 
lands  and  peaty  soils  have  been  observed  at  several  depths,  even  as  far 
down  as  300  feet  and  more  below  the  level  of  the  sea.  As  the  strata 
pierced  through  contained  freshwater  remains  of  recent  species  of  plants 
and  animals,  they  imply  a  subsidence  which  has  been  going  on  con- 
temporaneously with  the  accumulation  of  fluviatile  mud. 

In  the  English  coal-fields  the  same  association  of  fresh,  or  rather 
brackieh- water  strata,  with  marine,  in  close  connection  with  beds  of 
coal  of  terrestrial  origin,  has  been  frequently  recognized.  Thus,  for 
example,  a  deposit  near  Shrewsbury,  probably  formed  in  brackish  water, 
has  been  described  by  Sir  R,  Murchison  as  the  youngest  member  of 
the  carboniferous  series  of  that  district,  at  the  point  where  the  coal- 
measures  are  in  contact  with  the  Permian  or  "  Lower  New  Red."  It 
consists  of  shales  and  sandstones  about  150  feet  thick,  with  coal  and 
traces  of  plants  ;  including  a  bed  of  limestone  varying  from  2  to  9  feet 
in  thickness,  which  is  cellular,  and  resembles  some  lacustrine  limestones 

*  Principles  of  Geology,  9th  ed.,  1853,  p.  273  ;  and  Antiquity  of  Man,  3d  ed., 
Appendix  D,  p.  622. 


CH.  XXIV.]        BRACKISH-WATER  AND  MARINE  STRATA. 


of  France  and  Germany.  It  has  been  traced  for  thirty  miles  in  a 
straight  line,  and  can  be  recognized  at  still  more  distant  points.  Tho 
characteristic  fossils  are  a  small  bivalve,  having  the  form  of  a  Cyclas  or 
Cyrena,  also  a  small  entomostracan  which  may  be  a  Cypris,  or,  if 
marine,  a  Cythere  (fig.  546),  and  the  microscopic  shell  of  an  annelid 
of  an  extinct  genus  called  Microconchus  (fig.  545)  allied  to  Serpula  or 
Spirorbis. 


Fig.  545. 


Fig.  546. 


a.  Microconchus  (Spiror- 
Ms)  carbonarim.  Nat. 
size,  and  magnified. 

5.  Var.  of  same. 


Cypris  ?  inflata  (or  Cy- 
theref).  Nat.  size,  and 
magnified.  Murchison.* 


In  the  lower  coal-measures  of  Coalbrook  Dale,  the  strata,  accord- 
ing to  Mr.  Prestwich,  often  change  completely  within  very  short  dis- 
tances, beds  of  sandstone  passing  horizontally  into  clay,  and  clay  into 
sandstone.  The  coal-seams  often  wedge  out  or  disappear ;  and  sec- 
tions, at  places  nearly  contiguous,  present  marked  lithological  dis- 
tinctions. In  this  single  field,  in  which  the  strata  are  from  TOO  to 
800  feet  thick,  between  forty  and  fifty  species  of  terrestrial  plants 
have  been  discovered,  besides  several  fishes  of  the  genera  Megalich- 
tkys,  Holoptychius,  and  others.  Crustacea  are  also  met  with,  of  the 
genus  Limulus  (see  fig.  547),  resembling  in  all  essential  characters 


Fig.  547. 


Fig.  548. 


Limulus  rotundatus,  Prestwich. 
Coal,  Coalbrook  Dale. 


Glyphea  f  dubia,  Salter. 
Syn.  Apus  duMus,  Milne  Edwards. 
The  oldest  recorded  decapod  (or  long-tailed) 
crustacean.  Coal-measures,  Coalbrook  Dale. 


the  Limuli  of  the  Oolitic  period,  and  the  king-crab  of  the  modern 
seas.  They  were  smaller,  however,  than  the  living  form,  and  had  the 
abdomen  deeply  grooved  across,  and  serrated  at  its  edges.  In  this 


*  Silurian  System,  p.  84. 


494: 


CRUSTACEANS  OF  THE  COAL. 


[Cn.  XXIV. 


specimen  the  tail  is  wanting ;  but  in  another,  of  a  second  species, 
from  Coalbrook  Dale,  the  tail  is  seen  to  agree  with  that  of  the  living 
Limulus. 

The  perfect  carapace  of  a  long-tailed  or  decapod  crustacean  has 
also  been  found  in  the  iron-stone  of  these  strata  by  Mr.  Ick  (see  fig. 
548).  It  is  referred  by  Mr.  Salter  to  (rlyphea,  a  genus  also  occurring 
in  the  Lias  and  Oolite.  There  are  also  upwards  of  forty  species  of 
mollusca,  among  which  are  two  or  three  referred  to  the  freshwater 
genus  Uiriio,  and  others  of  marine  forms,  such  as  Nautilus,  Orthoce- 
ras,  Spirifer,  and  Productus.  Mr.  Prestwich  suggests  that  the  inter- 
mixture of  beds  containing  freshwater  shells  with  others  full  of  ma- 
rine remains  and  the  alternation  of  coarse  sandstone  and  conglomer- 
ate with  beds  of  fine  clay  or  shale  containing  the  remains  of  plants, 
may  be  explained  by  supposing  the  deposit  of  Coalbrook  Dale  to 
have  originated  in  a  bay  of  the  sea  or  estuary  into  which  flowed  a 
considerable  river  subject  to  occasional  freshes.*1 

One  or  more  species  of  scorpions,  two  beetles  of  the  family  Curcu- 
lionidce,  and  a  neuropterous  insect  resembling  the  genus  Corydalis,  and 
another  related  to  Phasmidce,  have  been  found  at  Coalbrook  Dale. 
From  the  coal  of  Wetting  in  Westphalia  several  specimens  of  the 
cockroach  or  JBlatta  family,  and  the  wing  of  a  cricket  (Acridites),  have 
been  described  by  Germar.f 

More  recently  (1854)  Mr.  Fr.  Goldenberg  has  published  descriptions 
of  no  less  than  twelve  species  of  insects  from  the  nodular  clay-iron-stone 
of  Saarbriick,  near  Treves.J  They  are  associated  with  the  leaves  and 
branches  of  fossil  ferns.  Among  them  are  several  Blattince,  three 
species  of  Neuroptera,  one  beetle  of  the  Scarabceus  family,  a  grass- 
hopper or  locust,  Gryllacris  (see  fig.  549),  and  several  white  ants  or 

Fig.  549. 


Wing  of  a  Grasshopper. 

Gryllaoris  ttthantliraca,  Goldenberg. 

Coal,  Saarbruck,  near  Treves. 

Termites.     These  newly  added  species  probably  outnumber  all  we 
knew  before  of  the  fossil  insects  of  the  coal. 


*  Prestwich,  Geol.  Trans.,  Second  Series,  vol.  v.  p.  440. 

f  See  Minister's  Beitr.,  vol.  v.  pi.  13,  1842. 

j  Palaeont.,  Bunker  and  V.  Meyer,  vol.  iv.  p.  17. 


CH.  XXIV.]  CLAY-IRON-STONE.  4.95 

In  the  Edinburgh  coal-field,  at  Birdiehouse,  fossil  fishes,  mollusks, 
and  cyprides  (?),  very  similar  to  those  in  Shropshire  and  Staffordshire, 
have  been  found  by  Dr.  Hibbert.  In  the  coal-field  also  of  Yorkshire, 
there  are  freshwater  strata,  some  ©f  which  contain  shells  referred  to 
the  family  Unionidce  ;  but  in  the  midst  of  the  series  there  is  one  thin 
but  very  widely  spread  stratum,  abounding  in  fishes  and  marine  shells, 
such  as  Goniatites  Listen  (fig.  550),  Orthoceras  and  Avicula  papyracea, 
Goldf.  (fig.  551). 

Fig.  550.  Fig.  551. 


Goniatites  Listeri,  Martin  sp.  Avicula  papyracea,  Goldf. 

(Pecten  papyraceus,  Sow.) 

No  similarly  intercalated  layer  of  marine  shells  has  been  noticed  in 
the  neighboring  coal-field  of  Newcastle,  where,  as  in  South  Wales  and 
Somersetshire,  the  marine  deposits  are  entirely  below  those  containing 
terrestrial  and  freshwater  remains.* 

Clay-iron-stone. — Bands  and  nodules  of  clay-iron-stone  are  common 
in  coal-measures,  and  are  formed,  says  Sir  H.  De  la  Beche,  of  carbon- 
ate of  iron  mingled  mechanically  with  earthy  matter,  like  that  con- 
stituting the  shales.  Mr.  Hunt,  of  the  Museum  of  Practical  Geology, 
instituted  a  series  of  experiments  to  illustrate  the  production  of  this 
substance,  and  found  that  decomposing  vegetable  matter,  such  as 
would  be  distributed  through  all  coal  strata,  prevented  the  farther 
oxidation  of  the  proto-salts  of  iron,  and  converted  the  peroxide  into 
protoxide  by  taking  a  portion  of  its  oxygen  to  form  carbonic  acid. 
Such  carbonic  acid,  meeting  with  the  protoxide  of  iron  in  solution, 
would  unite  with  it  and  form  a  carbonate  of  iron ;  and  this  mingling 
with  fine  mud,  when  the  excess  of  carbonic  acid  was  removed,  might 
form  beds  or  nodules  of  argillaceous  iron-stone.f 

*  Philips ;  art.  "  Geology,"  Encyc.  Metrop.,  p.  692. 
\  Memoirs  of  Geol.  Survey,  pp.  51,  255,  &c. 


4-96  COAL-FIELDS  OF  THE  UNITED  STATES.  |~CH.  XXV. 


CHAPTER  XXV. 

CARBONIFEROUS  GROUP,  continued. 

Coal-fields  of  the  United  States — Section  of  the  country  between  the  Atlantic  and 
Mississippi — Position  of  land  in  the  carboniferous  period  eastward  of  the  Alle- 
ghanies — Mechanically  formed  rocks  thinning  out  westward,  and  limestones 
thickening — Uniting  of  many  coal-seams  into  one  thick  bed — Horizontal  coal 
at  Brownsville,  Pennsylvania — Vast  extent  and  continuity  of  single  seams  of 
coal — Ancient  river-channel  in  Forest  of  Dean  coal-field — Climate  of  car- 
boniferous period — Insects  in  coal — Rarity  of  air-breathing  animals — Great 
number  of  fossil  fish — First  discovery  of  the  skeletons  of  fossil  reptiles — Foot- 
prints of  reptilians — First  land-shell  found — Rarity  of  air-breathers,  whether 
vertebrate  or  invertebrate,  in  Coal-measures — Mountain  limestone — Its  corals  and 
marine  shells. 

IT  was  stated  in  the  last  chapter  that  a  great  uniformity  prevails  in 
the  fossil  plants  of  the  coal-measures  of  Europe  and  North  America ; 
and  I  may  add  that  four-fifths  of  those  collected  in  Nova  Scotia  have 
been  identified  with  European  species.  Hence  the  former  existence, 
at  the  remote  period  under  consideration  (the  carboniferous),  of  a 
continent  or  chain  of  islands  where  the  Atlantic  now  rolls  its  waves 
seems  a  fair  inference.  Nor  are  there  wanting  other  and  independent 
proofs  of  such  an  ancient  land  situated  to  the  eastward  of  the  present 
Atlantic  coast  of  North  America ;  for  the  geologist  deduces  the  same 
conclusion  from  the  mineral  composition  of  the  carboniferous  and 
some  older  groups  of  rocks  as  they  are  developed  on  the  eastern 
flanks  of  the  AUeghanies,  contrasted  with  their  character  in  the  low 
country  to  the  westward  of  those  mountains. 

The  annexed  diagram  (fig.  552)  will  assist  the  reader  in  under- 
standing the  phenomena  now  alluded  to,  although  I  must  guard  him 
against  supposing  that  it  is  a  true  section.  A  great  number  of  details 
have  of  necessity  been  omitted,  and  the  scale  of  heights  and  horizon- 
tal distances  are  unavoidably  falsified. 

Starting  from  the  shores  of  the  Atlantic,  on  the  eastern  side  of  the 
Continent,  we  first  come  to  a  low  region  (A  B),  which  was  called  the 
alluvial  plain  by  the  first  geographers.  It  is  occupied  by  tertiary  and 
cretaceous  strata,  before  described  (pp.  242,  309,  and  338),  which  are 
nearly  horizontal.  The  next  belt,  from  B  to  c,  consists  of  granitic 
rocks  (hypogene),  chiefly  gneiss  and  mica-schist,  covered  occasionally 
with  unconformable  red  sandstone,  No.  4  (New  Red  or  Trias  ?),  re- 
markable for  its  footprints  (see  p.  454).  Sometimes,  also,  this  sand- 


CH.  XXV.]      GEOLOGICAL  STRUCTURE  OF  UNITED  STATES.  497 


ttii!  f|li: 
lilt!  1! 


ri 

s  gs 


s.s-35-e^ 


32 


498  CARBONIFEROUS  GROUP.  [On.  XXV. 

stone  rests  on  the  edges  of  the  disturbed  palaeozoic  rocks  (as  seen  in 
the  section).  The  region  (B  c),  sometimes  called  the  "Atlantic 
Slope,"  corresponds  nearly  in  average  width  with  the  low  and  flat 
plain  (A  B),  and  is  characterized  by  hills  of  moderate  height,  con- 
trasting strongly,  in  their  rounded  shape  and  altitude,  with  the  long, 
steep,  and  lofty  parallel  ridges  of  the  Alleghany  Mountains.  The  out- 
crop of  the  strata  in  these  ridges,  like  the  two  belts  of  hypogene  and 
newer  rocks  (A  B  and  B  c),  above  alluded  to,  when  laid  down  on  a 
geological  map,  exhibit  long  stripes  of  different  colors,  running  in  a 
N.  E.  and  S.  W.  direction,  in  the  same  way  as  the  lias,  chalk,  and 
other  secondary  formations  in  the  middle  and  eastern  half  of  Eng- 
land. 

The  narrow  and  parallel  zones  of  the  Appalachians,  here  mentioned, 
consist  of  strata,  folded  into  a  succession  of  convex  and  concave  flex- 
ures, subsequently  laid  open  by  denudation.  The  component  rocks 
are  of  great  thickness,  all  referable  to  the  Silurian,  Devonian,  and  Car- 
boniferous formations.  There  is  no  principal  or  central  axis,  as  in  the 
Pyrenees  and  many  other  chains — no  nucleus  to  which  all  the  minor 
ridges  conform;  but  the  chain  consists  of  many  nearly  equal  and 
parallel  foldings,  having  what  is  termed  an  anticlinal  and  synclinal 
arrangement  (see  above,  p.  48).  This  system  of  hills  extends,  geologi- 
cally considered,  from  Vermont  to  Alabama,  being  more  than  1000 
miles  long,  from  50  to  150  miles  broad,  and  varying  in  height  from 
2000  to  6000  feet.  Sometimes  the  whole  assemblage  of  ridges  runs 
perfectly  straight  for  a  distance  of  more  than  50  miles,  after  which  all 
of  them  wheel  round  altogether,  and  take  a  new  direction,  at  an  angle 
of  20  or  30  degrees  to  the  first. 

We  are  indebted  to  the  state  surveyors  of  Virginia  and  Pennsyl- 
vania, Prof.  W.  B.  Rogers  and  his  brother  Prof.  H;  D.  Rogers,  for  the 
important  discovery  of  a  clue  to  the  general  law  of  structure  prevail- 
ing throughout  this  range  of  mountains,  which,  however  simple  it  may 
appear  when  once  made  out  and  clearly  explained,  might  long  have 
been  overlooked,  amidst  so  great  a  mass  of  complicated  details.  It 
appears  that  the  bending  and  fracture  of  the  beds  is  greatest  on  the 
southeastern  or  Atlantic  side  of  the  chain,  and  the  strata  become  less 
and  less  disturbed  as  we  go  westward,  until  at  length  they  regain  their 
original  or  horizontal  position.  By  reference  to  the  section  (fig.  552), 
it  will  be  seen  that  on  the  eastern  side,  or  in  the  ridges  and  troughs 
nearest  the  Atlantic,  southeastern  dips  predominate,  in  consequence 
of  the  beds  having  been  folded  back  upon  themselves  as  in  i,  those  on 
the  northwestern  side  of  each  arch  having  been  inverted.  The  next 
set  of  arches  (such  as  k)  are  more  open,  each  having  its  western  side 
steepest ;  the  next  (1)  open  out  still  more  widely,  the  next  (m)  still 
more,  and  this  continues  until  we  arrive  at  the  low  and  level  part  of 
the  Appalachian  coal  field  (D  E). 

In  nature  or  in  a  true  section,  the  number  of  bendings  or  parallel 
folds  is  so  much  greater  that  they  could  not  be  expressed  in  a  diagram 


CH.  XXV.]  APPALACHIAN  CHAIN.  499 

without  confusion.  It  is  also  clear  that  large  quantities  of  rock  have 
been  removed  by  aqueous  action  or  denudation,  as  will  appear  if  we 
attempt  to  complete  all  the  curves  in  the  manner  indicated  by  the 
dotted  lines  at  i  and  Jc. 

The  movements  which  imparted  so  uniform  an  order  of  arrangement 
to  this  vast  system  of  rocks  must  have  been,  if  not  contemporaneous, 
at  least  parts  of  one  and  the  same  series,  depending  on  some  common 
cause.  Their  geological  date  is  well  defined,  at  least  within  certain 
limits,  for  they  must  have  taken  place  after  the  deposition  of  the  car- 
boniferous strata  (No.  5),  and  before  the  formation  of  the  red  sand- 
stone (No.  4).  The  greatest  disturbing  and  denuding  forces  have  evi- 
dently been  exerted  on  the  southeastern  side  of  the  chain ;  and  it  is 
here  that  igneous  or  plutonic  rocks  are  observed  to  have  invaded  the 
strata,  forming  dykes,  not  expressed  in  the  section,  some  of  which  run 
for  miles  in  lines  parallel  to  the  main  direction  of  the  Appalachians,  or 
KN.E.  and  S.S.W. 

The  thickness  of  the  carboniferous  rocks  in  the  region  c  is  very 
great,  and  diminishes  rapidly  as  we  proceed  to  the  westward.  The 
surveys  of  Pennsylvania  and  Virginia  show  that  the  southeast  was  the 
quarter  whence  the  coarser  materials  of  these  strata  were  derived,  so 
that  the  ancient  land  lay  in  that  direction.  The  conglomerate  which 
forms  the  general  baso  of  the  coal-measures  is  1500  feet  thick  in  the 
Sharp  Mountain,  where  I  saw  it  (at  c)  near  Pottsville ;  whereas  it  has 
only  a  thickness  of  500  feet,  about  thirty  miles  to  the  northwest,  and 
dwindles  gradually  away  when  followed  still  farther  in  the  same  direc- 
tion, until  its  thickness  is  reduced  to  30  feet.*  The  limestones,  on 
the  other  hand,  of  the  coal-measures  augment  as  we  trace  them  west- 
ward. Similar  observations  have  been  made  in  regard  to  the  Silurian 
and  Devonian  formations  in  New  York ;  the  sandstones  and  all  the 
mechanically-formed  rocks  thinning  out  as  they  go  westward,  and  the 
limestones  thickening,  as  it  were,  at  their  expense.  It  is,  therefore, 
clear  that  the  ancient  land  was  to  the  east,  where  the  Atlantic  now  is ; 
the  deep  sea,  with  its  banks  of  coral  and  shells  to  the  west,  or  where 
the  hydrographical  basin  of  the  Mississippi  is  now  situated. 

In  that  region,  near  Pottsville,  where  the  thickness  of  the  coal- 
measures  is  greatest,  there  are  thirteen  seams  of  anthracitic  coal,  sev- 
eral of  them  more  than  2  yards  thick.  Some  of  the  lowest  of  these 
alternate  with  beds  of  white  grit  and  conglomerate  of  coarser  grain 
than  I  ever  saw  elsewhere,  associated  with  pure  coal.  The  pebbles  of 
quartz  are  often  of  the  size  of  a  hen's  egg.  On  following  these  pudding- 
stones  and  grits  for  several  miles  from  Pottsville,  by  Tamaqua*,  to  the 
Lehigh  Summit  Mine,  in  company  with  Mr.  H.  D.  Rogers,  in  1841,  he 
pointed  out  to  me  that  the  coarse-grained  strata  and  their  accompany- 
ing shales  gradually  thin  out,  until  seven  seams  of  coal,  at  first  widely 
separated,  are  brought  nearer  and  nearer  together,  until  they  succes- 

*  H.  D.  Rogers,  Trans.  Assoc.  Amer.  Geol.,  1840-'42,  p.  440. 


500 


UNION  OF  COAL  SEAMS. 


[Cn.  XX\. 


sively  unite ;  so  that  at  last  they  form  one  mass,  between  40  and  50 
feet  thick.  I  saw  this  enormous  bed  of  anthraeitic  coal  quarried  in 
the  open  air  at  Mauch  Chunk  (or  the  Bear  Mountain),  the  overlying 
sandstone,  40  feet  thick,  having  been  removed  bodily  from  the  top  of 
the  hill,  which,  to  use  the  miner's  expression,  had  been  "  scalped." 
The  accumulation  of  vegetable  matter  now  constituting  this  vast  bed 
of  anthracite,  may  perhaps,  before  it  was  condensed  by  pressure  and 
the  discharge  of  its  hydrogen,  oxygen,  and  other  volatile  ingredients, 
have  been  between  200  and  300  feet  thick.  The  origin  of  such  a  vast 
thickness  of  vegetable  remains,  so  unmixed  with  earthy  ingredients, 
can,  I  think,  be  accounted  for  in  no  other  way,  than  by  the  growth, 
during  thousands  of  years,  of  trees  and  ferns,  in  the  manner  of  peat, — 
a  theory  which  the  presence  of  the  Stigmaria  in  situ  under  each  of  the 
seven  layers  of  anthracite,  fully  bears  out.  The  rival  hypothesis,  of 
the  drifting  of  plants  into  a  sea  or  estuary,  leaves  the  absence  of 
sediment,  or,  in  this  case,  of  clay,  sand,  and  pebbles,  wholly  unex- 
plained. 

But  the  student  will  naturally  ask,  what  can  have  caused  so  many 
seams  of  coal,  after  they  had  been  persistent  for  miles,  to  come  to- 
gether and  blend  into  one  single  seam,  and  that  one  equal  in  the 
aggregate  to  the  thickness  of  the  several  separate  seams?  Often  had 
the  same  question  been  put  by  English  miners  before  a  satisfactory 
answer  was  given  to  it  by  the  late  Mr.  Bowman.  The  following  is  his 
solution  of  the  problem :  Let  a  a',  fig.  553,  be  a  mass  of  vegetable 

Fig.  553. 


matter,  capable,  when  condensed,  of  forming  a  3-foot  seam  of  coal.  It 
rests  on  the  underclay  b  b',  filled  with  roots  of  trees  in  situ,  and  it 
supports  a  growing  forest  (c  D).  Suppose  that  part  of  the  same  forest 
D  E  had  become  submerged  by  the  ground  sinking  down  25  feet,  so 
that  the  trees  have  been  partly  thrown  down  and  partly  remain  erect 
in  water,  slowly  decaying,  their  stumps  and  the  lower  parts  of  their 
trunks  being  enveloped  in  layers  of  sand  and  mud,  which  are  gradually 
filling  up  the  lake  D  F.  When  this  lake  or  lagoon  has  at  length  been 
entirely  silted  up  and  converted  into  land,  say,  in  the  course  of  a 
century,  the  forest  c  D  will  extend  once  more  continuously  over  the 
whole  area  c  F,  as  in  fig.  554,  and  another  mass  of  vegetable  matter 


CH.  XXV.]  HORIZONTAL   COAL  STRATA.  501 

(g  g'),  forming  3  feet  more  of  coal,  may  accumulate  from  c  to  F.  We 
then  find  in  the  region  F,  two  seams  of  coal  (a1  and  g')  each  3  feet 
thick,  and  separated  by  25  feet  of  sandstone  and  shale,  with  erect  trees 
based  upon  the  lower  coal,  while,  between  D  and  c,  we  find  these  two 
seams  united  in  a  2-yard  coal.  It  may  be  objected  that  the  uninter- 
rupted growth  of  plants  during  the  interval  of  a  century  will  have 
caused  the  vegetable  matter  in  the  region  c  D  to  be  thicker  than  the  two 
distinct  scams  a'  and  g'  at  F  ;  and  no  doubt  there  would  actually  be  a 
slight  excess  representing  one  generation  of  trees  with  the  remains  of 
other  plants,  forming  half  an  inch  or  an  inch  of  coal ;  but  this  would 
not  prevent  the  miner  from  affirming  that  the  seam  a  g,  throughout 
the  area  c  D,  was  equal  to  the  two  seams  a'  and  g'  at  F. 

The  reader  has  seen,  by  reference  to  the  section  (fig.  552  p.  497), 
that  the  strata  of  the  Appalachian  coal-field  assume  an  horizontal  posi- 
tion west  of  the  mountains.  In  that  less  elevated  country,  the  coal- 
measures  are  intersected  by  three  great  navigable  rivers,  and  are 
capable  of  furnishing  for  ages,  to  the  inhabitants  of  a  densely  peopled 
region,  an  inexhaustible  supply  of  fuel.  These  rivers  are  the  Monon- 
gahela,  the  Alleghany,  and  the  Ohio,  all  of  which  lay  open  on  their 
banks  the  level  seams  of  coal.  Looking  down  the  first  of  these  at 
Brownsville,  we  have  a  fine  view  of  the  main  seam  of  bituminous  coal 
10  feet  thick,  commonly  called  the  Pittsburg  seam,  breaking  out  in 
the  steep  cliff  at  the  water's  edge;  and  I  made  the  accompanying 
sketch  of  its  appearance  from  the  bridge  over  the  river  (see  fig.  555). 
Here  the  coal,  10  feet  thick,  is  covered  by  carbonaceous  shale  (&),  and 
this  again  by  micaceous  sandstone  (c).  Horizontal  galleries  may  be 
driven  everywhere  at  very  slight  expense,  and  so  worked  as  to  drain 
themselves,  while  the  cars,  laden  with  coal  and  attached  to  each  other, 
glide  down  on  a  railway,  so  as  to  deliver  their  burden  into  barges 
moored  to  the  river's  bank.  The  same  seam  is  seen  at  a  distance,  on 
the  right  bank  (at  a),  and  may  be  followed  the  whole  way  to  Pitts- 
burg,  fifty  miles  distant.  As  it  is  nearly  horizontal,  while  the  river 
descends  it  crops  out  at  a  continually  increasing,  but  never  at  an  in- 
convenient, height  above  the  Monongahela.  Below  the  great  bed  of 
coal  at  Brownsville  is  a  fire-clay  1 8  inches  thick,  and  below  this,  sev- 
eral beds  of  limestone,  below  which  again  are  other  coal  seams.  I 
have  also  shown  in  my  sketch  another  layer  of  workable  coal  (at  d  d\ 
which  breaks  out  on  the  slope  of  the  hills  at  a  greater  height.  Here 
almost  every  proprietor  can  open  a  coal-pit  on  his  own  land,  and  the 
stratification  being  very  regular,  he  may  calculate  with  precision  the 
depth  at  which  coal  may  be  won. 

The  Appalachian  coal-field,  of  which  these  strata  form  a  part  (from 
c  to  E,  section,  fig.  552,  p.  497),  is  remarkable  for  its  vast  area;  for, 
according  to  Professor  H.  D.  Rogers,  it  stretches  continuously  from 
KE.  to  S.W.,  for  a  distance  of  720  miles,  its  greatest  width  being 
about  180  miles.  On  a  moderate  estimate,  its  superficial  area  amounts 
to  63,000  square  miles. 


502 


APPALACHIAN   COAL  STRATA. 


[Cn.  XXV. 


.M 

I 
.     I 

cc    0 

t>  I- 

of    "5 
I    ^ 

* 


i  s' 

II 


%'fs 


This  coal-formation,  before  its  original  limits  were  reduced  by  denu- 
dation, must  have  measured  900  miles  in  length,  and  in  some  places 
more  than  200  miles  in  breadth.  By  again  referring  to  the  section 
(fig.  552,  p.  497),  it  will  be  seen  that  the  strata  of  coal  are  horizontal 
to  the  westward  of  the  mountains  in  the  reo-ion  D  E,  and  become  more 

O 

and  more  inclined  and  folded  as  we  proceed  eastward.     Now  it  is 


CH.  XXV.]  CONVERSION  OF  LIGNITE  INTO   COAL.  593 

invariably  found,  as  Professor  H.  D.  Rogers  has  shown  by  chemical 
analysis,  that  the  coal  is  most  bituminous  towards  its  western  limit, 
where  it  remains  level  and  unbroken,  and  that  it  become  progressively 
debituminized  as  we  travel  southeastward  towards  the  more  bent  and 
distorted  rocks.  Thus,  on  the  Ohio,  the  proportion  of  hydrogen, 
oxygen,  and  other  volatile  matters,  ranges  from  40  to  50  per  cent. 
Eastward  of  this  line,  on  the  Monongahela,  it  still  approaches  40  per 
cent.,  where  the  strata  begin  to  experience  some  gentle  flexures.  On 
entering  the  Alleghany  Mountains,  where  the  distinct  anticlinal  axes 
begin  to  show  themselves,  but  before  the  dislocations  are  considerable, 
the  volatile  matter  is  generally  in  the  proportion  of  eighteen  or  twenty 
per  cent.  At  length,  when  we  arrive  at  some  insulated  coal-fields  (5', 
fig.  552)  associated  with  the  boldest  flexures  of  the  Appalachian  chain, 
where  the  strata  have  been  actually  turned  over,  as  near  Pottsville,  we 
find  the  coal  to  contain  only  from  6  to  12  per  cent,  of  bitumen,  thus 
becoming  a  genuine  anthracite.* 

It  appears  from  the  researches  of  Liebig  and  other  eminent  chemists, 
that  when  wood  and  vegetable  matter  are  buried  in  the  earth  exposed 
to  moisture,  and  partially  or  entirely  excluded  from  the  air,  they  de- 
compose slowly  and  evolve  carbonic  acid  gas,  thus  parting  with  a  por- 
tion of  their  original  oxygen.  By  this  means,  they  become  gradually 
converted  into  lignite  or  wood-coal,  which  contains  a  larger  propor- 
tion of  hydrogen  than  wood  does.  A  continuance  of  decomposition 
changes  this  lignite  into  common  or  bituminous  coal,  chiefly  by  the 
discharge  of  carburetted  hydrogen,  or  the  gas  by  which  we  illuminate 
our  streets  and  houses.  According  to  Bischoff,  the  inflammable  gases 
which  are  always  escaping  from  mineral  coal,  and  are  so  often  the 
cause  of  fatal  accidents  in  mines,  always  contain  carbonic  acid,  car- 
buretted hydrogen,  nitrogen,  and  olifiant  gas.  The  disengagement  of 
all  these  gradually  transforms  ordinary  or  bituminous  coal  into  anthra- 
cite, to  which  the  various  names  of  splint-coal,  glance-coal,  hard-coal, 
culm,  and  many  others,  have  been  given. 

We  have  seen  that,  in  the  Appalachian  coal-field,  there  is  an  inti- 
mate connection  between  the  extent  to  which  the  coal  has  parted  with 
its  gaseous  contents,  and  the  amount  of  disturbance  which  strata  have 
undergone.  The  coincidence  of  these  phenomena  may  be  attributed 
partly  to  the  greater  facility  afforded  for  the  escape  of  volatile  matter, 
where  the  fracturing  of  the  rocks  had  produced  an  infinite  number  of 
cracks  and  crevices,  and  also  to  the  heat  of  the  gases  and  water  pene- 
trating these  cracks,  when  the  great  movements  took  place,  which  have 
rent  and  folded  the  Appalachian  strata.  It  is  well  known  that,  at  the 
present  period,  thermal  waters  and  hot  vapors  burst  out  from  the  earth 
during  earthquakes,  and  these  would  not  fail  to  promote  the  disen- 
gagement of  volatile  matter  from  the  carboniferous  rocks. 

Continuity  of  seams  of  coaL — As  single  seams  of  coal  are  continuous 

*  Trans,  of  Assoc.  of  Amer.  Geol.,  p.  470. 


504:  CLIMATE  OF  COAL  PERIOD.  [Cn.  XXV. 

over  very  wide  areas,  it  lias  been  asked,  how  forests  could  have  pre- 
vailed uninterruptedly  over  such  wide  spaces.  In  reply,  it  may  be 
said  that  swamp-forests  in  one  delta  may  extend  for  25,  50,  or  100 
miles,  while  in  a  contiguous  delta,  as  on  the  borders  of  the  Gulf  of 
Mexico,  another  of  precisely  the  same  character  may  be  growing ;  and 
these  may  in  after  ages  appear  to  geologists  to  have  been  continuous, 
although  in  fact  they  were  simply  contemporaneous.  Denudation  may 
easily  be  imagined  in  such  cases  as  the  cause  of  interruptions,  which 
were  in  fact,  original.  But  as  in  all  the  American  coal-fields  there  are 
numerous  root-beds  without  any  superincumbent  coal,  we  may  pre- 
sume that  frequently  layers  of  vegetable  matter  were  removed  by 
floods ;  and  in  other  cases,  where  the  stigmaria-clays  are  for  a  certain 
space  covered  with  coal,  and  then  prolonged  without  any  such  cover- 
ing, the  inference  of  partial  denudation  is  still  more  obvious. 

In  the  Forest  of  Dean,  in  Gloucestershire,  ancient  river-channels  are 
found,  which  pass  through  beds  of  coal,  and  in  which  rounded  pebbles 
of  coal  occur.  They  are  of  older  date  than  the  overlying  and  undis- 
turbed coal-measures.  The  late  Mr.  Buddie,  who  described  them  to 
me,  told  me  he  had  seen  similar  phenomena  in  the  Newcastle  coal- 
field. Nevertheless,  instances  of  these  channels  are  much  more  rare 
than  we  might  have  anticipated,  especially  when  we  remember  how 
often  the  roots  of  trees  (Stigmarice)  have  been  torn  up,  and  drifted  in 
broken  fragments  into  the  grits  and  sandstones.  The  prevalence  of 
a  downward  movement  is,  no  doubt,  the  principal  cause  which  has 
saved  so  many  extensive  seams  of  coal  from  destruction  by  fluviatile 
action. 

Climate  of  Coal  Period. — So  long  as  the  botanist  taught  that  a 
tropical  climate  was  implied  by  the  carboniferous  flora,  geologists 
might  well  be  at  a  loss  to  reconcile  the  preservation  of  so  much  vege- 
table matter  with  a  high  temperature ;  for  heat  hastens  the  decompo- 
sition of  fallen  leaves  and  trunks  of  trees,  whether  in  the  atmosphere 
or  in  water.  It  is  well  known  that  peat,  so  abundant  in  the  bogs  of 
high  latitudes,  ceases  to  grow  in  the  swamps  of  warmer  regions.  It 
seems,  however,  to  have  become  a  more  and  more  received  opinion, 
that  the  coal-plants  do  not,  on  the  whole,  indicate  a  climate  resem- 
bling that  now  enjoyed  in  the  equatorial  zone.  Tree-ferns  range  as 
far  south  as  the  southern  part  of  New  Zealand,  and  Araucarian  pines 
occur  in  Norfolk  Island  and  Chili.  A  great  predominance  of  ferns 
and  lycopodiums  indicates  moisture,  equability  of  temperature,  and 
freedom  from  frost,  rather  than  intense  heat ;  and  we  know  too  little 
of  the  sigillariae,  calamites,  asterophyllites,  and  other  •  peculiar  forms 
of  the  Carboniferous  period,  to  be  able  to  speculate  with  confidence 
on  the  kind  of  climate  they  may  have  required. 

The  same  may  be  said  of  the  corals,  and  cephalopoda  of  the  Moun- 
tain Limestone, — they  belong  to  families  of  whose  climatal  habits  we 
know  nothing ;  and  even  if  they  should  be  thought  to  imply  that  a 
warm  temperature  characterized  the  northern  seas  in  the  carboniferous 


CH.  XXV.] 


CARBONIFEROUS  REPTILES. 


505 


era,  the  absence  of  cold  may  have  given  rise  (as  at  present  in  the  seas 
of  the  Bermudas,  under  the  influence  of  the  gulf-stream)  to  a  very- 
wide  geographical  range  of  stone-building  corals  and  shell-bearing 
cuttle-fish,  without  its  being  necessary  to  call  in  the  aid  of  tropical 
heat. 


CARBONIFEROUS    REPTILES. 

Where  we  have  evidence  in  a  single  coal-field,  as  in  that  of  Nova 
Scotia,  or  of  South  Wales,  of  fifty  or  even  a  hundred  ancient  forests 
buried  one  above  the  other,  with  the  roots  of  trees  still  in  their  origi- 
nal position,  and  with  some  of  the  trunks  still  remaining  erect,  we  are 
apt  to  wonder  that  until  the  year  1844  no  remains  of  contemporane- 
ous air-breathing  creatures  should  have  been  discovered.  No  verte- 
brated  animals  more  highly  organized  than  fish,  no  mammalia  or 
birds,  no  saurians,  frogs,  tortoises,  or  snakes  were  known  in  rocks  of 
such  high  antiquity.  In  the  coal-fields  of  Europe  mention  has  been 
made  of  beetles,  locusts,  and  a  few  other  insects,  but  no  land-shells 
have  even  now  been  met  with.  Agassiz  described  in  his  great  work 
on  fossil  fishes  more  than  one  hundred  and  fifty  species  of  ichthyo- 
lites  from  the  coal  strata,  ninety-four  belonging  to  the  families  of 
shark  and  ray,  and  fifty-eight  to  the  class  of  ganoids.  Some  of  these 
fish  are  very  remote  in  their  organization  from  any  now  living,  espe- 
cially those  of  the  family  called  Sauroid  by  Agassiz  ;  as  Megalich- 
thys,  Holoptychius,  and  others,  which  were  often 
of  great  size,  and  all  predaceous.  Their  oste- 
ology,  says  M.  Agassiz,  reminds  us  in  many  re- 
spects of  the  skeletons  of  saurian  reptiles,  both 
by  the  close  sutures  of  the  bones  of  the  skull, 
their  large  conical  teeth  striated  longitudinally, 
(see  fig.  556),  the  articulations  of  the  spinous 
processes  with  the  vertebrae,  and  other  charac- 
ters. Yet  they  do  not  form  a  family  interme- 
diate between  fish  and  reptiles,  but  are  true 
fish,  though  doubtless  more  highly  organized 
than  any  living  fish.* 

The  annexed  figure  represents  a  large  tooth 
of  the  Holoptychius,  found  by  Mr.  Horner  in 
the  Cannel  coal  of  Fifeshire.  This  fish  proba- 
bly inhabited  an  estuary,  like  many  of  its  con- 
temporaries, and  frequented  both  rivers  and  ihQ 

Fifeshire  coal-field. 
Sea.  Tooth  ;  natural  size. 

At  length,  in  1844,  the  first  skeleton  of  a 

true  reptile  was  announced  from  the  coal  of  Munster-Appel  in  Khen- 
ish  Bavaria,  by  H.  von  Meyer,  under  the  name  of  Apateon  pedestris, 


Fig.  556. 


*  Agassiz,  Poiss.  Foss.,  vol.  ii.  p.  88,  &c. 


506 


CARBONIFEROUS  REPTILES. 


[On.  XXV. 


Fisr.  557. 


the  animal  being  supposed  to  be  nearly  related  to  the  salamanders. 
Three  years  later,  in  1847,  Prof,  von  Dechen  found  in  the  coal-field 
of  Saarbriick,  at  the  village  of  Lebach,  between  Strasburg  and  Treves, 
the  skeletons  of  no  less  than  three  distinct  species  of  air-breathing 
reptiles,  which  were  described  by  the  late  Prof.  Goldfuss  under  the 
generic  name  of  Archegosaurus.  The  ichthyolites  and  plants  found 
in  the  same  strata  left  no  doubt  that  these  remains  belonged  to  the 

true  coal  period.  The  skulls, 
teeth,  and  the  greater  por 
tions  of  the  skeleton,  nay, 
even  a  large  part  of  the  skin, 
of  two  of  these  reptiles  have 
been  faithfully  preserved  in 
the  centre  of  spheroidal  con 
cretions  of  clay-iron-stone. 
The  largest  of  these  lizards, 
Archegosaurus  Decheni,  must 
have  been  3  feet  6  inches 
long.  The  annexed  drawing 
represents  the  skull  and  neck 
bones  of  the  smallest  of  the 
three,  of  the  natural  size. 
They  were  considered  by 
Goldfuss  as  saurians,  but  by 
Herman  von  Meyer  as  most 
nearly  allied  to  the  Laby- 
rinthodon  before  mentioned 
(p.  445),  and,  therefore,  as 
having  many  characters  in- 
termediate between  batra- 
chians  and  saurians.  The 
remains  of  the  extremities 
leave  no  doubt  that  they 
were  quadrupeds,  "  provid- 
ed," says  Von  Meyer,  "  with  hands  and  feet  terminating  in  distinct 
toes;  but  these  limbs  were  weak,  serving  only  for  swimming  or 

creeping."  The  same  anatomist  has  point- 
ed out  certain  points  of  analogy  between 
their  bones  and  those  of  the  Proteus  an- 
guinus ;  and  Professor  Owen  has  ob- 
served that  they  make  an  approach  to 
the  Proteus  in  the  shortness  of  their 
ribs.  Two  specimens  of  these  ancient 
reptiles  retain  a  large  part  of  the  outer 


Archegosanrua  minor,  Goldfuss.    Fossil  reptile  from 
the  coal-measures,  Saarbriick. 


Fig.  558. 


Imbricated  covering  of  skin  of 

Archegosaurua  medius,  Goldf. ; 

magnified.* 


*  Goldfuss,  Neue  Jenaische  Lit.  Zeit.,   1848 ;   and  Von  Meyer,   Quart.  Geol 
Journ.,  vol.  iv  Miscell.  p.  51. 


CP.  XXV.]       FOOTPRINTS  OF  AIR-BREATHltfG  REPTILES. 


507 


skin,  which  consisted  of  long,  narrow,  wedge-shaped,  tile-like,  and 
horny  scales,  arranged  in  rows  (see  fig.  558). 

Cheirotherian    Footprints   in     Coal-measures,    United    States. In 

1844,  the  very  year  when  the  Apateon  or  Salamander  of  the  coal 
was  first  met  with  in  the  country  between  the  Moselle  and  the 
Rhine,  Dr.  King  published  an  account  of  the  footprints  of  a  large 
reptile  discovered  by  him  in  North  America.  These  occur  in  the 
coal-strata  of  Greensburg,  in  Westmoreland  County,  Pennsylvania ; 
and  I  had  an  opportunity  of  examining  them  in  1846.  I  was  at  once 
convinced  of  their  genuineness,  and  declared  my  conviction  on  that 
point,  on  which  doubts  had  been  entertained  both  in  Europe  and  the 
United  States.  The  footmarks  were  first  observed  standing  out  in 
relief  from  the  lower  surface  of  slabs  of  sandstone,  resting  on  thin 
layers  of  fine  unctuous  clay.  I  brought  away  one  of  these  masses, 

Fig.  559. 


Scale  one-sixth  the  original. 

Slab  of  sandstone  from  the  coal-measures  of  Pennsylvania,  with  footprints  of  air 
breathing  reptile  and  casts  of  cracks. 


508 


FOOTPRINTS  OF 


[On.  XXV. 


which  is  represented  in  the  foregoing  drawing  (fig.  559).  It  dis- 
plays, together  with  footprints,  the  casts  of  cracks  (a,  a' )  of  various 
sizes.  The  origin  of  snch  cracks  in  clay,  and  casts  of  the  same,  has 
before  been  explained,  and  referred  to  the  drying  and  shrinking  of 
mud,  and  the  subsequent  pouring  of  sand  into  open  crevices.  It  will 
be  seen  that  some  of  the  cracks,  as  at  5,  c,  traverse  the  footprints, 
and  produce  distortion  in  them,  as  might  have  been  expected,  for  the 
mud  must  have  been  soft  when  the  animal  walked  over  it  and  left 


Fig.  560. 


Series  of  reptilian  footprints  in  the  coal-strata  of  Westmoreland  County,  Pennsylvania, 
a.  Mark  of  nail  ? 


Cii.  XXV.]  AIR-BREATHING  REPTILES.  509 

the  impressions  ;  whereas,  when  it  afterwards  dried  up  and  shrank,  it 
would  be  too  hard  to  receive  such  indentations. 

No  less  than  twenty-three  footsteps  were  observed  by  Dr.  King  in 
the  same  quarry  before  it  was  abandoned,  the  greater  part  of  them  so 
arranged  (see  fig.  560)  on  the  surface  of  one  stratum  as  to  imply  that 
they  were  made  successively  by  the  same  animal.  Everywhere  there 
was  a  double  row  of  tracks,  and  in  each  row  they  occur  in  pairs,  each 
pair  consisting  of  a  hind  and  fore  foot,  and  each  being  at  nearly  equal 
distances  from  the  next  pair.  In  each  parallel  row  the  toes  turn  the 
one  set  to  the  right,  the  other  to  the  left.  In  the  European  Cheiro- 
therium,  before  mentioned  (p.  443),  both  the  hind  and  the  fore  feet 
have  each  five  toes,  and  the  size  of  the  hind  foot  is  about  five  times 
as  large  as  the  fore  foot.  In  the  American  fossil  the  posterior  foot- 
print is  not  even  twice  as  large  as  the  anterior,  and  the  number  of 
toes  is  unequal,  being  five  in  the  hinder  and  four  in  the  anterior  foot. 
In  this,  as  in  the  European  Cheirotherium,  one  toe  stands  out  like  a 
thumb,  and  these  thumb-like  toes  turn  the  one  set  to  the  right,  and 
the  other  to  the  left.  The  American  Cheirotherium  was  evidently  a 
broader  animal,  and  belonged  to  a  distinct  genus  from  that  of  the 
triassic  age  in  Europe.* 

We  may  assume  that  the  reptile  which  left  these  prints  on  the 
ancient  sands  of  the  coal-measures  was  an  air-breather,  because  its 
weight  would  not  have  been  sufficient  under  water  to  have  made 
impressions  so  deep  and  distinct.  The  same  conclusion  is  also  borne 
out  by  the  casts  of  the  cracks  above  described,  for  they  show  that 
the  clay  had  been  exposed  to  the  air  and  sun,  so  as  to  have  dried  and 
shrunk. 

The  geological  position  of  the  sandstone  of  Greensburg  is  perfectly 
clear,  being  situated  in  the  midst  of  the  Appalachian  coal-field,  hav- 
ing the  main  bed  of  coal,  called  the  Pittsburg  seam,  above  mentioned 
(p.  501),  3  yards  thick,  100  feet  above  it,  and  worked  in  the  neigh 
borhood,  with  several  other  seams  of  coal  at  lower  levels.  The  im 
pressions  of  Lepidodendron,  Sigillaria,  Stigmaria,  and  other  charac- 
teristic carboniferous  plants  are  found  both  above  and  below  the  level 
of  the  reptilian  footsteps. 

Analogous  footprints  of  a  large  reptile  of  still  older  date  were 
afterwards  found  (1849)  at  Pottsville,  70  miles  N.E.  of  Philadelphia, 
by  Mr.  Isaac  Lea,  in  a  formation  of  red  shales,  called  No.  XI.  by 
Prof.  H.  D.  Rogers,  in  the  State  Survey  of  Pennsylvania,  and  re- 
ferred by  him  to  the  base  of  the  coal,  but  regarded  by  some  geolo- 
gists as  the  uppermost  part  of  the  Old  Red  Sandstone.  A  thickness 
of  1700  feet  of  strata  intervenes  between  the  footprints  of  Greens- 
burg,  before  described,  and  these  older  Pottsville  impressions.  In 
the  same  Red  Shale,  No.  XL,  the  "debatable  ground"  between  the 
Carboniferous  and  Devonian  group,  Prof.  H.  D.  Rogers  announced  in 

*  See  Lyell's  Second  Visit,  &c.,  vol.  ii.  p.  305. 


510  AIE-BREATHERS  IN  THE  COAL.  [On.  XXV. 

1851  that  he  had  discovered  other  footprints,  referred  by  him  to  three 
species  of  quadrupeds,  all  of  them  five-toed  and  in  double  rows,  with 
an  opposite  symmetry,  as  if  made  by  right  and  left  feet,  while  they 
likewise  display  the  alternation  of  fore  foot  and  hind  foot.  One  spe- 
cies, the  largest  of  the  three,  presents  a  diameter  for  each  footprint 
of  about  two  inches,  and  shows  the  fore  and  hind  feet  to  be  nearly 
equal  in  dimensions.  It  exhibits  a  length  of  stride  of  about  nine 
inches,  and  a  breadth  between  the  right  and  left  footsteps  of  nearly 
four  inches.  The  impressions  of  the  hind  feet  are  but  little  in  the 
rear  of  the  fore  feet.  The  animal  which  made  them  is  supposed  to 
have  been  allied  to  a  Saurian,  rather  than  to  a  Batrachian  or  Chelo- 
nian.  With  these  footmarks  were  seen  shrinkage  cracks,  such  as  are 
caused  by  the  sun's  heat  in  mud,  and  rain-spots,  with  the  signs  of  the 
trickling  of  water  on  a  wet,  sandy  beach  ;  all  confirming  the  conclu- 
sion derived  from  the  footprints,  that  the  quadrupeds  belonged  to  air- 
breathers,  and  not  to  aquatic  races. 

In  1852  the  first  osseous  remains  of  a  reptile  were  obtained  from 
the  coal-measures  of  America  by  Dr.  Dawson  and  myself.  We  de- 
tected them  in  the  interior  of  one  of  the  erect  Sigillarise  before  alluded 
to  as  of  such  frequent  occurrence  in  Nova  Scotia.  The  tree  was  about 
2  feet  in  diameter,  and  consisted,  as  usual,  of  an  external  cylinder  of 
bark,  converted  into  coal,  and  an  internal  stony  axis  of  black  sand- 
stone, or  rather  mud  and  sand  stained  black  by  carbonaceous  matter, 
and  cemented  together  with  fragments  of  wood  into  a  rock.  These 
fragments  were  in  the  state  of  charcoal,  and  seem  to  have  fallen  to  the 
bottom  of  the  hollow  tree  while  it  was  rotting  away.  The  skull,  jaws, 
and  vertebrae  of  a  reptile,  probably  about  2^-  feet  in  length  (Dendrer- 
peton  Acadianum,  Owen),  were  scattered  through  this  stony  matrix. 
The  shell,  also,  of  a  Pupa  (see  fig.  561,  p.  512),  the  first  land-shell  ever 
met  with  in  the  coal  or  in  beds  older  than  the  tertiary,  was  observed 
,  in  the  same  stony  mass.  Dr.  Wyman  of  Boston  pronounced  the  rep- 
tile to  be  allied  in  structure  to  Menobranchus  and  Menopoma,  species 
of  batrachians,  now  inhabiting  the  North  American  rivers.  The  same 
view  was  afterwards  confirmed  by  Professor  Owen,  who  also  pointed 
out  the  resemblance  of  the  cranial  plants  to  those  seen  in  the  skull  of 
Archegosaurus  and  Labyrinthodon*  Whether  the  creature  had  crept 
into  the  hollow  tree  while  its  top  was  still  open  to  the  air,  or  whether 
it  was  washed  in  with  mud  during  a  flood,  or  in  whatever  other  man- 
ner it  entered,  must  be  matter  of  conjecture. 

Footprints  of  two  reptiles  of  different  sizes  had  previously  been  ob- 
served by  Dr.  Harding  and  Dr.  Gesner  on  ripple-marked  flags  of  the 
lower  coal-measures  in  Nova  Scotia,  evidently  made  by  quadrupeds 
walking  on  the  ancient  beach,  or  out  of  the  water,  just  as  the  recent 
Menopoma  is  sometimes  observed  to  do. 

The  remains  of  a  second  and  smaller  species  of  Dendrerpeton,  D. 

*  Geol.  Quart.  Journ.,  vol.  ix.  p.  58. 


CH.  XXV.]  AIR-BREATHERS  IN  THE   COAL. 

Oweni,  were  also  found  accompanying  the  larger  one,  and  still  retain- 
ing some  of  its  dermal  appendages ;  and  in  the  same  tree  were  the 
bones  of  a  third  small  lizard-like  reptile,  Hylonomus  Lyelli,  7  inches 
long,  with  stout  hind  limbs,  and  fore  limbs  comparatively  slender 
supposed  by  Dr.  Dawson  to  be  capable  of  walking  and  running  on 
land.* 

In  1854,  Prof.  Owen  described  a  "sauroid  batrachian"  (Baphetes 
plankeps),  of  the  Labyrinthodon  family,  obtained  by  Dr.  Dawson  from 
the  coal  of  Pictou  in  Nova  Scotia.  In  1859,  another  species  of  Hylo- 
nomus, twice  as  large  as  that  above  mentioned,  was  met  with ;  and 
another  reptile  of  the  same  family,  but  distinct  genus,  was  obtained 
by  Dr.  Dawson,  named  by  Owen  Hylerpeton.  Lastly,  in  1862,  Mr. 
Marsh  discovered  in  the  coal-measures  of  the  South  Jospins  in  Nova 

OO 

Scotia,  two  large  caudal  biconcave  vertebrae,  supposed  at  first  to  be- 
long to  an  Enaliosor,  and  called  Eosaurus  Acadianus,  but  which, 
Mr.  Huxley  suggests,  may  probably  be  referable  to  a  labyrinthodont 
batrachian. 

Professor  Owen  had  announced  the  first  finding  of  fossil  reptilian 
remains  in  British  coal-measures  in  1853.  They  were  referred  to  a 
new  genus  of  Batrachoids  allied  to  Archegosaurus,  and  called  Para- 
batrachus.  In  1852,  a  large,  new  labyrinthodont  reptile,  Loxomma, 
from  the  Edinburgh  coal-field,  was '  described  by  Prof.  Huxley,  to- 
gether with  a  second,  from  the  same  series  of  strata,  of  another  new 
genus,  called  Pholidogaster,  a  specimen  of  which,  containing  the  head 
and  nearly  the  whole  vertebral  column,  measured  44  inches  in  length. 
In  the  same  year  a  third  genus,  denominated  Anthracosaurus,  was 
founded  by  the  same  anatomist  on  a  specimen  detected  by  Mr.  Eus 
sel  in  the  Airdrie  "  black-band  "  iron  of  the  Glasgow  coal-field.  This 
labyrinthodont  was  about  T  feet  long,  and  the  skull  15  inches  in 
length ;  thirty-seven  teeth  were  preserved  in  its  jaws,  and  its  vertebras 
were  highly  ossified,  so  as  to  resemble  those  of  the  Triassic  labyrintho- 
donts  of  the  Mastodonsaurian  type,  whereas  Pholidogaster  is  sup- 
posed by  Huxley  to  be  more  allied  to  the  Archegosaurian  division  of 
labyrinthodonts.f  Thus,  in  nineteen  years,  the  skeletons  or  bones 
of  twelve  or  more  species  of  reptiles  referred  to  nine  genera  have  been 
exhumed  from  the  coal-measures,  to  say  nothing  of  footprints,  some 
of  them,  like  that  represented  at  fig.  559,  seeming  to  differ  from  all 
those  to  which  any  of  the  known  bones  can  belong, 

A  single  species  of  land-shell,  Pupa  vetusta,  Dawson,  see  fig.  561, 
was  mentioned  as  having  been  found,  in  1852,  in  the  interior  of  an 
erect  fossil  Sigillaria  in  Nova  Scotia,  p.  510.  Dr.  Dawson  has  since 
discovered  another  bed  at  a  much  lower  level,  in  which  the  same  shell 
is  very  abundant,  a  bed  separated  from  the  tree  containing  Dendrer- 
peton  by  a  mass  of  strata  1217  feet  thick,  and  comprising  21  seams 

*  Dawson,  Air-Breathers  of  the  Coal  in  Nova  Scotia.     Montreal,  1863. 
f  Huxley,  Quart.  Geol.  Journ.,  1862,  1863. 


512 


AIR-BREATHERS  IN  THE  COAL. 
Fig.  56L 


[On.  XXV. 


a.  Pupa  vetusta,  Dawson.    Nat.  size. 
5.  The  same,  magnified. 
o.  View  of  the  depressed  apex. 
d.  Surface  striae,  magnified  50  diam. 


e.  Surface  striae,  of  the  recent  English  Pupa 
juniperi  for  comparison,  magnified  50 
diam. 

/.  Microscopic  structure  of  the  shell,  showing 
hexagonal  cells,  magnified  500  diam. 


of  coal.  This  lower  bed  is  an  underclay  7  feet  thick,  with  stigmarian 
rootlets,  and  the  small  land-shells  occurring  in  it  are  in  all  stages  of 
growth.  They  are  chiefly  confined  to  a  layer  about  2  inches  thick, 
and  are  unmixed  with  any  aquatic  shells.  They  were  all  originally 
entire  when  imbedded,  but  are  most  of  them  now  crushed,  flattened, 
and  distorted  by  pressure ;  they  must  have  been  accumulated,  says 
Dr.  Dawson,  in  mud  deposited  in  a  pond  or  creek.*  The  late  Prof. 
Quekett,  to  whom  I  submitted  the  first  specimen  found  in  1852  for 
microscopical  examination,  observed  that  the  surface  striae,  on  being 
magnified  50  diameters,  d,  fig.  561,  presented  exactly  the  same  appear- 
ance as  a  portion  corresponding  in  size  to  the  common  English  Pupa 
juniperi  (e,  fig.  561),  and  a  cross-section  of  the  fossil  shell  (/,  ibid.) 


a.  Nat.  size. 


Xylobius  Sigillarice,  Dawson.    Coal,  Nova  Scotia. 
&.  Anterior  part,  magnified.  c.  Caudal  extremity,  magnified. 


presents  the  hexagonal  cells  magnified  500  diameters,  so  like  those  of 
the  recent  Pupa  that  a  figure  of  the  latter  is  unnecessary.! 


*  Dawson,  Air-Breathers  of  the  Coal. 

|  Quart.  Geol.  Journ.   1853  vol.  is.  p.  68. 


CH.  XXV.]  AIR-BREATHERS  IN   THE  COAL. 

In  a  second  specimen  of  an  erect  stump  of  a  hollow  tree  15  inches 
in  diameter,  the  ribbed  bark  of  which  showed  that  it  was  a  Sigillaria, 
and  which  belonged  to  the  same  forest  as  the  specimen  examined  by 
us  in  1852,  Dr.  Dawson  obtained  not  only  fifty  specimens  of  Pupa 
vetusta  and  nine  skeletons  of  reptiles  belonging  to  four  species,  but  also 
several  examples  of  an  articulated  animal  resembling  the  recent  centi- 
pede or  gally-worm,  a  creature  which  feeds  on  decayed  vegetable  mat- 
ter, see  fig.  562.  Under  the  microscope,  the  head,  with  the  eyes, 
mandible,  and  labrum  are  well  seen.  It  is  interesting,  as  being  the 
earliest  known  representative  of  the  myriapods  none  of  which  had  pre- 
viously been  met  with  in  rocks  older  than  the  oolite  or  lithographic 
slate  of  Germany. 

Rarity  of  Vertebrate  and  Invertebrate  Air-breathers  in  Coal. 

Before  the  earliest  date  above  mentioned  (1844)  it  was  common  to 
hear  geologists  insisting  on  the  non-existence  of  vertebrate  animals  of 
a  higher  grade  than  fishes  in  the  Coal,  or  in  any  rocks  older  than  the 
Permian.  Even  now,  it  may  be  said  that  we  have  made  very  little 
progress  in  obtaining  a  knowledge  of  the  terrestrial  fauna  of  the  coal, 
since  the  reptiles  above  enumerated  seem  to  have  been  almost  all 
amphibious.  Negative  evidence  should  have  its  due  weight  in  palae- 
ontological  reasonings  and  speculations,  but  we  are  as  yet  quite  un- 
able to  appreciate  its  value.  In  the  United  States,  about  five  millions 
of  tons  of  coal  are  annually  extracted  from  the  coal-measures,  yet  I  am 
acquainted  with  no  fossil  insect  which  has  yet  been  met  with  in  the 
carboniferous  rocks  of  North  America.  But  as  we  have  detected  car- 
boniferous insects  in  Europe  (see  p.  494),  no  one  would  now  conclude 
that  at  the  period  of  the  Coal  this  class  of  invertebrata  was  unrepre- 
sented in  the  forests  of  the  Western  World.  In  like  manner,  no  land- 
shell,  no  Helix,  Bulimus,  Pupa,  or  Clausilia,  nor  any  aquatic  pulmonif- 
erous  mollusk,  such  as  Limnea  or  Planorbis,  is  recorded  to  have  come 
from  the  coal  of  Europe,  worked  for  centuries  before  America  was  dis- 
covered, and  now  quarried  on  so  enormous  a  scale.  But  no  one 
would  now  infer  that  land-shells  had  not  been  called  into  existence  in 
European  latitudes  until  after  the  Carboniferous  period. 

The  theory  of  progressive  development  might  account  plausibly  for 
the  absence  of  Chelonian  and  Saurian  reptiles,  or  of  Birds  and  Mam- 
mals, from  the  Coal-Measures,  because  it  may  be  supposed  that  at  so 
early  a  stage  in  the  earth's  history  no  organic  beings  higher  than 
sauroid  batrachians  had  made  their  appearance.  But  this  same  theory 
leaves  the  scarcity  of  the  invertebrata,  or  even  the  entire  absence  of 
many  important  sections  of  them,  wholly  unexplained.  When  we 
generalize  on  this  subject,  we  must  not  forget  that,  so  lately  as  the 
year  1851,  we  knew  of  only  two  or  three  individual  land-shells  and 
some  twenty  specimens  of  insects,  and  scarcely  double  that  number  of 
individual  reptiles  in  carboniferous  rocks,  and  some. of, .these  reptiles 
33 


514:  MOUNTAIN   LIMESTONE.  [On.  XXV. 

had  been  recognized  by  the  evidence  of  footprints  only.  We  have 
still  but  one  species  of  land-shell  and  one  centipede.  In  regard  to 
Archegosaurus,  of  which  there  are  two  species,  M.  Herman  von  Meyer 
informed  me  some  years  ago  that  the  remains  of  more  than  228  indi- 
viduals passed  through  his  hands  soon  after  the  true  nature  of  the  first 
specimen  was  recognized ;  and  we  have  seen  what  great  progress  has  since 
been  made  in  bringing  to  light  reptilian  genera  less  aquatic  in  their 
organization.  Nevertheless,  the  rarity  of  air-breathers  is  still  a  very 
remarkable  fact,  when  we  reflect  that  our  opportunities  of  examining 
strata  formed  in  close  connection  with  ancient  land  exceed  in  this  case 
all  that  we  enjoy  in  regard  to  any  other  formations,  whether  primary, 
secondary,  or  tertiary.  We  have  ransacked  hundreds  of  soils  re- 
plete with  the  fossil  roots  of  trees — have  dug  out  hundreds  of  erect 
trunks  and  stumps,  which  stood  in  the  position  in  which  they  grew 
— have  broken  up  myriads  of  cubic  feet  of  fuel  still  retaining  its  vege- 
table structure — and,  after  all,  we  continue  almost  as  much  in  the 
dark  respecting  the  invertebrate  air-breathers  of  this  epoch,  as  if  the 
Coal  had  been  thrown  down  in  mid-ocean.  The  early  date  of  the  car 
boniferous  strata  cannot  explain  the  enigma,  because  we  know  that 
while  the  land  supported  a  luxuriant  vegetation,  the  contemporaneous 
seas  swarmed  with  life — with  Articulata,  Mollusca,  Radiata,  and 
Fishes.  We  must,  therefore,  collect  more  facts,  if  we  expect  to  solve 
a  problem  which,  in  the  present  state  of  science,  cannot  but  excite 
our  wonder ;  and  we  must  remember  how  much  the  conditions  of  this 
problem  have  varied  within  the  last  twenty  years.  We  must  be  con- 
tent to  impute  the  scantiness  of  our  data  and  our  present  perplexity 
partly  to  our  want  of  diligence  as  collectors,  and  partly  to  our  want 
of  skill  as  interpreters.  We  must  also  confess  that  our  ignorance 
is  great  of  the  laws  which  govern  the  fossilization  of  land-animals, 
whether  of  high  or  low  degree. 


CARBONIFEROUS    OR   MOUNTAIN   LIMESTONE. 

It  has  been  already  stated  (p.  466),  that  this  formation  underlies 
the  Coal-Measures  in  the  South  of  England  and  Wales,  whereas  in 
the  North  and  in  Scotland  marine  limestones  alternate  with  Coal- 
Measures,  or  with  shale  and  sandstones,  sometimes  containing  seams 
of  Coal.  In  its  most  calcareous  form  the  Mountain  Limestone  is 
destitute  of  land-plants,  and  is  loaded  with  marine  remains — the 
greater  part,  indeed,  of  the  rock  being  made  up  bodily  of  corals  and 
crinoids. 

The  Corals  deserve  special  notice,  as  the  cup  and  star  corals,  which 
have  the  most  massive  and  stony  skeletons,  display  peculiarities  of 
structure  by  which  they  may  be  distinguished,  as  MM.  Milne  Edwards 
and  Haime  first  pointed  out,  from  all  species  found  in  strata  newer 
than  the  Permian.  There  is,  in  short,  an  ancient  or  Palceozoic,  and  a 


Cu.  XXV.]          FOSSILS  OF  THE   MOUNTAIN  LIMESTONE. 


515 


modern  or  Neozoic  type,  if,  by  the  latter  term,  we  designate  (as  pro- 
posed by  Prof.  E.  Forbes)  all  strata  from  the  triassic  to  the  most  mod- 
ern, inclusive.  The  accompanying  diagrams  (figs.  563,  564)  may 

Fig.  563. 

Palaeozoic  type  of  lamelliferous  cup-shaped  Coral.    Order  ZOANTHABIA  BUGOSA,  Milne  Ed- 
wards and  Jules  Haime. 

a.  Vertical  section  of  Campophyllum  fleayuoawm  (Oyo- 

thophyllum,  Goldfuss) ;  f  nat.  size :  from  the  Devo- 
nian of  the  Eitel.  The  lamellae  are  seen  around  the 
inside  of  the  cup ;  the  walls  consist  of  cellular  tis- 
sue; and  large  transverse  plates,  called  tabulae,  di- 
vide the  interior  into  chambers. 

b.  Arrangement  of  the  lamellae  in  Polycelia  profunda, 

Germar,  sp. ;  nat  size:  from  the  Magnesian  Lime- 
stone, Durham.  This  diagram  shows  the  quadripar- 
tite arrangement  of  the  lamellae  characteristic  of 
palaeozoic  corals,  there  being  4  principal  and  8  inter- 
mediate lamellae,  the  whole  number  in  this  type 
being  always  a  multiple  of  4. 

c.  Stauria  astrceformis,  Mime  Edwards.    Young  group, 

nat  size.  Upper  Silurian,  Gothland.  The  lamellae 
in  each  cup  are  divided  by  4  prominent  ridges  into  4 
groups. 


Fig.  564. 

Neozoic  type  of  lamelliferous  cup-shaped  Coral.    Order  ZOANTHABIA  APOBOSA,  M.  Edwards 

and  J.  Haime. 

a.  Parasmilia  centralis,  Man  tell,  sp.     Vertical  section,  nat 

size.  Upper  chalk,  Gravesend.  In  this  type  the  lamella 
are  massive,  and  extend  to  the  axis  of  loose  cellular  tissue, 
without  any  transverse  plates  like  those  in  fig.  563  a. 

b.  Cyalhina  Bowerbarikii,  Edwards  and  Haime.    Transverse 

section,  enlarged.  Gault,  Folkestone.  In  this  coral  the 
lamellae  are  a  multiple  of  six.  The  twelve  principal  plates 
reach  the  central  axis  or  columella,  and  between  each  pan- 
there  are  three  secondary  plates,  in  all  forty-eight  The 
short  intermediate  plates  which  proceed  from  the  columella 
are  not  counted.  They  are  called  paU. 

c.  Fungia  patellaris,  Lamk.    Eecent :  very  young  state.    Dia- 

gram of  its  eix  principal  and  six  intermediate  septa,  mag- 
nified. The  sextuple  arrangement  is  always  more  manifest 
in  the  young  than  in  the  adult  state. 

illustrate  these  types ;  and,  although  it  may  not  always  be  easy  for  any 
but  a  practised  naturalist  to  recognize  the  points  of  structure  here  de- 
scribed, every  geologist  should  understand  them,  as  the  reality  of  the 
distinction  is  of  no  small  theoretical  interest. 

It  will  be  seen  that  the  more  ancient  corals  have  what  is  called  a 
quadripartite  arrangement  of  the  stony  plates  or  lamellae — parts  of 
the  skeleton  which  support  the  organs  of  reproduction.  The  number 
of  these  lamellae  in  the  palaeozoic  type  is  4,  8,  16,  &c. ;  while  in  the 
newer  type  the  number  is  always  6,  12,  24,  or  some  other  multiple 
of  six ;  and  this  holds  good,  whether  they  be  simple  cup-like  forms, 
as  in  figs.  563  a  and  564  a,  or  aggregate  clusters  of  cups,  as  in  564  c. 

It  is  not  enough,  therefore,  to  say  that  the  primary  or  more  ancient 
corals  are  generically  and  specifically  dissimilar  from  the  secondary, 
tertiary,  and  living  corals, — for,  more  than  this,  all  the  most  conspicu- 


516 


FOSSILS  OF  THE   MOUNTAIN  LIMESTONE.          [On.  XXY. 


ous  forms,  viz.,  the  cup  and  star  corals,  belong,  as  before  mentioned 
(p.  515),  to  a  distinct  order,  although  they  are  often  so  like  in  out- 
ward form  as  to  have  boen  referred  in  many  cases  to  living  reef-build- 
ing genera.  Hence  we  must  not  too  confidently  draw  conclusions 
from  the  modern  to  the  palaeozoic  polyps,  respecting  climate  and  the 
temperature  of  the  waters  of  the  primeval  seas,  inasmuch  as  the  two 
groups  of  zoophytes  are  constructed  on  essentially  different  types. 
When  the  great  number  of  the  palaeozoic  and  neozoic  species  is  taken 
into  account,  it  is  truly  wonderful  to  find  how  constant  the  rule  above 


Fig.  565. 


Fig.  566. 


Liihostrotion  basaltiforme,  Phil.  sp.  (Li- 
thostrotion  striatum,  Fleming;  Astrcea 
bcwaltiformis,  Conyb.  and  Phill.)  Ken- 
dall; Ireland;  Kussia;  Iowa,  and  west- 
ward of  the  Mississippi,  United  States. 
(D.  D.  Owen.) 


Lonadalwa  floriformia  (Martin,  sp.),  M. 

Edwards.      (Lithostrotion  floriforme, 

Fleming.    /Strombodes.) 
a.  Young  specimen,  with  buds  on  the 

disk. 
&.  Part  of  a  full-grown  compound  mass. 

Bristol,  &c. ;  Bussia. 


explained  holds  good ;  only  one  exception  having  as  yet  occurred 
of  a  quadripartite  coral  in  a  neozoic  formation  (the  cretaceous),  and 
one  only  of  the  sextuple  class  (a  Fungia  ?)  in  palaeozoic  (Silurian) 
rocks. 

From  a  great  number  of  lamelliferous  corals  met  with  in  the  Moun- 
tain Limestone,  two  species  have  been  selected,  as  having  a  very  wide 
range,  extending  from  the  eastern  borders  of  Russia  to  the  British 
Isles,  and  being  found  almost  everywhere  in  each  country. 

These  fossils,  together  with  numerous  species  of  Zaphrentis,  Am- 
plexus,  Cyathophyllum,  Clisiophyllum,  Syringopora,  and  Michelinea* 
form  a  group  widely  different  from  any  that  preceded  or  followed 
them. 

Of  the  Hryozoa,  the  prevailing  forms  are  Fenestella  and  Polypora, 
and  these  often  form  considerable  beds.  Their  net-like  fronds  are 
easily  recognized. 

Crinoidea  are  also  numerous  in  the  Mountain  Limestone.  (See  figs. 
567,  568.) 


*  For  figures  of  these  corals,  see  PaUeontographical  Society's  Monographs,  1852. 


CH.  XXV.]          FOSSILS  OF  THE  MOUNTAIN  LIMESTONE. 


517 


Fig.  56T. 


Fig.  568. 


Cyathocrinites  planus,  Miller. 
Body  and  arms.  Mountain 
Limestone. 


Cyathocrlnus  caryocrinoides,  M'Coy. 
a.  Surface  of  one  of  the  joints  of  the  stem. 
&,  Pelvis  or  body ;  called  also  calyx  or  cup. 
c.  One  of  the  pelvic  plates. 


In  the  greater  part  of  them,  the  cup  or  pelvis,  fig.  568  6,  is  greatly 
developed  in  size  in  proportion  to  the  arms,  although  this  is  not  the 
case  in  fig.  567.  The  genera  Poteriocrinus,  Cyathocrinus,  Pentremites, 
Antinocrinus,  and  Platycrinm  are  all  of  them  characteristic  of  this 
formation.  Other  Echinoderms  are  rare,  a  few  Sea-Urchins  only  being 
known :  these  have  a  complex  structure,  with  many  more  plates  on 
their  surface  than  are  seen  in  the  modern  genera  of  the  same  group. 
One  genus,  the  Palcechinus  (fig.  569),  is  the  analogue  of  the  modern 


Fig.  569. 


Fig.  570. 


Palcechinus  gigas,  M'Coy.    Keduced. 

Mountain  Limestone. 

Ireland. 


Producing  semireticulatus,  Martin,  ep. 
(P.  antiquatus,  Sow.)  Mountain  Lime- 
stone. England ;  Eussia ;  the  Andes,  &c. 


JZchinus.  The  other,  Archceocidaris,  represents,  in  like  manner,  the 
Cidaris  of  the  present  seas. 

Of  Mollusca  the  JBrachiopoda  (or  Palliobranchiates)  constitute  the 
larger  part,  and  are  not  only  numerous,  but  often  of  large  size.  Per- 
haps the  most  characteristic  shells  of  the  formation  are  large  species 
of  Productus,  such  as  P.  giganteus,  P.  hemisphcericus,  P.  semireticulatus 
(fig.  570),  and  P.  scabriculus.  Large  plaited  spirifers,  as  Spirifer  stria- 
tus,  S.  rotundatus,  and  S.  trigonalis  (fig.  571),  also  abound;  and 
smooth  species,  such  as  Spirifer  glaber  (fig.  572),  with  its  numerous 
varieties. 

The  family  of  the  brachiopoda  to  which  these  shells  belong,  is  far 


518 


FOSSILS  OF  THE  MOUNTAIN  LIMESTONE.          [On.  XXV. 
Fig.  5Tt  *'1-  572. 


Spirifer  trigonalia,  Martin,  sp. 
Mountain  Limestone,    Derbyshire,  &c. 


Spirifer  gldber,  Martin,  sp. 
Mountain  Limestone. 


more  numerously  represented  in  these  carboniferous  rocks  than  in  the 
secondary  formations  described  in  former  chapters;  individually,  as 
Professor  Ramsay  has  observed,*  they  may  outnumber  the  lamellibran- 
chiate  mollusks,  although  the  species  of  carboniferous  lamellibranchiate 
more  than  double  the  contemporary  brachiopoda.  The  increasing  num 
ber  of  the  last-mentioned  group  among  the  bivalve  mollusca,  both  in 
genera,  species,  and  individuals,  will  be  found  to  be  a  marked  feature 
in  the  fauna  of  the  primary  rocks  the  lower  we  descend  in  the  series. 
Among  the  brachiopoda  or  palliobranchiate  mollusks,  Terebratula 
hastata  deserves  mention,  not  only  for  its  wide  range,  but  because  it 
often  retains  the  pattern  of  the  original  colored  stripes  which  orna- 
mented the  living  shell.  (See  fig.  573.)  These  colored  bands  are  also 
preserved  in  several  lamellibranchiate  bivalves,  as  in  Aviculopecten 
(fig.  574),  in  which  dark  stripes  alternate  with  a  light  ground.  In  some 
also  of  the  spiral  univalves,  the  pattern  of  the  original  painting  is  dis 
tinctly  retained,  as  in  Pleurotomaria  (fig.  575),  which  displays  wavy 
blotches,  resembling  the  coloring  in  many  recent  Trochidoe. 


Fig.  578. 


Fig.  574. 


Fig.  575. 


Terebratula  hastata,  Sow., 
with  radiating  bands  of 
color.  Mountain  Lime- 
stone. Derbyshire ;  Ire- 
land ;  Russia,  &c. 


Aviculopecten  sublobatus, 
Phill.  Mountain  Lime- 
stone, Derbyshire ; 
Yorkshire. 


Pleurotomaria  carinata,  Sow. 

(P.  ftammigera,  Phill.) 
Mountain    Limestone.      Derby- 
shire, &c. 


The  mere  fact  that  shells  of  such  high  antiquity  should  have  pre- 
served the  patterns  of  their  coloring  is  striking  and  unexpected ;  but 
Professor  E.  Forbes  has  deduced  from  it  an  important  geological  con- 
clusion. He  infers  that  the  depth  of  the  primeval  seas  in  which  the 
Mountain  Limestone  was  formed  did  not  exceed  fifty  fathoms.  To 


*  Geol.  Quart.  Journ.,  p.  41,  1864. 


CH.  XXV.]          FOSSILS  OF  THE  MOUNTAIN  LIMESTONE. 


519 


this  opinion  he  is  led  by  observing  tliat  in  the  existing  seas  the  testa- 
cea  which  have  colors  and  well-defined  patterns  rarely  inhabit  greatet 
depths  than  50  fathoms ;  and  the  greater  number  are  found  where 
t*here  is  most  light  in  very  shallow  water,  not  more  than  two  fathoms 
deep.  There  are  even  examples  in  the  British  seas  of  testacea  which 
are  always  white  or  colorless  when  taken  from  below  100  fathoms ; 
and  yet  individuals  of  the  same  species,  if  taken  from  shallower  zones, 
are  vividly  striped  or  banded. 

This  information,  derived  from  the  color  of  the  shells,  is  the  more 
welcome,  because  the  Radiata,  Articulata,  and  Mollusca  of  the  Car- 
boniferous period  belong  almost  entirely  to  genera  no  longer  found  in 
the  living  creation,  and  respecting  the  habits  of  which  we  can  only 
hazard  conjectures. 

Some  few  of  the  carboniferous  mollusca,  such  as  Avicula,  Nucula, 
Solemya,  and  Lithodomus,  belong  no  doubt  to  existing  genera ;  but 
the  majority,  though  often  referred  to  living  types,  such  as  Isocardia, 
Turritella,  and  Buccinum,  belong  really  to  forms  which  appear  to 
have  become  extinct  at  the  close  of  the  Palaeozoic  epoch.  Euom- 
pkalus  is  a  characteristic  univalve  shell  of  this  period.  In  the  inte- 

Fig.  576. 


Euomphalua  pentagulatus,  Sowerby.    Mountain  Limestone. 

a.  Upper  side.  5.  Lower,  or  umbilical  side.  o.  View  showing  mouth,  which  is  less 
pentagonal  in  older  individuals,  d.  View  of  polished  section,  showing  internal 
chambers. 

rior  it  is  often  divided  into  chambers  (fig.  576  d),  the  septa  or  parti- 
tions not  being  perforated  as  in  foraminiferous  shells,  or  in  those 
having  siphuncles,  like  the  Nautilus.  The  animal  appears  to  have 
retreated  at  different  periods  of  its  growth  from  the  internal  cavity 
previously  formed,  and  to  have  closed  all  communication  with  it  by 


520 


FOSSILS   OF  THE 


[Cn.  XXV. 


rig.  577.  a  septum.     The  number  of  chambers  is  irregu- 

lar, and  they  are  generally  wanting  in  the  in- 
nermost whorl.  The  animal  of  the  recent  Tur- 
ritella  communis  partitions  off  in  like  manner  as 
it  advances  in  age  &  part  of  its  spire,  forming  a 
shelly  septum. 

Nearly  twenty  species  of  the  genus  Bellero- 
Beiiwophon  costatus,  Sow.   phon  (see  fig.  577),  a  shell  without  chambers 

Mountain  Limestone.         ^  ^  ^^  Argonaut?  occur  jn  the   Mountain 

Limestone.  The  genus  is  not  met  with  in  strata  of  later  date.  It  is 
most  generally  regarded  as  belonging  to  the  Heteropoda,  and  allied  to 
the  Glass-Shell,  Carinaria  ;  but  by  some  few  it  is  thought  to  be  a 
simple  form  of  Cephalopod. 

The  carboniferous  Cephalopoda  do  not  depart  so  widely  from  the 
living  type  (the  Nautilus)  as  do  the  more  ancient  Silurian  representa* 
tives  of  the  same  order;  yet  they  offer  some  remarkable  forms 
scarcely  known  in  strata  newer  than  the  coal.  Among  these  is 
Orthoceras,  a  siphuncled  and  chambered  shell,  like  a  Nautilus  un- 
coiled and  straightened  (fig.  578).  Some  species  of  this  genus  are 

Fig.  57& 


Portion  of  OrtTtoceras  laterals,  Phillips.    Mountain  Limestone. 

several  feet  long.  The  Goniatite  is  another  genus,  nearly  allied  to  the 
Ammonite,  from  which  it  differs  in  having  the  lobes  of  the  septa  free 
from  lateral  denticulations,  or  crenatures  ;  so  that  the  outline  of  these 
is  continuous  and  uninterrupted. 


Fig.  579. 


Fig.  580. 


GoniaMtes  crentetria,  PhilL    Mountain  Lime- 
stone.   N.America;  Britain;  Germany,  &c, 
a.  Lateral  view. 
6.   Front  view,  showing  the  mouth. 


Goniatites  ewolutus,  Phillips. 

Mountain  Limestone. 

Yorkshire. 


The  species  represented  in  fig.  579  is  found  in  almost  all  localities, 
and  presents  the  zigzag  character  of  the  septal  lobes  in  perfection. 

In  another  species  (fig.  580),  the  septa  are  but  slightly  waved,  and 
*o  approach  nearer  to  the  form  of  those  of  the  Nautilus.  The  dorsal 


CH.  XXV.] 


LOWER  CARBONIFEROUS  STRATA. 


521 


position  of  the  siphuncle,  however,  clearly  distinguishes  the  Goniatite 
from  the  Nautilus,  and  proves  it  to  have  belonged  to  the  family  of 
the  Ammonites,  from  which,  indeed,  some  authors  do  not  believe  it 
to  be  generically  distinct. 

Fossil  Fish. — The  distribution  of  these  is  singularly  partial ;  so 
much  so,  that  M.  de  Koninck  of  Liege,  the  eminent  palaeontologist, 
once  stated  to  me  that,  in  making  his  extensive  collection  of  the  fos- 
sils of  the  Mountain  Limestone  of  Belgium,  he  had  found  no  more 
than  four  or  five  examples  of  the  bones  or  teeth  of  fishes.  Judging 
from  Belgian  data,  he  might  have  concluded  that  this  class  of  verte- 
brata  was  of  extreme  rarity  in  the  carboniferous  seas;  whereas  the 
investigation  of  other  countries  has  led  to  quite  a  different  result. 
Thus,  near  Clifton,  on  the  Avon,  there  is  a  celebrated  "  bone-bed," 
almost  entirely  made  up  of  ichthyolites ;  and  the  same  may  be  said 
of  the  "  fish-beds  "  of  Armagh,  in  Ireland.  They  consist  chiefly  of 
the  teeth  of  fishes  of  the  Placoid  order,  nearly  all  of  them  rolled  as 
if  drifted  from  a  distance.  Some  teeth  are  sharp  and  pointed,  as  in 
ordinary  sharks,  of  which  the  genus  Cladodus  affords  an  illustration  ; 
but  the  majority,  as  in  Psammodus  and  Cochliodus,  are,  like  the  teeth 
of  the  Cestracion  of  Port  Jackson  (see  above,  fig.  322,  p.  330),  mas- 
sive palatal  teeth  fitted  for  grinding.  (See  figs.  581,  582.) 


Fig.  581. 


Fig.  582. 


Psammodus  porosus,  Agass.    Bone-bed,  Moun 
tain  Limestone.    Bristol ;  Armagh. 


Cochliodus  contortus,  Agass.  Bone- 
bed,  Mountain  Limestone.  Bris- 
tol; Armagh. 


There  are  upwards  of  seventy  other  species  of  fossil  fish  known,  in 
the  Mountain  Limestone  of  the  British  Islands.  The  defensive  fin- 
bones  of  these  creatures  are  not  unfrequent  at  Armagh  and  Bristol ; 
those  known  as  Oracanthus  are  often  of  a  very  large  size.  Ganoid 
fish,  such  as  Holoptychius,  also  occur ;  but  these  are  far  less  numer- 
ous. The  great  Megalichthys  ffibberti  appears  to  range  from  the 
Upper  Coal-measures  to  the  lowest  Carboniferous  strata, 

Foraminifera. — In  the  upper  part  of  the  Mountain  Limestone  group 
in  the  S.W.  of  England,  near  Bristol,  limestones  having  a  distinct 
oolitic  structure  alternate  with  shales.  In  these  rocks  the  nucleus  of 
every  minute  spherule  is  seen,  under  the  microscope,  to  consist  of 
a  small  rhizopod  or  foraminifer.  This  division  of  the  lower  animals, 
which  is  represented  so  fully  at  later  epochs  by  the  Nummulites  and 
their  numerous  minute  allies,  appears  in  the  Mountain  Limestone  to 


522  MOUNTAIN  LIMESTONE.  [Cn.  XXV. 

be  restricted  to  a  very  few  species,  among  which  Textularia,  Nodo- 
saria,  Endothyra,  and  Fusulina  (fig.  583),  have  been 
Fig.  5S3.  recognized.     The  first  two  genera  are  common  to 

this  and  all  the  after  periods ;  the  third  has  been 
found  in  the  Upper  Silurian,  but  is  not  known  above 
the   Carboniferous   strata ;    the  fourth  (fig.  583)  is 
drica,  D'Orb.       peculiar  to  the  Mountain  Limestone,  and  is  charac- 
Magnifled  3  diam.     teristic  of  faQ  formation  in  the  United  States,  Arctic 

Mountain  Lime-  _.        .  i    A    ••*«•• 

stone.  America,  Russia,  and  Asia  Minor. 


STRATA    CONTEMPORANEOUS    WITH   THE    MOUNTAIN   LIMESTONE. 

In  countries  where  limestone  does  not  form  the  principal  part  of 
the  Lower  Carboniferous  series,  this  formation  assumes  a  very  differ- 
ent character,  as  in  the  Rhenish  Provinces  of  Prussia,  and  in  the 
Hartz.  The  slates  and  sandstones  called  Kiesel-schiefer  and  Younger 
Greywacke  (Jungere  Grauwacke)  by  the  Germans,  were  formerly  re- 
ferred to  the  Devonian  group,  but  are  now  ascertained  to  belong  to 
the  "Lower  Carboniferous."  The  prevailing  shell  which  character- 
izes the  carbonaceous  schists  of  this  series,  both  on  the  Continent  and 

in  England,  is  Posidonomya  Becheri 
(fig.  584).  Some  well-known  moun- 
tain-limestone species,  such  as  Go- 
niatites  crenistria  (see  fig.  579),  and 
G.  reticulatus,  also  occur  in  the 
Hartz.  In  the  associated  sandstones 
of  the  same  region,  fossil  plants,  such 
as  Lepidodendron  and  the  allied  ge- 
Posidonomija  Secheri,  Gold.  nus  Sagenaria,  are  common  ;  also 

8yn.  Estheria  Secfieri.  T;r          •         si  i        •*          ci      i 

Lower  Carboniferous.  JTwoma,    Calamites    Suckovn,    and 

C.  transitionis,  Gopp.,  some  peculiar, 

others  specifically  identical  with  ordinary  coal-measure  fossils.  The 
true  geological  position  of  these  rocks  in  the  Hartz  was  first  deter- 
mined by  MM.  Murchison  and  Sedgwick  in  1840.* 


CARBONIFEROUS   LIMESTONE    IN   NORTH   AMERICA. 

The  coal-measures  of  Nova  Scotia  have  been  described,  page  484. 
The  lower  division  contains,  besides  large  stratified  masses  of  gypsum, 
some  bands  of  marine  limestone  almost  entirely  made  up  of  encri- 
nites,  and,  in  some  places,  containing  shells  of  genera  common  to  the 
mountain  limestone  of  Europe. 

In  the  United  States  the  carboniferous  limestone  underlies  the  pro- 

*  Trans.,  Geol.  Soc.  London,  Second  Series,  vol.  vi.  p.  228. 


CH.  XXVL]  OLD  RED  SANDSTONE.  533 

ductive  coal-measures  ;  and,  although  very  inconspicuous  on  the  mar- 
gin of  the  Alleghany  or  Great  Appalachian  coal-field  in  Pennsylvania, 
it  expands  in  Virginia  and  Tennessee.  Its  still  greater  extent  and 
importance  in  the  Western  or  Mississippi  coal-fields,  in  Kentucky, 
Indiana,  Iowa,  Missouri,  and  other  Western  States,  has  been  well 
shown  by  Dr.  D.  Dale  Owen.  In  those  regions  *  it  is  about  400  feet 
thick,  and  abounds,  as  in  Europe,  in  shells  of  the  genera  Productus 
and  Spirifer,  with  Pentremites,  and  other  crinoids  and  corals.  Among 
the  latter,  Lithostrotion  basaltiforme  or  striatum  (fig.  565,  p.  516),  or 
a  closely-allied  species  is  common. 


CHAPTER  XXVL 


OLD    BED    SANDSTONE,    OB    DEVONIAN    GEOUP. 

Old  Red  Sandstone  of  the  Borders  of  Wales—  Of  Scotland  and  the  South  of  Ire- 
land  —  Fossil  Devonian  plants  at  Kilkenny  —  Holoptychius  of  the  Middle  and 
Cephalaspifs  of  the  Lower  Old  Red  of  Forfarshire  —  Pterygotus  and  supposed 
eggs  of  Crustaceans  —  Northern  type  of  Old  Red  in  Scotland  —  Classification  of 
the  Ichthyolites  of  the  Old  Red,  and  their  relation  to  living  types  —  Distinct 
lithological  type  of  Old  Red  in  Devon  and  Cornwall  —  Term  "  Devonian  "  —  Or- 
ganic remains  of  intermediate  character  between  those  of  the  Carboniferous  and 
Silurian  systems  —  Devonian  series  of  England  and  the  Continent  —  Upper  Devo- 
nian rocks  and  fossils  —  Middle  —  Lower  —  Old  Red  Sandstone  of  Russia  —  Prepon- 
derance of  Brachiopoda  —  Devonian  strata  of  the  United  States  and  Canada  — 
Coral  reefs  at  the  falls  of  the  Ohio  —  Gaspe  Sandstone  —  Vegetation  of  the  Devo- 
nian period. 

IT  has  been  already  shown  in  the  section  (p.  431),  that  the  car- 
boniferous strata  are  surmounted  by  a  system  called  "  The  New 
Red,"  and  underlaid  by  another  termed  the  "  Old  Red  Sandstone." 
The  last-mentioned  group  acquired  this  name  because  in  Hereford- 
shire and  Scotland,  where  it  was  originally  studied,  it  consisted 
chiefly  of  red  sandstone,  shale,  and  conglomerate.  It  was  afterwards 
termed  "  Devonian,"  for  reasons  which  will  be  explained  in  the 
sequel.  For  many  years  it  was  regarded  as  very  barren  of  organic 
remains  ;  and  such  is  undoubtedly  its  character,  over  very  wide 
areas  where  calcareous  matter  is  wanting,  and  where  its  color  is  de- 
termined by  the  red  oxide  of  iron. 

"  Old  Red  "  in  Herefordshire,  &c.—  In  Herefordshire,  Worcester- 
shire, Shropshire,  and  South  Wales,  this  formation  attains  a  great 

*  Owen's  Geol.  Survey  of  Wisconsin,  &c.,  1852. 


524  OLD  RED  SANDSTONE.  [On.  XXVI 

thickness,  sometimes  between  8000  and  10,000  feet.  In  these  re- 
gions  it  has  been  subdivided  into 

1st  Conglomerate. 

2dly.  Brownstone  series  —  chiefly  reddish-green  and  brown  sand- 
stones, with  large  Eurypterus. 

3dly.  Marl  and  Cornstone  —  red  and  green  argillaceous  spotted 
marls,  with  irregular  courses  of  impure  concretionary  limestone,  pro- 
vincially  called  Cornstone,  and  some  beds  of  white  sandstone.  In 
the  cornstones,  and  in  those  flagstones  and  marls  through  which  cal- 
careous matter  is  most  diffused,  some  spines  of  fish  of  the  family 
Acanthodid.ee,  and  remains  of  Cephalaspis  and  Pteraspis  occur. 

4thly.  Ledbury  Shales  —  thin  olive  shales  of  Ledbury  and  Ludlow, 
and  sandstones  intercalated  in  thick  beds  of  red  marl.  Fish  of  the 
genera  Cephalaspis,  Auchenaspis,  &c.,  specifically  distinct  from  those 
of  the  underlying  Silurian. 

Old  Red  Sandstone  of  Scotland  and  Ireland.  —  South  of  the  Gram- 
pians, in  Forfarshire,  Kincardineshire,  and  Fife,  the  Old  Red  Sand- 
stone may  be  divided  into  three  groups  : 

A.  Yellow  sandstone. 

B.  Red  shale,  sandstone  with  cornstone,  and  at  the  base  a  con 

glomerate  (Nos.  1,  2,  and  3,  Section,  p.  48). 

C.  Roofing  and  paving  stone,  highly  micaceous,  and  containing  a 

slight  admixture  of  carbonate  of  lime  (No.  4,  p.  48). 

The  united  thickness  of  A,  B,  and  C,  in  Fife  and  Forfarshire,  must 
amount  to  3000  or  4000  feet  ;  and  perhaps  in  some  places,  where  the 
conglomerates  of  B  are  largely  developed,  to  much  more  than  4000. 

A,  —  The  upper  member,  or  yellow  sandstone,  is  seen  at  Dura  Den, 
near  Cupar,  in  Fife,  immediately  underlying  the  coal.  It  consists  of 
a  yellow  sandstone  in  which  fish  of  the  genera  Pterichthys  (for  genus 
see  fig.  600),  Pamphractus,  Bothriolepis,  Glyptopomus,  Holoptychius, 
and  others  abound. 

In  Ireland  the  upper  beds  of  the  Old  Red,  or  yellow  sandstone  oi 
Kilkenny,  contain  fish  of  the  genera  Coccosteus  and  Dendrodus, 
characteristic  forms  of  this  period,  together  with  plants  specifically 
distinct  from  any  known  in  the  coal-measures,  but  referable  to  the 
genera  found  in  them;  as,  for  example,  Lepidodendron,  Cyclopteris 


Fig.  585.  Fi*.  586. 


Stem  of  Lepidodendron,  so  compressed  as  Cyclopteris  Hibemica,  Forbes. 

to  destroy  the  quincunx  arrangement  of  Upper  Devonian,  Kilkenny, 

the  scars.    Upper  Devonian,  Kilkenny. 


CH.  XXVI.] 


OLD  RED   SANDSTONE. 


525 


Fig.  587. 


(see  figs.  585  and  586).  The  stems  of  the  latter  have,  in  some  speci- 
mens, broad  bases  of  attachment,  and  may  therefore  have  been  tree- 
ferns. 

In  the  same  strata  shells  having  the  form  of  the  genus  Anodon,  and 
which  probably  belonged  to  freshwater  testacea,  occur.  Some  geolo- 
gists, it  is  true,  still  doubt  whether  these  beds  ought  not  rather  to  be 
classed  as  the  lowest  beds  of  the  carboniferous  series,  together  with 
the  yellow  sandstone  of  Sir  K.  Griffiths  (see  p.  466) ;  but  the  asso- 
ciated ichthyolites  and  the  distinct  specific  character  of  the  plants, 
strongly  favor  the  opinion  above  expressed. 

B. — We  come  next  to  the  middle  division  of  the  "  Old  Bed,"  as 
exhibited  south  of  the  Grampians,  and  consisting  of — 1st,  red  shale 
and  sandstone,  with  some  cornstone, 
occupying  the  Valley  of  Strathmore, 
in  its  course  from  Stonehaven  to  the 
Firth  of  Clyde ;  and,  2dly,  of  a  con- 
glomerate, seen  both  at  the  foot  of 
the  Grampians,  and  on  the  flanks. of 
the  Sidlaw  Hills,  as  shown  .in  the 
section  at  p.  48,  Nos.  1,  2,  and  3. 
In  the  uppermost  part  of  the  di- 
vision No.  1,  or  in  the  beds  which, 
in  Fife,  underlie  the  yellow  sand- 
stone, the  scales  of  a  large  ganoid 
fish,  of  the  genus  Holoptychius,  were 
first  observed  by  Dr.  Fleming  at 
Clashbinnie,  near  Perth,  and  an  en- 
tire specimen,  more  than  2  feet  in 

length,  was  afterwards  found  by  Mr.  Noble.  Some  of  these  scales 
(see  fig.  587)  measured  3  inches  in  length  and  2-J  in  breadth. 


Scale  of  Holoptychius  nobiliasimua, 
Agass.    Clashbinnie.    Nat.  size. 


Holoptychiua.    As  restored  by  Professor  Huxley. 

For  tooth  of  this  genus,  see  p.  505,  fig.  556. 
a.  The  fringed  pectoral  fins.  c.  Anal  fin. 

6.  The  fringed  ventral  fins.  d ,  e.  Dorsal  fins. 


C   (Table,  p.   524).— The  third,  or  lowest  division  south  of  the 


526  FOSSILS  OF  THE  [Cn.  XXVI. 

Grampians  consists  of  gray  paving-stone  and  roofing-slate,  with  asso- 
ciated red  and  gray  shales  ;  these  strata  underlie  a  dense  mass  of  con- 
glomerate. In  these  gray  beds  several  remarkable  fish  have  been 
found  of  the  genus  named  by  Agassiz  Cephalaspis,  or  "buckler- 
headed,"  from  the  extraordinary  shield  which  covers  the  head  (see 
fig.  589),  and  which  has  often  been  mistaken  for  that  of  a  trilobite, 
such  as  Asaphus. 

Fig.  589. 


CepJialaspia  Lyellii,  Agass.  '  Length  6|  inches. 
From  a  specimen  in  my  collection  found  at  Glammiss,  in  Forfarsliire ;  see  other  figures, 

Agassiz,  vol.  ii.  tab.  1  a  and  1  6. 
a.  One  of  the  peculiar  scales  with  which  the  head  is  covered  when  perfect.    These  scales 

are  generally  removed,  as  in  the  specimen  above  figured, 
ft,  c.  Scales  from  different  parts  of  the  body  and  tail. 

A  species  of  Pteraspis,  of  the  same  family,  has  also  been  found  by 
the  Rev.  Hugh  Mitchell  in  beds  of  corresponding  age  in  Perthshire, 
and  Mr.  Powrie  enumerates  no  less  than  five  genera  of  the  family 
Acanthodidae,  the  spines,  scales,  and  other  remains  of  which  have 
been  detected  in  the  gray  flaggy  sandstones.* 

O        J  OO»7 

In  the  same  formation  at  Carmylie,  in  Forfarshire,  commonly 
known  as  the  Arbroath  paving-stone,  fragments  of  a  huge  crustacean 
have  been  met  with  from  time  to  time.  They  are  called  by  the 
Scotch  quarrymen  the  "  Seraphim,"  from  the  wing-like  form  and 
feather-like  ornament  of  the  thoracic  appendage,  the  part  most  usu- 
ally met  with.  Agassiz,  having  previously  referred  some  of  these 
fragments  to  the  class  of  fishes,  was  the  first  to  recognize  their  crus- 
tacean character,  and,  although  at  the  time  unable  correctly  to  deter- 
mine the  true  relation  of  the  several  parts,  he  figured  the  portions  on 
which  he  founded  his  opinion,  in  the  first  plate  of  his  "  Poissons 
Fossiles  du  Yieux  Ores  Rouge." 

A  restoration  in  correct  proportion  to  the  size  of  the  fragments  of 
P.  anglicus,  from  the  Lower  Old  Red  Sandstone  of  Perthshire  and 
Forfarshire,  would  give  us  a  creature  measuring  from  5  to  6  feet  in 
length,  and  more  than  1  foot  across ;  and  Mr.  Salter  is  of  opinion 
that  P.  proUematicus,  Ag.,  from  the  Downton  Sandstone,  and  P. 

*  Powrie,  Geol.  Quart.  Journ.,  vol.  xx  p.  4 IT. 


CH.  XXVI.] 


OLD  RED  SANDSTONE. 


527 


gigas,  Salt.,  from  the  Upper  Ludlow  Rock,  attained  dimensions  fully 
as  large,  even  up  to  7  feet. 


Fig.  590. 


Portion  of  the  Pterygotus  anglicus,  Agassiz. 

1.  Middle  portion  of  the  "  Seraphim,"  or  back  of  the  head,  with  the  scale-like  sculpturing. 

2.  Portion  of  the  dilated  base  of  one  of  the  anterior  feet,  with  its  strong  spines  or  teeth, 

used  as  masticating  organs. 

8.  The  proximal  portion  of  one  of  the  great  anterior  claws. 
4.  Termination  of  the  same,  with  the  serrated  pincers.    (See  Agass.,  Poiss.  Foss.  da  Vietuc 

Gres  Rouge,  plate  A.) 

1  and  2  are  of  the  natural  size ;  3  and  4  are  reduced  one-halt 


Pterygotus  anglicus.  Ag.,  Forfarshire. 
Ventral  aspect.  Restored  by  H.  Wood- 
ward, F.G.S.,  from  nearly  perfect  specimens 
of  allied  species,  found  in  the  Upper  Lud- 
low Rock  of  Lesmahagow. 

a.  Carapace,  showing  the  large  sessile 
eyes  at  the  anterior  angles. 

ft.  The  metastoma  or  post-oral  plate 
(serving  the  office  of  a  lower  lip). 

c.  c.  Chelate  appendages  (antennules). 

d.  First  pair  of  simple  palpi  (antenna}. 

e.  Second  pair  of  simple  palpi  (mandi- 
bles). 

f.  Third  pair  of  simple  palpi  (first  max- 
illa). 

ff.  Pair  of  swimming  feet  with  their 
broad  basal  joints,  whose  serrated  edges 
serve  the  office  of  maxillce. 

h.  Thoracic  or  genital  plate  covering  the 
reproductive  organs  (and  probably  also  the 
branchiae),  composed  of  two  broad  lateral 
alse,  and  a  slender  median  lobe,  varying  in 
form  according  to  the  sex.  This  thoracic 
plate  covers  the  first  two  thoracic  seg- 
ments, which  are  indicated  by  figures  and  a 
dotted  line. 

1-6.  Thoracic  segments. 

7-12.  Abdominal  segments. 
;    18.  Telson,  or  tail -plate. 


Fig:  591. 


The  largest  crustaceans  living  at  the  present  day  are  the  Inachus 
Kccmpferi  of  De  Haan,  from  Japan  (a  brachyurous  or  short-tailed 
crab),  chiefly  remarkable  for  the  extraordinary  length  of  its  limbs ; 
the  fore  arm  measuring  4  feet  in  length,  and  the  others  in  proportion, 


528  FOSSILS  OF  THE  [Cn.  XXVI. 

so  that  it  covers  about  25  square  feet  of  ground;  and  the  Limulus 
Moluccanus,  the  great  King  Crab  of  China  and  the  eastern  seas, 
which,  when  adult,  measures  1-j-  foot  across  its  carapace,  and  is  3  feet 
in  length. 

Parka  decipiens. — In  the  same  gray  paving-stones  and  coarse  roof- 
ing-slates in  which  the  Cephalaspis  and  Pterygotus  occur,  in  Forfar- 
shire  and  Kincardineshire,  the  remains  of  grass-like  plants  abound  in 
such  numbers  as  to  be  useful  to  the  geologist  by  enabling  him  to 
identify  corresponding  strata  at  distant  points.  Whether  these  be 
fucoids,  as  I  formerly  conjectured,  or  freshwater  plants  of  the  family 
Fluviales,  as  some  botanists  suggest,  cannot  yet  be  determined. 
They  are  often  accompanied  by  fossils,  called  "  berries "  by  the 
quarrymen,  and  which  are  not  unlike  the  form  which  a  compressed 
blackberry  or  raspberry  might  assume  (see  figs.  592  and  593).  Some 
of  these  were  first  observed  in  the  year  1828,  in  gray  sandstone  of 
the  same  age  as  that  of  Forfarshire,  at  Parkhill  near  Newburgh,  in 
the  north  of  Fife,  by  Dr.  Fleming.  I  afterwards  found  them  on  the 
north  side  of  Strathmore,  in  the  vertical  shale  beneath  the  conglom- 
erate, and  in  the  same  beds  in  the  Sidlaw  Hills,  at  all  points  where 
fig.  4  is  introduced  in  the  section,  p.  48. 

Dr.  Fleming  has  compared  these  fossils  to  the  panicles  of  a  Juncus, 
or  the  catkins  of  Sparganium,  or  some  allied  plant,  and  he  was  con- 
firmed in  this  opinion  by  finding  a  speeimen  at  Balrudderie,  showing 
the  under  surface  smoother  than  the  upper,  and  displaying  what  may 

Fig.  592.  Fig.  593. 


Parka  decipiens,  Fleming.  parlca  decipiens,  Fleming. 

In  sandstone  of  lower  beds  of  Old  Eed,  In  shale  of  lower  beds  of  Old  Bed,  Fife 

Ley's  Mill,  Forfarshire. 

Fig.  594.  be  the  place  of  attachment  of  a  stalk.     I  have  met 

with  some  specimens  in  Forfarshire  imbedded  in 
sandstone,  and  not  associated  with  the  leaves  of 
plants  (see  fig.  592),  which  bore  a  considerable  re- 
semblance to  the  spawn  of  a  recent  Natica  (fig. 

Fragment  of  spawn    5f94)'  ™  ^f  ^  ^  ™G  «™»ged  ™  *  thin  layer 

of  British  species  °     san<i>  and   seem  to  have  acquired  a  polygonal 

of  Natica.  form  by  pressing  against  each  other ;   but,  as  no 

gasteropodous  shells  have  been  detected  in  the  same 

formation,  the  Parka  has  probably  no  connection  with  this  class  of 

organisms. 


CH.  XXVI.] 


OLD  RED  SANDSTONE. 


529 


The  late  Dr.  Mantell  was  so  much  struck  with  the  resemblance  of 
one  of  my  specimens  (see  fig.  595)  to  a  small  bundle  of  the  dried-up 
eggs  of  the  common  English  frog,  which  he  had  obtained  in  a  black 
and  carbonaceous  state  (see  fig.  596)  from  the  mud  of  a  pond  near 


Fig.  595. 


Fossil.— Old  Bed. 


Fig.  595.    Slab  of  Old  Eed  Sandstone, * 
Fig.  596.  Forfarshire,  with  bodies  like  the  ova 

of  Batrachians. 

a.  Ova?  in  a  carbonized  state. 
&.  Egg-cells  ?  the  ova  shed. 

Fig.  596.    Eggs  of  the  common  frog, 
Rana  t&mporaria,  in  a  carbonized 
state,  from  a  dried-up  pond  in  Clap- 
ham  Common. 
a.  The  ova. 

&.  A    transverse    section   of  the 
mass,  exhibiting  the  form  of  the 
Eecent.  egg-cells.  J 


London,  that  he  suggested  a  batrachian  origin  for  the  fossil ;  and  Mr. 
Newport  concurred  in  the  idea,  adding  that  other  larger  and  more 
circular  fossils  (fig.  597),  which  I  procured  from  shale  in  the  same 
"  Old  Red,"  occurring  singly  or  in  pairs,  and  attached  to  the  leaves 
of  plants,  might  possibly  be  the  ova  of  some  gigantic  Triton  or  Sala- 
mander. 

Fig.  597. 


Fig.  59T.  Shale  of  Old  Eed  Sandstone,  or 
Devonian.  Forfarshire,  with  impres- 
sion of  plants  and  eggs  of  Crustaceans. 

a.  Two  pair  of  ova?  resembling  those 
of  large  Salamanders  or  Tritons. 

&,  &.  Detached  ova. 


The  general  absence  of  reptilian  remains  from  strata  of  the  Devonian 
period  always  weighed  strongly  with  most  geologists  against  such  con- 
jectures, and  Mr.  Salter  in  1859,  and  more  lately  Mr.  Powrie,  have 
suggested  that  Parka  decipiens  occurs  too  often  associated  with  Ptery- 
gotus  not  to  incline  one  to  suspect  that  they  are  the  eggs  of  that  crus- 
tacean. They  have  not  only  been  found  with  P.  anglicus  in  Forfar- 
shire and  Perthshire,  but  also  with  P.  problematicus  at  Ludlow,  and 
with  P.  ludensis  at  Kidderminster,  in  the  uppermost  Silurian  strata, 
Against  the  hypothesis  of  these  bodies  being  seed-vessels,  it  is  urged 
that  there  is  no  trace  of  a  style  nor  of  a  leafy  involucrum.  They  are 
supposed  to  have  constituted  a  single  layer  of  ova  enclosed  in  a  mem- 
brane, and  not  a  number  of  eggs  lying  crowded  one  over  the  other  in 
a  sack. 

"  Old  Red  "  in  the  North  of  Scotland.— -The  whole  of  the  northern 
part  of  Scotland,  from  Cape  Wrath  to  the  southern  flank  of  the  Gram- 
34 


530  "OLD  RED"  IN  THE  NORTH  OF  SCOTLAND.        [Cn.  XXVI. 

plans,  lias  been  well  described  by  the  late  Hugh  Miller  as  consisting 
of  a  nucleus  of  granite,  gneiss,  and  other  hypogene  rocks,  which  seem 
as  if  set  in  a  sandstone  frame.  The  beds  of  the  Old  Red  Sandstone 
constituting  this  frame  may  once  perhaps  have  extended  continuously 
over  the  entire  Grampians  before  the  upheaval  of  that  mountain  range ; 
for  one  band  of  the  sandstone  follows  the  course  of  the  Moray  Frith 
far  into  the  interior  of  the  Great  Caledonian  valley,  and  detached  hills 
and  island-like  patches  occur  in  several  parts  of  the  interior,  capping 
some  of  the  higher  summits  in  Sutherlandshire,  and  appearing  in 
Morayshire  like  oases  among  the  granite  rocks  of  Strathspey. 

As  the  mineral  character  of  the  "  Old  Red  "  north  of  the  Grampians 
differs  considerably  from  that  of  the  south,  especially  in  the  middle 
and  lower  divisions,  I  shall  now  allude  to  it  separately.  The  upper- 
most portion  was  formerly  supposed  to  include  certain  light-colored 
sandstones  near  Elgin  containing  reptilian  remains  (Telerpeton,  &c.), 
which  we  have  now  good  reason  to  suspect  are  of  much  newer  or 
Triassic  date  ;  *  but,  besides  these  whitish  sandstones,  there  are  others 
of  a  yellowish  color  near  Elgin,  which  are  perhaps  the  true  equivalents 
of  the  yellow  sandstone  of  Fife  (A,  p.  524).  This  upper  division 
passes  downwards  into  red  and  variegated  sandstone  and  conglomerate, 
which  may  correspond  with  the  beds  called  B  of  the  same  table, 
p.  524. 

In  this  part  of  the  series  certain  bituminous  schists  and  flagstones 
occur  in  the  Orkneys  and  Caithness,  Cromarty,  Moray,  Nairn,  and 
Banff,  which  are  very  rich  in  fossil  fishes.  Below  the  fish-beds  are 
sandstones  and  shales,  barren  of  organic  remains,  several  hundred  and 
sometimes  nearly  a  thousand  feet  thick.  As  the  ichthyolitic  zone  was 
the  lowest  in  which  fossils  had  been  discovered  in  the  North,  it  was 
classed  palaeontologically  by  Hugh  Miller  as  the  base  of  the  Old  Red 

*  Supposed  Reptilian  Remains  of  the  Old  Red. — In  a  former  edition  of  this  work 
I  noticed  the  discovery  of  the  bones  of  a  reptile  found  in  some  white  sandstone 
charged  with  carbonate  of  lime  forming  the  upper  part  of  a  long  series  of  conform- 
able strata  in  the  neighborhood  of  Elgin.  To  this  reptile  the  late  Dr.  Mantell  gave 
the  name  of  Telerpeton  Elginense  ;  it  was  associated  with  scales  or  scutes  supposed 
by  Agassiz  to  be  those  of  a  fish,  and  called  by  him  Stagonolepis,  but  which  Prof. 
Huxley  has  since  shown  to  be  crocodilian,  and  of  the  Teleosaurian  type.  The  jaw, 
teeth,  femur,  and  some  caudal  vertebra  have  now  been  found,  and  they  indicate  an 
animal  about  eight  feet  long.  Another  reptile,  Hyperodapedon,  Huxley,  closely 
allied  to  the  triassic  Rhynchosaurus,  has  also  been  met  with  in  the  same  beds,  so 
that  it  appears  highly  probable  that  the  light-colored  stones  near  Elgin  containing 
these  fossils  are  referable  to  the  Triassic,  and  not,  as  was  formerly  imagined,  to  the 
"  Old  Red,"  or  Devonian  period. 

The  strata  in  question  have  been  shown  in  1863  by  Prof.  Harkness  to  be  per- 
fectly conformable,  both  near  Elgin  and  in  Ross-shire,  with  sandstones  containing 
unequivocal  "  Old  Red  "  fishes,  but  between  these  and  the  reptiliferous  strata  there 
intervenes  everywhere  a  conglomerate,  and  Mr.  C.  Moore  has  justly  remarked 
(Harkness,  Geol.  Quart.  Journ.,  vol.  xx.  p.  429,  1864),  that  the  destruction  of  older 
rocks  attested  by  such  pebble  beds  may  imply  a  break  in  the  series,  and  a  lapse  of 
unrepresented  time  of  indefinite  extent. 


CH.  XXVI.]        FOSSIL  FISH  OF  THE  OLD  RED  SANDSTONE. 

system,  and  considered  by  him  to  be  older  than  the  division  C,  of  the 
table,  p.  524,  or  those  paving-stones  and  roofing-slates  of  Forfarshire, 
which  contain  Cephalaspis  and  Pterygotus  before  described,  p.  526. 
He  fell  naturally  into  this  mistake  by  observing  that  the  fish-beds 
where  he  studied  them  most  carefully,  at  Cromarty,  were  in  almost 
immediate  juxtaposition  with  certain  crystalline  or  metamorphic  rocks, 
so  that  they  seemed  to  form  the  base  of  the  Devonian  system. 
Another  source  of  error,  says  Sir  R.  Murchison,  arose  from  the  grad- 
ual thinning  out  of  the  bituminous  and  calcareous  schists  and  flag 
stones  as  we  proceed  from  north  to  south.  Already  these  schists, 
when  we  reach  Nairn  and  Elgin,  are  represented  by  clays  with  calcare- 
ous nodules  only ;  and  this  is  still  more  the  case  at  Gamrie  in  Banff. 
Still  further  southwards  even  these  nodules  are  no  longer  traceable  in 
the  middle  portion  of  the  Old  Red  Sandstone.* 

Hence  the  relative  position  of  the  middle  and  lower  beds  could  not 
be  proved  by  direct  superposition,  the  Caithness  fish-beds  being  want- 
ing in  Forfarshire,  and  the  Forfarshire  Cephalaspis  beds  alike  absent 
in  Caithness.  But  all  doubt  as  to  the  true  order  of  superposition,  if  any 
still  remained,  was  set  at  rest  in  1861,  when  Mr.  Peach,  under  the  direc- 
tion of  Sir  R.  Murchison,  searching  for  fossils  in  Caithness,  found  in 
sandstones,  many  hundreds  of  feet  below  the  fish-zone,  undoubted  re- 
mains of  Pterygotus.  These  crustaceans  are  characteristic  of  the  Cepha- 
laspis zone,  and  have  never  been  found  in  the  great  fish-bed  of  the  mid- 
dle division  of  the  Old  Red.  This  discovery,  therefore,  confirmed  the 
anticipations  of  Sir  Roderick,  who  had  previously  maintained  that  the 
lower  sandstones  of  Caithness  were  the  equivalents  of  the  Forfarshire 
paving-stone,  and  of  certain  beds  of  Herefordshire  and  Shropshire, 
which  immediately  overlie  the  bone-bed  of  the  Upper  Ludlow.f 

Mr.  Powrie  remarks  that  very  few  genera  and  no  species  of  fish  are 
common  to  this  Lower  or  Cephalaspis  division,  and  to  the  Middle  or 
Caithness  beds,  whereas  no  such  marked  break  occurs  between  the 
ichthyic  forms  of  the  Middle  and  those  of  the  Upper  or  Yellow  Sand- 
stone division.J 


Classification  of  the  Fossil  Fish  of  the  Old  Red  Sandstone. 

The  fish  of  the  schists  and  flagstones  in  question  are  very  peculiar 
and  characteristic.  They  were  first  successfully  studied  by  the  late 
Hugh  Miller,  who  gave  an  admirable  description  and  restorations  of 
many  of  them.  They  were  also  the  subject  in  1844  of  a  special  mono- 
graph by  Agassiz,  in  which  he  described  no  less  than  sixty-five  British 
species  alone,  and  several  important  memoirs  on  Pterichthys  and  other 

*  Murchison,  Siluria,  3d  ed.,  p.  286,  1859. 

f  Powrie,  Geol.  Quart.  Journ.,  vol.  xiv.  p.  503,  1858 ;  and  Murchison,  Siluria, 
3d  ed.,  p.  280,  &c.,  1859. 
\  Powrie,  ibid.,  p.  428. 


532  FOSSIL  FISH  OF  THE  [On.  XXVI. 

genera  were  afterwards  published  by  Sir  P.  Egerton,  whose  labors  in 
this  field  (including  a  synopsis  of  all  the  genera  known  in  1857)  have 
been  acknowledged  by  Professor  Huxley  as  having  powerfully  con- 
tributed to  clear  up  his  ideas  when  he  undertook,  in  1861,  the  difficult 
task  of  classifying  these  fishes.  To  the  Russian  zoologist,  Pander,  we 
are  also  indebted  for  a  most  able  treatise  on  these  ichthyolites.  Pro- 
fessor Huxley's  masterly  essay  is  of  a  later  date  than  Pander's,  and 
contains  a  systematic  arrangement  of  the  British  Devonian  fish,  which, 
he  observes,  are  of  surpassing  interest,  as  comprising  the  oldest  assem- 
blage of  vertebrate  animals  of  which  we  can  be  said  to  have  any  toler- 
ably complete  knowledge ;  for  no  reptiles  have  yet  been  found  older 
than  those  of  the  coal,  and  the  Silurian  fish  are  confined  to  a  few 
isolated  specimens,  affording  us  a  very  scanty  insight  into  the  character 
of  the  piscine  fauna  anterior  to  the  period  of  the  Old  Red  Sandstone. 

The  Devonian  fish  were  referred  by  Agassiz  to  two  of  his  great 
orders,  namely,  the  Placoids  and  Ganoids.  Of  the  first  of  these,  which 
in  the  Recent  period  comprise  the  shark,  the  dog-fish,  and  the  ray,  no 
entire  skeletons  are  preserved,  but  fin-spines  called  Ichthyodorulites, 
and  teeth  occur.  On  such  remains  the  genera  Onchus,  Odontacanthus 
and  Ctenodus,  a  supposed  cestraciont,  and  some  others,  have  been 
established.  There  are  also  some  spiny  fish  of  a  family  called  Acan- 
thodidae,  not  yet  well  understood,  and  thought  by  Huxley  to  have 
some  connection  with  the  Placoids,  although  he  admits  that  they  may 
perhaps  have  still  more  claims  to  rank  with  the  Ganoids,  with  which 
they  have  been  usually  classed. 

Among  the  Ganoids  are  the  Cephalaspidse  (see  fig.  589,  p.  526),  rep- 
resented by  several  genera,  Cephalaspis,  Pteraspis,  &c.,  and  forming  a 
very  distinct  family,  but  having,  according  to  Huxley,  a  considerable 
relationship  with  the  sturgeon. . 

By  far  the  greater  number,  however,  of  the  Old  Red  Sandstone  fishes 
belong  to  a  sub-order  of  Ganoids  instituted  by  Huxley  in  1861,  and  for 
which  he  has  proposed  the  name  of  Crossopterygidce*  or  the  fringe- 
finned,  in  consideration  of  the  peculiar  manner  in  which  the  fin-rays 
of  the  paired  fins  are  arranged  so  as  to  form  a  fringe  round  a  central 
lobe,  as  in  the  Polypterus  (see  a,  fig.  598),  a  genus  of  which  there  are 


Polypterus.    See  Agassiz,  "  Keclierches  sur  les  Poissons  Fossiles." 

Living  in  the  Nile  and  other  African  rivers. 
a.  One  of  the  fringed  pectoral  fins,  c.  Anal  fin. 

&.  One  of  the  ventral  fins.  a.  Dorsal  fin,  or  row  of  finleis. 

Abridged  from  Kpocauroc,  crossotos,  a  fringe,  and  7rrepv£,  pteryx,  a  fin. 


CH.  XXVL]  OLD   RED  SANDSTONE.  533 

several  species  now  inhabiting  the  Nile  and  other  African  rivers.     The 
reader  will  at  once  recognize  in  Osteolepis  (fig.  599)  one  of  the  com 


Kestoration  of  Osteolepis.    Pander. 
Old  Eed  Sandstone,  or  Devonian. 

a.  One  of  the  fringed  pectoral  fins.  c.  Anal  fin. 

&.  One  of  the  ventral  fins.  d,  e.  Dorsal  fins. 

mon  fishes  of  the  Old  Red  Sandstone,  many  points  of  analogy  with 
Polypterus.  They  not  only  agree  in  the  structure  of  the  fin,  as  first 
pointed  out  by  Huxley,  but  also  in  the  position  of  the  pectoral,  ventral, 
and  anal  fins,  and  in  having  an  elongated  body  and  rhomboidal  scales. 
On  the  other  hand,  the  tail  is  more  symmetrical  in  the  recent  fish, 
which  has  also  an  apparatus  of  dorsal  finlets  of  a  very  abnormal  char- 
acter, both  as  to  number  and  structure.  As  to  the  dorsals  of  Osteolepis, 
they  are  regular  in  structure  and  position,  having  nothing  remarkable 
about  them,  except  that  there  are  two  of  them,  which  is  comparatively 
unusual  in  living  fish. 

Among  the  "  fringe-fumed  "  Ganoids  we  find  some  with  rhomboidal 
scales,  such  as  Osteolepis,  above  figured,  and  Diplopterus,  Glyptolcemus, 
and  Glyptopomus  ;  others  with  cycloidal  scales,  as  Holoptychius  (see 
fig.  588,  p.  525),  Dipterus,  <fec.  The  new  genus  Glyptolcemus,  founded 
by  Huxley  on  specimens  from  the  Devonian  yellow  sandstone  of  Dura 
Den  in  Fife,  is  remarkable  for  having  not  only  a  fringe  of  rays  entirely 
surrounding  a  central  lobe  in  the  pectoral  and  ventral  fins,  but  in  hav- 
ing the  same  structure  repeated  in  the  anal  and  both  the  dorsal  fins. 
In  the  genera  Dipterus  and  Diplopterus,  as  Hugh  Miller  pointed  out, 
and  in  several  other  of  the  fringe-finned  genera,  as  in  Gyroptychius  and 
Glytolepis,  the  two  dorsals  are  placed  far  backwards,  or  directly  over 
the  ventral  and  anal  fins. 

The  Asterolepis  was  a  ganoid  fish  of  gigantic  dimensions.  A.  As- 
musii,  Eichwald,  a  species  characteristic  of  the  Old  Red  Sandstone 
of  Russia,  as  well  as  that  of  Scotland,  attained  the  length  of  between 
20  and  30  feet.  It  was  clothed  with  strong  bony  armor,  embossed  with 
star-like  tubercles,  but  it  had  only  a  cartilaginous  skeleton.  The 
mouth  was  furnished  with  two  rows  of  teeth,  the  outer  ones  small  and 
fish-like,  the  inner  larger,  but  with  a  reptilian  character.  The  Astero- 
lepis occurs  also  in  the  Devonian  rocks  of  North  America. 

If  we  except  the  Placoids  already  alluded  to,  and  a  few  other 
families  of  doubtful  affinities,  all  the  Old  Red  Sandstone  fishes  are 
Ganoids,  an  order  so  named  by  Agassiz  from  the  shining  outer  surface 


534 


FOSSIL  FISH  OF  THE  OLD  BED  SANDSTONE.       [On.  XXVI. 


of  their  scales.  The  same  remark  would  hold  true  of  the  fish  of  the 
primary  and  secondary  formations  generally,  those  of  the  primary  and 
older  secondary  type  having  heterocercal  tails,  while  the  tails  of  those  of 
the  tertiary  rocks  are  almost  all  equilobed  or  homocercal,  like  the  vast  ma- 
jority of  living  fish ;  but  Prof.  Huxley  has  also  called  our  attention  to  the 
fact  that,  while  a  few  of  the  primary  and  the  great  majority  of  the  sec- 
ondary Ganoids  resemble  the  living  Lepidosteus,  or  bony  pike,  or  the 
Amia,  genera  now  found  in  North  American  rivers,  and  one  of  them, 
Lepidosteus,  extending  as  far  south  as  Guatemala,  the  Crossopterygii, 
or  fringe-finned  Ichthyolites,  of  the  Old  Red  are  closely  related  to  the 
African  Polypterus,  which  is  represented  by  five  or  six  species  now 
inhabiting  the  Nile  and  the  rivers  of  Senegal.  These  North  American 
and  African  Ganoids  are  quite  exceptional  in  the  living  creation ;  they 
are  entirely  confined  to  the  northern  hemisphere,  unless  some  species 
of  Polypterus  range  to  the  south  of  the  line  in  Africa ;  and,  out  of 
about  9000  living  species  of  fish  known  to  M.  Giinther,  and  of  which 
more  than  6000  are  now  preserved  in  the  British  Museum,  they  prob- 
ably constitute  no  more  than  27. 

All  the  living  fish,  exclusive  of  the  27  species  just  mentioned,  and 
the  Elasmobranchii  or  Placoids,  have  equilobed  or  homocercal  tails, 
and  are  called  Teleostei,  because  their  skeletons  are  perfectly  ossified.* 
The  living  Ganoids,  however,  most  resembling  those  of  the  primary 
and  secondary  periods,  namely,  the  Lepidostei  and  Polypteri,  have  also 
internal  skeletons  as  perfect  as  those  of  any  Telostei ;  and  we  find  the 
same  combination  of  a  hard  external  or  dermal  skeleton,  and  a  well- 
ossified  endo-skeleton  in  Dipterus,  one  of  the  Old  Red  Ganoids  already 
alluded  to.  In  this  respect,  therefore,  Dipterus  and  Polypterus  agree, 
although  they  differ  in  their  scales,  Dipterus  having  cycloidal,  and 

Polypterus  rhomboidal  scales.  Me- 
galichthys,  a  carboniferous  genus, 
agrees  with  Polypterus  in  the  form 
of  its  scales,  which  are  rhomboidal, 
while  its  internal  sketeton,  as  first 
observed  by  Huxley,  is  so  far  ossi- 
fied that  in  each  vertebra  there  is 
a  ring  or  hoop  of  bone. 

The  fossil  Ganoids,  therefore,  al- 
though generally  contrasted  with 
the  Teleostei,  cannot  be  said  to 
have  in  all  cases  imperfect  inter- 
nal skeletons  any  more  than  the 
most  typical  living  representatives 
of  the  order. 
Among  the  anomalous  forms  of 

upper  side,  snowing  o 

mouth :  as  restored  by  H.  Miller.         Old  Red   fishes  not   referable   to 


*  From 


,  teleos,  perfect,  and  otrreov,  osteon,  a  bone. 


OH.  XXVL]  STRATA  OF  SOUTH  DEVON.  535 

Huxley's  Crossopterygii  is  the  Pterichthys,  of  which  five  species 
have  been  found  in  the  middle  division  of  the  Old  Red  of  Scotland. 
Some  writers  have  compared  their  shelly  covering  to  that  of  Crusta- 
ceans, with  which,  however,  they  have  no  real  affinity.  The  wing- 
like  appendages,  whence  the  genus  is  named,  were  first  supposed  by 
Hugh  Miller  to  be  paddles,  like  those  of  the  turtle ;  and  there  can 
now  be  no  doubt  that  they  do  really  correspond  with  the  pectoral 
fins.  Professor  Huxley,  when  speaking  of  the  allied  genus  Coccosteus, 
has  speculated  on  its  relationship  with  the  Siluridse,  a  large  family  of 
living  Teleosteans,  the  bony  shields  covering  the  roof  of  the  cranium 
in  Coccosteus  being  compared  by  him  with  those  which  cover  the 
head  and  anterior  part  of  the  body  of  certain  Siluroids,  more  par- 
ticularly those  belonging  to  the  genus  Clarias. 

South  Devon  and  Cornwall. — Term  Devonian. — A  great  step  was 
made  in  the  classification  of  the  slaty  and  calciferous  strata  of  South 
Devon  and  Cornwall  in  1837,  when  a  large  portion  of  the  beds,  pre- 
viously referred  to  the  "  transition  "  or  Silurian  series,  were  found  to 
belong  in  reality  to  the  period  of  the  Old  Red  Sandstone.  For  this 
reform  we  are  indebted  to  the  labors  of  Professor  Sedgwick  and  Sir 
R.  Murchison,  assisted  by  a  suggestion  of  Mr.  Lonsdale,  who,  in  1837, 
after  examining  the  South  Devonshire  fossils,  perceived  that  some  of 
them  agreed  with  those  of  the  Carboniferous  group,  others  with  those 
of  the  Silurian,  while  many  could  not  be  assigned  to  either  system, 
the  whole  taken  together  exhibiting  a  peculiar  type,  but  of  intermediate 
character  between  the  older  and  newer  groups  alluded  to.  But  these 
palseontological  observations  alone  would  not  have  enabled  us  to  assign, 
with  accuracy,  the  true  place  in  the  geological  series  of  these  slate- 
rocks  and  limestones  of  South  Devon,  had  not  Messrs.  Sedgwick  and 
Murchison,  in  1836  and  1837,  discovered  that  the  culmiferous  or 
anthracitic  shales  of  North  Devon  belonged  to  the  Coal,  and  not,  as 
preceding  observers  had  imagined,  to  the  "  transition"  period. 

As  the  strata  of  South  Devon  here  alluded  to  are  far  richer  in 
organic  remains  than  the  red  sandstones  of  contemporaneous  date  in 
Herefordshire  and  Scotland,  the  new  name  of  the  "  Devonian  system  " 
was  proposed  as  a  substitute  for  that  of  Old  Red  Sandstone. 

The  link  supplied  by  the  whole  assemblage  of  imbedded  fossils, 
connecting  as  it  does  the  palaeontology  of  the  Silurian  and  Carbon- 
iferous groups,  is  one  of  the  highest  interest,  and  equally  striking 
whether  we  regard  the  genera  of  the  corals  or  of  the  shells.  The 
species  are  mostly  distinct  except  in  the  upper  group. 

The  rocks  of  this  group  in  South  Devon  consist,  in  great  part,  of 
green  chloritic  slates,  alternating  with  large  quartzose  slates  and  sand- 
stones. Here  and  there  calcareous  slates  are  interstratified  with  blue 
crystalline  limestone,  and  in  some  divisions  conglomerates,  passing 
into  red  sandstone.  But  the  whole  series  is  much  altered  and  dis- 
turbed by  the  intrusion  of  the  granite  of  Dartmoor  and  other  igneous 
rocks. 


536  DEVONIAN  SERIES.  [On.  XXVI. 

In  North  Devon,  on  the  contrary,  the  Devonian  group  has  been  less 
changed,  and  its  relations  to  the  overlying  carboniferous  rocks  or 
"  Culm  Measures  "  are  somewhat  more  clearly  seen.  The  following 
sequence  is  exhibited  in  the  coast  section  on  the  Bristol  Channel 
between  Barnstaple  and  the  North  Foreland.* 

Devonian  Series  in  North  Devon. 

f       fa.  Calcareous  brown  slates;   with  fossils,  some  of  them 

1.  J  common  to  the  Carboniferous  group,  but  most  of 
Upper  or  Pilton  J                   them  distinct.     (Barnstaple,  Pilton,  &c.) 

group.  {        [b.  Brown  and  yellow  sandstone,  with  marine  shells  and 

land-plants — Stigmaria,  Saffenaria,  and  others.    Bag- 
gy Point,  Marwood,  &c. 

2.  Hard  gray  and  reddish  sandstones  and  micaceous  flags,  with- 

out fossils,  resting  on  soft  greenish  schists  of  consider- 
able thickness.     (Morte  Bay,  Bull  Point,  &c.) 

3.  Calcareous  slates,  with  eight  or  nine  courses  of  limestone, 


Middle  or  Ilfra- 
combe  group. 


full  of  corals  and  shells  like  those  of  the  Plymouth  lime- 


stone, viz.,  Cyathophyllum  ccespitosurn,  see  fig.  606,  Fa- 
vosites  polymorpha,  see  fig.  605,  &c.      (Combe  Martin, 
Ilfracombe  Harbor,  &c.) 
C  4.  Hard,  greenish,  red,  and  purple  sandstones ;  with  occasional 
Lower  or  Linton  J  fossils,  Spirifers,  &c.     (Linton,  North  Foreland,  &c.) 

group.  1  5.  Soft  chloritous  slates,  with  some  sandstones  ;   Orthis,  JSpiri- 

fer,  and  Corals.     (Valley  of  Rocks,  Lynmouth,  &c.) 

The  successive  beds  of  this  section  have  been  compared  with  those 
of  South  Devon  and  Cornwall  both  by  the  authors  of  the  "  Devonian  " 
system  and  by  other  observers.  And  Professor  Sedgwick  has  again 
lately  brought  them  into  closer  comparison.f  Other  geologists  at 
home  and  abroad  have  successively  identified  them  with  the  Devonian 
series  in  France,  Belgium,  the  Rhenish  Provinces,  Central  Germany, 
and  America.];  I  shall  proceed  first  to  treat  of  the  main  divisions 
which  have  been  established  in  Europe. 

Upper  Devonian  RocJcs. 

Pilton  Group. — The  slates  and  sandstone  of  Barnstaple  (No.  1,  a,  ft, 
of  the  preceding  section)  were  formerly  considered  to  be  represented 
in  Cornwall  by  the  limestones  of  Petherwyn,  which  rise  from  under 
the  Culm  Measures,  constituting  the  Petherwyn  group  of  Professor 
Sedgwick.  But  later  researches  §  have  rendered  it  probable  that  these 
beds  overlie  the  Petherwyn  group;  they  contain  the  shell  Spirifer 

*  Sedgwick  and  Murchison,  Trans.  Geol.  Soc.,  New  Series,  vol.  v.  p.  644.  De  la 
Beche,  Geol.  Report,  Devon  and  Cornwall,  pi.  3.  Murchison's  Siluria,  p.  256. 

|  Quart.  Journ.  Geol.  Soc.,  vol.  viii.  p.  1,  et  seq. 

%  See  Dr.  Fridolin  Sandberger  on  the  Devonian  Rocks  of  Nassau  (Geol.  Verhalt. 
Nassau) ;  Fried.  A.  Romer,  on  the  Hartz  Devonian  Rocks,  in  Dunker  and  Von 
Meyer's  Palaeontographica,  3d  vol.  pt.  1. 

§  See  Murchison's  Siluria,  2d  ed.,  p.  247. 


CH.  XXVI.] 


UPPER  DEVONIAN  ROCKS. 


537 


disjunctus,  Sow.  (S.  Verneuilii,  Murcli.),  (see  fig.  601),  found  in 
Europe,  Asia  Minor,  and  even  China ;  Spirifer  Barriensis,  8.  Urii,  and 
Strophalosia  caperata,  together  with  the  large  trilobite  Phacops  lati- 
frons,  Bronn.  (see  fig.  602),  which  is  all  but  world-wide  in  its  distribu- 
tion. The  fossils  are  numerous,  and  80  per  cent,  of  them  are  distinct 
from  those  of  even  the  Lower  Carboniferous. 

Fig.  602. 


Spirifer  disjunctus,  Sow. 
Syn.  Sp.  Verneuilii,  March. 
Upper  Devonian,  Boulogne. 


Phacops  latifrons,  Bronn. 
Characteristic  of  the  Devonian  in  Eu- 
rope, Asia,  and  N.  and  S.  America. 


Petherwyn  Group. — A  series  of  limestones  and  slates  best  developed 
at  Petherwyn,  in  Cornwall.  Among  many  other  fossils,  the  Clymenia 
lincaris  (fig.  603)  and  the  minute  crustacean,  Cypridina  serrato-striata 
(fig.  604),  are  so  characteristic  of  these  upper  beds  in  Belgium,  the 


Fig.  603. 


Fig.  604. 


•  t 


Cypridina  serrato-striata,  Sand- 
berger,  Weilburg,  &c, ;  Nassau ; 
Saxony;  Belgium. 


Clymenia  linearis,  Minister. 
Petherwyn,  Cornwall ;  Elbersreuth,  Bavaria. 


Rhenish  Provinces,  the  Hartz,  Saxony,  and  Silesia,  that  strata  of  this 
division  in  Germany  are  distinguished  by  the  names  of  "  Clymenien- 
Kalk  "  and  "  Cypridinen-schiefer."  * 

With  these  are  many  Goniatites  (G.  subsulcatus,  Miinster,  and  other 


*  See  Murchison's  Siluria,  2d  ed.,  chaps,  x.,  xiv.,  and  xv. 


538 


MIDDLE  DEVONIAN. 


[On.  XXVI. 


species),  both  in  England  and  on  the  Continent.  In  Germany  they 
are  usually  confined  to  distinct  beds,  as  at  Oberscheld,  also  at  Couvin 
in  Belgium,  &c.  Trilobites  are  not  unfrequent  in  Cornwall ;  they  are 
chiefly  restricted  to  species  of  Phacops,  P.  Icevis,  <fec.,  but  in  the  upper 
Devonian  limestones  of  the  Fichtelgebirge,  as  at  Elbersreuth  in  Bava- 
ria, there  are  numerous  other  genera  and  species,  such  as  Brontes, 
Cyphastis,  &c.,  which  never  rise  higher  in  the  series  or  appear  in  any 
portion  of  the  carboniferous  limestone. 


Middle  Devonian. 

The  unfossiliferous  series  (No.  2,  p.  536)  of  North  Devon,  and  the 
calcareous  beds  of  Ilfracombe  (3),  correspond  to  the  Dartmouth  and 
Plymouth  groups  of  Prof.  Sedgwick's  South  Devon  series,  and  are 
the  most  typical  portion  of  the  Devonian  system.  They  include  the 
great  limestones  of  Plymouth  and  Torbay,  replete  with  shells,  trilobites, 
and  corals.  A  thick  accumulation  of  slate  and  schist,  full  of  the  same 
fossils,  occupies  nearly  all  the  southern  portion  of  Devonshire  and  a 
large  part  of  Cornwall.  Among  the  corals  we  find  the  genera  Favo- 
sites,  Heliolites  and  Cyathophyllum,  the  last  genus  equally  abundant 
in  the  Silurian  and  Carboniferous  systems,  the  two  former  so  frequent 
in  Silurian  rocks.  Some  few  even  of  the  species  are  common  to  the 
Devonian  and  Silurian  groups,  as,  for  example,  Favosites  polymorpha 
(fig.  605),  one  of  the  commonest  of  all  the  Devonshire  fossils.  The 
Cyathophyllum  ccespitosum  (fig.  606)  and  Heliolites  pyriformis  (fig. 


Fig.  605. 


Fig.  605. 


Favositea  polymorpha,  Goldf.    8.  Devon,  from 

a  polished  specimen. 

a.  Portion  of  the  same  magnified,  to  show  the 
pores. 


a.  Oya  thophyllum  cccspitosum,  G  old£ 
Plymouth  and  Ilfracomba 

Z>.  A  terminal  star. 

c.  Vertical  section,  exhibiting  trans- 
verse plates,  and  part  of  another 
branch. 


607)  are  peculiarly  characteristic;  as  is  another  very  common  species, 
the  Aulopora  serpens  (fig.  608),  which  creeps  over  corals  and  shells  in 
its  young  state,  as  here  figured,  but  afterwards  grows  upwards  and 


CH.  XXVL]  FOSSILS  OF  MIDDLE  DEVONIAN. 

Fig.  607.  Fig. 


539 


SelioUtes  porosa,  Goldf.,  sp.    Porites  pyrif&rmis, 

Lonsd. 

a.  Portion  of  the  same,  magnified.    Middle  Devo- 
nian, Torquay ;  Plymouth ;  Eifel. 


Aulopora  serpens,  Goldf. 

(The  young  basal  portion  of  a  Syrin- 

gopora,  Milne  Edw.  and  Haime.) 


becomes  a  cluster  of  tubes  connected  by  minute  processes.  In  this 
state  it  has  been  supposed  to  be  a  distinct  coral,  and  has  been  called 
Syringopora. 

With  the  above  are  found  many  stone-lilies  or  crinoids,  some  of 
them,  such  as  Cuprcssocrinites,  of  forms  generically  distinct  from  those 
of  the  Carboniferous  Limestone.  The  mollusks  also  are  no  less  char- 
acteristic, among  which  the  genus  Stringocephalus  (fig.  609)  may  be 


Stringoeephalus  Burtini,  Defr.    (Terebratula  porrecta,  Sow.)    Eifel;  also  South  Devon. 

a.  Valves  united.  J.  Side  view  of  same. 

c.  Interior  of  larger  valve,  showing  thick  partition,  and  part  of  a  large  process  which 
projects  from  the  other  valve  quite  across  the  shell. 

mentioned  as  exclusively  Devonian.  Many  other  Brachiopod  shells, 
of  the  genus  Spirifer,  &c.,  abounded,  and  among  them  the  Atrypa 
reticularis,  Linn.  sp.  (fig.  627,  p.  554),  which  seems  to  have  been  a 
cosmopolite  species  occurring  in  Devonian  strata  from  America  to 
Asia  Minor,  and  which,  as  we  shall  hereafter  see  (p.  554),  lived  also  in 
the  Silurian  seas.  Among  the  peculiar  lamellibranchiate  bivalves  com- 
mon to  the  Plymouth  Limestone  of  Devonshire  and  the  Continent,  we 
find  the  Megalodon  (fig.  610),  together  with  many  spiral  univalves, 
such  as  Murchisonia,  Euomphalus,  and  Macrocheilus  ;  and  Pteropods 
such  as  Conularia  (fig.  611).  The  cephalopoda,  such  as  Cyrtoceras, 
Gyroceras,  and  others,  are  nearly  all  of  genera  distinct  from  those  pre- 
vailing in  the  Upper  Devonian  Limestone,  or  Clymenien-Kalk  of  the 
Germans  already  mentioned  (p.  537).  Although  but  few  species  of 
Trilobites  occur,  the  characteristic  Brontes  flabellifer  (fig.  612)  is  far 
from  rare,  and  all  collectors  arc  familiar  with  its  fan-like  tail.  The 


640 


MIDDLE  DEVONIAN. 


Fig.  610. 


Megalodon  cucullatus,  Sow.    Eifel;  also  Bradley, 

S.  Devon, 

a.  The  valves  united. 
&.  Interior  of  valve,  showing  the  large  cardinal  tooth. 


Conularia  omata,  D'Arch. 

and  De  Vern. 

(Geol.  Trans.,  Sec.  Sen,  vol.  vi. 
pi.  29.)    Kefrath,  near  Cologne. 


head  is  seldom  found  perfect ;  a  restoration  of  it  has  been  attempted 
by  Mr.  Salter,  (fig.  613). 


Fig.  612. 


Fig.  618. 


Bestored  outline  of  head  of 
Brontes  flabellifer. 


Brontes  flabelltfer,  Goldf.    Eifel;  also  8.  Devon. 

In  this  same  formation,  comprising  in  it  the  "  Stringocephalus  lime- 
stone," or  "  Eifel  Limestone  "  of  Germany,  several  remains  of  Coccosteus 
and  other  ichthyolites  have  been  detected,  and  they  serve,  as  Sir  R. 
Murchison  observes  (Siluria,  p.  371),  to  identify  the  rock  with  the 

Old    Red    Sandstone    of 
Britain  and  Russia. 

Beneath  the  Eifel  Lime- 
stone (the  great  central 
and  typical  member  of 
"the  Devonian"  on  the 
.  Continent)  lie  certain 
schists  called  by  German 

Calceola8andaMna,~La.m.    Eifel ;  also  South  Devon.  _.  .  ^    . 

a.  Ventral  valve,         &.  Inner  side  of  dorsal  valve.          writers  Calceola-Schie- 


CH.  XXVI.] 


LOWER  DEVONIAN. 


541 


fer,"  because  they  contain  in  abundance  a  fossil  body  of  very  curious 
structure,  Calceola  sandalina  (fig.  614),  which  has  been  usually  con- 
sidered a  brachiopod,  but  which  some  naturalists  have  lately  referred 
to  a  coral.  They  suppose  it  to  be  an  abnormal  form  of  the  order 
Zoantharia  rugosa  (see  fig.  563,  p.  515),  differing  from  all  other 
corals  in  being  furnished  with  a  strong  operculum. 


Lower  Devonian. 

Beneath  the  Middle  Devonian  limestones  and  schists  already  enu- 
merated, a  series  of  slaty  beds  and  quartzose  sandstones,  the  latter 
constituting  the  "Older  Rhenish  Greywacke"  of  Romer,  and  the 
"  Spirifer  sandstone  "  of  Sandberger,  are  exhibited  between  Coblentz 
and  Caub.*  A  portion  of  these  rocks  on  the  Rhine  and  in  some  of 
the  adjacent  countries  was  regarded  as  "  Upper  Silurian "  by  Prof. 
Sedgwick  and  Sir  R.  Murchison  in  1839,  but  their  true  age  has  since 
been  determined.  Their  equivalents  are  found  in  England  in  the 
sandstones  and  slates  of 

the  Foreland  and  Linton  Fi-  615- 

in  Devon  (Nos.  4  and  5 
of  the  table,  p.  536), 
and,  according  to  Mr.  Sal- 
ter,  in  the  sandstone  of 
Torquay  in  South  Devon, 

where   many   of  the   char-  Spirifer  mucronatus,  Hall.    Devonian  of  Pennsylvania. 


Fig.  616. 


JTomalonotus  armatus,  Burmeister.  Lower 
Devonian  ;  Daun,  in  the  Eifel. 

Obs.  The  two  rows  of  spines  down  the  body 
give  an  appearance  of  more  distinct  trilo- 
bation  than  really  occurs  in  this  or  most 
other  species  of  the  genus. 


Fig.  617. 


Pleurodictywn  problematicum,  Goldfuss. 
Lower  Devonian;  of  Plymouth  and  Tor- 
quay ;  Looe ;  Forez,  &c. ;  also  in  Germany 
at  Dietz,  Nassau,  &c. 

Obs.  Attached  to  a  worm -like  body  (Serpula). 
The  specimen  is  a  cast  in  sandstone,  the 
thin  expanded  base  of  the  coral  being  re- 
moved, and  exposing  the  large  polygonal 
cells ;  the  walls  of  these  cells  are  perforated, 
and  the  casts  of  these  perforations  produce 
the  chain-like  rows  of  dots  between  the 
cells. 


*  Murchison's  Siluria,  p.  368. 


54:2  DEVONIAN  BRACHIOPODA.         [Cn.  XXVI. 

acteristic  Rhenish  fossils  are  met  with.  The  broad-winged  Spirifers 
which  distinguish  the  "  Spirifer-sandstein "  of  Germany  have  their 
representatives  in  the  Devonian  strata  of  North  America  (see  fig.  615). 

Among  the  Trilobites  of  this  era  several  large  species  of  Homa- 
lonotus  (fig.  616)  are  conspiucous.  The  genus  is  still  better  known  as 
a  Silurian  form,  but  the  spinose  species  -appear  to  belong  .exclusively  to 
the  "  Lower  Devonian,"  and  are  found  in  Britain,  Europe,  and  the 
Cape  of  Good  Hope. 

With  the  above  are  associated  many  species  of  Brachiopods,  such 
as  Orthis,  Leptcena,  and  Chonetes,  and  numerous  Lamellibranchiata, 
such  as  Pterinea  ;  also  the  very  remarkable  fossfl  coral  called  Pleuro- 
dictyum  problematicum  (fig.  617). 

Devonian  of  Russia. — The  Devonian  strata  of  Russia  extend,  accord- 
ing to  Sir  R.  Murchison,  over  a  region  more  spacious  than  the  British 
Isles ;  and  it  is  remarkable  that,  where  they  consist  of  sandstone  like 
the  "  Old  Red"  of  Scotland  and  Central  England,  they  are  tenanted 
by  fossil  fishes  often  of  the  same  species  and  still  often er  of  the  same 
genera  as  the  British,  whereas  when  they  consist  of  limestone  they 
contain  shells  similar  to  those  of  Devonshire ;  thus  confirming,  as  Sir 
Roderick  observes,  the  contemporaneous  origin  previously  assigned  to 
formations  exhibiting  two  very  distinct  mineral  types  in  different  parts 
of  Britain.*  The  calcareous  and  the  arenaceous  rocks  of  Russia  above 
alluded  to  alternate  in  such  a  manner  as  to  leave  no  doubt  of  their 
having  been  deposited  at  the  same  period.  Among  the  fish  common 
to  the  Russian  and  the  British  strata  are  Asterolepis  Asmusii  before 
mentioned ;  a  smaller  species,  A.  Minor,  Ag. ;  Holoptychius  nobilissimus 
(p.  525);  Dendrodus  strigatus,  Owen;  Pterichthys  major,  Ag. ;  and 
many  others.  But  some  of  the  most  marked  of  the  Scottish  genera, 
such  as  Cephalaspis,  Coccosteus,  Diplacanthus,  Cheir acanthus,  <fec., 
have  not  yet  been  found  in  Russia,  owing  perhaps  to  the  present  im- 
perfect state  of  our  researches,  or  possibly  to  geographical  causes 
limiting  the  range  of  the  extinct  species.  On  the  whole,  no  less  than 
forty  species  of  placoid  and  ganoid  fish  have  been  already  collected  in 
Russia,  some  of  the  placoids  being  of  enormous  size,  as  before  stated, 
p.  533. 

Devonian  Brachiopoda. 

The  preponderance  of  the  Brachiopods  or  Palliobranchiata  among 
the  bivalve  shells  forms  a  decided  feature  in  the  conchology  of  the 
Devonian  strata  as  contrasted  with  that  of  rocks  newer  in  the  series, 
such  as  have  been  described  in  the  preceding  chapters.  In  a  table  of 
British  fossils,  constructed  by  Professor  Ramsay,  it  appears  that  there 
are  twice  as  many  species  of  Brachiopods  as  of  Lamellibranchiate 
bivalves  in  the  Devonian  rocks,  there  being  ninety-six  known  Brachio- 

*  Siluria,  p.  329. 


CH.  XXVI.]      DEVONIAN  STRATA  IN  UNITED  STATES,  ETC.  543 

pods  to  forty-seven  Lamellibranchiata.  In  the  antecedent  Silurian 
rocks  the  relative  numbers  are  still  more  in  favor  of  the  Brachiopods, 
whereas,  in  the  more  modern  Carboniferous  formation,  the  proportions 
are  more  than  reversed,  for  there  are  of  the  Carboniferous  Lamelli 
branchiata  282  species,  and  only  123  Brachi(5poda. 

The  reader  will  of  course  conclude  from  what  was  said  at  p.  414 
that  all  these  oolitic  species  were  not  living  at  one  and  the  same  time, 
there  having  been  continual  changes  going  on  in  the  fauna  from  the 
period  of  the  lowest  to  that  of  the  uppermost  member  of  the  oolitic 
series ;  but  the  proportions  of  the  two  families  of  shells  may  be  cor- 
rectly deduced  from  the  data  above  given.  If  we  consult  the  same 
table  to  obtain  the  relative  numbers  of  these  same  orders  of  mollusca 
in  the  oolites,  we  find  536  Lamellibranchiata  and  only  sixty-nine 
Brachiopoda,  these  last  therefore  being  reduced  to  nearly  an  eighth 
part  of  the  whole  bivalve  fauna.  If  we  then  turn  to  the  actual  British 
seas,  we  observe  that  Forbes  and  Hanley  give  220  living  species  of 
Lamellibranchiata  and  only  five  Brachiopods,  the  latter  being  reduced 
to  a  forty-fourth  part  of  the  whole  fauna.  As  the  lamellibranchiate 
mollusks  have  an  organization  of  a  more  complex  and  higher  grade, 
the  fact  of  their  increasing  preponderance  from  the  earliest  to  the 
latest  times  has  been  often  cited,  and  not  without  reason,  as  favoring 
the  theory  of  progressive  development. 

Devonian  Strata  in  the  United  States  and  Canada. 

In  no  country  hitherto  explored  is  there  so  complete  a  series  of 
strata  intervening  between  the  Carboniferous  and  Silurian  as  in  the 
United  States.  This  intermediate  or  Devonian  group  was  first  studied 
in  all  its  details,  and  with  due  attention  to  its  fossil  remains,  by  the 
Government  Surveyors  of  New  York.  In  its  geographical  extent, 
that  State,  taken  singly,  is  about  equal  in  size  to  Great  Britain ;  and 
the  geologist  has  the  advantage  of  finding  the  Devonian  rocks  there 
in  a  nearly  horizontal  and  undisturbed  condition,  so  that  the  relative 
position  of  each  formation  can  be  ascertained  with  certainty. 

Subdivisions  of  the  New  York  Devonian  Strata,  in  the  Reports  of 
the  Government  Surveyors. 

Names  of  Groups.  Thickness  in  Feet. 

1.  Catskill  group,  or  Old  Red  Sandstone,  -  -  -      2000 

2.  Chemung  group,          -    ,-        -  -  -  -  -       1500 

3.  Portage,    )  100Q 

4.  Genesee,    f 

6.  Tully,  -                        ......  15 

6.  Hamilton,        .......  1000 

7.  Marcellus,        -            -                         -            -            -  50 

8.  Corniferous,  )  Kft 

9.  Onondaga,     f 

10.  Schoharie,  )  -in 

11.  Cauda-Galli  grit,   ] 

12.  Oriskany  sandstone,    -  -  -  •  •  -5  to  30 


544  DEVONIAN  STRATA  [On.  XXVI. 

These  subdivisions  are  of  very  unequal  value,  whether  we  regard 
the  thickness  of  the  beds  or  the  distinctness  of  their  fossils ;  but  they 
have  each  some  mineral  or  organic  character  to  distinguish  them  from 
the  rest.  Moreover,  it  has  been  found,  on  comparing  the  geology  of 
other  North  American  States  with  the  New  York  standard,  that  some 
of  the  above-mentioned  groups,  such  as  Nos.  2  and  3,  which  are 
respectively  1500  and  1000  feet  thick  in  New  York,  are  very  local,  and 
thin  out  when  followed  into  adjoining  States ;  whereas  others,  such  as 
Nos.  8  and  9,  the  total  thickness  of  which  is  scarcely  50  feet  in  New 
York,  can  be  traced  over  an  area  nearly  as  large  as  Europe. 

Respecting  the  upper  limit  of  the  above  system,  there  has  been  very 
little  difference  of  opinion,  since  the  Red  Sandstone  No.  1  contains 
Holoptychius  nobilissimus  and  other  fish  characteristic  generically  or 
specifically  of  the  European  Old  Red.  More  doubt  has  been  enter- 
tained in  regard  to  the  classification  of  Nos.  10,  11,  and  12.  M.  de 
Verneuil  proposed  in  1847,  after  visiting  the  United  States,  to  in- 
clude the  Oriskany  sandstone  in  the  Devonian ;  and  Mr.  D.  Sharpe, 
after  examining  the  fossils  which  I  had  collected  in  America  in  1842, 
arrived  independently  at  the  same  conclusion.*  The  resemblance  of 
the  Spirifers  of  this  Oriskany  sandstone  to  those  of  the  Lower  Devo- 
nian of  the  Eifel  was  the  chief  motive  assigned  by  M.  de  Yerneuil  for 
his  view ;  and  the  overlying  Schoharie  grit,  No.  10,  was  classed  as 
Devonian  because  it  contained  a  species  of  Asterolepis.  On  the  other 
hand,  Prof.  Hall  adduces  many  fossils  from  Nos.  10  and  12  which 
resemble  more  nearly  the  Ludlow  group  of  Murchison  than  any  other 
European  type ;  and  he  thinks,  therefore,  that  those  groups  may  be 
"  Upper  Silurian."  Sir  William  Logan  has  shown  that  the  fossils  of 
the  Gaspe  limestones  in  Eastern  Canada  favor  the  same  opinion,  and 
demonstrate  at  least  how  difficult  it  is  to  draw  a  dividing  line  in  that 
country  between  the  Devonian  and  Silurian  systems.  Although  the 
Oriskany  sandstone  is  no  more  than  30  feet  thick  in  New  York,  it  is 
sometimes  300  feet  thick  in  Pennsylvania  and  Virginia,  where,  to- 
gether with  other  primary  or  palaeozoic  strata,  it  has  been  well  stud- 
ied by  Professors  W.  B.  and  H.  D.  Rogers. 

The  upper  divisions  (from  the  Catskill  to  the  Genesee  groups 
inclusive,  Nos.  1  to  4)  consist  of  arenaceous  and  shaly  beds,  and  may 
have  been  of  littoral  origin.  They  vary  greatly  in  thickness,  and  few 
of  them  can  be  traced  into  the  "  far  West ; "  whereas  the  calcareous 
groups,  Nos.  8  and  9,  although  in  New  York  they  have  seldom  a 
united  thickness  of  more  than  50  feet,  are  observed  to  constitute  an 
almost  continuous  coral-reef  over  an  area  of  not  less  than  500,000 
square  miles,  from  the  State  of  New  York  to  the  Mississippi,  and  be- 
tween Lakes  Huron  and  Michigan,  in  the  north,  and  the  Ohio  River 
and  Tennessee  in  the  south.  In  the  Western  States  they  are  repre- 

*  De  Verneuil,  Bulletin,  4,  678,  1847 ;  D.  Sharpe,  Quart.  Journ.  Geol.  Soc.,  vol. 
iv.  p.  145,  1347. 


CH.  XXVI.]  IN  UNITED  STATES  AND   CANADA.  545 

sented  by  the  upper  part  of  what  is  termed  "  the  Cliff  Limestone." 
There  is  a  grand  display  of  this  calcareous  formation  at  the  falls  or 
rapids  of  the  Ohio  River  at  Louisville  in  Kentucky,  where  it  much 
resembles  a  modem  coral-reef.  A  wide  extent  of  surface  is  exposed 
in  a  series  of  horizontal  ledges,  at  all  seasons  when  the  water  is  not 
high ;  and,  the  softer  parts  of  the  stone  having  decomposed  and  wasted 
away,  the  harder  calcareous  corals  stand  out  in  relief,  their  erect  stems 
sending  out  branches  precisely  as  when  they  were  living.  Among 
other  species  I  observed  single  corals,  not  less  than  5  feet  in  diameter, 
of  Favosites  gothlandica,  with  its  beciutiful  honeycomb  structure  well 
displayed,  and,  by  the  side  of  it,  the  Favistella,  combining  a  simi- 
lar honeycombed  form  with  the  star  of  the  Astrcea.  There  was  also 
the  cup-shaped  Cyatkapkyllum,  and  the  delicate  network  of  the 
Fenestella,  and  that  elegant  and  well-known  European  species  of  fossil 
called  "the  chain  coral,"  Catenipora  escharoides  (see  fig.  631,  p.  557), 
with  a  profusion  of  others.  These  coralline  forms  were  mingled  with 
the  joints,  stems,  and  occasionally  the  heads  of  lily  encrinites. 
Although  hundreds  of  fine  specimens  have  been  detached  from  these 
rocks  to  enrich  the  museums  of  Europe  and  America,  another  crop  is 
constantly  working  its  way  out,  under  the  action  of  the  stream,  and 
of  the  sun  and  rain  in  the  warm  season  when  the  channel  is  laid  dry. 
The  waters  of  the  Ohio,  when  I  visited  the  spot  in  April,  1846,  were 
more  than  40  feet  below  their  highest  level,  and  20  feet  above  their 
lowest,  so  that  large  spaces  of  bare  rock  were  exposed  to  view.* 

No  less  than  46  species  of  British  Devonian  corals  are  described  in 
the  monograph  published  in  1853  by  Messrs.  M.  Edwards  and  Jules 
Haime  (Palseontographical  Society),  and  only  six  of  these  occur  in 
America ;  a  fact,  observes  Prof.  E.  Forbes,  which,  when  we  call  to 
mind  the  wide  latitudinal  range  of  the  Anthozoa,  has  an  important 
bearing  on  the  determination  of  the  geography  of  the  northern  hemi- 
sphere during  the  Devonian  epoch.  We  must  also  remember  that  the 
more  conspicuous  corals  of  these  ancient  reefs,  viz.,  those  which  are 
like  our  cup  and  star  corals,  all  belong  to  the  Zoantharia  rugosa,  a 
sub-order  which,  as  before  stated  (p.  515  et  seq.),  has  no  living  repre- 
sentative. Hence  great  caution  must  be  used  in  admitting  all  induc- 
tions drawn  from  the  presence  and  forms  of  these  zoophytes,  respect- 
ing the  prevalence  of  a  warm  or  tropical  climate  in  high  latitudes  at 
the  time  when  they  flourished — for  such  inductions,  says  Prof.  E. 
Forbes,  have  been  founded  "on  the  mistaking  of  analogies  for 
affinities."  f 

This  calcareous  division  also  contains  Cfoniatites,  Spirifers,  Pen- 
tremiteSj  and  many  other  genera  of  Mollusca  and  Crinoidea,  corre- 
sponding to  those  which  abound  in  the  Devonian  of  Europe,  and  some 
few  of  the  forms  are  the  same.  But  the  difficulty  of  deciding  on  the 

*  Lyell's  Second  Visit  to  the  United  States,  vol.  ii.  p.  277. 
f  Geol.  Quart.  Journ.,  vol.  x.  p.  60,  1854. 
35 


546  VEGETATION   OF  THE  [Cn.  XXVI. 

exact  parallelism  of  the  New  York  subdivisions,  as  above  enumerated, 
with  the  members  of  the  European  Devonian,  is  very  great,  so  few  are 
the  species  in  common.  This  difficulty  will  best  be  appreciated  by 
consulting  the  critical  essay  published  by  Mr.  Hall  in  1851,  on  the 
writings  of  European  authors  on  this  interesting  question.*  Indeed 
we  are  scarcely  as  yet  able  to  decide  on  the  parallelism  of  the  principal 
groups  even  of  the  north  and  south  of  Scotland,  or  on  the  agreement 
of  these  again  with  the  Devonian  and  Rhenish  subdivisions. 

Canada. — In  Western  Canada  many  of  the  subdivisions  of  the  New 
York  Devonian  system,  as  above  enumerated,  from  the  Chemung  to 
the  Oriskany  formation,  have  been  recognized  by  the  British  survey- 
ors, and  are  even  traceable  continuously,  as  in  the  Niagara  district, 
from  the  one  country  to  the  other. 

In  Eastern  Canada,  or  in  the  peninsula  of  Gaspe,  south  of  the  estuary 
of  St.  Lawrence,  there  is  a  great  thickness  of  sandstone,  conglomerate, 
and  shales,  referable  to  the  Devonian  period,  and  rich  in  fossil  plants. 
The  conglomerates  occur  in  massive  beds,  one  of  them  being  156  feet 
thick,  including  pebbles  of  white  quartz,  black  chert,  jaspers  of  various 
colors,  porphyries  and  limestones,  with  a  base  of  sandstone.  They 
contain  fragments  of  plants  and  fish-spines  or  Ichthyodorulites  of  the 
genera  Onchus  and  Machceracanihum.  Above  these  beds  occur  sand- 
stones and  shales  of  great  thickness,  some -of  the  sandstones  being 
ripple-marked.  Towards  the  upper  part  of  the  whole  series  a  small 
seam  of  coal  has  been  observed  with  carbonaceous  shale,  measuring- 
together  about  three  inches ;  it  rests  on  a  bed  of  clay,  in  which  arc  the 
roots  of  Psilophyton  (see  fig.  518),  while  stems  and  leaflets  of  the  same 
plant  are  met  with  in  the  shale  above  the  coal,  and  in  the  carbonaceous 
shale  associated  with  it.  At  several  other  levels  strata  much  like  the 
fine  clays  of  the  Carboniferous  period  are  penetrated  vertically  by  the 
rootlets  of  this  same  Psilophyton.\ 

South  Africa. — The  researches  of  Mr.  Bain  and  Mr.  Rubidge,  at 
the  Cape  of  Good  Hope,  have  established  the  existence  of  a  large 
Lower  Devonian  formation  in  that  part  of  the  southern  hemisphere. 
Curiously  enough,  the  fauna  is  strictly  representative  of  that  in  north- 
ern regions,  even  to  minute  coincidences.  The  late  Daniel  Sharpe 
and  Mr.  Salter  described  many  species  referable  to  Trilobites  (Homa- 
lonotus  and  Phacops),  Annelids  (Tentaculites),  Mollusks  (Cucullella), 
and  large  species  of  Crinoids  allied  to  Rhodocrinus,  &c.,  all  of  the  same 
genera  as  those  found  in  Cornwall  and  Germany. 

Vegetation  of  the  Devonian  Period. 

From  the  works  of  Goppert,  linger,  and  Bronn,  we  learn  that  the 
fossil  plants  of  the  Devonian  rocks  in  Europe  resemble  generically, 
with  very  few  exceptions,  those  of  the  coal-measures,  and  more  ample 

*  Report  of  Foster  and  Whitney  on  Geol.  of  L.  Superior,  p.  302,  Washington,  1851. 
f  Sir  W.  E.  Logan,  Report  of  Geol.  Survey  of  Canada,  p.  394,  1863. 


CH.  XXVI.]  DEVONIAN  PERIOD.  54.7- 

botanical  data  obtained  from  Canada  and  the  United  States  lead  to 
a  similar  conclusion  respecting  tlie  flora  of  the  same  age  in  America. 
Dr.  Dawson,  of  Montreal,  in  an  important  memoir  *  on  this  subject, 
after  enumerating  thirty-two  genera  of  Devonian  plants  and  sixty-nine 
species  collected  in  the  State  of  New  York  and  in  Canada,  observes 
that  they  belong  chiefly,  as  in  the  Carboniferous  period,  to  Gymno- 
sperms  and  Cryptogams.  When  we  peruse  his  catalogue  of  Coniferce, 
Sigillarice,  Calamites,  Asterophyllites,  Lepidodendra,  Lepidostrobi,  and 
ferns  of  the  genera  Cyclopteris,  Neuropteris,  Sphenopteris,  &c.,  together 
with  fruits,  such  as  Cardiocarpum  and  Trigonocarpum,  we  might  well 
suppose  that  we  were  presented  with  a  list  of  carboniferous  fossils ; 
and,  if  told  that  the  species  differed,  and  that  there  was  some  admix- 
ture even  of  genera  unknown  in  Europe,  we  might  be  inclined  to 
ascribe  such  a  want  of  agreement  to  geographical  circumstances,  and 
especially  to  the  distance  of  the  New  from  the  Old  World.  But 
fortunately  the  coal  formation  is  most  fully  developed  on  the  other 
side  of  the  Atlantic,  and  is  singularly  like  that  of  Europe,  both  litho- 
logically  and  in  a  large  proportion  even  of  the  species  of  its  fossil 
plants.  There  is  also  the  most  unequivocal  evidence  of  relative  age 
afforded  by  superposition,  for  the  Devonian  strata  in  the  United 
States  are  seen  to  crop  out  from  beneath  the  carboniferous  on  the 
borders  of  Pennsylvania  and  New  York,  where  both  formations  are  of 
great  thickness. 

On  comparing  the  species  of  the  Middle  Devonian  in  these  coun- 
tries with  those  of  the  Middle  Coal-Measures,  we  find  them  all  dis- 
tinct, whereas  some  few  species  pass  from  the  Upper  Devonian  into 
the  Lower  Carboniferous  rocks.  The  genus  most  characteristic  of  the 
Devonian,  and  not  found  in  the  Coal,  is  one  already  alluded  to,  name- 
ly, PsilopTiyton^  believed  by  Dr.  Dawson  to  be  a  lycopodiaceous  plant, 
branching  dichotomously  (see  P.  princeps,  fig.  618  A),  with  stems 
springing  from  a  rhizome,  A  6,  which  last  has  circular  areoles,  d  e,  much 
resembling  those  of  Stigmaria,  and  like  it  sending  forth  cylindrical  root- 
lets, such  as  at  A  c.  The  extreme  points  of  some  of  the  branchlets  are 
rolled  up  so  as  to  resemble  the  croziers  or  circinate  vernation  of  ferns, 
h ;  the  leaves  or  bracts,  i,  supposed  to  belong  to  the  same  plant,  are 
described  by  Dawson  as  having  enclosed  the  fructification.  The  re- 
mains of  Psilophyton  princeps  have  been  traced  through  all  the  mem- 
bers of  the  Devonian  series  in  Canada  and  the  State  of  New  York. 
Some  underclays  in  Gaspe  are  filled,  as  already  stated,  with  its  vertical 
rootlets  just  as  are  the  fire-clays  of  the  coal,  both  in  Europe  and  Ameri- 
ca, with  those  of  Stigmaria. 

One  fragment  of  fossil  wood,  found  some  years  ago  by  Professor 
Hall,  in  a  Devonian  limestone  of  the  Hamilton  group,  on  Lake  Erie, 
has,  according  to  Dawson,f  the  structure  of  an  angiospermous  exo- 

*  Geol.  Quart.  Journ.,  vol.  xv.  p.  477,  1859;  also  vol.  xviii.  p.  296,  1862. 
f  Ibid.,  vol.  xviii.  p.  305,  1862. 


54:8 


VEGETATION  OF  THE  DEVONIAN  PERIOD.        [Cn.  XXVI. 
Fig.  618 

A  h 


Psilophyton  princeps.     Dawson,  Geol.  Quart.  Journ.,  vol.  xv.,  1868  ;  and  Canada  Survey, 

1863.    Species  characteristic  of  the  whole  Devonian  period  in  North  America. 
A.  Psilophyton  princeps,  plant  restored  by  Dawson.      /.  Stem,  twice  natural  size. 
AZ>.  Ehizome,  or  underground  root-like  stem. 
Ac.  Cylindrical  rootlets. 

d.  Ehizome. 

e.  Areole  of  rhizome. 


g.  Termination  of  branches. 

h.  Crozier-like,  or  circinate  vernation. 

i.  Fructification. 


gen  ;  but  with  this  single  exception  the  American  Devonian  flora 
affords,  like  the  Carboniferous,  no  evidence  of  the  existence  of  plants 
of  higher  organization  than  the  gymnosperms. 

The  monotonous  character  of  the  Carboniferous  flora  might  be  ex- 
plained ,by  imagining  that  we  have  only  the  vegetation  handed  down 
to  us  of  one  set  of  stations,  consisting  of  wide  swampy  flats.  But 
Dr.  Dawson  supposes  that  the  geographical  conditions  under  which 
the  Devonian  plants  grew  were  more  varied,  and  had  more  of  an  up- 
land character.  If  so,  the  limitation  of  a  flora  represented  by  so 
many  genera  and  species  to  the  gymnospermous  and  cryptogamous 
orders,  and  the  absence  of  plants  of  higher  grade,  admit  of  no  expla- 


CH.  XXVI.]  SILURIAN  STRATA.  549 

nation  hitherto  advanced  save  that  afforded  by  the  theory  of  progres- 
sive development.  Nothing  is  known  of  the  insects,  land-shells,  or 
other  terrestrial  animals  which  coexisted  with  this  Devonian  flora,  but 
we  need  not  despair  of  future  discoveries  in  this  direction  when  we 
remember  that  slow  as  has  been  our  progress,  we  have  at  length  be- 
gun to  learn  something  respecting  the  terrestrial  fauna  of  the  Coal 
period. 

Allusion  has  already  been  made  to  freshwater  shells  and  to  Lepi- 
dodendra  and  ferns  (see  figs.  585  and  586,  p.  524)  found  in  Ireland 
associated  with  Devonian  genera  of  fish. 


CHAPTER   XXVII. 

SILURIAN    AND    CAMBRIAN    GROUPS. 

Siluriaii  strata  formerly  called  Transition — Term  "  Grauwacke  " — Subdivisions  of 
Upper,  Middle,  and  Lower  Silurians — Ludlow  formation  and  fossils — Oldest 
known  remains  of  fossil  fish — Wenlock  formation,  corals,  cystideans,  trilobites — 
Middle  Silurian  or  Llandovery  Beds — Lower  Silurian  rocks — Caradoc  and  Bala 
Beds — Upper  and  Lower  Llandeilo  formations — Cystideae — Trilobites — Grapto- 
lites — Vast  thickness  of  Lower  Silurian  strata,  sedimentary  and  volcanic,  in 
Wales — Foreign  Silurian  equivalents  in  Europe — Silurian  strata  of  the  United 
States — Amount  of  specific  agreement  of  fossils  with  those  of  Europe — Canadian 
equivalents — Whether  Silurian  strata  of  deep-sea  origin — Cambrian  rocks — 
Classification  and  nomenclature  —  Barrande's  primordial  fauna — Upper  Cam- 
brian of  Wales — Tremadoc  slates  —  Lingula  flags — Lower  Cambrian — Long- 
mynd  group — Oldest  organic  remains  known  in  Europe — Foreign  equivalents  of 
the  Cambrian  group— Primordial  zone  of  Bohemia — Characteristic  trilobites — 
Metamorphosis  of  trilobites — Alum  schists  of  Sweden  and  Norway — Potsdam 
sandstone  of  United  States  and  Canada — Footprints  near  Montreal — Quebec 
strata  and  Huronian  rocks — Minnesota  trilobites — Rocks  older  than  the  Cam- 
brian— Laurentian  group,  Upper  and  Lower — Oldest  known  fossil,  JEozoon  Cana- 
dense — No  remains  of  vertebrate  animals  known  in  strata  below  the  Upper 
Silurian — Progressive  discovery  of  vertebrata  in  older  rocks — Theoretical  infer- 
ences from  the  rarity  or  absence  of  vertebrata  in  the  most  ancient  fossiliferous 
formations. 

WE  come  next  in  the  descending  order  to  the  most  ancient  of  the 
primary  fossiliferous  rocks,  that  series  which  comprises  the  greater 
part  of  the  strata  formerly  called  "  Transition "  by  Werner,  for  rea- 
sons explained  in  Chapter  VIIL,  p.  89.  Geologists  were  also 
in  the  habit  of  applying  to  these  older  strata  the  general  name 
of  "  Grauwacke,"  by  which  the  German  miners  designate  a  particular 
variety  of  sandstone,  usually  an  aggregate  of  small  fragments  of 
quartz,  flinty  slate  (or  Lydian  stone),  and  clay-slate  cemented  to- 


550 


SUBDIVISIONS  OF  SILURIAN  ROCKS. 


[Cn.  XXVII. 


gether  by  argillaceous  matter.  Far  too  much  importance  lias  been 
attached  to  this  kind  of  rock,  as  if  it  belonged  to  a  certain  epoch  in 
the  earth's  history,  whereas  a  similar  sandstone  or  grit  is  found  in 
the  Old  Red,  and  in  the  Millstone  Grit  of  the  Coal,  and  sometimes 
in  certain  Cretaceous  and  even  Eocene  formations  in  the  Alps. 

The  annexed  table  will  explain  to  the  reader  the  successive  forma- 
tions into  which  the  strata  called  Silurian  by  Sir  Roderick  Murchison 
may  be  subdivided : 

UPPER  SILURIAN  ROCKS. 

1.  LUDLOW  FORMATION. 


Upper 
Ludlow. 


Lower 
Ludlow. 


Prevailing  Lithological  Characters. 

a.  Downton    Sandstone. — Fine-  "1 
grained  yellowish  sandstones 
and  hard  reddish  grits ;   at  y 
the  base  a  "bone-bed"  with 
fish  remains. 

b.  Micaceous  gray  sandstone  and 
mudstone. 

a.  Aymestry  Limestone. — Argil- 
laceous limestone. 

b.  Lower  Ludlow  Shale. — Shale 
with   calcareous  concretions, 
often  of  large  size. 


Thickness 
in  feet 


80 


TOO 


50 
1000 


Organic  Eemains. 


Marine  Mollusca  of  almost 
every  order,  the  Brachio- 
poda  most  abundant ; 
Annelides,  Crinoides,and 
corals;  Placoid  and  Ga- 
noid fish  (oldest  remains 
of  fish  yet  known) ;  a  few 
Graptolites ;  Crustacea 
of  the  Eurypterid  order ; 
Seaweeds. 


2.  WENLOCK  FORMATION. 


Upper 
Wenlock. 


Lower 
Wenlock. 


Wenlock  limestone.  —  Concre- 
tionary and  thick-bedded  lime- 
stone. 

a.  Wenlock  Shale.— Argillaceous 
shale,  frequently  flagstone. 

b.  Woolhope Limestone  and  Den- 
bighshire Grit. — Argillaceous 
limestone  and    shale,   some- 
times replaced  by  felspathic 
sandstones  and  grit. 


Above 
3000 


Marine  Mollusca  and  Ka- 
diata;  Crustaceans  of  the 
Trilobite  and  Eurypte- 
rid orders;  Graptolites 
abundant. 


MIDDLE  SILURIAN  ROCKS. 


LLANDOVERY  FORMATION. 


Upper 
Llandovery. 


Lower 
Llandovery. 


a.  Tarannon  Shale. — Purple  or  ) 
pale-colored  shales. 

b.  May-Hill  Sandstone  and  Pen- 
tamerus  Limestone. — Nodular 
limestone  and  dark  shale ;  cal- 
careous sandstone,   with  un- 
derlying coarse    grits,    often 
red-colored. 

Llandovery  Slates. — Hard  sand- 
stone and  slate,  frequently 
with  conglomerate  beds. 


,  nnn 


600 

to 

1000 


Crinoidea  and  corals  very 
abundant ;  Cystidese  ; 
Mollusca,  chiefly  Bra- 
chiopoda  ;  Pentameria 
la/cis  being  characteris- 
tic of  the  limestones. 


CH.  XXVII.]  SUBDIVISIONS  OF  SILURIAN  ROCKS. 

LOWER  SILURIAN  ROCKS. 


551 


Caradoc. 


1.  CARADOC  FORMATION. 


a.  Caradoc  Sandstone.  —  Shelly  "1 
sandstones  and  conglomerates  | 
and  shales.  I 

6.  ZalaLimestone.-Aren&ceous  f 
limestone  ;   slate,  and  sand- 
stones with  trappean  tuffs.       } 


Brachiopoda,  numerous ; 
Lamellibranchiata ;  Ce- 
phalopoda ;  Pteropoda 
(Conularia)  of  large  size; 
Cystidese,  abundant  ; 
Trilobites,  reaching  their 
maximum  in  species ; 
Graptolites  numerous. 


2.  LLANDEILO  FORMATION. 


Upper 
Llandeilo. 


Lower 
Llandeilo. 


a.  Upper  Llandeilo. — Dark-col- 
ored slates,  with  calcareous 
flags  and  sandstones. 

6.  Lower  Llandeilo  or  Arenig 
Beds. — Quartzose  sandstones 
and  grits,  with  argillaceous 
slates. 


c.   Volcanic  Hocks  contempora-  ~\ 
neous  with  a  and  b. — Strati-  | 
fled  tuffs  (3300  ft.);  felspathic  V 
and  porphyritic  lavas  (2500 
ft.). 


{Mollusca,  chiefly  Cepha- 
lopods  of  large  size ; 
Heteropoda  (Bell&ro- 
pJion)  numerous ;  Grap- 
tolites ;  Trilobites  of 
large  size. 

i  RAA     f  Fossils  of  the  same  genera, 
but  all  differing  in  species 
J       from  those  of  the  Upper 
Llandeilo.  Trilobites  nu- 
merous ;  Graptolitcs  of 
*•     various  species. 


KQAA    J   Organic  remains,  as  in  a 
5800   1      and*. 


The  name  of  Silurian  was  first  proposed  by  Sir  Roderick  Mur- 
chison  for  that  great  series  of  fossiliferous  strata  which  lie  immediately 
below  the  Old  Red  Sandstone,  and  occupy  that  part  of  Wales  and 
some  contiguous  counties  of  England  which  once  constituted  the 
kingdom  of  the  Silures,  a  tribe  of  ancient  Britons. 


UPPER      SILURIAN      ROCKS. 


1.  Ludlow  Formation. 

This  member  of  the  Upper  Silurian  group,  as  will  be  seen  by  the 
above  table,  is  about  800  feet  thick,  and  subdivided  into  two  parts — 
the  Upper  Ludlow  and  the  Lower  Ludlow — at  or  near  the  top  of 
which  last  occurs  the  Aymestry  limestone.  Each  of  these  may  be 
distinguished  near  the  town  of  Ludlow,  and  at  other  places  in  Shrop- 
shire and  Herefordshire,  by  peculiar  organic  remains. 

Upper  Ludlow. — a.  Downton  Sandstone. — This  uppermost  sub- 
division was  originally  classed  by  Sir  R.  Murchison,  under  the  name 
of  "  Tilestones,"  with  the  Old  Red  Sandstone,  the  beds  being  often  of 
a  similar  red  color.  The  whole  was  regarded  as  a  transition  group 
forming  a  passage  from  the  Silurian  strata  to  Old  Red  Sandstone ;  but 
it  is  now  ascertained  that  the  fossils  agree  in  great  part  specifically, 
and  in  general  character  entirely,  with  those  of  the  underlying  Upper 
Ludlow  rocks.  ^  Among  these  are  Orthoceras  bullatum,  Platyschisma 


552  LUDLOW  FORMATION.  [On.  XXVII. 

helicites,  Bellerophon  trilobatus,  Chonetes  lata,  &c.,  with  numerous 
defences  of  fishes.  These  beds  are  well  seen  at  Kington  in  Hereford- 
shire, and  at  Downton  Castle  near  Ludlow,  where  they  are  quarried 
for  building. 

Bone-bed. — The  bone-bed  of  the  Upper  Ludlow  deserves  especial 
notice  as  affording  the  most  ancient  example  of  fossil  fish  occurring  in 
any  considerable  quantity.  It  usually  consists  of  one  or  two  thin 
brown  layers  full  of  bony  fragments  near  the  junction  of  the  Old  Red 
Sandstone  and  the  Ludlow  rocks,  and  was  first  observed  by  Sir  R. 
Murchison  near  the  town  of  Ludlow,  where  it  is  three  or  four  inches 
thick.  It  has  since  been  traced  to  a  distance  of  45  miles  from  that 
point  into  Gloucestershire  and  other  counties,  and  is  commonly  not 
more  than  an  inch  thick,  but  varies  to  nearly  a  foot.  At  May-Hill 
two  bone-beds  are  observable,  with  14  feet  of  intervening  strata  full 
of  Tipper  Ludlow  fossils.*  At  that  point  immediately  above  the 
upper  fish-bed  numerous  small  globular  bodies  have  been  found,  which 
were  determined  by  Dr.  Hooker  to  be  the  sporangia  of  a  cryptogamic 
land-plant,  probably  lycopodiaceous.  These  beds  occur  just  beneath 
the  lowest  strata  of  the  "  Old  Red,"  forming  the  uppermost  part  of  the 
Downton  sandstone. 

Most, of  the  fish  have  been  referred  by  Agassiz  to  his  placoid  order, 
some  of  them  to  the  genus  Onchus,  to  which  the  spine  (fig.  619)  and 
the  minute  scales  (fig.  620)  are  supposed  to  belong.  It  has  been  sug- 

Fig.  619.  Fig.  620. 


Onchua  tenwstriatus,  Agass.  Shagreen  scales  of  a  placoid  fish 

Bone-bed.    Upper  Silurian ;  Ludlow.  (Thelodus). 

Bone-bed.    Upper  Ludlow. 

gested,  however,  that  Onchus  may  be  one  of  those  Acanthodian  fish, 
referred  by  Agassiz  to  his  Ganoid  order,  which  are  so  characteristic 
of  the  base  of  the  Old  Red  Sandstone  in 
Fig.  621.  Forfarshire,  although  the   species   of  the 

Old  Red  are  all  different  from  those  of  the 
Silurian   beds  now  under   consideration.! 

The  JaW   and  teeth  °f  an°tlier  predaCCOUS 

Bone-bed.  Upper  Ludlow.  genus  (fig.  621)  have  also  been  detected, 
together  with  some  specimens  of  Pteraspis 

Ludensis.  As  usual  in  bone-beds,  the  teeth  and  bones  are,  for  the 
most  part,  fragmentary  and  rolled. 

1.  Gray  Sandstone  and  Mudstone,  &c. — The  next  subdivision  of 
the  Upper  Ludlow  consists  of  gray  calcareous  sandstone,  or  very  com-. 

*  Murchisou's  Siluria,  pp.  137-237. 

f  Powrie,  Geol.  Quart.  Journ.,  vol.  xx.  p.  438.     • 


Cn.  XXVIL]  AYMESTRY  LIMESTONE.  553 

monly  a  micaceous  stone,  decomposing  into  soft  mud,  and  contains, 
besides  the  shells  just  quoted,  a  Lingula,  which  is  common  to  it  and 
the  "  Tilestone  "  (or  Ledbury)  beds  at  the  base  of  the  Old  Red.  The 
Orthis  orbicularis,  a  round  variety  of  0.  elegantula,  is  characteristic 
of  the  Upper  Ludlow ;  and  the  lowest  or  mudstone  beds  contain  Rhyn- 
chonella  navicula  (fig.  623),  which  is  common  to  this  bed  and  the 

Fig.  622.  Fig.  623. 


Orthis  elegantula.  Dalm.    Var.  orbicularis,       Athyris  (Rhynchonella)  navicula, 
J.  Sow.    Delbury.  J.  Sow. 

Upper  Ludlow.  Aymeslry  limestone ;  also  in 

Upper  and  Lower  Ludlow. 

Lower  Ludlow.  As  usual  in  the  strata  of  Primary  periods  older  than 
the  coal,  the  brachiopodous  mollusca  greatly  outnumber  the  lamilli- 
branchiate  (see  above,  p.  543) ;  but  the  latter  are  by  no  means  unrep- 
resented. Among  other  genera,  for  example,  we  observe  Avicula  and 
Pterinea,  Cardiola,  Ctenodonta  (subgenus  of  Nucula),  Orthonota,  and 
Modiola. 

Some  of  the  Upper  Ludlow  sandstones  are  ripple-marked,  thus 
affording  evidence  of  gradual  deposition ;  and  the  same  may  be  said 
of  the  accompanying  fine  argillaceous  shales  which  are  of  great  thick- 
ness, and  have  been  provincially  named  "  mudstones."  In  some  of 
these  shales  stems  of  crinoidea  are  found  in  an  erect  position,  having 
evidently  become  fossil  on  the  spots  where  they  grew  at  the  bottom 
of  the  sea.  The  facility  with  which  these  rocks,  when  exposed  to  the 
weather,  are  resolved  into  mud,  proves  that,  notwithstanding  their 
antiquity,  they  are  nearly  in  the  state  in  which  they  were  first  thrown 
down. 

Lower  Ludlow. — a.  Aymestry  Limestone. — The  next  group  is  a 
subcrystalline  and  argillaceous  limestone,  which  is  in  some  places  50 
feet  thick,  and  distinguished  around  Aymestry  and  at  Sedgley  by 
the  abundance  of  Pentamerus  Knightii,  Sow.  (fig.  624),  also  found  in 
the  Lower  Ludlow.  This  genus  of  brachiopoda  was  first  found 
in  Silurian  strata,  and  is  exclusively  a  palaeozoic  form.  The  name 
was  derived  from  rrevre,  pente,  five,  and  pepog,  meros,  a  part,  because 
both  valves  are  divided  by  a  central  septum,  making  four  chambers, 
and  in  one  valve  the  septum  itself  contains  a  small  chamber,  making 
five.  The  size  of  these  septa  is  enormous  compared  with  those  of  any 
other  brachiopod  shell ;  and  they  must  nearly  have  divided  the  animal 
into  two  equal  halves ;  but  they  are,  nevertheless,  of  the  same  nature 
as  the  septa  or  plates  which  are  found  in  the  interior  of  Spirifer, 
Terebratula,  and  many  other  shells  of  this  order.  Messrs.  Murchison 
and  De  Verneuil  discovered  this  species  dispersed  in  myriads  through 


554 


AYMESTRY  LIMESTONE. 
Fig.  624. 


Pentamerus  Knightii,  Sow.    Aymestry.    \  nat  size. 
a.  View  of  both  valves  united. 

Z>.  Longitudinal  section  through  both  valves,  showing  the  cen- 
tral plates  or  septa. 


Lingula  Lewisii, 

J.  Sow. 
Abberley  Hills. 


a  white  limestone  of  Upper  Silurian  age,  on  the  banks  of  the  Is,  on 
the  eastern  flank  of  the  Urals  in  Russia,  and  a  similar  species  is  fre- 
quent in  Sweden. 

Three  other  abundant  shells  in  the  Aymestry  limestone  are,  1st, 
Lingula  Lewisii  (fig.  625);  2d,  Rhynchonella  Wilsoni,  Sow.  (fig.  626), 

Fig.  626. 


RJiynchonella  (TerebratulaL)  Wilsoni.  Sow.    Aymestry. 

which  is  also  common  to  the  Lower  Ludlow  and  Wenlock  limestone ; 
3d,  Atrypa  reticularis,  Linn.  (fig.  627),  which  has  a  very  wide  range, 
being  found  in  every  part  of  the  Upper  Silurian  system,  and  as  far 
down  as  the  Lower  Llandovery  rocks. 


Fig.  62T. 


Fig.  628. 


Atrypa  reticularis,  Linn.    (Terebratula  affinia,  Min.  Con.)      Phragmoceras  ventricosum, 

Aymestry.  J.  Sow. 

a.  Upper  valve.  5.  Lower  valve.  (Orthoceras  ventricosum,  Stein.) 

c.  Anterior  margin  of  the  valves.  Aymestry;  \  nat.  size. 


The  Aymestry  Limestone  contains  so  many  shells,  corals,  and  trilo- 


CH.  XXVII.]  LOWER  LUDLOW  SHALE.  555 

bites,  agreeing  specifically  with  those  of  the  subjacent  Wenlock  lime- 
stone, that  it  is  scarcely  distinguishable  from  it  by  its  fossils  alone. 
Nevertheless,  many  of  the  organic  remains  are  common  to  the  Aymes- 
try  limestone  and  the  Upper  Ludlow,  and  several  of  these  are  not 
found  in  the  Wenlock.* 

According  to  Mr.  Lightbody,  the  Aymestry  limestones  should  be 
considered  as  subordinate  to  the  Lower  Ludlow  shales  next  to  be  men- 
tioned, as  in  some  places  these  shales  with  their  characteristic  fossils 
occur  both  above  and  below  it.f 

b.  Lower  Ludlow  Shale. — This  mass  is  a  dark  gray  argillaceous  de- 
posit, containing,  among  other  fossils,  many  large  chambered  shells  of 
genera  scarcely  known  in  newer  rocks,  as  the  Phragmoceras  of  Brod- 
erip,  and  the  Trochoceras  of  Barrande  (see  figs.  628,  629).  The  latter 
is  partly  straight  and  partly  convoluted  in  a  very  flat  spire. 

The  Orthoceras  Ludense  (fig.  630),  as  well  as  the  cephalopod  last 
mentioned,  is  almost  peculiar  to  this  member  of  the  series. 

Fig.  629.  Fig.  630. 


Trochoceras  (Litwtes)  giganteus,  J.  Sow.  Fragment  of  Orthoceras  Ludense,  J.  Sow. 

Near  Ludlow ;  also  in  the  Aymestry  and  Leiutwardine,  Shropshire. 

Wenlock  limestones.    £  nat.  size. 

A  species  of  Graptolite,  6f.  Ludensis,  Murch.  (fig.  640,  p.  559),  a 
form  of  zoophyte  or  polyp  which  has  not  yet  been  met  with  in  strata 
above  the  Silurian,  occurs  plentifully  in  the  Lower  Ludlow. 

Starfish,  as  Sir  R.  Murchison  points  out,  are  by  no  means  rare  in 
the  Lower  Ludlow  rock.  These  fossils  present  us  with  new  genera, 
but  they  remind  us  of  various  living  forms  now  found  in  our  British 
seas,  both  of  the  families  Asteriadce  and  Ophiuridce. 

Oldest  known  fossil  fish. — In  1855,  when  the  last  edition  of  this 
work  was  published,  I  was  unable  to  cite  any  example  of  a  fossil  fish 
older  than  the  bone-bed  of  the  Upper  Ludlow,  but  in  1859,  a  specimen 
of  Pteraspis  was  found  at  Church  Hill,  near  Leintwardine  in  Shrop- 
shire, by  Mr.  J.  E.  Lee  of  Caerleon,  F.G.S.,  in  shale  below  the  Aymes- 
try limestone,  associated  with  fossil  shells  of  the  Lower  Ludlow  forma- 
tion— shells  which  differ  considerably  from  those  characterizing  the 
Upper  Ludlow  already  described. 

The  genus  Pteraspis,  as  we  have  seen  (p.  532),  is  regarded  by  Prof. 

*  Murchison's  Siluria,  p.  133. 

f  Quart.  Geol.  Journ.,  vol.  xix.  p.  371,  1863. 


556  OLDEST  KNOWN  FOSSIL  FISH.  [On.  XXVH. 

Huxley  as  allied  to  the  Sturgeon,  and  therefore  by  no  means  of 
low  grade  in  the  piscine  class.  Hence  its  detection  in  the  rocks 
lower  in  the  series  than  those  to  which  the  earliest  known  verte- 
brata  had  previously  been  traced,  is  a  fact  of  no  slight  interest; 
for  they  who  have  full  faith  in  the  doctrine  of  progressive  develop- 
ment will  naturally  expect  to  meet  with  the  earliest  vestiges  of 
the  piscine  class  in  still  more  ancient  strata.  They  may  look, 
for  example,  in  the  Lower  Silurian,  or  in  the  Cambrian  rocks,  for 
representatives  of  such  orders  as  the  Marsipobranchii  and  Pharyn- 
gobranchii,  to  which  the  Lamprey  and  Amphioxus  respectively  be- 
long. Professor  Huxley  remarks  that  some  might  argue  that  fish  of 
those  orders  may  be  absent  from  the  older  rocks  for  the  same  reason 
that  they  are  entirely  missing  in  all  the  newer  ones,  whether  palaeozoic 
or  neozoic,  namely,  because  they  are  without  bony  skeletons  or  hard 
scales.*  But  the  same  author  reminds  us  that  the  Lampreys  at  least 
might  have  left  some  definite  traces  of  their  horny  teeth.  Besides, 
the  advocates  of  progression  would  scarcely  be  satisfied  with  such  a 
way  of  accounting  for  the  total  absence  of  all  traces  of  ichthyolites  in 
strata  more  ancient  than  the  Upper  Silurian,  for,  according  to  them, 
the  earliest  types  of  each  class  resembling  the  embryonic  states  of 
more  highly  organized  beings,  exhibit,  when  they  are  first  developed, 
a  great  diversity  of  form  and  structure,  as,  according  to  their  view, 
did  the  batrachoid  reptiles,  before  the  true  saurians  came  into  exist- 
ence, or  the  saurians  before  the  placental  mammalia  'had  entered  on 
the  stage.  Each  primitive  type,  whether  vertebrate  or  invertebrate, 
when  first  it  became  dominant  and  had  the  world  to  itself,  unchecked 
in  its  struggle  for  life  by  the  competition  of  rivals  of  more  advanced 
structure,  deviated  in  shape  and  organization  in  an  infinite  variety  of 
ways,  sometimes  imitating  in  certain  of  its  characters  beings  of  higher 
grade.  Under  favorable  conditions  of  this  kind,  we  might  expect  some 
members  of  the  lamprey  and  Amphioxus  orders  to  have  exchanged  a 
gelatinous  or  serai-cartilaginous  spiral  cord  for  an  ossified  one,  or  to 
have  acquired  hard  and  scaly  dermal  coverings,  or  even  to  have  been 
armed  with  teeth  of  more  than  horny  consistency,  and  this  without 
departing  from  the  types  of  their  respective  orders.  Had  any  such 
fossils  been  found  in  very  ancient  rocks,  the  progressionists  would 
certainly  have  claimed  them  triumphantly  as  corroborating  their 
views,  and  they  are  therefore  bound  in  fairness  to  draw,  from  the  ab- 
sence of  such  remains  in  ancient  strata  which  teem  with  organic  forms, 
one  of  two  conclusions ;  namely,  either  that  the  progressive  theory  is 
doubtful,  or  that  we  can  place  no  reliance  whatever  on  negative  evi- 
dence as  establishing  the  non-existence  of  certain  types  at  remote 
eras.  The  latter  is  the  alternative  to  which  it  appears  to  me  we  ought 
to  incline  in  the  present  state  of  our  knowledge. 

*  Memoirs  of  Survey  Decade,  vol.  x.  p.  40. 


CH.  XXVII.] 


WENLOCK  FORMATION. 


557 


2.    Wenlock  Formation. 

We  next  come  to  the  Wenlock  formation,  which  has  been  divided 
(see  Table,  p.  550)  into  the  Upper  Wenlock,  or  Wenlock  Limestone, 
and  the  Lower  Wenlock,  including,  first,  the  Wenlock  shale,  and  sec- 
ondly, the  Woolhope  limestone  and  Denbighshire  grits. 

Upper  Wenlock. —  Wenlock  Limestone. — This  limestone,  otherwise 
well  known  to  collectors  by  the  name  of  the  Dudley  limestone,  forms  a 
continuous  ridge  in  Shropshire,  ranging  for  about  twenty  miles  from 
S.W.  to  N.E.,  about  a  mile  distant  from  the  nearly  parallel  escarpment 
of  the  Aymestry  limestone.  This  ridgy  prominence  is  due  to-  the 
solidity  of  the  rock,  and  to  the  softness  of  the  shales  above  and  below  it. 
Near  Wenlock  it  consists  of  thick  masses  of  gray  subcrystalline  lime- 
stone, replete  with  corals  and  encrinites.  It  is  essentially  of  a  con- 
cretionary nature ;  and  the  concretions,  termed  "  ball-stones  "  in  Shrop- 
shire, are  often  enormous,  even  80  feet  in  diameter.  They  are  of  pure 
carbonate  of  lime,  the  surrounding  rock  being  more  or  less  argilla- 
ceous.* Sometimes  in  the  Malvern  Hills  this  limestone,  according  to 
Professor  Phillips,  is  oolitic. 

Among  the  corals  in  which  this  formation  is  so  rich,  the  "  chain- 
coral,"  Holy  sites  catenularius,  or  Catenipora  escharoides  (fig.  631),  may 


Fig.  631. 


Fig.  632. 


Fig.  633. 


Halysites  catenularius,  Linn. 
8p.  Syn.  Catenipora  escha- 
roides, Goldf.  Upper  and 
Lower  Silurian. 


Favosites  Gothlandica,  Lam. 

Dudley. 
a.  Portion  of  a  large  mass ;  less 

than  the  natural  size. 
5.  Magnified  portion,  to  show 

the  pores  and  the  partitions 

in  the  tubes. 


OmpJiyma  turbinatum, 
Linn.  sp.  Cyathophyl- 
lum,  Goldf. 

Wenlock  Limestone, 
Shropshire. 


be  pointed  out  as  one  very  easily  recognized,  and  widely  spread  in 
Europe,  ranging  through  all  parts  of  the  Silurian  group,  from  the  Ay- 
mestry limestone  to  near  the  bottom  of  the  series.  Another  coral, 
the  Favorites  Gothlandica  (fig.  632),  is  also  met  with  in  profusion  in 
large  hemispherical  masses,  which  break  up  into  prismatic  fragments, 


Murehison's  Siluria,  chap.  vi. 


558  FOSSILS  OF  THE   WENLOCK  LIMESTONE.        [On.  XXVII. 

like  that  here  figured  (fig.  632).  Another  common  form  in  the  Wen- 
lock  limestone  is  the  Omphyma  (fig.  633),  which,  like  many  of  its 
companions,  reminds  us  of  some  modern  cup-corals,  but  all  the  Silurian 
genera  belong  to  the  palaeozoic  type  before  mentioned  (p.  515),  ex- 
hibiting the  quadripartite  arrangement  of  the  lamellae  within  the  cup. 

Among  the  numerous  Crinoids,  several  peculiar  species  of  Cyatho- 
crinus  (for  genus,  see  figs.,  p.  517)  contribute  their  calcareous  stems, 
arms,  and  cups  towards  the  composition  of  the  Wenlock  limestone. 
Of  Cystideans  there  are  a  few  very  remarkable  forms,  some  of  them 
peculiar  to  the  Upper  Silurian  formation,  as,  for  example,  the  Pseudo- 
crinites,  which  was  furnished  with  pinnated  fixed  arms,*  as  represented 
in  the  annexed  figure  (fig.  633). 

The  Brachiopoda  are,  many  of  them,  of  the  same  species  as  those 
of  the  Aymestry  limestone ;  as,  for  example,  Atrypa  reticularis  (fig.  627, 
p.  554),  and  Strophomena  depressa,  Sow.,  sp.  (fig,  635) ;  but  the  latter 

Fig.  634. 

Fig.  635. 


Strophomena  (Leptcena)  depressa,  Sow. 

Wenlock  and  Ludlow  Eocks. 
Pseudocrinites  bifasciatus,  Pearce. 
Wenlock  Limestone,  Dudley. 

species  range  also  from  the  Ludlow  rocks,  Wenlock  shale,  and  to  the 
Caradoc  Sandstone.  There  are  some  species,  however,  peculiar  to  the 
Upper  Wenlock,  of  the  genera  Rhynchonella  JRetzia,  Spirifer,  Athy- 
ris,  &c. 

The  Crustaceans  are  represented  almost  exclusively  by  Trilobites, 
which  are  very  conspicuous.  The  Calymene  Blumeribachii,  called  the 
"  Dudley  Trilobite,"  was  known  to  collectors  long  before  its  true  place 
in  the  animal  kingdom  was  ascertained.  It  is  often  found  coiled  up 
like  the  common  Oniscus,  or  wood-louse,  and  this  is  so  common  a 
circumstance  among  the  trilobites  as  to  lead  us  to  conclude  that  they 
must  have  habitually  resorted  to  this  mode  of  protecting  themselves 
when  alarmed.  The  other  common  species  is  the  Phacops  caudatus 
(Asaphus  caudatus),  Brong.  (see  fig.  637),  and  this  is  conspicuous  for 
its  large  size  and  flattened  form.  Sphcerexochus  mirus  (fig.  638)  is 
almost  a  globe  when  rolled  up,  the  forehead  of  this  species  being  ex- 
tremely inflated.  The  Homalonotus,  a  form  of  Trilobite  in  which  the 

*  E.  Forbes,  Mem.  Geol.  Survey,  vol.  ii.  p.  496. 


CH.  XXVU.] 


Fig.  636. 


LOWER  WENLOCK. 

Fig.  637. 


559 


Oalymene  BlumeribacMi, 

Brong. 

Wenlock,  Ludlow,  and 
Aymestry  limestones. 


Fig.  633 


Sphcerexochus  mirus,  Beyrich, 

coiled  up. 

Dudley ;  also  in  Ohio, 
N.  America 


Phaeopa  (Asaplms)  caudatus,  Brong. 
Wenlock,  Aymestry,  and  Ludlow  rocks. 


tripartite  division  of  the  dorsal  crust  is  almost  lost  (see  fig.  639),  is 
very  characteristic  of  this  division  of  the  Silurian  series ;  and  there  are 
numerous  other  genera  and  species. 


Fig.  639. 


Fig.  C40. 


***$HSSS$^^ 

Graptolithus  Ludensis,  Murchison. 
Ludlow  and  Wenlock  Shales. 


H&nalonotm  delpfiinocephalus,  Konig. 
Dudley  Castle.    £  nat.  size. 

Lower  Wenlock. — a.  Wenlock  Shale. — This,  observes  Sir  R.  Mur- 
chison, is  infinitely  the  largest  and  most  persistent  member  of  the 
Wenlock  formation,  for  the  limestone  often  thins  out  and  disappears. 
The  shale,  like  the  Lower  Ludlow,  often  contains  elliptical  concretions 
of  impure  earthy  limestone.  In  the  Malvern  district  it  is  a  mass  of 
finely  levigated  argillaceous  matter,  attaining,  according  to  Prof. 
Phillips,  a  thickness  of  640  feet,  but  is  sometimes  more  than  1000  feet 
thick  in  Wales,  and  is  worked  for  flagstones  and  slates.  The  prevail- 
ing fossils,  besides  corals  and  trilobites,  and  some  crinoids,  are  several 
small  species  of  Orthis,  Cardiola,  and  numerous  thin-shelled  species  of 
Orthoceratites.  More  than  one  species  of  Graptolite,  a  group  of  zoo- 
phytes before  alluded  to  as  being  confined  to  Silurian  rocks,  is  very 


560       *  MIDDLE  SILURIAN  ROCKS.  [On.  XXVII. 

abundant  in  this  shale,  and  occurs  more  sparingly  in  "  the  Ludlow." 
Of  these  fossils,  which  are  more  characteristic  of  the  Lower  Silurian, 
I  shall  again  speak  in  the  sequel  (p.  565). 

b.  Woolhope  Limestone  and  Grit. — Though  not  always  recognized 
as  a  separate  subdivision  of  the  Wenlock,  the  Woolhope  beds  which 
underlie  the  Wenlock  shale  are  of  great  importance.  Usually  they 
occur  as  massive  or  nodular  limestones,  underlaid  by  a  fine  shale  or 
flagstone ;  and  in  other  cases,  as  in  the  noted  Denbighshire  sandstones, 
as  a  coarse  grit  of  very  great  thickness.  This  grit  forms  mountain 
ranges  through  North  and  South  Wales,  and  is  generally  marked  by 
the  great  sterility  of  the  soil  where  it  occurs.  It  contains  the  usual 
Wenlock  fossils,  but  with  the  addition  of  some  common  in  the  upper- 
most Ludlow  rock,  such  as  Chonetes  lata  and  Bellerophon  trilobatus.* 
The  chief  fossils  of  the  Woolhope  limestone  are  Ulcenus  Barriensis, 
Homalonotus  delphinocephalus  (fig.  639),  Strophomena  imbrex,  and 
Rhynchonella  Wilsoni  (fig.  626).  The  latter  attains  in  the  Woolhope 
beds  an  unusual  size  for  the  species,  the  specimens  being  sometimes 
twice  as  large  as  those  found  in  the  Wenlock  limestone. 


MIDDLE    SILURIAN    ROCKS. 

Upper  Llandovery. — a.  Tarannon  shale. — Next  below  the  Wenlock 
formation  are  found  in  some  places  the  Tarannon  shales  or  pale  slates, 
sometimes  purple,  which  are  of  small  thickness  near  Llandovery,  but 
acquire  large  dimensions  at  Tarannon  in  Montgomeryshire,  being, 
according  to  Ramsay,  about  1000  feet  thick  in  that  locality ;  according 
to  Mr.  Jukes  and  Mr.  Aveline,  they  form  a  band  of  great  persistence, 
extending  from  Llandovery,  through  Radnor  and  Montgomerey,  to 
North  Wales.  Fossils  are  rare  in  them,  and  most  of  them  are  of  spe- 
cies common  to  the  Wenlock  formation. 

b.  May-Hill  Sandstone. — Next  in  descending  order  comes  the  May- 
Hill  sandstone,  which  may  be  advantageously  studied  at  May-Hill  in 
Gloucestershire,  and  in  the  Malvern  and  Abberley  Hills ;  its  position 
was  first  accurately  determined  by  Prof.  Sedgwick,  who  considered  it 
as  the  true  base  of  the  Upper  Silurian  rocks.  In  the  Malvern  range  it 
attains  a  thickness  of  600  feet.  These  beds  were  formerly  called 
Upper  Caradoc,  when  they  were  supposed  to  be  part  of  the  Caradoc 
formation,  to  be  mentioned  in  the  sequel;  but  this  nomenclature  has 
been  abandoned  for  good  reasons,  with  which  I  need  not  here  detain 
the  reader.  They  are  named  Upper  Llandovery  by  Sir  R.  Murchison 
in  the  last  edition  of  his  "  Siluria,"  Conjointly  with  the  Lower  Llan- 
dovery rocks,  they  have  been  called  the  Pentamerus  beds,  because  Pen- 
tamerus  Icevis  is  very  abundant  in  them,  a  brachiopod  wanting  both 
in  the  Upper  and  Lower  Silurian.  It  is  usually  accompanied  by  P. 

*  Sedgwick,  Quart.  Geol.  Journ.,  vol.  i.  p.  20,  1845. 


CH.  XXVII.] 


LLANDOVERY    ROCKS. 


561 


oblongus,  which  some  zoologists  consider  as  the  young  of  P.  Icevis, 
others  as  a  distinct  species:  both  forms  have  a  wide  geographical 
range,  being  also  met  with  in  the  same  part  of  the  Silurian  series  in 
Russia  and  the  United  States. 

Fig.  64L 


Fig.  642. 


Pentamerua  Icevis,  Sow.    Upper  and  Lower  Llandovery  beds. 

Perhaps  the  young  of  Pentamerus  oblongus. 
«,  &.  Views  of  the  shell  itself,  from  figures  in  Murchison's  "  Silurian  System." 

c.  Cast  with  portion  of  shell  remaining,  and  with  the  hollow  of  the  central  septum  filled 

with  spar. 

d.  Internal  cast  of  a  valve,  the  space  once  occupied  by  the  septum  being  represented  by  a 

hollow  in  which  is  seen  a  cast  of  the  chamber  within  the  septum. 

The  May-Hill  or  Upper  Llandovery  group  sometimes  consists  of 
a  conglomerate,  but  oftener  of  limestones  and  shales,  especially  in  the 
upper  part.  It  ranges  from  the  skirts  of  the  Longmynd  by  Builth, 
Llandovery,  and  Llandeilo,  to  the  sea  in  MarlowV  Bay,  where  it  is 
particularly  well  exhibited  in  the  cliffs.  The  conglomerate  is  derived 
from  the  waste  of  the  Lower  Silurian  rocks.  About  sixty  species  of 
fossils  are  known  in  the  May-Hill  divis- 
ion, more  than  half  of  which  are,  ac- 
cording to  Mr.  Salter,  Wenlock  species. 
They  consist  of  trilobites  of  the  genera 
Illcenus  and  Calymene ;  Brachiopods 
of  the  genera  Orthis,  Atrypa,  Leptcena, 
Pentamerus,  Strophomena,  and  others ; 
Gasteropods  of  the  genera  Turbo,  Mur- 
chisonia,  and  Better ophon ;  and  Ptero- 
pods  of  the  genus  Conularia.  The 
Brachiopods  are  almost  all  Upper  Silu- 
rian species. 

Among  the  fossils  of  the  May-Hill 

shelly  sandstone  at  Malvern,  Tentaculites  annulatus  (fig. .  642),  an 
annelid  probably  allied  to  Serpula,  is  found.  It  is  also  abundant  in 
the  Caradoc  or  Lower  Silurian. 

Llandovery  Rocks  (Lower  Llandovery  of  Murchison). — Below  the 
May-Hill  group  are  the  Llandovery  Rocks,  so  named  from  a  town  in 
36 


Tentaculites  annulatus,  Schlot. 

Interior  casts  in  sandstone. 
Upper  Llandovery  and  Caradoc  sand- 
stone, Eastnor  Park,  near  Malvern. 
Nat.  size  and  magnified. 


562  LOWER  SILURIAN  ROCKS.  [Cn.  XXVII. 

South  Wales,  where  they  are  well  developed,  and  where  they  are  over- 
laid unconformably  by  the  equivalent  of  the  May-Hill  sandstone. 
They  consist  chiefly  of  hard  slaty  rocks,  with  bands  of  sandstone  and 
beds  of  conglomerate  from  600  to  1000  feet  in  thickness.  The  fossils, 
which  are  somewhat  rare,  consist  of  twenty-eight  known  species,  some 
few  peculiar,  a  part  agreeing  with  the  May-Hill  beds,  and  the  rest,  six- 
teen in  number,  belonging  to  Lower  Silurian  species ;  besides  these, 
no  less  than  fifty-four  species  of  fossils  are  given  by  Sir  R.  Murchison 
as  common  to  the  Lower  Silurian  (Caradoc)  and  the  Wenlock  forma- 
tions, and  we  cannot  doubt  that  all  these  existed  in  the  intermediate 
Llandovery  and  May-Hill  periods. 

The  whole  May-Hill  and  Llandovery  series  has  been  considered  by 
some  geologists  as  constituting  beds  of  passage  between  the  Lower 
and  Upper  Silurian,  while  others  have  assigned  to  it  the  rank  of  a 
Middle  Silurian  group.  It  may,  with  some  reason,  be  objected  that 
the  number  of  peculiar  fossils  are  not  sufficient  to  entitle  it  to  so  im- 
portant a  distinction ;  but  there  is  no  small  difficulty  at  present  in 
adopting  any  other  classification.  The  two  formations,  the  May-Hill 
and  the  Llandovery,  are  intimately  connected  by  their  fossils,  the 
Lower  having  about  two-thirds  of  its  species  common  to  the  Upper 
zone.  Again,  half  the  species  of  the  Llandovery  pass  down  into  the 
Lower  Silurian,  just  as  half  the  May-Hill  species  pass  up  into  the 
Wenlock.  In  England  we  might  draw  the  line,  as  Sir  R.  Murchison 
inclines  to  do,  between  Upper  and  Lower  Silurian,  by  classing  the 
May-Hill  with  the  higher  division,  and  the  Llandovery  with  the 
lower ;  but  in  countries  where  there  is  no  unconformability  of  strata 
between  the  two  zones,  such  a  line  of  demarcation  between  the  middle 
of  the  Pentamerus  beds  would  be  impracticable.  It  has  been  some- 
times suggested  that  we  might  form  a  better  tripartite  division  of  the 
Silurian  rocks  by  including  the  Wenlock  with  the  May-Hill  and  Llan- 
dovery beds  as  a  middle  group,  classing  the  two  Ludlow  formations  as 
Upper,  and  the  Caradoc  and  Llandeilo  formations  as  Lower  Silurian ;  * 
but  I  am  not  prepared  to  adopt  so  great  a  change  in  the  generally- 
received  classification. 


LOWER    SILURIAN    ROCKS. 

Caradoc  and  Bala  Beds. — The  Lower  Silurian  has  been  divided 
into — 1st,  Caradoc  Sandstone  and  Bala  Beds;  2dly,  the  Llandeilo 
Flags;  and  3dly,  the  Lower  Llandeilo  or  Arenig  formation.  The 
Caradoc  sandstone  was  originally  so  named  by  Sir  R.  I.  Murchison 
from  the  Mountain  called  Caer  Caradoc  in  Shropshire ;  it  consists  of 
shelly  sandstones  of  great  thickness,  and  sometimes  containing  much 
calcareous  matter.  The  rock  is  frequently  laden  with  the  beautiful 
trilobite  called  by  Murchison  Trinudeus  Caractaci  (see  fig.  647), 

*  See  Report  of  Canada  Survey  Table  of  Equivalents,  p.  932,  1863. 


CH.  XXVII.] 


CARADOC  AND  BALA  BEDS. 


563 


which  ranges  from  the  base  to  the  summit  of  the  formation,  usu- 
ally accompanied  by  Strophomena  grandis  (see  fig.  645),  and  Orthis 
vespertilio  (fig.  644),  with  many  other  fossils. 


£*.  644. 


Fig.  645. 


Orthis  tricenaria, 

Hall. 

New  York.    Canada, 
i  nut  size. 


Orthis  vespertilio,  Sow. 
Shropshire ;  N.  and  S. 

Wales, 
i  nat  size. 


Strophomena  (Orthis)  grandis,  Sow- 

erby.    §  nat.  size. 

Horderly,  Shropshire ;  also  Coniston, 
Lancashire. 


Burmeister,  in  his  work  on  the  organization  of  trilobites,  supposes 
them  to  have  swum  at  the  surface  of  the  water  in  the  open  sea  and 
near  coasts,  feeding  on  smaller  marine  animals,  and  to  have  had  the 
power  of  rolling  themselves  into  a  ball  as  a  defence  against  injury. 
He  was  also  of  opinion  that  they  underwent  various  transformations 
analogous  to  those  of  living  crustaceans.  M.  Barrande,  author  of  an 
admirable  work  on  the  Silurian  rocks  of  Bohemia,  confirms  the 
doctrine  of  their  metamorphosis,  having  traced  more  than  twenty 
species  through  different  stages  of  growth  from  the  young  state  just 
after  its  escape  from  the  egg  to  the  adult  form.  He  has  followed 
some  of  them  from  a  point  in  which  they  show  no  eyes,  no  joints  to 
the  body,  and  no  distinct  tail,  up  to  the  complete  form  with  the  full 


Fig.  647. 


Young   individuals  of    Trinucleus 
eoncentricus  (T.  ornatiis,  Barr). 

a.  Youngest  state.    Natural  size  and 
magnified ;  the  body  rings  not  at 
all  developed. 

b.  A  little  older.    One  thorax  joint 

c.  Still  more  advanced.    Three  tho- 
rax joints.    The  fourth,  fifth,  and 
sixth  segments  are   successively 
produced,  probably  each  time  the 
animal  moulted  its  crust. 


Trinucleus  concentricus,  Eaton. 

Syn.  T.  Caractaci,  Murch, 

N.  Ireland ;  Wales ;  Shropshire ; 

N.  America ;  Bohemia. 


number  of  segments.  This  change  is  brought  about  before  the 
animal  has  attained  a  tenth  part  of  its  full  dimensions,  and  hence 
such  minute  and  delicate  specimens  are  rarely  met  with.  Some  of 


564  CARADOC  AND  BALA  BEDS.  [Cn.  XXVII. 

his   figures  of  the  metamorphoses  of  the  common   Trinucleus  are 
copied  in  the  foregoing  woodcuts  (figs.  646,  647). 

In  Mr.  Baiter's  monograph  of  the  British  trilobites,  he  expresses 
his  opinion  that  their  habit  was  to  live  on  the  sea-bottom  and  devour 
the  silt  charged  with  organic  matter  as  sea-worms  do,  or  else,  possi- 
bly, to  devour  the  worms  themselves.  He  supposes  the  trilobite  to 
have  had  no  jaws,  and  to  have  been  provided  with  a  suctorial 
mouth.* 

It  has  been  ascertained  that  a  great  thickness  of  slaty  and  crys- 
talline rocks  of  South  Wales,  as  well  as  those  of  Snowdon  and  Bala 
in  North  Wales,  which  were  first  supposed  to  be  of  older  date  than 
the  Silurian  sandstones  and  mudstones  of  Shropshire,  are  in  fact 
identical  in  age  with  the  Caradoc  formation  now  under  considera- 
tion, and  contain  the  same  organic  remains.  At  Bala  in  Merioneth- 
shire, a  limestone  rich  in  fossils  occurs,  'and  below  it  sandstones 
some  thousands  of  feet  in  thickness.  In  this  limestone  several  rare 
starfishes  are  found,  and  abundance  of  those  peculiar  bodies  called 
Cystidce.  These  last  are  amongst  the  most  recent  additions  made  by 
palaeontologists  to  the  Radiata.  Their  structure  and  relations  were 
first  elucidated  in  an  essay  published  by  Yon  Buch  at  Berlin  in 
1845.  They  are  the  Sphceronites  of  old  authors,  and  are  usually 
met  with  as  spheroidal  bodies  covered  with  polygonal  plates,  with  a 
mouth  on  the  upper  side,  and  a  point  of  attachment  for  a  stem 

(which  is  almost  always  broken  off) 
on  the  lower  (fig.  648  b).  They 
were  considered  by  Prof.  E.  Forbes 
as  intermediate  between  the  crinoids 
and  echinoderms.  The  Echinosphce- 
ronite  here  represented  (fig.  648)  is 
characteristic  of  the  Caradoc  beds  in 
Wales,f  and  of  their  equivalents  in 
Sweden  and  Russia. 

With  it  have  been  found  several 
other  genera  of  the  same  family,  such 
as  Sphceronites,  Hemicosmites,  <fec. 

Echinosphasrites  balticw,  Eichwald,  sp.  * 

(Of  the  family  CyaUdece.)  Among  the  mollusca  are  Pteropods 

a.  Mouth.  of  t^  o-enus  Conularia  of  large  size 

&.  Point  of  attachment  of  stem.  ,„ 

Lower  Silurian,  S.  and  N.  Wales.  (for    genUS,    866    fig.     611,    p.     540); 

Graptolites  are  rare,  except  in  pecu- 
liar localities  where  black  mud  abounds.  The  formation,  when  traced 
into  South  Wales  and  Ireland,  assumes  a  greatly  altered  mineral 
aspect,  but  still  retains  its  characteristic  fossils.  In  Tyrol  it  is  espe- 
cially rich  in  organic  remains.^  It  is  worthy  of  remark  that,  when  it 


*  Palaeontographica,  vol.  xvL  p.  9,  1864. 

f  Quart.  Geol.  Journ.,  vol.  vii.  p.  11 ;  and  Mem.  Geol.  Surv.,  vol.  ii.  p.  518. 

i  See  Portlock's  Report  of  Londonderry,  1843. 


CH.  XXVII.]  LLANDEILO  FLAGS. 

occurs  under  the  form  of  trappean  tuff  (volcanic  ashes  of  De  la 
Beche),  as  in  the  crest  of  Snowdon,  the  peculiar  species  which  dis- 
tinguish it  from  the  Llandeilo  beds  are  still  observable.  The  forma- 
tion generally  appears  to  be  of  shallow-water  origin,  and  in  that 
respect  is  contrasted  with  the  group  next  to  be  described.  Professor 
Ramsay  estimates  the  thickness  of  the  Bala  Beds,  including  the  con- 
temporaneous volcanic  rocks,  stratified  and  unstratified,  as  being  from 
10,000  to  12,000  feet  in  thickness. 

Llandeilo  Flags. — The  Lower  Silurian  strata  were  originally  divided 
by  Sir  R.  Murchison  into  the  upper  group  already  described,  under 
the  name  of  Caradoc  Sandstone,  and  a  lower  one,  called,  from  a  town 
in  Caermarthenshire,  the  Llandeilo  flags.  The  last-mentioned  strata 
consist  of  dark-colored  micaceous  flags,  frequently  calcareous,  with  a 
great  thickness  of  shales,  generally  black,  below  them.  The  same 
beds  are  also  seen  at  Builth  in  Radnorshire,  and  here  they  are  inter- 
stratified  with  volcanic  matter. 

A  still  lower  part  of  the  Llandeilo  rocks  consists  of  a  black  car- 
bonaceous slate  of  great  thickness,  frequently  containing  sulphate  of 
alumina,  and  sometimes,  as  in  Dumfriesshire,  beds  of  anthracite.  It 
has  been  conjectured  that  this  carbonaceous  matter  may  be  due  in 
great  measure  to  large  quantities  of  imbedded  animal  remains,  for 
the  number  of  Graptolites  included  in  these  slates  was  certainly  very 
great.  I  collected  these  same  bodies  in  great  numbers  in  Sweden  and 
Norway  in  1835— '6,  both  in  the  higher  and  lower  graptolitic  shales 
of  the  Silurian  system ;  and  was  informed  by  Dr.  Beck  of  Copen- 

»i ,  <l  Fig.  649.  Fig.  650. 

(Old  plate,  fig.  599,  p.  442.) 


Didymograpsus  (Graptolites)  Diplograpsus  prtetis, 

Murchisonii,  Beck.  Hisinger,  sp. 

Llandeilo  flags.    Wales.  Shropshire ;  "Wales  ;  Sweden,  &c. 

Llandeilo  flags. 

Fig.  651. 

fa 

Fig.  652. 


Rastrites  p&regrinus,  Barrande.  Diplograpw*  folium,  Hisinger. 

Scotland;  Bohemia;  Saxony:  Dumfriesshire;  Sweden. 

Llandeilo  flags.  Llandeilo  flags. 

hagen  that  they  were  fossil  zoophytes  related  to  the  Virgularia  and 
Pennatula,  genera  of  which  the  living  species  now  inhabit  mud  and 


566 


FOSSILS  OF  THE 


[Cn.  XXVII. 


slimy  sediment.  Some  of  our  most  eminent  naturalists  still  hold  to 
this  opinion,  others  refer  them  to  Bryozoa. 

The  brachiopoda  of  the  Llandeilo  flags,  which  are  very  abundant, 
are  in  the  main  the  same  as  those  of  the  Caradoc  Sandstone,  but 
the  other  mollusca  are  in  great  part  of  different  species. 

In  Europe  generally,  as,  for  example,  in  Sweden  and  Russia,  no 
shells  are  so  characteristic  of  this  formation  as  Orthoceratites,  usu- 
ally of  great  size,  and  with  a  wide  siphuncle  placed  on  one  side 
instead  of  being  central  (see  fig.  653).  The  same  form  also  occurs  in 

Fig.  653. 


Orfhoceras  duplex,  Wahlenberg.    Eussia  and  Sweden. 

(From  Murchison's  "  Siluria.") 

a.  Lateral  siphuncle  laid  bare  by  the  removal  of  a  portion  of  the  chambered  shell. 
&.  Continuation  of  the  same  seen  in  a  transverse  section  of  the  shell. 

the  Bala  beds  in  England.  Among  other  Cephalopods  in  the  Llan- 
deilo flags  are  Lituites  (see  fig.  629) ;  in  the  same  beds  also  are  found 
Bellerophon  (see  fig.  577,  p.  520)  and  some  Pteropod  shells  (Conula- 
ria,  Theca,  &c.),  also  in  spots  where  sand  abounded  lamellibranchiate 
bivalves  of  large  size.  The  Crustaceans  were  plentifully  represented 
by  the  Trilobites,  which  appear  to  have  swarmed  in  the  Silurian  seas 
just  as  crabs  and  shrimps  do  in  our  own.  The  genera  Asaphus  (fig. 
654),  Ogygia  (fig.  655),  and  Trinucleus  (figs.  646,  647),  form  a 
marked  feature  of  the  rich  and  varied  Trilobitic  fauna  of  this  age. 


.  654. 


Fig.  655. 


Asaphus  tyrannus.  March. 
Llandeilo ;  Bishop's  Castle,  &c. 


Ogygia  BucMi,  Burm. 
Syn.  Asaphus  Buchii,  Brongn. 
Builth,  Eadnorshire ;  Llandeilo,  Caermarthenshire. 


Beneath  the  black  slates  above  described  of  the  Llandeilo  forma- 
tion, graptolites  are  still  found  in  great  variety  and  abundance,  and 
the  characteristic  genera  of  shells  and  trilobites  of  the  Lower  Silurian 
rocks  are  still  traceable  downwards,  in  Shropshire,  Cumberland,  and 


CH.  XXVII.]  LLANDEILO  FLAGS.  567 

North  and  South  Wales,  through  a  vast  depth  of  shaly  beds,  inter- 
stratified  with  trappean  formations  of  contemporaneous  origin  ;  these 
consist  of  tuffs  and  lavas,  the  tuffs  being  formed  of  such  materials  as 
are  ejected  from  craters  and  deposited  immediately  on  the  bed  of  the 
ocean,  or  washed  into  it  from  the  land.  According  to  Professor 
Ramsay,  their  thickness  is  about  3300  feet  in  North  Wales,  including 
those  of  the  Lower  Llandeilo.  The  lavas  are  felspathic,  and  of  por- 
phyritic  structure,  and,  according  to  the  same  authority,  of  an  aggre- 
gate thickness  of  2500  feet. 

Lower  Llandeilo  Formation,  Murchison  ;  Arenig,  Sedgwick. — Next 
in  the  descending  order  are  the  shales  and  sandstones  in  which  the 
quartzose  rocks  called  Stiper-stones  in  Shropshire  occur.  When  the 
term  "Silurian"  was  given  by  Sir  R.  Murchison,  in  1835,  to  the 
whole  series,  he  considered  the  Stiper-stones  as  the  base  of  the  Silu- 
rian system,  but  no  fossil  fauna  had  then  been  obtained,  such  as  could 
alone  enable  the  geologist  to  draw  a  definite  line  between  this^  mem- 
ber of  the  series  and  the  Llandeilo  flags  above,  or  a  vast  thickness 
of  rock  below  which  was  seen  to  form  the  Longmynd  hills,  and  was 
called  "  unfossiliferous  graywacke."  Professor  Sedgwick  had  de- 
scribed strata  now  ascertained  to  be  of  the  same  age  as  largely  de- 
veloped in  the  Arenig  mountain  in  Merionethshire,  in  1843,  and  the 
Skiddaw  slates,  studied  by  the  same  author,  were  of  corresponding 
date,  though  the  number  of  fossils  was,  in  both  cases,  too  few  for  the 
determination  of  their  true  chronological  relations.  The  subsequent 
researches  of  MM.  Sedgwick  and  Harkness  in  Cumberland,  and  of 
Sir  R.  I.  Murchison  and  the  Government  surveyors  in  Shropshire, 
have  increased  the  species  to  more  than  sixty.  These  have  been 
examined  by  Mr.  Salter,  and 

shown  in  the  last  edition  of  F5s-  656- 

"Siluria"  (p.  52,  1859)  to 
be  quite  distinct  from  the 
fossils  of  the  overlying  Llan- 

,    ..      n  Didymograpsm  geminus,  Hi  singer,  sp. 

deilo  nags.    Among  these  the  Sweden. 

Lingula    plumbea,     ufflglina 

binodosa,  Ogygia  Selwynii,  and  Didymograpsus  geminus  (fig.  656), 

and  D.  hirundo,  are  characteristic. 

In  reference  to  the  classification  of  the  Silurian  rocks,  two  questions 
have  been  raised ;  first,  whether  the  Lower  Silurian,  comprising  the 
Caradoc  and  Llandeilo  beds  already  described,  should  be  separated 
from  the  Upper  Silurian  under  some  new  title,  such  as  Cambro- 
Silurian ;  and  secondly,  whether,  if  we  reject  this,  the  Arenig  or  Stiper- 
stones  group  (Lower  Llandeilo  of  Murchison)  should  be  regarded  as 
the  base  of  the  Lower  Silurian  or  as  the  top  of  a  distinct  and  older 
series.  In  reference  to  the  first  question  Sir  R.  Murchison,  in  his  im- 
portant work  above  cited,*  has  given  a  list  of  no  less  than  fifty  or 

*  Siluria,  p.  485. 


568  LLANDEILO  FLAGS.  [Cn.  XXVII. 

sixty  species  of  fossils  (of  which  specimens  had  been  examined  either 
by  Mr.  Salter  or  Prof.  McCoy),  all  common  to  the  Upper  and  Lower 
Silurian  strata,  or,  in  other  words,  which,  being  found  in  the  Caradoc, 
are  also  met  with  in  the  Wenlock  formation.  The  range  upwards  of 
so  many  species  from  the  inferior  to  the  superior  group  shows  that, 
independently  of  the  link  supplied  by  the  Llandovery  or  Middle 
Silurian,  there  is  such  a  connection  between  the  two  principal  divisions 
(Upper  and  Lower  Silurian)  as  makes  it  natural  to  assign  the  whole 
to  one  great  system.  To  attempt,  therefore,  to  give  a  new  name  to 
the  Llandeilo  beds,  or  to  call  them  Cambrian  or  Cambro- Silurian,  as 
has  been  proposed,  would  be  to  act  in  violation  of  the  ordinary  rules 
of  classification,  and  would  create  much  confusion  by  disturbing  a 
nomenclature  long  received  and  originally  established,  by  Sir  B.  I. 
Murchison,  on  well-defined  palaeontological  and  stratigraphical  data. 

As  to  the  second  question,  whether  a  line  should  not  be  drawn 
between  the  Llandeilo  flags  and  the  subjacent  Stiper-stones  or  Arenig 
group,  more  may  be  said  in  its  favor,  since  while  so  many  species  pass 
from  Lower  to  Upper  Silurian,  there  are  none,  according  to  Mr. 
Salter,  which  pass  down  from  the  Llandeilo  flags  or  Upper  Llandeilo, 
into  the  Arenig  or  Lower  Llandeilo  beds.  But,  although  the  species 
are  distinct,  the  genera  are  the  same  as  those  which  characterize  the 
Silurian  rocks  above,  and  none  of  the  primordial  or  Cambrian  forms, 
presently  to  be  mentioned,  are  intermixed.  This  Arenig  group  may 
therefore  be  conveniently  regarded  as  the  base  of  the  great  Silurian 
system,  which,  by  the  thickness  of  its  strata  and  the  changes  in  animal 
life  of  which  it  contains  the  record,  is  more  than  equal  in  value  to  the 
Devonian,  or  Carboniferous,  or  other  principal  divisions,  whether  of 
primary  or  secondary  date. 

It  would  be  unsafe  to  rely  on  the  mere  thickness  of  the  strata,  con- 
sidered apart  from  the  great  fluctuations  in  organic  life  which  took 
place  between  the  era  of  the  Llandeilo  and  that  of  the  Ludlow  forma- 
tion, especially  as  the  enormous  pile  of  Silurian  rocks  observed  in 
Great  Britain,  and  especially  in  Wales,  is  derived  in  great  part  from 
igneous  action,  and  is  not  confined  to  the  ordinary  deposition  of  sedi- 
ment from  rivers  or  the  waste  of  cliffs. 

In  volcanic  arphipelagoes,  such  as  the  Canaries,  we  see  the  most 
active  of  all  known  causes,  aqueous  and  igneous,  simultaneously  at 
work  to  produce  great  results  in  a  comparatively  moderate  lapse  of 
time.  The  outpouring  of  repeated  streams  of  lava — the  showering 
down  upon  land  and  sea  of  volcanic  ashes — the  sweeping  seaward  of 
loose  sand  and  cinders,  or  of  rocks  ground  down  to  pebbles  and  sand, 
by  rivers  and  torrents  descending  steeply  inclined  channels — the 
undermining  and  eating  away  of  long  lines  of  sea-cliff  exposed  to  the 
swell  of  a  deep  and  open  ocean — these  operations  combine  to  pro- 
duce a  considerable  volume  of  superimposed  matter,  without  there 
being  time  for  any  extensive  change  of  species.  Nevertheless,  there 
would  seem  to  be  a  limit  to  the  thickness  of  stony  masses  formed 


CH.  XXVH.]          SILURIAN  EQUIVALENTS  IN  EUROPE.  569 

even  under  such  favorable  circumstances,  for  the  analogy  of  tertiary 
volcanic  regions  lends  no  countenance  to  the  notion  that  sedimentary 
and  igneous  rocks  25,000,  much  less  45,000  feet  thick,  like  those  of 
Wales,  could  originate  while  one  and  the  same  fauna  should  continue 
to  people  the  earth.  If,  then,  we  allow  that  about  25,000  feet  of  mat- 
ter may  be  ascribed  to  one  system,  such  as  the  Silurian,  as  above  de- 
scribed, we  may  be  prepared  to  discover  in  the  next  series  of  subjacent 
rocks  a  distinct  assemblage  of  species,  or  even  in  great  part  of  genera, 
of  organic  remains.  Such  appears  to  be  the  fact,  and  I  shall  therefore 
conclude,  with  the  Lower  Llandeilo  or  Arenig  beds,  my  enumeration 
of  the  Silurian  formations  in  Great  Britain,  and  proceed  to  say  some- 
thing of  their  foreign  equivalents,  before  treating  of  rocks  older  than 
the  Silurian. 

SILURIAN    STRATA    OF    THE    CONTINENT    OF    EUROPE. 

When  we  turn  to  the  Continent  of  Europe,  we  discover  the  same 
ancient  series  occupying  a  wide  area,  but  in  no  region  as  yet  has  it 
been  observed  to  attain  great  thickness.  Thus,  in  Norway  and 
Sweden,  the  total  thickness  of  strata  of  Silurian  age  is  scarcely  equal  to 
1000  feet,*  although  the  representatives  both  of  the  Upper  and  Lower 
Silurian  of  England  are  not  wanting  there,  and  even  some  beds  of 
schist  have  been  included,  which,  as  we  shall  hereafter  see,  lie  below 
the  Llandeilo  group.  In  Russia  the  Silurian  strata,  so  far  as  they  are 
yet  known,  seem  to  be  even  of  smaller  vertical  dimensions  than  in 
Scandinavia,  and  they  appear  to  consist  chiefly  of  Middle  and  Lower 
Silurian,  or  of  a  limestone  containing  Pentamerus  oblongus,  below 
which  are  strata  with  fossils  corresponding  to  those  of  the  Llandeilo 
beds  of  England.  The  lowest  rock  with  organic  remains  yet  dis- 
covered is  "  the  Ungulite  or  Obolus  grit "  of  St.  Petersburg,  probably 
coeval  with  the  Llandeilo  flags  of  Wales. 

The  shales  and  grits  near  St.  Petersburg,  above  alluded  to,  contain 
green  grains  in  their  sandy  layers,  and  are  in  a  singularly  unaltered 
state,  taking  into  account  their  high  antiquity.  The  prevailing 

Shells  of  the  lowest  known  Fossiliferous  Beds  in  Rwsia. 
Fig.  65T.  Fig.  658. 


Siphonotreta  unguiculala,  Eichwald.  Obolus  Apollinis,  Eichwald. 

From  the  Lowest  Silurian  Sandstone  "  Obolus  From  the  same  locality. 

grits,"  of  Petersburg.  a.  Interior  of  the  larger  or  ventral  valve. 

a.  Outside  of  perforated  valve.  Z>.  Exterior  of  the  upper  (dorsal)  valve. 
&.  Interior  of  same,  showing  the  termination  (Davidson,  "  Palaeontograph.  Monog.") 

of  the  foramen  within.    (Davidson.) 

*  Murcbison's  Siluria,  p.  321. 


570  SILURIAN  STRATA  OF  UNITED  STATES.         [On.  XXVII. 

brachiopods  consist  of  the  Obolus  or  Ungulite  of  Pander,  and  a 
Siphonotreta  (figs.  657,  658).  Notwithstanding  the  antiquity  of  this 
Russian  formation,  it  should  be  stated  that  both  of  these  genera  of 
brachiopods  have  been  also  found  in  the  Upper  Silurian  of  England, 
i.  e.  in  the  Dudley  limestone. 

Among  the  green  grains  of  the  sandy  strata  above  mentioned,  Prof. 
Ehrenberg  has  announced  (1854)  his  discovery  of  remains  of  foram- 
inifera.  These  are  casts  of  the  cells ;  and  amongst  five  or  six  forms 
three  are  considered  by  him  as  referable  to  existing  genera  (e.  g. 
Textularia,  Rotalia,  and  Guttulind). 

SILURIAN    STRATA    OF   THE    UNITED    STATES. 

The  position  of  some  of  these  strata,  where  they  are  bent  and  highly 
inclined  in  the  Appalachian  chain,  or  where  they  are  nearly  horizontal 
to  the  west  of  that  chain,  is  shown  in  the  section,  fig.  552,  p.  49*7. 
But  these  formations  can  be  studied  still  more  advantageously  north 
of  the  same  line  of  section,  in  the  States  of  New  York,  Ohio,  and  other 
regions  north  and  south  of  the  great  Canadian  lakes.  Here  they  are 
found,  as  in  Russia,  nearly  in  horizontal  position,  and  are  more  rich  in 
well-preserved  fossils  than  in  almost  any  spot  in  Europe.  In  the  State 
of  New  York,  where  the  succession  of  the  beds  and  their  fossils  have 
been  most  carefully  worked  out  by  the  Government  surveyors,  the 
subdivisions  given  in  the  first  column  of  the  annexed  list  have  been 
adopted. 

Subdivisions  of  the  Silurian  Strata  of  New   York.      (Strata  below 
the  OrisJcany  Sandstone,  see  Table,  p.  543.) 

New  York  Names.  British  Equivalents. 

1.  Upper  Pentamerus  Limestone.    ~] 

2.  Encrinal  Limestone. 

3.  Delthyris  Shaly  Limestone. 

4.  Pentameras    and     Tentaculite  I  Upper    Silurian    (or    Ludlow    and 

Limestones.  f      Wenlock  Formations). 

5.  Water  Lime  Group. 

6.  Onondaga  Salt  Group. 

7.  Niagara  Group. 

8.  Clinton  Group. 

Medina  Sandstone.  I  Middle  Silurian  (or  May-Hill  and 

Llandovery  Groups). 


10.  Oneida  Conglomerate. 

11.  Gray  Sandstone. 

12.  Hudson  River  Group. 

13.  Utica  Slate. 

14.  Trenton  Limestone. 

15.  Black-River  Limestone. 

16.  Bird's-Eye  Limestone. 

17.  Chazy  Limestone. 

18.  Calciferous  Sandstone. 

19.  Potsdam  Saudstone.  Upper  Cambrian. 


Lower    Silurian    (or   Caradoc    and 
Upper  and  Lower  Llandeilo). 


In  the  second  column  of  the  same  table  I  have  added  the  supposed 
British  equivalents.     All  palaeontologists,  European  and  American, 


CH.  XXVH.]  SPECIFIC  AGREEMENT  OF  FOSSILS.  571 

such  as  MM.  de  Verneuil,  D.  Sharpe,  Prof.  Hall,  E.  Billings,  and 
others,  who  have  entered  upon  this  comparison,  admit  that  there  is 
a  marked  general  correspondence  in  the  succession  of  fossil  forms,  and 
even  species,  as  we  trace  the  organic  remains  downwards  from  the 
highest  to  the  lowest  beds ;  but  it  is  impossible  to  parallel  each  minor 
subdivision.  In  regard  to  the  three  following  points  there  is  little 
difference  of  opinion. 

1st.  That  the  Niagara  limestone,  No.  V,  over  which  the  river  of  that 
name  is  precipitated  at  the  great  cataract,  together  with  its  underlying 
shales,  corresponds  to  the  Wenlock  limestone  and  shale  of  England. 
Among  the  species  common  to  this  formation  in  America  and  Europe 
are  Calymene  Ulumenbachii,  Homalonotus  delphinocephalus  (fig.  639, 
p.  559),  with  several  other  trilobites ;  Rhynchonella  Wilsoni,  and 
Retzia  cuneata  ;  Or  this  elegantula,  Pentamerus  galeatus,  with  many 
more  brachiopods ;  Orthoceras  annulatum,  among  the  cephalopodous 
shells ;  and  Favosites  gothlandica,  with  other  large  corals. 

2d.  That  the  Clinton  Group,  No.  8,  containing  Pentamerus  oblongus 
and  P.  lewis,  and  related  more  nearly  by  its  fossil  species  with  the 
beds  above  than  with  those  below,  is  the  equivalent  of  the  Middle 
Silurian  as  above  defined,  p.  560. 

3d.  That  the  Hudson  River  Group,  No.  12,  and  the  Trenton  Lime- 
stone, No.  14,  agree  palseontologically  with  the  Caradoc  or  Bala  group, 
containing  in  common  with  them  several  species  of  trilobites,  such  as 
Asaphus  (Isotelus)  gigas,  Trinucleus  concentricus  (fig.  647,  p.  563) ; 
and  various  shells,  such  as  Orthis  striatula,  Or  this  biforata  (or  0.  lynx), 
0.  porcata  (0.  occidentalis  of  Hall),  Bellerophon  bilobatus,  &c.* 

Mr.  D.  Sharpe,  in  his  report  on  the  mollusca  collected  by  me  from 
these  strata  in  North  America,f  has  concluded  that  the  number  of 
species  common  to  the  Silurian  rocks  on  both  sides  of  the  Atlantic  is 
between  30  and  40  per  cent. ;  a  result  which,  although  no  doubt  liable 
to  future  modification,  when  a  larger  comparison  shall  have  been 
made,  proves,  nevertheless,  that  many  of  the  species  had  a  wide 
geographical  range.  It  seems  that  comparatively  few  of  the  gastero- 
pods  and  lamellibranchiate  bivalves  of  North  America  can  be  identified 
specifically  with  European  fossils,  while  no  less  than  two  fifths  of  the 
brachiopoda,  of  which  my  collection  chiefly  consisted,  are  the  same. 
In  explanation  of  these  facts,  it  is  suggested  that  most  of  the  recent 
brachiopoda  (especially  the  orthidiform  ones)  are  inhabitants  of  deep 
water,  and  that  they  may  have  had  a  wider  geographical  range  than 
shells  living  near  shore.  The  predominance  of  bivalve  mollusca  of 
this  peculiar  class  has  caused  the  Silurian  period  to  be  sometimes 
styled  "  the  age  of  brachiopods." 

The  calcareous  beds,  Nos.  15,  16,  17,  and  18,  below  the  Trenton 
Limestone,  have  been  considered  by  M.  de  Verneuil  as  Lower  Silurian, 

*  See  Murchison's  Siluria,  p.  414. 
f  Quart.  Geol.  Journ.,  vol.  iv. 


572 


CANADIAN  EQUIVALENTS. 


[On.  XXVII. 


because  they  contain  certain  species,  such  as  Asaphus  (Isotelus)  gigas, 
Illcenus  crassicauda  and  Orthoceras  bilineatum,  in  common  with  the 
overlying  Trenton  Limestone.*  But,  according  to  Prof.  Hall,  the 
Illcenus  was  erroneously  identified,  an  error  to  which  he  confesses 
that  he  himself  contributed ;  and  on  the  whole  these  lower  beds  con- 
tain, he  thinks,  a  very  distinct  set  of  species,  only  3  or  4  of  them 
out  of  83  passing  upwards  into  the  incumbent  formation s.f 

Be  this  as  it  may,  the  Black  River  Limestone,  No.  15,  contains 
certain  forms  of  Orthoceras  of  enormous  size  (some  of  them  8  or  9 
feet  long !),  of  the  subgenera  Ormoceras  and  Endoceras,  seeming  to 
represent  the  Lower  Silurian  or  Orthoceras  limestone  of  Sweden. 
Moreover,  the  general  facies  of  the  fauna  of  all  these  beds  is  essen- 
tially similar.  Another  ground  for  extending  our  comparison  of  the 
Llandeilo  beds  of  Europe  as  far  down  as  the  calciferous  sandstone  is 
derived  from  the  researches  of  Sir  William  Logan  in  Canada,  and  the 
study  by  Mr.  Salter  of  the  fossils  collected  by  the  Canadian  surveyor 
near  the  S.E.  end  of  the  Ottawa  River,  where  one  mass  of  limestone 

Fossils  from  Allumette  Rapids,  River  Ottawa,  Canada, 
a  Fig.  659. 

i 


Macltirea  Logani,  Salter. 
a.  Yiew  of  the  shell.  Z>.  Its  curious  operculum. 

Fig.  660.  encloses  species  common  to  all  the  beds  from 

the  Calciferous  Sandstone  (No.  18)  up  to  the 
Trenton  Limestone  (No.  14).  In  this  rock, 
the  Asaphus  gigas  and  other  well-known  Tren- 
ton species  are  blended  with  the  Maclurea 
(fig.  659),  a  left-handed  shell,  considered  by 
Woodward  as  probably  a  massive  heteropod, 
a  genus  characteristic  of  the  Chazy  Limestone, 
or  No.  17 ;  and  Murchisonia  gracilis  (fig. 
660)  is  another  Trenton  Limestone  species 
found  in  the  same  Silurian  limestone  of  Cana- 
da ;  J  while  one  of  the  most  common  shells  in 

it  is  the  Rapliistoma  ?  (Euomphalus)  uniangulatum.  Hall,  a  species 
characteristic  in  New  York  of  the  Calciferous  Sandstone  itself.  On 
the  whole,  if  we  identify  the  beds  from  the  Black  River  Limestone 


Murchisonia  gracilis,  Hall. 

A  fossil  characteristic  of  the 
Trenton  Limestone.  The 
genus  is  common  in  Lower 
Silurian  rocks. 


*  Soc.  Geol.  France,  Bulletin,  vol.  iv.  p.  651,  184Y. 

f  Hall ;  Forster  and  Whitney's  Report  on  Lake  Superior,  Ft.  II.,  1851. 

J  Logan,  Report,  Brit.  Assoc.  Ipswich,  pp.  59,  63. 


CH.  XXVIL]  CAMBRIAN   GROUP.  5Y3 

down  to  the  Calciferous  Sandstone  inclusively  with  the  Upper  and 
Lower  Llandeilo,  we  shall  be  in  harmony  with  the  latest  opinions  of 
American  and  British  geologists. 

In  Canada,  as  in  the  State  of  New  York,  the  Potsdam  Sandstone 
underlies  the  above-mentioned  calcareous  rocks,  but  contains  a  dif- 
ferent suite  of  fossils,  as  will  be  hereafter  explained.  In  parts  of  the 
globe  still  more  remote  from  Europe  the  Silurian  strata  have  also  been 
recognized,  as  in  South  America,  Australia,  and  recently  by  Captain 
Strachey  in  India.  In  all  these  regions  the  facies  of  the  fauna,  or 
the  types  of  organic  life,  enable  us  to  recognize  the  contemporane- 
ous origin  of  the  rocks ;  but  the  fossil  species  are  distinct,  showing 
that  the  old  notion  of  a  universal  diffusion  throughout  the  "  primeval 
seas  "  of  one  uniform  specific  fauna  was  quite  unfounded,  geographical 
provinces  having  evidently  existed  in  the  oldest  as  in  the  most  modern 
times. 

Whether  the  Silurian  rocks  are  of  deep-water  origin. — The  grounds 
relied  upon  by  Professor  E.  Forbes  for  inferring  that  the  larger  part 
of  the  Silurian  Fauna  is  indicative  of  a  sea  more  than  70  fathoms 
deep,  are  the  following :  first,  the  small  size  of  the  greater  number  of 
conchifera ;  secondly,  the  paucity  of  pectinibranchiata  (or  spiral  uni- 
valves) ;  thirdly,  the  great  number  of  floating  shells,  such  as  Bellero- 
phon,  Orthoceras,  &c. ;  fourthly,  the  abundance  of  orthidiform  brachi- 
opoda ;  fifthly,  the  absence  or  great  rarity  of  fossil  fish. 

It  is  doubtless  true  that  some  living  Terebratulce,  on  the  coast  of  Aus- 
tralia, inhabit  shallow  water ;  but  all  the  known  species,  allied  in  form 
to  the  extinct  Or  this,  inhabit  the  depths  of  the  sea.  It  should  also  be 
remarked  that  Mr.  Forbes,  in  advocating  these  views,  was  well  aware 
of  the  existence  of  shores,  bounding  the  Silurian  sea  in  Shropshire,  and 
of  the  occurrence  of  littoral  species  of  this  early  date  in  the  northern 
hemisphere.  Such  facts  are  not  inconsistent  with  his  theory  ;  for  he 
has  shown,  in  another  work,  how,  on  the  coast  of  Lycia,  deep-sea 
strata  are  at  present  forming  in  the  Mediterranean,  in  the  vicinity  of 
high  and  steep  land. 

Had  we  discovered  the  ancient  delta  of  some  large  Silurian  river, 
we  should  doubtless  have  known  more  of  the  shallow-water,  brackish- 
water,  and  fluviatile  animals,  and  of  the  terrestrial  flora  of  the  period 
under  consideration.  To  assume  that  there  were  no  such  deltas  in 
the  Silurian  world,  would  be  almost  as  gratuitous  an  hypothesis,  as  for 
the  inhabitants  of  the  coral  islands  of  the  Pacific  to  indulge  in  a  similar 
generalization  respecting  the  actual  condition  of  the  globe. 


"CAMBRIAN  GROUP." 
(Primordial  Zone  of  Barrande.) 

The  characters  of  the  Upper  and  Lower  Silurian  rocks  were  estab- 
lished so  fully,  both  on  stratigraphical  and  palaeontological  data,  by 


5T4  CAMBRIAN  GROUP.  [On.  XXVII. 

Sir  Roderick  Murchison  after  five  years'  labor,  in  1839,  when  his 
"Silurian  System"  was  published,  that  these  formations  could  from 
that  period  be  recognized  and  identified  in  all  other  parts  of  Europe 
and  in  North  America,  even  in  countries  where  the  fossils  differed 
specifically  from  those  of  the  classical  region  in  Britain,  where  they 
were  first  studied.  But  it  was  not  till  the  year  1846  that  M.  Joachim 
Barrande,  after  ten  years'  exploration  of  Bohemia,  and  after  collecting 
more  than  a  thousand  species  of  fossils,  ascertained  the  existence  in 
that  country  not  only  of  the  equivalents  of  the  two  formations  above 
alluded  to,  but  of  another  set  of  strata,  characterized  by  a  new  and 
distinct  fauna,  to  which,  in  the  introduction  to  a  treatise  on  trilobites, 
he  gave  the  name  of  3£tage  C,  or  the  "  first  fauna."  His  two  first 
stages,  A  and  B,  consisted  of  crystalline  and  metamorphic  rocks,  and 
unfossiliferous  schists.  In  the  zone  C,  called  soon  afterwards  by  him 
"primordial,"  he  had  discovered  in  1846  no  less  than  twenty-six  spe- 
cies of  trilobites  contained  in  shales  and  slates  of  considerable  thick- 
ness, all  of  them  belonging  to  new  species  and  the  greater  part  of 
them  to  new  genera,  called  by  him  Paradoxides,  Conocephalus  (syn. 
Conocoryphe),  Ellipsocephalus,  Arion,  Sao,  and  Hydrocephalus,  and 
some  of  them  to  the  genus  Agnostus,  the  only  form  common  to  his 
first  and  second  fauna,  the  latter  corresponding  to  the  Lower  Silurian 
of  Murchison.  M.  Barrande  classed  this  first  fauna  as  the  oldest 
member  of  the  Silurian  period,  applying  the  term  Silurian  in  Sir  R. 
Murchison's  sense  as  comprehending  all  the  fossiliferous  strata  older 
than  the  Devonian.  He  spoke  of  it  as  occupying  "  le  mcme  horizon 
que  les  formations  fossiliferes  les  plus  anciennes  de  Suede,  de  Norvege 
et  des  Isles  Britanniques ; "  and  he  added,  still  speaking  of  Etage  C, 
"  II  forme  done  la  base  des  terrains  protozoiques,  selon  la  derniere 
classification  du  Rev.  Professeur  Sedgwick."  *  It  was  impossible  in 
1846  for  M.  Barrande  to  make  a  nearer  approach  towards  a  just  cor- 
relation of  the  Bohemian  and  British  groups  of  strata,  since  at  that 
time  the  Lower  Silurian  of  Murchison  had  no  well-defined  base-line, 
physical  or  zoological,  while  the  Cambrian  or  protozoic  of  Sedgwick,  as 
distinguished  from  the  Lower  Silurian,  was  without  a  fauna.  Even 
the  Lingula  Davisii,  which  will  presently  be  mentioned,  was  not  dis- 
covered till  1846,  at  which  time  the  new  organic  types  of  Bohemia, 
older  than  the  Lower  Llandeilo  beds  above  described,  were  so  peculiar 
as  to  enable  geologists  from  that  time  forth  to  identify  by  their  means 
alone  in  Scandinavia,  Russia,  Canada,  and  the  United  States,  strata  of 
corresponding  age.  It  was  some  years  before  a  sufficient  number  of 
British  fossils  were  found  below  the  Lower  Llandeilo  beds  to  enable 
the  geologist  to  identify  the  different  members  of  the  Cambrian 
group  with  their  equivalents  in  Ireland  and  Scotland,  and  other 
parts  of  Europe.  If,  therefore,  M.  Barrande  had,  in  1846,  called  the 
fossiliferous  rocks  of  his  3£tage  C  "Bohemian,"  that  name  would, 

*  Trilobites  de  Boheme,  Leipsig,  1846. 


CH.  XXVII.] 


CAMBRIAN  GROUP. 


575 


I  have  little  doubt,  have  been  universally  accepted,  since  he  had 
acquired  full  right  to  give  a  name  to  the  new  group  or  system  of 
rocks,  the  position  and  characteristic  fossils  of  which  he  had  first 
truly  defined. 

The  term  "primordial"  was  intended  to  express  M.  Barrande's  own 
belief  that  the  fossils  of  fitage  C  afforded  evidence  of  the  first  ap- 
pearance of  vital  phenomena  on  this  planet,  and  that  consequently 
no  fossiliferous  strata  of  older  date  would  or  could  ever  be  dis- 
covered. 

I  have  been  opposed  from  the  first  to  a  nomenclature  the  adoption 
of  which  would  seem  to  imply  the  acceptance  of  such  a  theory,  for  I 
always  felt  sure,  on  contemplating  the  past  history  of  geology,  that 
we  had  not  yet  pushed  our  inquiries  into  the  past  so  far  as  to  lead  us 
to  despair  of  extending  our  discoveries  at  some  future  day,  when  vast 
portions  of  the  globe  hitherto  unexplored  should  have  been  thoroughly 
surveyed. 

The  term  "  Cambrian  "  had,  long  before  1846,  been  applied  by  Prof. 
Sedgwick  to  rocks,  some  of  which  we  now  know  to  be  of  contem- 
poraneous date  with  Barrande's  "primordial  zone."  Sedgwick  had 
begun  his  exploration  of  these  rocks  in  1831,  and  in  1843  published 
memoirs  on  what  he  then  termed  the  protozoic  rocks  of  North  Wales, 
giving  detailed  sections  by  which  the  geological  structure  of  an  intri- 
cate region  was  admirably  worked  out. 

Large  portions  of  the  strata  both  of  South  and  North  Wales  at  first 
called  Cambrian,  and  supposed  to  be  older  than  the  Silurian  rocks  of 
Murchison,  were  afterwards  proved  by  our  surveyors,  chiefly  by  the 
labors  of  Prof.  Ramsay,  to  be  the  equivalents  of  the  Lower  Silurian 
rocks  above  described. 

The  following  table  will  show  the  succession  of  the  strata  in  England 
and  Wales  which  belong  to  the  Cambrian  group  or  the  fossiliferous 
rocks  older  than  the  Lower  Llandeilo,  to  which  are  added  the  Lau- 
rentian  formations  of  Canada,  as  the  oldest  in  the  world  in  which 
organic  remains  have  yet  been  found : 


CAMBRIAN  GROUP. 


1.  Upper 
Cambrian 
Rocks.— 
("Primor-  - 
dial  Zone" 
of  Bar- 
rande). 


a.  Tremadoc 
slates. 


Prevailing  Litho-       Thickness 
logical  Characters.        in  Feet. 

Dark  earthy  slates ) 
with        pisolitic  [•  2000 
ore.  ) 


b.  Lingula 


(Micaceous 
stones 
shales. 


and 


about 
6000 


Organic  Kemains. 
Trilobites  of  genera 
partly  Silurian  and 
partly  Primordial 
ofBarrande.  Bel- 
lerophon  ;  Ortho- 
ceratite ;  Theca. 

Trilobites  ;  Olenus, 
Conocoryphe ;  Pa- 
radoxides  ;  Phyl- 
lopod  crustacean  • 
Brachiopoda;  Cys- 
tideans. 


576 


TREMADOC  SLATES. 


[CH.  XXVII. 


2.  Lower 

Ia.  Harlech    j  Sandstones 

Cambrian 

grits.        (      grit. 

Rocks.— 

(Long- 
mynd 
Group). 

*    TI     u    •    I  Slates,  witt 

-"1  ±. 

and)  6000 

[  to 

)  7000 

with  sandy  |  b     t 

inter- j-  3000 


Annelids,  five  spe- 
cies (Arenicolites 
sparsus,  &c. ;  one 
crustacean  ;  Old- 

liamia. 


LAURENTIAN   GROUP. 


1.  Upper  Laurentian,  or  Lab- 
rador Series. 


2.  Lower  Laurentian. 


Stratified  highly "] 
crystalline  rocks,  j 
with  much  La-  ! 
bradorite,  and  J 
other  varieties  of  I 
felspar. 

Gneiss  ;  Quartzite5) 
Hornblendic  and 

micaceous 
schists,  with 
dense  intercala- 
ted limestones, 
one  above  1000 
ft.  in  thickness. 


18,000- 


None, 


Foraminifera      (J£o> 
zoon  Canadense). 


UPPER    CAMBRIAN. 

Tremadoc  Slates. — Tlie  Tremadoc  slates  of  Sedgwick  are  more  than 
1000  feet  in  thickness,  and  consist  of  dark  earthy  slates  occurring 
near  the  little  town  of  Tremadoc,  situated  on  the  north  side  of  Car- 
digan Bay  in  Carnarvonshire.  These  slates  were  first  examined  by 
Sedgwick  in  1831,  and  were  reexamined  by  him  and  described  in 
1846,*  after  some  fossils  had  been  found  in  the  underlying  Lingula 
flags  by  Mr.  Davis.  The  inferiority  in  position  of  these  Lingula  flags 
to  the  Tremadoc  beds  was  at  the  same  time  established.  The  over- 
lying Tremadoc  beds  were  traced  by  their  pisolitic  ore  from  Tremadoc 
to  Dolgelly.  No  fossils  proper  to  the  Tremadoc  slates  were  then 
observed,  but  subsequently,  when  the  same  beds  were  well  searched 
by  the  collectors  of  the  Government  Survey  in  1853  and  1857,  thirty- 
one  species  of  all  classes  were  found  in  them  and  determined  by  Mr. 
Salter.  By  their  means  he  was  able  to  separate  the  beds  into  an 
upper  and  lower  division:  in  the  upper  of  which  there  are  about 
twenty  species,  and  about  fifteen  in  the  lower.  We  have  already 
seen  that  in  the  Lower  Llandeilo  (Stiper-stones  or  Arenig  group), 
where  the  species  are  distinct,  the  genera  agree  with  Silurian  types ; 
but  in  these  Tremadoc  slates,  where  the  species  are  also  peculiar, 
there  is  about  an  equal  admixture  of  Silurian  types  with  those  which 
Barrande  has  termed  "  primordial."  Here,  therefore,  it  may  truly  be 
said  that  we  are  entering  upon  a  new  domain  of  life  in  our  retro- 
spective survey  of  the  past.  The  trilobites  of  new  species,  but  of 


*  Geol.  Quart.  Journ.,  vol.  iii.  p.  156. 


CH.  XXVII.] 


LINGULA  FLAGS. 


577 


Lower  Silurian  forms,  belong  to  the  genera,  Ogygia,  Asaphus,  and 
Cheirurus ;  whereas  those  belonging  to  primordial  types,  or  Bar- 
rande's first  fauna,  as  well  as  to  the  Lingula  flags  of  Wales,  comprise 
Gonocoryphe*  Olenus,  several  species,  and  Angelina.  In  the  Upper 
Tremadoc  slates  are  found  Bellerophon,  Orthoceras,  and  Cyrtoceras, 
all  specifically  distinct  from  Lower  Silurian  fossils  of  the  same  genera : 
the  Pteropod  Theca  ranges  throughout  these  slates;  there  are  no 
Graptolites.  The  only  Tremadoc  species  which,  according  to  Salter, 
is  not  peculiar,  is  Lingula  Davisii,  which  ranges  from  the  top  to  the 
bottom  of  the  formation,  and  links  it  with  the  zone  next  to  be  de- 
scribed. The  Tremadoc  slates  are  very  local,  and  seem  to  be  con- 
fined to  a  small  part  of  North  Wales ;  and  Prof.  Ramsay  supposes 
them  to  lie  unconformably  on  the  Lingula  flags,  and  that  a  long  inter- 
val of  time  elapsed  between  these  formations. 

Lingula  Flags. — Next  below  the  Tremadoc  slates  in  North  Wales, 
lie  micaceous  flagstones  and  slates,  in  which,  in  1846,  Mr.  E.  Davis 
discovered  the  Lingula  named  after  him,  and  from  which  was  de- 
rived the  name  of  Lingula  Flags.f  In  these  flags  and  shales,  other 
fossils  were  found  by  subsequent  researches,  which  were  observed  to 
differ  specifically  from  those  of  the  Llandeilo  beds,  or  the  lowest  por- 
tion of  the  Lower  Silurian  then  palaeontologically  known.  Trilobites 
of  the  genera  Olenus  and  Conocoryphe  (for  genus,  see  fig.  667),  and 
other  forms,  which  will  soon  be  published  by  our  Government  Sur- 
vey, were  detected ;  and  Paradoxides  (for  genus,  see  fig.  666),  another 


Fossils  of  the  "Lingula  Flags"  or  lowest  Fossiliferous  Rocks  of  Britain. 
Fig.  661.  Fig.  662.  Fig.  663. 


Lingula  Davisii,  M'Coy. 

a.  i  nat.  size. 

5.  Distorted  by  cleavage. 


Hymenocaris  vermicauda, 

Salter. 

A  Phyllopod  Crustacean, 
i  nat.  size. 

"Lingula  Flags"  of  Dolgolly,  and  Ffestiniog;  N.  Wales.:]: 


Olenus  micrurus, 

Salter. 
i  nat.  size. 


of  Barrande's  primordial  forms  of  Bohemia,  was  also  found  both  in 
North  and  South  Wales,  in  the  black  slates  of  this  era.     With  these 


*  This  genus  has  been  substituted  for  Barrande's  Conocephalus,  as  the  latter 
term  had  been  preoccupied  by  the  entomologists. 

f  This  shell  has  since  been  referred  by  Salter  to  a  subgenus  Lingulella,  but  I 
retain  the  original  name  in  this  chapter,  because  it  has  long  been  used  by  geolo- 
gists in  their  designation  of  the  beds  where  it  is  so  abundant. 

\  These  figures  were  given  in  Sir  R.  Murchison's  Siluria  (2d  ed.,  1854),  chap.  ii. 
37 


578  LOWER  CAMBRIAN— LONGMYND  GROUP.        [On.  XXVII. 

also  a  phyllopod  crustacean  (fig.  661),  and  several  genera  of  Brachio- 
poda,  with  a  rare  Cystidean  and  a  sponge,  were  obtained.  In  all, 
about  forty  or  forty-five  species  are  already  described  by  Mr.  Salter, 
and  other  forms  are  still  in  his  hands  for  investigation. 

In  Merionethshire,  says  Prof.  Ramsay,  the  Lingula  flags  are  from 
5000  to  6000  feet  thick ;  in  Carnarvonshire,  near  Llanberis,  only 
about  2000  feet,  having,  in  the  space  of  about  11  miles,  lost  4000 
feet  of  their  thickness.  In  Anglesea  and  on  the  Menai  Straits,  the 
Llandeilo  and  Bala  Beds  lie  directly  on  (Lower)  Cambrian  strata, 
both  the  Lingula  flags  and  Tremadoc  slates  being  absent.* 


LOWER      CAMBRIAN. 

(Longmynd  Group.) 

Harlech  Grits. — Older  than  the  Lingula  flags  are  stratified  forma- 
tions of  great  thickness,  but  which  have  as  yet  proved  very  barren 
of  organic  remains,  and  have  been  variously  called  by  Prof.  Sedg- 
wick  the  Longmynd  and  Bangor  group,  comprising,  first,  the  Bar- 
mouth  and  Harlech  sandstones,  and  secondly,  the  Llanberis  slates. 
The  sandstones  of  this  period  attain  in  the  Longmynd  Hills  in 
Shropshire  a  thickness  of  no  less  than  6000  feet,  without  any  inter- 
position of  volcanic  matter.  In  some  places  in  Merionethshire  they 
are  still  thicker.  The  labors  of  Mr.  Salter  in  Shropshire  and  those 
of  the  late  Dr.  Kinahan  in  Wicklow  have  brought  to  light  at  least 
five  species  of  Annelides  in  these  rocks,  two  of  which  have  been 
named  Arenicolites  sparsus  and  A.  didymus.  They  occur  in  count- 
less myriads  through  a  mile  of  thickness  in  the  Longmynd,  where 
also  an  obscure  crustacean  form  has  been  discovered  and  named 
Paloeopyge  Ramsayi.  The  sands  of  this  formation  are  often  rippled, 
and  were  evidently  left  dry  at  low  tides,  so  that  the  surface  was  dried 
by  the  sun  and  made  to  shrink  and  present  sun-cracks.  There  are 
also  distinct  impressions  of  rain-drops,  like  those  figured  at  p.  490, 
on  many  surfaces.f 

Llanberis  Slates. — The  slates  of  Llanberis  and  Penrhyn  in  Car- 
narvonshire, with  their  associated  sandy  strata,  attain  a  great  thick- 
ness, sometimes  about  3000  feet.  They  are  perhaps  not  more  ancient 
than  the  Harlech  and  Barmouth  beds  last  mentioned,  for  they  may 
represent  the  deposits  of  fine  mud  thrown  down  in  the  same  sea,  on 
the  borders  of  which  the  sands  above  mentioned  were  accumulating. 
In  some  of  these  slaty  rocks  in  Ireland,  immediately  opposite  Angle- 
sea  and  Carnarvon,  two  species  of  zoophytes  have  been  found,  to 
which  the  late  Prof.  E.  Forbes  gave  the  name  of  Oldhamia.  They 


*  Anniversary  Address,  Geol.  Quart.  Journ.,  vol.  xix.  p.  39,  1863. 
f  Salter,  Quart.  Geol.  Journ.,  vol.  xiii.,  1857. 


CH.  XXVIL]  CAMBRIAN  ROCKS  OF  BOHEMIA.  579 

may  be    considered   as   the    most    ancient    fossils    yet  known    in 
Europe. 

We  may  reasonably  anticipate  that  the  Longmynd  fauna,  if  ever 
it  shall  become  extensively  known  in  the  British  Isles  or  elsewhere, 
will  be  found  to  differ  considerably  from  that  of  the  Upper  Cambrian 
rocks,  for  the  thickness  of  the  beds  unmixed  with  volcanic  matter  is 
very  great,  and  they  must  have  required  a  great  lapse  of  time  for 
their  deposition. 

The  most  ancient  fossils  yet  known  in  Europe  (1864). 

Fig.  665. 


Fig.  664. 


OldJiamia  radiata,  Forbes. 
Wicklow,  Ireland. 


Oldhamia  antiqua,  Forbes. 
Wicklow,  Ireland. 


CAMBRIAN  ROCKS   OF  BOHEMIA. 

(Primordial  Zone  of  Barrande.} 

I  have  already  spoken  (p.  574)  of  the  splendid  results  of  M.  Bar- 
rande's  labors,  published  in  1846,  in  which  year,  after  a  prolonged 
investigation  of  the  geology  of  Bohemia,  he  discovered  a  great  series 
of  palaeozoic  formations,  for  which  he  adopted  Sir  R.  Murehison's 
general  name  of  Silurian.  The  first  or  most  ancient  of  his  three 
Silurian  faunas,  called  by  him  primordial,  corresponds  with  the  Brit- 
ish Upper  Cambrian,  as  above  described.  The  second  tallies  with 
Murchison's  Lower  Silurian,  and  the  third  with  the  Upper  Silurian  of 
the  same  author.  When  M.  Barrande,  a  French  naturalist,  undertook 
single-handed  the  survey  of  Bohemia,  all  the  described  species  of 
fossils  previously  obtained  from  that  country  scarcely  exceeded 
twenty  in  number,  whereas  he  had  already  acquired  in  1850  no  less 
than  1100  species;  namely,  250  crustaceans  (chiefly  trilobites),  250 
cephalopods,  160  gasteropoda  and  pteropods,  130  acephalous  mol- 
lusks,  210  brachiopods,  and  110  corals  and  other  fossils.  At  a  later 
period,  1856,  M.  Barrande  states  that  he  had  in  his  collection  be- 


580 


TRILOBITES  OF  UPPER  CAMBRIAN. 


[Cn.  XXVII. 


tween  1400  and  1500  species  from  the  same  Silurian  and  primordial 
rocks  of  Bohemia.* 

In  the  primordial  zone  he  discovered  trilobites  of  the  genera 
Paradoxides,  Conocephalus  (Conocoryphe),  Ellipsocephalus,  Sao,  Ario- 
nellus,  Hydrocephalus,  and  Agnostus.  These  primordial  trilobites 
have  a  peculiar  facies  of  their  own  dependent  on  the  multiplication 
of  their  thoracic  segments  and  the  diminution  of  their  caudal  shield 
or  pygidium. 

One  of  the  "  primordial "  or  Upper  Cambrian  Trilobites  of  the 
genus  Sao,  a  form  not  found  as  yet  elsewhere  in  the  world,  has 
afforded  M.  Barrande  a  fine  illustration  of  the  metamorphosis  of 
these  creatures,  for  he  has  traced  them  through  no  less  than  twenty 
stages  of  their  development.  A  few  of  these  changes  have  been 
selected  for  representation  in  the  accompanying  figures,  that  the 

Fossils  of  the  lowest  Fossiliferous  Beds  in  Bohemia,  or  "  Primordial  Zone  "  of 

Barrande. 


Fig,  666. 


Fig.  66T. 


Conocoryphe,  striata. 

Syn.  Conocephalus  striatiis,  Emmrich. 

£  nat.  size.    Ginetz  and  Skrey. 

Fig.  668.  Fig.  669. 


Paradoxides  Bohemicus,  Barr. 

About  £  natural  size.  Agnostus  integer,  Beyrich.          Agnostus  Rex,  Barr. 

•Lowest  Silurian  beds "  of  Ginetz,       Nat.  size  and  magnified.  Nat.  size.    Skrey. 

Bohemia.  (^tageCof  Barrande.) 


Sao  Mrwta,  Barrande,  in  its  various  stages  of 
growth.  Skrey. 

The  small  lines  beneath  indicate  the  true  size.  In 
the  youngest  state,  a,  no  segments  are  visible ; 
as  the  metamorphosis  progresses,  &,  c,  the  body 
segments  begin  to  be  developed ;  in  the  stage  d 
the  eyes  are  introduced,  but  the  facial  sutures 
are  not  completed  ;  at  e  the  full-grown  animal, 
half  its  true  size,  is  shown. 


reader  may  learn  the  gradual  manner  in  which  different  segments  of 
the  body  and  the  eyes  make  their  appearance.  When  we  reflect  on 
the  altered  and  crystalline  condition  usually  belonging  to  rocks  of 


*  Paraltele  entre  les  Depots  Silurians  de  Boh&me  et  de  Scandinavie. 


CH.  XXVII.]       POTSDAM  SANDSTONE— UNITED  STATES. 

this  age,  and  how  devoid  of  life  they  are  for  the  most  part  in  North 
Wales,  Ireland,  and  Shropshire,  the  information  respecting  such 
minute  details  of  the  Natural  History  of  these  crustaceans,  as  is  sup- 
plied by  the  Bohemian  strata,  may  well  excite  our  astonishment,  and 
may  reasonably  lead  us  to  indulge  a  hope  that  geologists  may  one 
day  gain  an  insight  into  the  condition  of  the  planet  and  its  inhabit- 
ants at  eras  long  antecedent  to  the  Cambrian  ;  for  those  areas  which 
have  been  subjected  to  a  scrutiny  as  rigorous  as  North  Wales  and 
Bohemia  form  truly  insignificant  spots  on  a  map  of  the  whole  globe. 

In  Bohemia  the  primordial  fauna  of  Barrande  derived  its  impor- 
tance exclusively  from  its  numerous  and  peculiar  trilobites.  Besides 
these,  however,  the  same  ancient  schists  have  yielded  two  genera  of 
brachiopods,  Orthis  and  Orbicula,  a  pteropod  of  the  genus  Theca, 
and  four  echinoderms  of  the  Cystidean  family. 

All  the  Bohemian  species  differ  as  yet  from  any  found  in  England, 
which  may  be  due  entirely  to  the  influence  of  geographical  causes. 
It  seems,  nevertheless,  to  confirm  the  view  here  taken,  of  the  "pri- 
mordial zone  "  being  characterized  by  fossils  distinguishable  from  the 
whole  Lower  Silurian  group ;  because  the  other  and  higher  Silurian 
formations  of  Barrande  have  each  of  them  several  species  in  common 
with  the  successive  subdivisions  of  the  British  series. 

Sweden  and  Norway. — The  Upper  Cambrian  beds  of  North  Wales 
are  represented  in  Sweden  by  strata,  the  fossils  of  which  have  been 
described  by  a  most  able  naturalist,  M.  Angelin,  in  his  "  Palseonto- 
logica  Suecica  (1855-'4)".  The  "alum-schists,"  as  they  are  called 
in  Sweden,  resting  on  a  fucoid-sandstone,  contain  trilobites  belonging 
to  the  genera  Paradoxides,  Olenus,  Agnostus,  and  others,  some  of 
which  present  rudimentary  forms,  like  the  genus  last  mentioned, 
without  eyes,  and  with  the  body  segments  scarcely  developed,  and 
others  again  have  the  number  of  segments  excessively  multiplied, 
as  in  Paradoxides.  These  peculiarities  agree  with  the  characters 
of  the  crustaceans  met  with  in  the  Upper  Cambrian  strata,  before 
mentioned. 

The  Swedish  rocks  have  also  yielded  crustaceans  of  the  family 
Cytherinidce,  and  among  the  mollusca  a  small  species  of  Orthoceras, 
the  only  primordial  cephalopod  yet  known,  and  also  a  Graptolite, 
together  with  most  of  the  fossil  forms  discovered  by  Barrande  in  the 
Bohemian  strata  of  the  same  age. 

United  States  and  Canada. — In  the  table  at  p.  570,  I  have  already 
pointed  out  the.  relative  position  of  the  Potsdam  Sandstone,  which 
has  long  been  supposed  to  be  the  lowest  fossiliferous  formation  in  the 
United  States  and  Canada.  The  late  Dr.  Dale  Owen  published  in 
1852  a  graphic  sketch,  in  his  survey  of  Wisconsin,  of  the  lowest 
sedimentary  rocks  near  the  head-waters  of  the  Mississippi,  lying  at 
the  base  of  the  whole  Silurian  series.  They  are  many  hundred  feet 
thick,  and  for  the  most  part  similar  in  character  to  the  Potsdam  sand- 
stone above  described,  but  including  in  their  upper  portions  interca- 


582  PERIOD  OF  INVERTEBRATE  ANIMALS.         [On.  XXVII. 

lated  bands  of  magnesian  limestone,  and  in  their  lower  some  argilla- 
ceous beds.     Among  the  shells  of  these  strata  are  species  of  Lingula 
and   Orthis,  and  several  trilobites  of  the  new  genus  DiJcelocephalus 
(fig.  671).     These  rocks,  occurring  in  Iowa, 
6T1-  Wisconsin,  and   Minnesota,   seem   destined 

hereafter  to  throw  great  light  on  the  state 
of  organic  life  in  the  Cambrian  period. 
Six  beds  containing  trilobites,  separated  by 
strata  from  10  to  150  feet  thick,  are  already 
enumerated. 

I  have  seen  the  Potsdam  sandstone  on 
the  banks  of  the  St.  Lawrence  in  Canada, 
and  on  the  borders  of  Lake  Champlain, 
where,  as  at  Keesville,  it  is  a  white  quartz- 
ose  fine-grained  grit,  almost  passing  into 
quartzite.  It  is  divided  into  horizontal 
Dikeiocephaius  Minnesotewis,  ripple-marked  beds,  very  like  those  of  the 

Dale  Owen.    £  diameter.          T  f r     ,      _  *  -r»_L  •  i          i   ,.         -^ 

A  large  crustacean  of  the  oienoid  Lingula  flags  of  Britain,  and  replete  with  a 
group.     Potsdam    Sandstone,  small   round-shaped   Lingula    (Obolella   of 
'  Billings),  in  such  numbers  as  to  divide  the 

rock  into  parallel  planes,  in  the  same  man- 
ner as  do  the  scales  of  mica  in  some  micaceous  sandstones.  This 
formation,  as  we  learn  from  Sir  W.  Logan,  is  700  feet  thick  in  Cana- 
da ;  the  lower  portion  consisting  of  a  conglomerate  with  quartz  peb- 
bles ;  the  upper  part  of  sandstone  containing  fucoids,  and  perforated 
by  small  vertical  holes,  which  are  very  characteristic  of  the  rock,  and 
appear  to  have  been  made  by  annelids  (Scolithus  linearis). 

On  the  banks  of  the  St.  Lawrence,  near  Beauharnois  and  elsewhere, 
many  fossil  footprints  have  been  observed  on  the  surface  of  its  rippled 
layers.  These  impressions  were  first  noticed  by  Mr.  Abraham,  of 
Montreal,  in  1847,  and  were  supposed  to  be  tracks  of  a  tortoise;  but 
Sir  W.  Logan  brought  in  1851  some  of  the  slabs  to  London,  together 
with  numerous  casts  of  other  slabs,  enabling  Professor  Owen  to  cor- 
rect the  idea  first  entertained,  and  to  decide  that  they  were  not  due 
to  a  chelonian,  nor,  as  he  imagines,  to  any  vertebrate  creature.  The 
Professor  inclines  to  the  belief  that  they  are  the  trails  of  more  than 
one  species  of  articulate  animal,  probably  allied  to  the  King  Crab,  or 
Limulus.  Between  the  two  rows  of  foot-tracks  runs  an  impressed 
median  line  or  channel,  supposed  by  the  Professor  to  have  been  made 
by  a  caudal  appendage  rather  than  by  a  prominent  part  of  the  trunk. 
Some  individuals  appear  to  have  had  three,  and  others  five  pairs,  of 
limbs  used  for  locomotion.  The  width  of  the  tracks  between  the 
outermost  impressions  varies  from  3-J  to  5^  inches,  which  would 
imply  a  creature  of  much  larger  dimensions  than  any  organic  body 
yet  obtained  from  strata  of  such  antiquity.  In  this  respect  they  agree 
with  the  gigantic  Eurypteridce,  detected  in  the  Lowest  Devonian 
and  uppermost  Silurian  rocks.  Their  size  alone  is  important,  as 


CH.  XXVII.]  LAURENTIAN  ROCKS.  583 

warning  us  of  the  danger  of  drawing  any  inference  from  mere  negative 
evidence,  as  to  the  extreme  poverty  of  the  fauna  of  the  earlier  seas. 

Recent  investigations  by  the  naturalists  of  the  Canadian  survey 
have  rendered  it  certain  that  below  the  level  of  the  Potsdam  sand- 
stone there  are  slates  and  schists  extending  from  New  York  to  New- 
foundland, occupied  by  a  series  of  trilobitic  forms  similar  in  genera 
though  not  in  species  to  those  found  in  the  European  Upper  Cambrian 
strata. 

Quebec  Group. — The  Dikelocephalus  above  mentioned  is  one  of 
the  most  striking  fossils  found  in  the  limestones  of  Quebec,  which 
have  recently  attracted  much  attention.  But  there  seems  in  these 
limestones  to  be  a  mixed  fauna,  which  renders  it  probable  that  the 
Quebec  group,  as  defined  by  Sir  W.  Logan  and  Mr.  E.  Billings,  is  the 
representative  of  our  Lower  Llandeilo  (Arenig)  and  Tremadoc  groups 
united.  The  characteristic  graptolites  lie  in  the  upper  portion,  and 
are  identical  with  those  of  Skiddaw ;  and  the  mixture  of  primordial 
and  Lower  Silurian  genera  in  the  lower  portion  exactly  reminds  us  of 
the  similar  mixture  in  the  Tremadoc  slate,  while,  according  to  Mr. 
Billings,  there  are  many  species  identical  with  those  of  the  calciferous 
sand-rock,  the  formation  which  immediately  overlies  the  Potsdam 
sandstone  and  passes  down  into  it  imperceptibly. 

Huronian  Series. — Next  below  the  Upper  Cambrian  occur  strata 
called  the  Huronian  by  Sir  W.  Logan,  which  are  of  vast  thickness, 
consisting  chiefly  of  quartzite,  with  great  masses  of  greenish  chloritic 
slate,  which  sometimes  include  pebbles  of  crystalline  rocks  derived 
from  the  Laurentian  formation,  next  to  be  described.  Limestones 
are  rare  in  this  series,  but  one  band  of  300  feet  in  thickness  has  been 
traced  for  considerable  distances  to  the  north  of  Lake  Huron.  Beds 
of  greenstone  are  intercalated  conformably  with  the  quartzose  and 
argillaceous  members  of  this  series.  No  organic  remains  have  yet 
been  found  in  any  of  the  beds ;  and  whether  they  may  be  altered 
Lower  Cambrian  or  some  still  older  sedimentary  formation  in  a  semi- 
metamorphic  state  is  uncertain.  The  Huronian  strata  are  about 
18,000  feet  thick,  and  rest  unconforraably  on  the  Laurentian,  next  to 
be  described. 


LAURENTIAN    ROCKS. 

In  the  course  of  the  geological  survey  carried  on  under  the  direc- 
tion of  Sir  W.  E.  Logan,  it  has  been  shown  that,  northward  of  the 
river  St.  Lawrence,  there  is  a  vast  series  of  crystalline  rocks  of  gneiss, 
mica-schist,  quartzite,  and  limestone,  more  than  30,000  feet  in  thick- 
ness, which  have  been  called  Laurentian,  and  which  are  already 
known  to  occupy  an  area  of  about  200,000  square  miles.  They  are 
not  only  more  ancient  than  the  fossiliferous  Cambrian  formations 
above  described,  but  are  older  than  the  Huronian  last  mentioned,  and 
had  undergone  great  disturbing  movements  before  the  Potsdam  sand- 


584:  UPPER  AND   LOWER  LAURENTIAN.  [Cn.  XXVH. 

stone  and  the  other  "  primordial "  rocks  were  formed.  The  older 
half  of  this  Laurentian  series  is  unconformable  to  the  newer  portion 
of  the  same. 

Upper  Laurentian  or  Labrador  Series. — The  Upper  Group,  more 
than  10,000  feet  thick,  consists  of  stratified  crystalline  rocks  in  which 
no  organic  remains  have  yet  been  found.  They  consist  in  great  part 
of  felspars,  which  vary  in  composition  from  anorthite  to  andesine,  or 
from  those  kinds  in  which  there  is  less  than  one  per  cent,  of  potash 
and  soda  to  those  in  which  there  is  more  than  seven  per  cent,  of  these 
alkalies,  the  soda  preponderating  greatly.  These  felsparites  sometimes 
form  mountain  masses  almost  without  any  admixture  of  other  minerals ; 
but  at  other  times  they  include  pyroxene,  which  passes  into  hyper- 
sthene.  They  are  often  granitoid  in  structure.  One  of  the  varieties 
is  the  same  as  the  opalescent  labradorite  rock  of  Labrador.  The  Adi- 
rondack Mountains  in  the  State  of  New  York  are  referred  to  the  same 
series,  and  it  is  conjectured  that  the  hypersthene  rocks  of  Skye,  which 
resemble  this  formation  in  mineral  character,  may  be  of  the  same  geo- 
logical age. 

Lower  Laurentian. — This  series,  about  20,000  feet  in  thickness,  is, 
as  before  stated,  unconformable  to  that  last  mentioned ;  it  consists  in 
great  part  of  gneiss  of  a  reddish  tint  with  orthoclase  felspar.  Beds  of 
nearly  pure  quartz,  from  400  to  600  feet  thick,  occur  in  some  places. 
Hornblendic  and  micaceous  schists  are  often  interstratified,  and  beds 
of  limestone  usually  crystalline. 

There  are  several  of  these  limestones  which  have  been  traced  to 
great  distances,  and  one  of  them  is  from  TOO  to  1500  feet  thick.  In 
the  most  massive  of  them  Sir  W.  Logan  observed  in  1859  what  he 
considered  to  be  an  organic  body  much  resembling  the  Silurian  fossil 
called  Stromatopora  rugosa.  It  had  been  obtained  the  year  before  by 
Mr.  J.  McCulloch  at  the  Grand  Calumet  on  the  river  Ottawa.  This 
fossil  was  examined  in  1864  by  Dr.  Dawson  of  Montreal,  who  detected 
in  it,  by  aid  of  the  microscope,  the  distinct  structure  of  a  Rhizopod  or 
Foraminifer.  Dr.  Carpenter  and  Prof.  T.  Rupert  Jones  have  since 
confirmed  this  opinion,  comparing  the  structure  to  that  of  the  well- 
known  nummulite.  It  appears  to  have  grown  one  layer  over  another, 
and  to  have  formed  reefs  of  limestone  as  do  the  living  coral-building 
polyp  animals.  Parts  of  the  original  skeleton,  consisting  of  carbonate 
of  lime,  are  still  preserved ;  while  certain  interspaces  in  the  calcareous 
fossil  have  been  filled  up  with  serpentine  and  white  augite.  On  this 
oldest  of  known  organic  remains  Dr.  Dawson  has  conferred  the  name 
of  Eozoon  Canadense  ;  its  antiquity  is  such  that  the  distance  of  time 
which  separated  it  from  the  Upper  Cambrian  period,  or  that  of  the 
Potsdam  sandstone,  may,  says  Sir  W.  Logan,  be  equal  to  the  time 
which  elapsed  between  the  Potsdam  sandstone  and  the  nummulitic 
limestones  of  the  Tertiary  period.  The  Laurentian  and  Huronian 
rocks  united  are  about  50,000  feet  in  thickness,  and  the  Lower  Lauren- 
tian was  disturbed  before  the  newer  series  was  deposited.  We  may 


CH.  XXVII.]       SUPPOSED  PERIOD  OF  INVERTEBRATE  ANIMALS.      585 

naturally  expect  that  other  proofs  of  unconformability  will  hereafter  be 
detected  at  more  than  one  point  in  so  vast  a  succession  of  strata. 

The  mineral  character  of  the  Upper  Laureutian  differs,  as  we  have 
seen,  from  that  of  the  Lower,  and  the  pebbles  of  gneiss  in  the  Huronian 
conglomerates  are  thought  to  prove  that  the  Laurentian  strata  were 
already  in  a  metamorphic  state  before  they  were  broken  up  to  supply 
materials  for  the  Huronian.  Even  if  we  had  not  discovered  the 
Eozoon,  we  might  fairly  have  inferred  from  analogy  that  as  the  quartz- 
ites  were  once  beds  of  sand,  and  the  gneiss  and  mica-schist  derived 
from  shales  and  argillaceous  sandstones,  so  the  calcareous  masses,  from 
400  to  1000  feet  and  more  in  thickness,  were  originally  of  organic 
origin.  This  is  now  generally  believed  to  have  been  the  case  with  the 
Silurian,  Devonian,  Carboniferous,  Oolitic,  and  Cretaceous  limestones 
and  those  nummulitic  rocks  of  tertiary  date  which  bear  the  closest 
affinity  to  the  Eozoon  reefs  of  the  Lower  Laurentian.  The  oldest 
stratified  rock  in  Scotland  is  that  called  by  Sir  R.  Murchison  "  the 
fundamental  gneiss,"  which  forms  the  whole  of  the  Island  of  Lewis  in 
the  Hebrides.  On  this  gneiss,  in  parts  of  the  Western  Highlands,  the 
Lower  Cambrian  and  various  metamorphic  rocks  rest  un conformably. 
It  is  conjectured  that  this  ancient  gneiss  of  Scotland  may  correspond 
in  date  with  part  of  the  great  Laurentian  group  of  North  America. 

ON    THE    ABSENCE    OF    VEBTEBBATA   IN    BOOKS    BELOW    THE    UPPEB 
SILUBIAN. 

Supposed  Period  of  Invertebrate  Animals. — We  have  seen  that  in 
the  upper  part  of  the  Silurian  system  a  bone-bed  occurs  near  Ludlow, 
in  which  the  remains  of  fish  are  abundant,  and  amongst  them  some 
of  highly  organized  structure,  referred  to  the  genera  Onchus  and 
Pteraspis.  We  are  indebted  to  Sir  E.  Murchison  for  having  first 
announced,  in  1840,  the  discovery  of  these  ichthyolites,  and  he  then 
spoke  of  them  as  "  the  most  ancient  beings  of  their  class."  In  the 
third  edition  of  his  classical  work,*  he  has  reverted  to  the  opinion 
formerly  expressed  by  him,  observing  that  the  active  researches  of  the 
last  twenty  years  in  Europe  and  America  "had  failed  to  modify  that 
generalization."  He  also  adds :  "  The  Silurian  system  therefore  may 
be  regarded  as  representing  a  long  period  in  which  no  vertebrated 
animals  had  been  called  into  existence." 

In  the  same  year  (1859)  in  which  this  remark  was  hazarded,  the 
discovery  of  the  Pteraspis,  mentioned  by  us  at  p.  555,  in  the  Lower 
Ludlow  rocks,  carried  back  our  knowledge  of  the  existence  of  fish  one 
step  farther  into  the  history  of  the  past.  But  it  is  still  a  fact  well 
worthy  of  notice,  that  no  remains  of  vertebrata  have  yet  been  met  with 
in  any  strata  older  than  the  Lower  Ludlow. 

When  we  reflect  on  the  hundreds  of  Mollusks,  Echinoderms,  Trilo- 

*  Siluria,  p.  268,  1859. 


586      SUPPOSED  PERIOD  OF  INVERTEBRATE  ANIMALS.       [Cn.  XXVII. 

bites,  Corals,  and  other  fossils  already  obtained  from  more  ancient 
Silurian  formations,  Upper,  Middle,  and  Lower,  we  may  well  ask 
whether  any  set  of  fossiliferous  rocks  newer  in  the  series  were  ever 
studied  with  equal  diligence  and  over  so  vast  an  area  without  yielding 
a  single  ichthyolite. 

Yet  we  ought  to  hesitate  before  we  accept,  even  on  such  evidence, 
so  sweeping  a  conclusion,  as  that  the  globe,  for  ages  after  it  was 
inhabited  by  all  the  great  classes  of  invertebrata,  remained  wholly  un- 
tenanted  by  vertebrate  animals.  In  the  first  place,  we  must  remember 
that  we  have  detected  no  insects,  or  land-shells,  or  freshwater  pulmon- 
iferous  mollusks,  or  terrestrial  crustaceans,  or  plants  (with  the  excep- 
tion of  fucoids),  in  rocks  below  the  Upper  Silurian.  Their  absence 
may  admit  of  explanation,  by  supposing  almost  all  the  deposits  of  that 
era  hitherto  examined  to  have  been  formed  in  seas  far  from  land  or 
beyond  the  influence  of  rivers.  Here  and  there,  indeed,  a  shallow- 
water  or  even  a  littoral  deposit  may  have  been  met  with  in  North 
Wales  or  North  America ;  but,  speaking  generally,  the  Silurian  de- 
posits, as  at  present  known,  have  certainly  a  more  pelagic  character 
than  any  other  of  equal  extent  and  thickness. 

It  is  a  curious  fact,  and  not  perhaps  a  mere  fortuitous  coincidence, 
that  the  only  stratum  in  which  land-plants  occur  is  also  the  only  one 
which  has  yielded  the  remains  of  fish  in  any  considerable  abundance. 
Bone-beds  in  general,  such  as  that  of  the  uppermost  Trias  at  Bristol 
and  Stuttgart,  or  that  of  the  Carboniferous  Limestone  near  Bristol 
and  Armagh,  or,  lastly,  that  of  the  "  Upper  Ludlow,"  are  remarkable 
for  containing  teeth  and  bones,  much  rolled,  and  implying  transporta- 
tion from  a  distance.  The  association  of  the  sporangia  of  Lycopodi- 
acese  (see  p.  552)  with  the  Ludlow  fish-bones  shows  that  plants  had 
been  washed  from  some  dry  land  then  existing,  and  had  been  drifted 
into  a  common  submarine  receptacle  with  the  bones  ;  and  it  is  well 
known  that  in  the  present  state  of  the  globe  fish  occur  in  the  greatest 
numbers  at  the  junction  of  rivers  with  the  sea.  Where  the  Upper 
Ludlow  is  devoid  of  plants,  as  is  usually  the  case,  it  is  as  destitute  of 
ichthyolites  as  are  the  Wenlock  or  Llandeilo  beds. 

It  has  been  suggested  in  explanation,  that  Cephalopoda  were  so 
abundant  in  the  Silurian  period  that  they  may  have  discharged  the 
functions  of  fish ;  to  which  we  may  reply  that  both  classes  coexisted 
in  the  Upper  Silurian  period,  and  both  of  them  swarmed  together  in 
the  Carboniferous  and  Liassic  seas,  as  they  do  now  in  certain  parts  of 
the  ocean.  We  may  also  remark  that  we  are  too  imperfectly  ac- 
quainted with  the  distribution  of  scattered  bones  and  teeth  or  the 
skeletons  of  dead  fish  on  the  floor  of  the  existing  ocean,  to  have  a  right 
to  theorize  with  confidence  on  the  absence  of  such  relics  over  wide 
spaces  at  any  former  era. 

They  who  in  our  own  times  have  explored  the  bed  of  the  sea  in- 
form us  that  it  is  in  general  as  barren  of  vertebrate  remains  as  the 
soil  of  a  forest  on  which  thousands  of  mammalia  and  reptiles  have 


CH.  XXVII.]        ABSENCE  OF  FISH  IN  LOWER  SILURIAN.  587 

flourished  for  centuries.  In  the  summer  of  1850,  Prof.  E.  Forbes  and 
Mr.  McAndrew  dredged  the  bed  of  the  British  seas  from  the  Isle  of 
Portland  to  the  Land's  End  in  Cornwall,  and  thence  again  to  Shet- 
land, recording  and  tabulating  the  numbers  of  the  various  organic 
bodies  brought  up  by  them  in  the  course  of  140  distinct  dredgings, 
made  at  different  distances  from  the  shore,  some  a  quarter  of  a  mile, 
others  forty  miles  distant.  The  list  of  species  of  marine  invertebrate 
animals,  whether  -Radiata,  Mollusca,  or  Articulata,  was  very  great,  and 
the  number  of  individuals  enormous ;  but  the  only  instances  of  verte- 
brate animals  consisted  of  a  few  ear-bones,  and  two  or  three  vertebrae 
of  fish,  in  all  not  above  six  relics. 

It  is  still  more  extraordinary  that  Mr.  McAndrew  should  have 
dredged  the  great  "  Ling  Banks "  or  cod-fishery  grounds  off  the 
Shetland  Islands  for  shells  without  obtaining  the  bones  or  teeth  of 
any  dead  fish,  although  he  sometimes  drew  up  live  fish  from  the 
mud.  This  is  the  more  singular  because  there  are  some  areas  where 
recent  fish-bones  occur  in  the  same  northern  seas  in  profusion,  as  I 
have  shown  in  the  "  Principles  of  Geology "  (see  Index,  "  Vidal ") ; 
two  bone-beds  having  been  discovered  by  British  hydrographers,  one 
in  the  Irish  Sea,  and  the  other  in  the  sea  near  the  Faroe  Isles,  the 
first  of  them  two,  and  the  other  three  and  a  half  miles  in  length, 
where  the  lead  brings  up  everywhere  the  vertebras  of  fish  from  vari- 
ous depths  between  45  to  235  fathoms.  These  may  be  compared  to 
the  Upper  Ludlow  bone-bed  ;  and  on  the  floor  of  the  ocean  of  our 
times,  as  on  that  of  the  Silurian  epoch,  there  are  other  wide  spaces 
where  no  bones  are  imbedded  in  mud  or  sand. 

It  may  be  true,  though  it  sounds  somewhat  like  a  paradox,  that 
fish  leave  behind  them  no  memorials  of  their  presence  in  places 
where  they  swarm  and  multiply  freely ;  whereas  currents  may  drift . 
their  bones  in  great  numbers  to  regions  wholly  destitute  of  living 
fish.  Such  a  state  of  things  would  be  quite  analogous  to  what  takes 
place  on  the  habitable  land,  where,  instead  of  the  surface  becoming 
encumbered  with  heaps  of  skeletons  of  quadrupeds,  birds,  and  land- 
reptiles,  all  solid  bony  substances  are  removed  after  death  by  chemi- 
cal processes,  or  by  the  digestive  powers  of  predaceous  beasts ;  so 
that,  if  at  some  future  period  a  geologist  should  seek  for  monuments 
of  the  former  existence  of  such  creatures,  he  must  look  anywhere 
rather  than  in  the  area  where  they  flourished.  He  must  search  for 
them  in  spots  which  were  covered  at  the  time  with  water,  and  to 
which  some  bones  or  carcases  may  have  been  occasionally  carried  by 
floods  and  permanently  buried  in  sediment. 

In  the  annexed  Table,  a  few  dates  are  set  before  the  reader  of  the 
discovery  of  different  classes  of  animals  in  ancient  rocks,  to  enable 
him  to  perceive  at  a  glance  how  gradual  has  been  our  progress  in 
tracing  back  the  signs  of  vertebrata  to  formations  of  high  antiquity. 
Such  facts  may  be  useful  in  warning  us  not  to  assume  too  hastily 
that  the  point  which  our  retrospect  may  have  reached  at  the  present 


588  DISCOVERY  OF  FOSSIL  VERTEBRATA.         [Cn.  XXVIL 

moment  can  be  regarded  as  fixing  the  date  of  the  first  introduction 
of  any  one  class  of  beings  upon  the  earth. 

Dates  of  the  Discovery  of  different  Classes  of  Fossil  Vertebrata  ; 
showing  the  gradual  Progress  made  in  tracing  them  to  Rocks  of 
higher  antiquity. 

Tear.  Formations.  Geogi-aphical  Localities. 

C  1798.     Upper  Eocene.  Paris    (Gypsum    of    Mont- 

Mammalia,    -f  Lower0olitet  Sto'nesfiefd.2 


Aves. 


1847.     Upper  Trias.  Stuttgart.3 

1782.    Upper  Eocene.  Paris    (Gypsum    of    Mont- 

martre).4 
1839.     Lower  Eocene.  Isle    of    Sheppey    (London 

Clay).6 


1854.  Woolwich  Beds.6 

I   1855.         «          "  Meudon  (Plastic  Clay).7 

|   1858.  Upper  Greensand.  Cambridge.8 

L  1863.  Upper  Oolite.  Solenhofen.9 

RP  tilifl          j   1<710-  Permian  (or  Zechstein).  Thuringia.10 

11844.  Carboniferous.  Saarbruck,  near  Treves." 

1709.  Permian  (or  Kupfer-Scbiefer).  Thuringia.12       ^    : 

1793.  Carboniferous  (Mountain  Lime-  Glasgow.13 


Pisces.  Caithness.14 


1840.     Upper  Ludlow.  Ludlow.15 

1859.     Lower  Ludlow.  Leintwardine.16 

1  George  Cuvier.     Bulletin  Soc.  Philom.,  xx.     Scattered  bones  had  been  found 
in  the  gypsum  some  years  before  ;  but  they  were  determined  osteologically,  and 
their  true  geological  position  was  assigned  to  them  in  this  memoir. 

2  In  1818,  Cuvier,  visiting  the  Museum  of  Oxford,  decided  on  the  mammalian 
character  of  a  jaw  from  Stonesfield.     See  also  above,  p.  408. 

3  Plieninger,  Prof.     See  above,  p.  432. 

4  M.  Darcet  discovered,  and  Lamanon  figured,  as  a  fossil  bird,  some  remains 
from  Montmartre,  afterwards  recognized  as  such  by  Cuvier  (Ossemens  Foss.,  Art. 
"Oiseaux"). 

6  Owen,  Prof.,  Geol.  Trans.,  Second  Ser.,  vol.  vi.  p.  203,  1839.  The  fossil  bird  dis- 
covered in  the  same  year  in  the  slates  of  Glaris  in  the  Alps,  and  at  first  referred  to 
the  chalk,  is  now  supposed  to  belong  to  the  Nummulitic  beds,  and  may  therefore 
be  of  newer  date  than  the  Sheppey  Clay. 

6  A  bird's  bone  is  also  recorded  by  Mr.  Prestwich  as  having  been  found  by  M. 
de  la  Condamine  in  the  Upper  part  of  the  Woolwich  beds.  (Quart.  Geol.  Journ., 
voL  x.  p.  157.) 

T  Early  in  1855  the  tibia  and  femur  of  a  large  bird  equalling  at  least  the  ostrich 
in  size  were  found  at  Meudon  near  Paris,  at  the  base  of  the  Plastic  Clay.  This 
bird,  to  which  the  name  of  Gfastornis  Pariaiensis  has  been  assigned,  appears,  from 
the  Memoirs  of  MM.  Hebert,  Lartet,  and  Owen,  to  belong  to  an  extinct  genus. 
Professor  Owen  refers  it  to  the  class  of  wading  land-birds  rather  than  to  an  aquatic 
species.  (Quart.  Geol.  Journ.,  vol.  xii.  p.  204,  1856.) 

8  Mr.  Louis  Barrett  found  many  parts  of  the  skeleton  of  a  bird  of  the  gull  tribe 
in  the  coprolitic  bed,  in  the  Upper  Greensand  (see  above,  p.  332). 

0  The  Archceopteryx  macrura,  Owen,  was  determined  to  be  a  bird  by  Owen 
in  1863.  It  occurred  in  the  lithographic  stone  of  Solenhofen,  in  which  a  single 
feather,  probably  of  the  same  bird,  had  previously  been  found  (see  above,  p. 
396). 


CH.  XXVII.]          DISCOVERY  OF  FOSSIL  VERTEBRATA.  539 

10  The  fossil  monitor  of  Thuringia  (Protorosaurus  Speneri,  V.  Meyer)  was  fig- 
ured by  Spener,  of  Berlin,  in  1810.     (Miscel.  Berlin.) 

11  See  above,  p.  506. 

12  Memorabilia  Saxonise  Subterr.,  Leipsic,  1709. 

13  History  of  Rutherglen,  by  Rev.  David  Ure,  1793. 

14  Sedgwick  and  Murchison,  Geol.  Trans.,  Second  Sep.,  vol.  iii.  p.  141,  1828. 

15  Sir  R.  Murchison.     See  above,  p.  551. 

16  Mr.  Lee,  of  the  Priory,  Caerleon  (see  above,  p.  655),  found  Pteraspis  in  pres- 
ence of  Mr.  Lightbody,  F.G.S. 

Obs. — The  evidence  derived  from  footprints,  though  often  to  be  relied  on,  is  omit- 
ted in  the  above  table,  as  being  less  exact  than  that  founded  on  bones  and  teeth. 

There  are  many  writers  still  living  who,  before  the  year  1854, 
generalized  fearlessly  on  the  non-existence  of  reptiles  in  times  ante- 
cedent to  the  Permian ;  yet  in  the  course  of  nineteen  years  they 
have  lived  to  see  the  remains  of  reptiles  of  more  than  one  family 
exhumed  from  various  parts  of  the  Carboniferous  series.  Before  the 
year  1818,  it  was  the  popular  belief  that  the  Palseotherium  of  the 
Paris  gypsum  and  its  associates  were  the  first  warm-blooded  quadru- 
peds that  ever  trod  the  surface  of  this  planet.  So  fixed  was  this 
idea  in  the  minds  of  the  majority  of  naturalists,  that,  when  at  length 
the  Stonesfield  Mammalia  were  brought  to  light,  they  were  most  un- 
willing to  renounce  their  creed.  First,  the  antiquity  of  the  rock  was 
called  in  question  ;  and  then  the  mammalian  character  of  the  relics. 
But  when  at  length  all  controversy  was  set  at  rest  on  this  point,  the 
real  import  of  the  new  revelation,  as  bearing  on  the  doctrine  of  pro- 
gressive development,  was  far  from  being  duly  appreciated. 

Their  significance  arose  from  the  aid  they  afforded  us  in  estimating 
the  true  value  of  negative  evidence,  when  adduced  to  establish  the 
non-existence  of  certain  classes  of  animals  at  given  periods  of  the 
past.  Every  zoologist  will  admit  that  between  the  first  creation  and 
the  final  extinction  of  any  one  of  the  oolitic  mammalia  now  known, 
whether  at  Stonesfield  or  Purbeck,  there  were  many  successive  gen- 
erations ;  and,  even  if  the  geographical  range  of  each  species  was 
very  limited  (which  we  have  no  right  to  assume),  still  there  must 
have  been  several  hundred  individuals  in  each  generation,  and  proba- 
bly when  the  species  reached  its  maximum,  several  thousands. 
When,  therefore,  we  encounter  for  the  first  time  in  1854  two  or 
three  jaws  of  Stereognathus  or  Spalacotherium,  after  countless  speci- 
mens of  Mollusca  and  Crustacese,  and  many  insects,  fish,  and  reptiles 
had  been  previously  collected  from  the  same  beds,  we  are  not  simply 
taught  that  these  individual  quadrupeds  flourished  at  the  eras  in 
question,  but  that  thousands,  perhaps  hundreds  of  thousands,  of  the 
same  species  peopled  the  land  without  leaving  behind  them  any  trace 
of  their  existence,  whether  in  the  shape  of  fossil  bones  or  footprints  ; 
or,  if  they  left  any  traces,  these  have  eluded  a  long  and  most  labori- 
ous search. 

Moreover,  we  must  never  forget  how  many  of  the  dates  given  in 
the  above  table  (p.  588)  are  due  to  British  skill  and  energy,  Great 


590  DISCOVERY  OF  FOSSIL  VERTEBRATA.          [On.  XXVII. 

Britain  being  still  the  only  country  in  tlie  world  in  which  mammalia 
have  been  found  in  oolitic  rocks.  And  if  geology  had  been  culti- 
vated with  less  zeal  in  our  island,  we  should  know  very  little  as  yet 
of  two  extensive  assemblages  of  tertiary  mammalia  of  higher  anti- 
quity than  the  fauna  of  the  Paris  gypsum  (already  cited  as  having 
once  laid  claim  to  be  the  earliest  that  ever  nourished  on  the  earth) — 
namely,  first,  that  of  the  Headon  series  (see  above,  p.  284),  and,  sec- 
ondly, one  long  prior  to  it  in  date,  and  antecedent  to  the  London 
Clay.  This  last  has  already  afforded  us  indications  of  Cheiroptera, 
Pachydermata,  and  Marsupialia  (see  p.  292).  How  then  can  we 
doubt,  if  the  globe  were  to  be  studied  with  the  same  diligence,  if  the 
six  great  continents,  Europe,  Asia,  Africa,  North  and  South  America, 
and  Australia,  were  equally  well  known,  that  every  date  assigned  by 
us  in  the  above  Table  for  the  earliest  recorded  appearance  of  fish, 
reptiles,  birds,  and  mammals,  would  have  to  be  altered  and  shifted 
back  ?  Nay,  if  one  other  area,  such  as  part  of  Spain,  of  the  size  of 
England  and  Scotland,  were  subjected  to  the  same  scrutiny  (and  we 
are  still  very  imperfectly  acquainted  even  with  Great  Britain),  each 
class  of  vertebrata  would  perhaps  recede  one  or  more  steps  farther 
back  into  the  abyss  of  time;  fish  might  penetrate  into  the  Lower 
Silurian — reptiles  into  the  Upper  Devonian — mammalia  into  the 
Lower  Trias — birds  into  the  Middle  Oolite — and,  if  we  turn  to  the 
Invertebrata,  Trilobites  and  Cephalopods  might  descend  into  the 
Lower  Cambrian — and  Foraminifera  into  rocks  now  styled  Azoic,  and 
older  than  the  Lower  Laurentian. 

Yet,  after  these  and  many  more  analogous  revisions  of  the  Table, 
the  order  of  chronological  succession  in  the  different  classes  of  fossil 
animals  would  probably  continue  the  same  as  now  ; — in  other  words, 
our  success  in  tracing  back  the  remains  of  each  class  to  remote  eras 
would  be  the  greatest  in  fishes,  next  in  reptiles,  and  least  in  mamma- 
lia and  birds. 

We  have  of  late  years  acquired  striking  proofs  of  the  difficulty  of 
detecting  the  bones  of  man  in  those  strata  in  which  the  works  of 
his  hands  in  the  shape  of  flint  implements  abound.  There  are  also 
large  tracts  of  Eocene  rocks  very  prolific  of  shells  and  other  organ 
isms,  as  in  Belgium,  for  example,  which  have  been  diligently  studied 
for  nearly  a  century  without  yielding  a  single  bone  of  a  mammifer. 
In  the  whole  world  the  cretaceous  and  oolitic  rocks  have  each  of 
them  only  afforded  as  yet  a  single  example  of  a  fossil  bird.  It  would 
almost  seem  as  if  the  higher  the  type  of  organization  the  more  pow- 
erful the  spell  required  to  evoke  the  remains  of  a  fossil  being  from 
its  stony  sepulchre. 

"  Unwilling  I  my  lips  unclose — 
Leave,  oh !  leave  me  to  repose." 

That  we  should  meet  with  ichthyolites  more  universally  at  each 
era,  and  at  greater  depths  in  the  series,  than  any  other  class  of  fossil 


CH.  XXVII.1  EARLIEST  KNOWN  VERTEBRATA.  591 

vertehrata,  would  follow  partly  from  our  having  as  palaeontologists  to 
do  chiefly  with  strata  of  marine  origin,  and  partly  because  bones  of 
fish,  however  partial  and  capricious  their  distribution  on  the  bed  of 
the  sea,  are  nevertheless  more  easily  met  with  than  those  of  reptiles 
or  mammalia.  In  like  manner  the  extreme  rarity  of  birds  in  Recent 
and  Pliocene  strata,  even  in  those  of  freshwater  origin,  might  lead  us 
to  anticipate  that  their  remains  would  be  obtained  with  the  greatest 
difficulty  in  the  older  rocks,  as  the  Table  proves  to  be  the  case — even 
in  tertiary  strata,  wherein  we  can  more  readily  find  deposits  formed 
in  lakes  and  estuaries. 

The  only  incongruity  between  the  geological  results  and  those 
which  our  dredging  experiences  might  have  led  us  to  anticipate 
a  priori,  consists  in  the  frequency  of  fossil  reptiles,  and  the  com- 
parative scarcity  of  mammalia.  It  would  appear  that  during  all  the 
secondary  periods,  not  even  excepting  the  newest  part  of  the  creta- 
ceous, there  was  a  greater  development  of  reptile  life  than  is  now  wit- 
nessed in  any  part  of  the  globe.  The  preponderance  of  this  class 
over  the  mammalia  may  have  depended  in  part  on  climatal  condi- 
tions, but  it  seems  also  clearly  to  imply  the  limited  development,  if 
not  the  total  absence,  before  the  Tertiary  period,  of  the  placental 
mammalia,  whether  terrestrial  or  aquatic,  which,  when  they  became 
dominant,  acquired  power  to  check  and  keep  down  the  class  of  verte- 
brata  nearly  allied  to  them  in  structure,  and  coming  most  directly  in 
competition  with  them  in  the  struggle  for  life.  For  notwithstanding 
the  impossibility  of  assigning  even  conjectural  limits  to  the  chrono- 
logical extension  of  each  class  of  vertebrata  as  we  trace  them  farther 
and  farther  back  into  the  past,  it  cannot  be  denied  that  our  failure  to 
detect  signs  of  them  in  older  strata,  in  proportion  to  the  rank  of  their 
organization,  favors  the  doctrine  of  development,  or  at  least  of  the 
successive  appearance  on  the  earth  of  beings  more  and  more  highly 
organized,  culminating  at  last  in  the  advent  of  Man  himself. 


592  TRAP  ROCKS.  [On.  XXVIII. 


CHAPTER  XXVIII. 

VOLCANIC    ROCKS. 

Trap  Rocks — Name,  whence  derived — Their  igneous  origin  at  first  doubted — Their 
general  appearance  and  character — Volcanic  cones  and  craters,  how  formed — 
Mineral  composition  and  texture  of  volcanic  rocks — Varieties  of  felspar — 
Hornblende  and  augite — Isomorphism — Rocks,  how  to  be  studied — Basalt, 
trachyte,  greenstone,  porphyry,  scoria,  amygdaloid,  lava,  tuff — Agglomerate — • 
Laterite — Alphabetical  list,  and  explanation  of  names  and  synonyms,  of  volcanic 
rocks — Table  of  the  analyses  of  minerals  most  abundant  in  the  volcanic  and 
hypogene  rocks. 

THE  aqueous  or  fossiliferous  rocks  having  now  been  described,  we 
have  next  to  examine  those  which  may  be  called  volcanic,  in  the  most 
extended  sense  of  that  term.  Suppose  a  a,  in  the  annexed  diagram, 

Fig.  672. 


a.  Hypogene  formations,  stratified  and  uustratified. 
&.  Aqueous  formations.  c.  Volcanic  rocks. 

to  represent  the  crystalline  formations,  such  as  the  granitic  and  meta- 
morphic ;  b  b  the  fossiliferous  strata ;  and  c  c  the  volcanic  rocks. 
These  last  are  sometimes  found,  as  was  explained  in  the  first  chapter, 
breaking  through  a  and  6,  sometimes  overlying  both,  and  occasionally 
alternating  with  the  strata  b  b.  They  also  are  seen,  in  some  instances, 
to  pass  insensibly  into  the  unstratified  division  of  a,  or  the  Plutonic 
rocks. 

When  geologists  first  began  to  examine  attentively  the  structure 
of  the  northern  and  western  parts  of  Europe,  they  were  almost  en- 
tirely ignorant  of  the  phenomena  of  existing  volcanoes.  They  found 
certain  rocks,  for  the  most  part,  without  stratification,  and  of  a  pecu- 
liar mineral  composition,  to  which  they  gave  different  names,  such  as 
basalt,  greenstone,  porphyry,  and  amygdaloid.  All  these,  which 
were  recognized  as  belonging  to  one  family,  were  called  "  trap  "  by 
Bergmann,  from  trappa,  Swedish  for  a  flight  of  steps — a  name  sijice 
adopted  very  generally  into  the  nomenclature  of  the  science ;  for  it 
was  observed  that  many  rocks  of  this  class  occurred  in  great  tabular 
masses  of  unequal  extent,  so  as  to  form  a  succession  of  terraces  or 
steps  on  the  sides  of  hills.  This  configuration  appears  to  be  derived 
from  two  causes.  First,  the  abrupt  original  terminations  of  sheets  of 
melted  matter,  which  have  spread,  whether  on  the  land  or  bottom  of 
the  sea,  over  a  level  surface.  For  we  know,  in  the  case  of  lava  flow 


CH.  XXVIII.]  CONES  AND   CRATERS.  593 

ing  from  a  volcano,  that  a  stream,  when  it  has  ceased  to  flow,  and 
grown  solid,  very  commonly  ends  in  a  steep  slope,  as  at  a,  fig.  673. 
But,   secondly,  the  step-like  appearance 
arises  more  frequently  from  the  mode  in  Fig.  673. 

which  horizontal  masses  of  igneous  rock, 
such  as  b  c,  intercalated  between  aqueous 
strata,  or  showers  of  volcanic  dust  and 
ashes,  have,  subsequently  to  their  origin, 
been  exposed,  at  different  heights,  by  de- 
nudation. Such  an  outline,  it  is  true,  is 

not  peculiar  to  trap  rocks  ;    great  beds  of  Step-like  appearance  of  trap. 

limestone,  and  other  hard  kinds  of  stone, 

often  presenting  similar  terraces  and  precipices  :  but  these  are  usually 
on  a  smaller  scale,  or  less  numerous,  than  the  volcanic  steps,  or  form 
less  decided  features  in  the  landscape,  as  being  less  distinct  in  struc- 
ture and  composition  from  the  associated  rocks. 

Although  the  characters  of  trap  rocks  are  greatly  diversified,  the 
beginner  will  easily  learn  to  distinguish  them  as  a  class  from  the 
aqueous  formations.  Sometimes  they  present  themselves,  as  already 
stated,  in  tabular  masses,  which  are  not  divided  by  horizontal  planes 
of  stratification  in  the  manner  of  sedimentary  deposits.  Sometimes 
they  form  chains  of  hills  often  conical  in  shape.  Not  unfrequently 
they  are  seen  as  "  dikes  "  or  wall-like  masses,  intersecting  fossiliferous 
beds.  The  rock  is  occasionally  columnar,  the  columns  sometimes  de- 
composing into  balls  of  various  sizes,  from  a  few  inches  to  several  feet 
in  diameter.  The  decomposing  surface  very  commonly  assumes  a 
coating  of  a  rusty  iron  color,  from  the  oxidation  of  ferruginous  matter, 
so  abundant  in  the  traps  in  which  augite  or  hornblende  occur ;  or,  in 
the  felspathic  varieties  of  trap,  it  acquires  a  white  opaque  coating,  from 
the  bleaching  of  the  mineral  called  felspar.  On  examining  any  of 
these  volcanic  rocks,  where  they  have  not  suffered  disintegration,  we 
rarely  fail  to  detect  a  crystalline  arrangement  in  one  or  more  of  the 
component  minerals.  Sometimes  the  texture  of  the  mass  is  cellular  or 
porous,  or  we  perceive  that  it  has  once  been  full  of  pores  and  cells, 
which  have  afterwards  become  filled  with  carbonate  of  lime,  or  other 
infiltrated  mineral. 

Most  of  the  volcanic  rocks  produce  a  fertile  soil  by  their  disintegra- 
tion. It  seems  that  their  component  ingredients,  silica,  alumina,  lime, 
potash,  iron,  and  the  rest,  are  in  proportions  well  fitted  for  the  growth 
of  vegetation.  As  they  do  not  effervesce  with  acids,  a  deficiency  of 
calcareous  matter  might  at  first  be  suspected ;  but  although  the  carbon- 
ate of  lime  is  rare,  except  in  the  nodules  of  amygdaloids,  yet  it  will  be 
seen  that  lime  sometimes  enters  largely  into  the  composition  of  augite 
and  hornblende.  (See  Table,  p.  608.) 

Cones  and  Craters. — In  regions  where  the  eruption  of  volcanic  mat- 
ter has  taken  place  in  the  open  air,  and  where  the  surface  has  never 
since  been  subjected  to  great  aqueous  denudation,  cones  and  craters 
38 


594:  VOLCANIC  KOCKS.  [On.  XXVIII. 

constitute  the  most  striking  peculiarity  of  this  class  of  formations. 
Many  hundreds  of  these  cones  are  seen  in  central  France,  in  the  an- 
cient provinces  of  Auvergne,  Velay,  and  Vivarais,  where  they  observe, 
for  the  most  part,  a  linear  arrangement,  and  form  chains  of  hills. 
Although  none  of  the  eruptions  have  happened  within  the  historical 
era,  the  streams  of  lava  may  still  be  traced  distinctly  descending  from 
many  of  the  craters,  and  following  the  lowest  levels  of  the  existing 
valleys.  The  origin  of  the  cone  and  crater-shaped  hill  is  well  under- 

Fig.  674. 


Part  of  the  chain  of  extinct  volcanoes  called  the  Mont3  Dome,  Auvergne.    (Scrope.) 

stood,  the  growth  of  many  having  been  watched  during  volcanic  erup- 
tions. A  chasm  or  fissure  first  opens  in  the  earth,  from  which  great 
volumes  of  steam  and  other  gases  are  evolved.  The  explosions  are  so 
violent  as  to  hurl  up  into  the  air  fragments  of  broken  stone,  parts  of 
which  are  shivered  into  minute  atoms.  At  the  same  time  melted 
stone  or  lava  usually  ascends  through  the  chimney  or  vent  by  which 
the  gases  make  their  escape.  Although  extremely  heavy,  this  lava  is 
forced  up  by  the  expansive  power  of  entangled  gaseous  fluids,  chiefly 
steam  or  aqueous  vapor,  exactly  in  the  same  manner  as  water  is  made 
to  boil  over  the  edge  of  a  vessel  when  steam  has  been  generated  at 
the  bottom  by  heat.  Large  quantities  of  the  lava  are  also  shot  up 
into  the  air,  where  it  separates  into  fragments,  and  acquires  a  spongy 
texture  by  the  sudden  enlargement  of  the  included  gases,  and  thus 
forms  scorice,  other  portions  being  reduced  to  an  impalpable  powder 
or  dust.  The  showering  down  of  the  various  ejected  materials  round 
the  orifice  of  eruption  gives  rise  to  a  conical  mound,  in  which  the 
successive  envelopes  of  sand  and  scoriae  form  layers,  dipping  on  all 
sides  from  a  central  axis.  In  the  mean  time  a  hollow,  called  a  crater, 
has  been  kept  open  in  the  middle  of  the  mound  by  the  continued 
passage  upwards  of  steam  and  other  gaseous  fluids.  The  lava  some- 
times flows  over  the  edge  of  the  crater,  and  thus  thickens  and 
strengthens  the  sides  of  the  cone ;  but  sometimes  it  breaks  down  the 
cone  on  one  side  (see  fig.  674),  and  often  flows  out  from  a  fissure  at 
the  base  of  the  hill,  or  at  some  distance  from  its  base.* 

Composition  and  Nomenclature. — Before  speaking  of  the  connection 
between  the  products  of  modern  volcanoes  and  the  rocks  usually  styled 
trappean,  and  before  describing  the  external  forms  of  both,  and  the 

*  For  a  description  and  theory  of  active  volcanoes,  see  Principles  of  Geology, 
chaps,  xxiv.  et  seq.  and  xxxii. 


CH.  XXVIIL]  VOLCANIC  ROCKS.  595 

manner  and  position  in  which  they  occur  in  the  earth's  crust,  it  will 
be  desirable  to  treat  of  their  mineral  composition  and  names.  The 
varieties  most  frequently  spoken  of  are  basalt  and  trachyte,  to  which 
dolerite,  greenstone,  clinkstone,  and  others  might  be  added;  while 
those  founded  chiefly  on  peculiarities  of  texture,  are  porphyry,  amyg- 
daloid, lava,  volcanic  breccia  or  agglomerate,  turf,  scoria,  and  pumice. 
It  may  be  stated  generally,  that  all  these  are  mainly  composed  of  two 
minerals,  or  families  of  simple  minerals,  felspar  and  hornblende  ;  but 
the  felspar  preponderates  greatly  even  in  those  rocks  to  which  the  horn- 
blendic  mineral  imparts  its  distinctive  character  and  prevailing  color. 

The  two  minerals  alluded  to  may  be  regarded  as  two  groups,  rather 
than  species.  Felspar,  for  example,  may  be,  first,  common  felspar 
(often  called  Orthoclase),  that  is  to  say,  potash-felspar,  in  which  the 
predominant  alkali  is  potash  (see  Table,  p.  608) ;  or,  secondly,  albite, 
i.  e.  soda-felspar,  where  the  predominant  alkali  is  soda ;  or,  thirdly, 
Oligoclase,  in  which  there  is  also  more  soda  than  potash,  but  which 
contains  less  silica  than  albite ;  or,  fourthly,  Labrador-felspar  (Labra- 
dorite),  which  differs  not  only  in  its  iridescent  hues  and  cleavage,  but 
also  in  containing  less  silica  than  albite,  and  in  having  lime  in  its 
base.  Anorthite,  so  called  from  the  oblique  interfacial  angles  of  its 
rhomboidal  prisms,  is  nearly  allied  in  composition  with  Labradorite. 
As  to  "  glassy  felspar "  and  "  compact  felspar,"  they  cannot  rank  as 
varieties  of  equal  importance,  for  both  the  albitic  and  common  felspar 
appear  sometimes  in  transparent  or  glassy  crystals ;  and  compact  fel- 
spar, or  petrosilex,  is  a  compound  of  a  less  definite  nature,  sometimes 
containing  largely  both  soda  and  potash.  It  might  be  called  a  fel- 
spathic  paste,  being  the  residuary  matter  after  portions  of  the  original 
matrix  have  crystallized.  Recent  analysis  has  shown  that  all  the 
varieties  of  felspar  may  contain  both  potash  and  soda,  although  in 
some  of  them  the  potash,  and  in  others  the  soda,  greatly  prevails. 

The  hornblendic  group  consists  principally  of  two  varieties ;  first, 
hornblende,  and,  secondly,  augite,  which  were  once  regarded  as  very 
distinct,  although  now  some  eminent  mineralogists  are  in  doubt 
whether  they  are  not  one  and  the  same  mineral,  differing  only  as  one 
crystalline  form  of  native  sulphur  differs  from  another. 

The  history  of  the  changes  of  opinion  on  this  point  is  curious  and 
instructive.  Werner  first  distinguished  augite  from  hornblende ;  and 
his  proposal  to  separate  them  obtained  afterwards  the  sanction  of 
Haiiy,  Mohs,  and  other  celebrated  mineralogists.  It  was  agreed  that 
the  form  of  the  crystals  of  the  two  species  were  different,  and  their 
structure,  as  shown  by  cleavage,  that  is  to  say,  by  breaking  or  cleaving 
the  mineral  with  a  chisel,  or  a  blow  of  the  hammer,  in  the  direction 
in  which  it  yields  most  readily.  It  was  also  found  by  analysis  that 
augite  usually  contained  more  lime,  less  alumina,  and  no  fluoric  acid ; 
which  last,  though  not  always  found  in  hornblende,  often  enters  into 
its  composition  in  minute  quantity.  In  addition  to  these  characters, 
it  was  remarked  as  a  geological  fact,  that  augite  and  hornblende  are 


596  THEORY  OF  ISOMORPHISM.  [On.  XXVIII. 

very  rarely  associated  together  in  the  same  rock ;  and  that  when  this 
happened,  as  in  some  lavas  of  modern  date,  the  hornblende  occurs  in 
the  mass  of  the  rock,  where  crystallization  may  have  taken  place  more 
slowly,  while  the  augite  merely  lines  cavities  where  the  crystals  may 
have  been  produced  rapidly.  It  was  also  remarked,  that  in  the  crys- 
talline slags  of  furnaces,  augitic  forms  were  frequent,  the  hornblendic 
entirely  absent ;  hence  it  was  conjectured  that  hornblende  might  be 
the  result  of  slow,  and  augite  of  rapid  cooling.  This  view  was  con- 
firmed by  the  fact,  that  Mitscherlich  and  Berthier  were  able  to  make 
augite  artificially,  but  could  never  succeed  in  forming  hornblende. 
Lastly,  Gustavus  Rose  fused  a  mass  of  hornblende  in  a  porcelain  fur- 
nace, and  found  that  it  did  not,  on  cooling,  assume  its  previous  shape, 
but  invariably  took  that  of  augite.  The  same  mineralogist  observed 
certain  crystals  in  rocks  from  Siberia  which  presented  a  hornblende 
cleavage,  while  they  had  the  external  form  of  augite. 

If,  from  these  data,  it  is  inferred  that  the  same  substance  may 
assume  the  crystalline  forms  of  hornblende  or  augite  indifferently, 
according  to  the  more  or  less  rapid  cooling  of  the  melted  mass,  it  is 
nevertheless  certain  that  the  variety  commonly  called  augite,  and 
recognized  by  a  peculiar  crystalline  form,  has  usually  more  lime  in  it, 
and  less  alumina,  than  that  called  hornblende,  although  the  quantities 
of  these  elements  do  not  seem  to  be  always  the  same.  Unquestionably 
the  facts  and  experiments  above  mentioned  show  the  very  near  affinity 
of  hornblende  and  augite ;  but  even  the  convertibility  of  one  into  the 
other,  by  melting  and  recrystallizing,  does  not  perhaps  demonstrate 
their  absolute  identity.  For  there  is  often  some  portion  of  the  mate- 
rials in  a  crystal  which  are  not  in  perfect  chemical  combination  with 
the  rest.  Carbonate  of  lime,  for  example,  sometimes  carries  with  it  a 
considerable  quantity  of  silex  into  its  own  form  of  crystal,  the  silex 
being  mechanically  mixed  as  sand,  and  yet  not  preventing  the  car- 
bonate of  lime  from  assuming  the  form  proper  to  it.  This  is  an  ex- 
treme case,  but  in  many  others'  some  one  or  more  of  the  ingredients 
in  a  crystal  may  be  excluded  from  perfect  chemical  union ;  and  after 
fusion,  when  the  mass  recrystallizes,  the  same  elements  may  combine 
perfectly  or  in  new  proportions,  and  thus  a  new  mineral  may  be  pro- 
duced. Or  some  one  of  the  gaseous  elements  of  the  atmosphere,  the 
oxygen  for  example,  may,  when  the  melted  matter  reconsolidates, 
combine  with  some  one  of  the  component  elements. 

The  different  quantity  of  the  impurities  or  refuse  above  alluded  to, 
which  may  occur  in  all  but  the  most  transparent  and  perfect  crystals, 
may  partly  explain  the  discordant  results  at  which  experienced  chem- 
ists have  arrived  in  their  analysis  of  the  same  mineral.  For  the  reader 
will  find  that  crystals  of  a  mineral  determined  to  be  the  same  by  physi- 
cal characters,  crystalline  form,  and  optical  properties,  have  often  been 
declared  by  skilful  analyzers  to  be  composed  of  distinct  elements. 
(See  the  table  at  p.  608.)  This  disagreement  seemed  at  first  subver- 
sive of  the  atomic  theory,  or  the  doctrine  that  there  is  a  fixed  and 


CH.  XXVIII.]  PYROXENE— AMPHIBOLE.  597 

constant  relation  between  the  crystalline  form  and  structure  of  a 
mineral  and  its  chemical  composition.  The  apparent  anomaly,  how- 
ever, which  threatened  to  throw  the  whole  science  of  mineralogy  into 
confusion,  was  in  a  great  degree  reconciled  to  fixed  principles  by  the 
discoveries  of  Professor  Mitscherlich  at  Berlin,  who  ascertained  that 
the  composition  of  the  minerals  which  had  appeared  so  variable,  was 
governed  by  a  general  law,  to  which  he  gave  the  name  of  isomorphism 
(from  100$)  isos,  equal,  and  |«op</>7/,  morphe,  form).  According  to  this 
law,  the  ingredients  of  a  given  species  of  mineral  are  not  absolutely 
fixed  as  to  their  kind  and  quality ;  but  one  ingredient  may  be  replaced 
by  an  equivalent  portion  of  some  analogous  ingredient.  Thus,  in 
augite,  the  lime  may  be  in  part  replaced  by  portions  of  protoxide  of 
iron,  or  of  manganese,  while  the  form  of  the  crystal,  and  the  angle  of 
its  cleavage  planes,  remain  the  same.  These  vicarious  substitutions, 
however,  of  particular  elements  cannot  exceed  certain  defined  limits. 

Pyroxene,  a  name  of  Haiiy's,  is  often  used  for  augite  in  descriptions 
of  volcanic  rocks.  It  is  properly,  according  to  M.  Delesse,  a  general 
name,  under  which  Augite,  Diallage,  and  Hypersthene  may  be  united, 
for  these  three  are  varieties  of  one  and  the  same  mineral  species,  hav- 
ing the  same  chemical  formula  with  variable  bases. 

Amphibole  is  in  like  manner  a  general  term  under  which  Hornblende 
and  Actinolite  may  be  united. 

Having  been  led  into  this  digression  on  some  recent  steps  made  in 
the  progress  of  mineralogy,  I  may  here  observe  that  the  geological 
student  must  endeavor  as  soon  as  possible  to  familiarize  himself  with 
the  characters  of  five  at  least  of  the  most  abundant  simple  minerals  of 
which  rocks  are  composed.  These  are  felspar,  quartz,  mica,  horn- 
blende, and  carbonate  of  lime.  This  knowledge  cannot  be  acquired 
from  books,  but  requires  personal  inspection,  and  the  aid  of  a  teacher. 
It  is  well  to  accustom  the  eye  to  know  the  appearance  of  rocks  under 
the  lens.  To  learn  to  distinguish  felspar  from  quartz  is  the  most  im- 
portant step  to  be  first  aimed  at.  In  general  we  may  know  the  fel- 
spar because  it  can  be  scratched  with  the  point  of  a  knife,  whereas 
the  quartz,  from  its  extreme  hardness,  receives  no  impression.  If  both 
minerals  are  crystalline,  the  felspar  may  be  known  by  its  lamellar,  and 
the  quartz  by  its  glass-like  fracture ;  but  when  they  occur  in  a  granu- 
lar or  uncrystallized  state,  the  young  geologist  must  not  be  dis- 
couraged if,  after  considerable  practice,  he  often  fails  to  distinguish 
them  by  the  eye  alone.  If  the  felspar  is  granular,  the  blow-pipe  may 
be  used,  for  the  edges  of  the  grains  can  be  rounded  in  the  flame, 
whereas  those  of  quartz  are  infusible.  In  order  to  detect  the  varieties 
of  felspar  above  enumerated,  and  to  distinguish  hornblende  from 
augite,  the  reflecting  goniometer  will  often  be  useful,  enabling  the 
mineralogist  to  ascertain  the  angle  of  cleavage  and  shape  of  the 
crystal. 

The  external  characters  and  composition  of  the  felspars  are  extreme- 
ly different  from  those  of  augite  or  hornblende ;  so  that  the  volcanic 


598  BASALT— AUGITE.  [On.  XXVffl. 

rocks  in  which  either  of  these  minerals  play  a  conspicuous  part  are 
easily  recognizable.  But  there  are  mixtures  of  the  two  elements  in 
very  different  proportions,  the  mass  being  sometimes  exclusively  com- 
posed of  felspar,  and  at  other  times  largely  of  augite.  Between  the 
two  extremes  there  is  almost  every  intermediate  gradation ;  yet  cer- 
tain compounds  prevail  so  extensively  in  nature,  and  preserve  so  much 
uniformity  of  aspect  and  composition,  that  it  is  useful  in  geology  to 
regard  them  as  distinct  rocks,  and  to  assign  names  to  them,  such  as 
basalt,  greenstone,  trachyte,  and  others  presently  to  be  mentioned. 

Basalt. — As  an  example  of  rocks  in  which  augite  is  a  conspicuous 
ingredient,  basalt  may  first  be  mentioned.  Although  we  are  more 
familiar  with  this  term  than  with  that  of  any  other  kind  of  trap,  it  is 
difficult  to  define  it,  the  name  having  been  used  so  comprehensively, 
and  sometimes  so  vaguely.  It  has  been  generally  applied  to  any  trap 
rock  of  a  black,  bluish,  or  leaden-gray  color,  having  a  uniform  and 
compact  texture.  Most  strictly,  it  consists  of  an  intimate  mixture  of 
felspar,  augite,  and  iron,  to  which  a  mineral  of  an  olive-green  color, 
called  olivine,  is  often  superadded,  in  distinct  grains  or  nodular  masses. 
The  iron  is  usually  magnetic  (oxydulated  iron),  and  is  often  accom- 
panied by  another  metal,  titanium.  The  term  "  Dolerite "  is  now 
much  used  for  this  rock,  when  the  felspar  is  of  the  variety  callec}  Lab- 
radorite,  as  in  the  lavas  of  Etna.  Basalt,  according  to  Dr.  Daubeny, 
in  its  more  strict  sense,  is  composed  of  "  an  intimate  mixture  of  augite 
with  a  zeolitic  mineral  which  appears  to  have  been  formed  out  of 
Labradorite  by  the  addition  of  water,  the  presence  of  water  being  in 
all  zeolites  the  cause  of  that  bubbling  up  under  the  blow-pipe  to  which 
they  owe  their  appellation."  *  Of  late  years  the  analyses  of  M.  Delesse 
and  other  eminent  mineralogists  have  shown  that  the  opinion  once 
entertained  that  augite  was  the  prevailing  mineral  in  basalt,  or  even 
in  the  most  augitic  trap  rocks,  must  be  abandoned.  Although  its 
presence  gives  to  these  rocks  their  distinctive  character  as  contrasted 
with  trachytes,  still  the  principal  element  in  their  composition  is  fel- 


Augite  rock  has,  indeed,  been  defined  by  Leonhard  as  being  made 
up  principally  or  wholly  of  augite,f  and  in  some  veinstones,  says 
Delesse,  such  a  rock  may  be  found;  but  the  greater  part  of  what 
passes  by  the  name  of  augite  rock  is  more  rich  in  green  felspar  than 
in  augite.  Amphibolite,  in  like  manner,  or  Hornblende  rock,  is  a  trap 
of  the  basaltic  family,  in  which  there  is  much  hornblende,  and  in 
which  this  mineral  has  been  supposed  to  predominate ;  but  Delesse 
finds,  by  analysis,  that  the  felspar  may  be  in  excess,  the  base  being 
felspathic. 

In  some  varieties  of  basalt  the  quantity  of  olivine  is  very  great ;  and 
as  this  mineral  differs  but  slightly  in  its  chemical  composition  from 
serpentine  (see  Table  of  Analyses,  p.  608),  containing  even  a  larger 

*  Volcanoes,  2d  ed.  p.  18.  f  Mineralreich,  2d  ed.  p.  85. 


Co.  XXVIH.]  TRACHYTE— CLINKSTONE.  599 

proportion  of  magnesia  than  serpentine,  it  has  been  suggested  with 
much  probability  that  in  the  course  of  ages  some  basalts  highly 
charged  with  olivine  may  be  turned,  by  metamorphic  action,  into 
serpentine. 

Trachyte. — This  name,  derived  from  rpa%v£,  rough,  has  been  given 
to  the  felspathic  class  of  volcanic  rocks  which  have  a  coarse,  cellular 
paste,  rough  and  gritty  to  the  touch.  This  paste  has  commonly  been 
supposed  to  consist  chiefly  of  albite,  but  according  to  M.  Delesse  it  is 
variable  in  composition,  its  prevailing  alkali  being  soda.  Through  the 
base  are  disseminated  crystals  of  glassy  felspar,  mica,  and  sometimes 
quartz  and  hornblende,  although  in  the  trachyte,  properly  so  called, 
there  is  no  quartz.  The  varieties  of  felspar  which  occur  in  trachyte 
are  trisilicates,  or  those  in  which  the  silica  is  to  the  alumina  in  the 
proportion  of  three  atoms  to  one.* 

Trachytic  Porphyry,  according  to  Abich,  has  the  ordinary  compo  - 
sition  of  trachyte,  with  quartz  superadded,  and  without  any  augite  or 
titaniferous  iron.  Andesite  is  a  name  given  by  Gustavus  Rose  to  a 
trachyte  of  the  Andes,  which  contains  the  felspar  called  Andesin, 
together  with  glassy  felspar  (orthoclase)  and  hornblende  disseminated 
through  a  dark-colored  base. 

Clinkstone,  or  Phonclite. — Among  the  felspathic  products  of  vol- 
canic action,  this  rock  is  remarkable  for  its  tendency  to  lamination, 
which  is  sometimes  such  that  it  affords  tiles  for  roofing.  It  rings 
when  struck  with  the  hammer,  whence  its  name ;  is  compact,  and 
usually  of  a  grayish  blue  or  brownish  color ;  is  variable  in  composition, 
but  almost  entirely  composed  of  felspar,  and  in  some  cases,  according 
to  Gmelin,  of  felspar  and  mesotype.  When  it  contains  disseminated 
crystals  of  felspar,  it  is  called  Clinkstone  porphyry. 

Greenstone  is  the  most  abundant  of  those  volcanic  rocks  which  are 
intermediate  in  their  composition  between  the  Basalts  and  Trachytes. 
The  name  has  usually  been  extended  to  all  granular  mixtures,  whether 
of  hornblende  and  felspar,  or  of  augite  and  felspar.  The  term  diorite 
has  been  applied  exclusively  to  compounds  of  hornblende  and  felspar. 
According  to  the  analyses  of  Delesse  and  others,  the  chief  cause  of 
the  green  color,  in  most  greenstones,  is  not  green  hornblende  nor 
augite,  but  a  green  siliceous  base,  very  variable  and  indefinite  in  its 
composition.  The  dark  color,  however,  of  diorite  is  usually  derived 
from  disseminated  plates  of  hornblende. 

The  Basalts  contain  a  smaller  quantity  of  silica  than  the  Trachytes, 
and  a  larger  proportion  of  lime  and  magnesia.  Hence,  independently 
of  the  frequent  presence  of  iron,  basalt  is  heavier.  Abich  has  there- 
fore proposed  that  we  should  weigh  these  rocks,  in  order  to  appreciate 
their  composition  in  cases  where  it  it  is  impossible  to  separate  their 
component  minerals.  Thus,  the  variety  of  basalt  called  dolerite,  which 
contains  53  per  cent,  of  silica,  has  a  specific  gravity  of  2-86 ;  whereas 

*  Dr.  Daubeny  on  Volcanoes,  2d  ed.  pp.  14,  15. 


600  PORPHYRY.  [Cn.  XXVIII. 

trachyte,  which  has  66  per  cent,  of  silica,  has  a  sp.  gr.  of  only  2'68 ; 
trachytic  porphyry,  containing  69  per  cent,  of  silica,  a  sp.  gr.  of  only 
2*58.  If  we  then  take  a  rock  of  intermediate  composition,  such  as 
that  prevailing  in  the  Peak  of  TenerifFe,  which  Abich  calls  Trachyte- 
dolerite,  its  proportion  of  silica  being  intermediate,  or  58  per  cent.,  it 
weighs  2*78,  or  more  than  trachyte,  and  less  than  basalt.*  The  basalts 
are  generally  dark  in  color,  sometimes  almost  black,  whereas  the  tra- 
chytes are  gray,  and  even  occasionally  white.  As  compared  with  the 
granitic  rocks,  basalts  and  trachytes  contain  both  of  them  more  soda 
in  their  composition,  the  potash-felspars  being  generally  abundant  in 
the  granites.  The  volcanic  rocks  moreover,  whether  basaltic  or  tra- 
chytic, contain  less  silica  than  the  granites,  in  which  last  the  excess  of 
silica  has  gone  to  form  quartz.  This  mineral,  so  conspicuous  in  gran- 
ite, is  usually  wanting  in  the  volcanic  formations,  and  never  predomi- 
nates in  them. 

The  fusibility  of  the  igneous  rocks  generally  exceeds  that  of  other 
rocks,  for  the  alkaline  matter  and  lime  which  commonly  ab.ound  in 
their  composition  serve  as  a  flux  to  the  large  quantity  of  silica,  which 
would  be  otherwise  so  refractory  an  ingredient. 

We  may  now  pass  to  the  consideration  of  those  igneous  rocks,  the 
characters  of  which  are  founded  on  their  form  rather  than  their  com- 
position. 

Porphyry  is  one  of  this  class,  and  very  characteristic  of  the  volcanic 
formations.  When  distinct  crystals  of  one  or  more  minerals  are  scat- 
tered through  an  earthy  or  compact  base,  the  rock  is  termed  a  por- 
phyry (see  fig.  675).  Thus  trachyte  is  porphyritic;  for  in  it,  as  in 

Fig.  675.  Fig.  676. 


Porphyry.  Scoriaceous  lava  in  part  converted  into 

.White  crystals  of  felspar  in  a  dark  an  amygdaloid, 

base  of  hornblende  and  felspar.  Montagne  de  la  Veille,  Department  of 

Puy  de  Dome,  France. 

many  modern  lavas,  there  are  crystals  of  felspar ;  but  in  some  porphy- 
ries the  crystals  are  of  augite,  olivine,  or  other  minerals.     If  the  base 

*  Dr.  Daubeny  on  Volcanoes,  2d  ed.  pp.  14,  15. 


CH.  XXVIR]  AMYGDALOID— LAVA.  601 

be  greenstone,  basalt,  or  pitchstone,  the  rock  may  be  denominated 
greenstone-porphyry,  pitch-stone  porphyry,  and  so  forth.  The  old 
classical  type  of  this  form  of  rock  is  the  red  porphyry  of  Egypt,  or  the 
well  known  "  Kosso  antico."  It  consists,  according  to  Delesse,  of  a 
red  felspathic  base  in  which  are  disseminated  rose-colored  crystals  of 
the  felspar  called  oligoclase,  with  some  plates  of  blackish  hornblende 
and  grains  of  oxidized  iron-ore  (fer  oligiste).  Red  quartziferous  por- 
phyry is  a  much  more  siliceous  rock,  containing  about  70  or  80  per 
cent,  of  silex,  while  that  of  Egypt  has  only  62  per  cent. 

Amygdaloid. — This  is  also  another  form  of  igneous  rock,  admitting 
of  every  variety  of  composition.  It  comprehends  any  rock  in  which 
round  or  almond-shaped  nodules  of  some  mineral,  such  as  agate,  chal- 
cedony, calcareous  spar,  or  zeolite,  are  scattered  through  a  base  of 
wacke,  basalt,  greenstone,  or  other  kind  of  trap.  It  derives  its  name 
from  the  Greek  word  amygdala,  an  almond.  The  origin  of  this  struc- 
ture cannot  be  doubted,  for  we  may  trace  the  process  of  its  forma- 
tion in  modern  lavas.  Small  pores  or  cells  are  caused  by  bubbles  of 
steam  and  gas  confined  in  the  melted  matter.  After  or  during  con- 
solidation, these  empty  spaces  are  gradually  filled  up  by  matter  sepa- 
rating from  the  mass,  or  infiltered  by  water  permeating  the  rock.  As 
these  bubbles  have  been  sometimes  lengthened  by  the  flow  of  the 
lava  before  it  finally  cooled,  the  contents  of  such  cavities  have  the 
form  of  almonds.  In  some  of  the  amygdaloidal  traps  of  Scotland, 
where  the  nodules  have  decomposed,  the  empty  cells  are  seen  to  have 
a  glazed  or  vitreous  coating,  and  in  this  respect  exactly  resemble  sco- 
riaceous  lavas,  or  the  slags  of  furnaces. 

The  foregoing  figure  (676)  represents  a  fragment  of  stone  taken 
from  the  upper  part  of  a  sheet  of  basaltic  lava  in  Auvergne.  One- 
half  is  scoriaceous,  the  pores  being  perfectly  empty ;  the  other  part 
is  amygdaloidal,  the  pores  or  cells  being  mostly  filled  up  with  carbon- 
ate of  lime,  forming  white  kernels. 

Lava. — This  term  has  a  somewhat  vague  signification,  having  been 
applied  to  all  melted  matter  observed  to  flow  in  streams  from  volcanic 
vents.  When  this  matter  consolidates  in  the  open  air,  the  upper  part 
is  usually  scoriaceous,  and  the  mass  becomes  more  and  more  stony  as 
we  descend,  or  in  proportion  as  it  has  consolidated  more  slowly  and 
under  greater  pressure.  At  the  bottom,  however,  of  a  stream  of  lava, 
a  small  portion  of  seoriaceous  rock  very  frequently  occurs,  formed  by 
the  first  thin  sheet  of  liquid  matter,  which  often  precedes  the  main 
current,  or  in  consequence  of  the  contact  with  water  in  or  upon  the 
damp  soil. 

The  more  compact  lavas  are  often  porphyritic,  but  even  the  scoria- 
ceous part  sometimes  contains  imperfect  crystals,  which  have  been 
derived  from  some  older  rocks,  in  which  the  crystals  preexisted,  but 
were  not  melted,  as  being  more  infusible  in  their  nature. 

Although  melted  matter  rising  in  a  crater,  and  even  that  which 
enters  a  rent  on  the  side  of  a  crater,  is  called  lava,  yet  this  term  be- 


602  SCORLE— PUMICE— VOLCANIC  TUFF.          [Cu.  XXVIIL 

longs  more  properly  to  that  which  has  flowed  either  in  the  open  air 
or  on  the  bed  of  a  lake  or  sea.  If  the  same  fluid  has  not  reached 
the  surface,  but  has  been  merely  injected  into  fissures  below  ground, 
it  is  called  trap. 

There  is  every  variety  of  composition  in  lavas  ;  some  are  trachytic, 
as  in  the  Peak  of  Teneriffe  ;  a  great  number  are  basaltic,  as  in  Vesu- 
vius and  Auvergne  ;  others  are  Andesitic,  as  those  of  Chili ;  some  of 
the  most  modern  in  Vesuvius  consist  of  green  augite,  and  many  of 
those  of  Etna  of  augite  and  Labrador-felspar.* 

Scorice  and  Pumice  may  next  be  mentioned  as  porous  rocks,  pro- 
duced by  the  action  of  gases  on  materials  melted  by  volcanic  heat. 
Scorice  are  usually  of  a  reddish-brown  and  black  color,  and  are  the 
cinders  and  slags  of  basaltic  or  augitic  lavas.  Pumice  is  a  light, 
spongy,  fibrous  substance,  produced  by  the  action  of  gases  on  trachy- 
tic and  other  lavas  ;  the  relation,  however,  of  its  origin  to  the  compo- 
sition of  lava  is  not  yet  well  understood.  Von  Buch  says  that  it 
never  occurs  where  only  Labrador-felspar  is  present. 

Volcanic  Tuff,  Trap  Tuff. — Small  angular  fragments  of  the  scoriae 
and  pumice,  above  mentioned,  and  the  dust  of  the  same,  produced  by 
volcanic  explosions,  form  the  tuffs  which  abound  in  all  regions  of 
active  volcanoes,  where  showers  of  these  materials,  together  with 
small  pieces  of  other  rocks  ejected  from  the  crater,  fall  down  upon 
the  land  or  into  the  sea.  Here  they  often  become  mingled  with 
shells,  and  are  stratified.  Such  tuffs  are  sometimes  bound  together 
by  a  calcareous  cement,  and  form  a  stone  susceptible  of  a  beautiful 
polish.  But  even  when  little  or  no  lime  is  present,  there  is  a  great 
tendency  in  the  materials  of  ordinary  tuffs  to  cohere  together.  Be- 
sides the  peculiarity  of  their  composition,  some  tuffs,  or  volcanic  grits, 
as  they  have  been  termed,  differ  from  ordinary  sandstones  by  the 
angularity  of  their  grains,  and  they  often  pass  into  volcanic  breccias. 

According  to  Mr.  Scrope,  the  Italian  geologists  confine  the  term  tuff, 
or  tufa,  to  felspathose  mixtures,  and  those  composed  principally  of 
pumice,  using  the  term  peperino  for  the  basaltic  tuffs.f  The  peperinos 
thus  distinguished  are  usually  brown,  and  the  tuffs  gray  or  white. 

We  meet  occasionally  with  extremely  compact  beds  of  volcanic 
materials,  interstratified  with  fossiliferous  rocks.  These  may  some- 
times be  tuffs,  although  their  density  or  compactness  is  such  as  to 
cause  them  to  resemble  many  of  those  kinds  of  trap  which  are  found 
in  ordinary  dikes.  The  chocolate-colored  mud,  which  was  poured  for 
weeks  out  of  the  crater  of  Graham's  Island,  in  the  Mediterranean,  in 
1831,  must,  when  unmixed  with  other  materials,  have  constituted  a 
stone  heavier  than  granite.  Each  cubic  inch  of  the  impalpable  pow- 
der which  has  fallen  for  days  through  the  atmosphere,  during  some 
modern  eruptions,  has  been  found  to  weigh,  without  being  com- 

*  G.  Rose,  Ann.  des  Mines,  torn.  viii.  p.  32. 
f  Geol.  Trans.,  Second  Series,  vol.  ii.  p.  211. 


CH.  XXVm.]     PALAGONITE  TUFF— AGGLOMERATE— LATERITE.          603 

pressed,  as  much  as  ordinary  trap  rocks,  and  to  be  often  identical 
with  these  in  mineral  composition. 

Palagonite  Tuff. — The  nature  of  volcanic  tuffs  must  vary  according 
to  the  mineral  composition  of  the  ashes  and  cinders  thrown  out  of  each, 
vent,  or  from  the  same  vent,  at  different  times.  In  descriptions  of 
Iceland,  we  read  of  Palagonite  tuffs  as  very  common.  The  name  Pa- 
lagoiiite  was  first  given  by  Prof.  Bunsen  to  a  mineral  occurring  in  the 
volcanic  formations  of  Palagonia,  in  Sicily.  It  is  rather  a  mineral 
substance  than  a  mineral,  as  it  is  always  amorphous,  and  has  never 
been  found  crystallized.  Its  composition  is  variable,  but  it  may  be  de- 
fined as  a  hydrosilicate  of  alumina,  containing  oxide  of  iron,  lime, 
magnesia,  and  some  alkali.  It  is  of  a  brown  or  blackish-brown  color, 
and  its  specific  density,  2*43.  It  enters  largely  into  the  composition 
of  volcanic  tuffs  and  breccias,  and  is  considered  by  Bunsen  as  an 
altered  rock,  resulting  from  the  action  of  steam  on  volcanic  tuff's. 

Agglomerate. — In  the  neighborhood  of  volcanic  vents,  we  frequently 
observe  accumulations  of  angular  fragments  of  rock,  formed  during 
eruptions  by  the  explosive  action  of  steam,  which  shatters  the  subja- 
cent stony  formations,  and  hurls  them  up  into  the  air.  They  then  fall 
in  showers  around  the  cone  or  crater,  or  may  be  spread  for  some  dis- 
tance over  the  surrounding  country.  The  fragments  consist  usually  of 
different  varieties  of  scoriaceous  and  compact  lavas ;  but  other  kinds 
of  rock,  such  as  granite  or  even  fossiliferous  limestones,  may  be  inter- 
mixed; in  short,  any  substance  through  which  the  expansive  gases 
have  forced  their  way.  The  dispersion  of  such  materials  may  be 
aided  by  the  wind,  as  it  varies  in  direction  or  intensity,  and  by  the 
slope  of  the  cone  down  which  they  roll,  or  by  floods  of  rain,  which 
often  accompany  eruptions.  But  if  the  power  of  running  water,  or 
of  the  waves  and  currents  of  the  sea,  be  sufficient  to  carry  the  frag- 
ments to  a  distance,  it  can  scarcely  fail  (unless  where  ice  intervenes) 
to  wear  off  their  angles,  and  the  formation  then  becomes  a  conglom- 
erate. If  occasionally  globular  pieces  of  scoriae  abound  in  an  agglom- 
erate, they  do  not  owe  their  round  form  to  attrition. 

The  size  of  the  angular  stones  in  some  agglomerates  is  enormous ; 
for  they  may  be  two  or  three  yards  in  diameter.  The  mass  is  often 
50  or  100  feet  thick,  without  showing  any  marks  of  stratification. 
The  term  volcanic  breccia  may  be  restricted  to  those  tuffs  which  are 
made  up  of  small  angular  pieces  of  rock. 

The  slaggy  crust  of  a  stream  of  lava  will  often,  while  yet  in  mo- 
tion, split  up  into  angular  pieces,  some  of  which,  after  the  current  has 
ceased  to  flow,  may  be  seen  to  stick  up  five  or  six  feet  above  the  gen- 
eral surface.  Such  broken-up  crusts  resemble  closely  in  structure  the 
agglomerate  above  described,  although  the  composition  of  the  mate- 
rials will  usually  be  more  homogeneous. 

Laterite  is  a  red  or  brick-like  rock  composed  of  silicate  of  alumina 
and  oxide  of  iron.  The  red  layers,  called  "  ochre  beds,"  dividing  the 
lavas  of  the  Giant's  Causeway,  are  laterites.  These  were  found  by 


604  MINERAL  COMPOSITION  [Cn.  XXVIII. 

Delesse  to  be  trap  impregnated  with  the  red  oxide  of  iron,  and  in 
part  reduced  to  kaolin.  When  still  more  decomposed  they  were 
found  to  be  clay  colored  by  red  ochre.  As  two  of  the  lavas  of  the 
» Giant's  Causeway  are  parted  by  a  bed  of  lignite,  it  is  riot  improbable 
that  the  layers  of  laterite  seen  in  the  Antrim  cliffs  resulted  from 
atmospheric  decomposition.  In  Madeira  and  the  Canary  Islands 
streams  of  lava  of  subaerial  origin  are  often  divided  by  red  bands  of 
laterite,  probably  ancient  soils  formed  by  the  decomposition  of  the 
surfaces  of  lava-currents,  many  of  these  soils  having  been  colored  red 
in  the  atmosphere  by  oxide  of  iron,  others  burnt  into  a  red  brick  by 
the  overflowing  of  heated  lavas.  These  red  bands  are  sometimes 
prismatic,  the  small  prisms  being  at  right  angles  to  the  sheets  of  lava. 
Red  clay  or  red  marl,  formed  as  above  stated  by  the  disintegration  of 
lava,  scoria?,  or  tuff,  has  often  accumulated  to  a  great  thickness  in  the 
valleys  of  Madeira,  being  washed  into  them  by  alluvial  action ;  and 
some  of  the  thick  beds  of  laterite  in  India  may  have  had  a  similar 
origin.  In  India,  however,  especially  in  the  Deccan,  the  term  "  later- 
ite "  seems  to  have  been  used  too  vaguely. 

It  would  be  tedious  to  enumerate  all  the  varieties  of  trap  and  lava 
which  have  been  regarded  by  different  observers  as  sufficiently  abun- 
dant to  deserve  distinct  names,  especially  as  each  investigator  is  too 
apt  to  exaggerate  the  importance  of  local  varieties  which  happen  to 
prevail  in  districts  best  known  to  him.  It  will  be  useful,  however,  to 
subjoin  here,  in  the  form  of  a  glossary,  an  alphabetical  list  of  the 
names  and  synonyms  most  commonly  in  use,  with  brief  explanations, 
to  which  I  have  added  a  table  of  the  analysis  of  the  simple  minerals 
most  abundant  in  the  volcanic  and  hypogene  rocks. 


Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of 
the  more  abundant  Volcanic  Rocks. 

AGGLOMERATE.  A  coarse  breccia,  composed  of  fragments  of  rock,  cast  out  of  vol- 
canic vents,  for  the  most  part  angular  and  without  any  admixture  of  water- 
worn  stones.  "  Volcanic  conglomerates "  may  be  applied  to  mixtures  in 
which  water-worn  stones  occur. 

APHANITE.     See  Corceon. 

AMPHIBOLITE,  or  HORNBLENDIC  KOCK,  which  see. 

AMYGDALOID.     A  particular  form  of  volcanic  rock  ;  see  p.  601. 

AUGITE  ROCK.  A  rock  of  the  basaltic  family,  composed  of  felspar  and  augite.  See 
p.  598.- 

AUGITIC-PORPHYRY.  Crystals  of  Labrador-felspar  and  of  augite,  in  a  green  or  dark 
gray  base.  (Rose,  Ann.  des  Mines,  torn.  8,  p.  22,  1835.) 

BASALT.     An  intimate  mixture  of  felspar  and  augite  with  magnetic  iron,  olivine,  &e. 

See  p.  598. 
BASANITE.     Name  given  by  Alex.  Brongniart  to  a  rock,  having  a  base  of  basalt, 

with  more  or  less  distinct  crystals  of  augite  disseminated  through  it. 

CLAYSTONE  and  CLAYSTONE-POEPHYRY.     An  earthy  and  compact  stone,  usually  of  a 


CE.  XXVHL]  OF  VOLCANIC  ROCKS.  (JQ5 

purplish  color,  like  an  indurated  clay ;  passes  into  hornstone ;  generally  con- 
tains scattered  crystals  of  felspar  and  sometimes  of  quartz. 

CLINKSTONE.  Syn.  Phonolite,  fissile  Petrosilex,  see  p.  699;  a  grayish-blue  rock, 
having  a  tendency  to  divide  into  slabs ;  hard,  with  clean  fracture,  ringing 
under  the  hammer;  principally  composed  of  felspar,  and,  according  to 
Gmelin,  of  felspar  and  mesotype.  (Leonhard,  Mineralreich,  p.  102.) 

COMPACT  FELSPAR,  which  has  also  been  called  Petrosilex ;  the  rock  so  called  in- 
cludes the  hornstone  of  some  mineralogists,  is  allied  to  clinkstone,  but  is 
harder,  more  compact,  and  translucent.  It  is  a  varying  rock,  of  which  the 
chemical  composition  is  not  well  denned.  (MacQullocKs  Classification  of 
Rocks,  p.  481.) 

CORNEAN  or  APHANITE.  A  compact  homogeneous  rock  without  a  trace  of  crystalli- 
zation, breaking  with  a  smooth  surface  like  some  compact  basalts  ;  consists 
of  hornblende,  quartz,  and  felspar  in  intimate  combination.  It  derives  its 
name  from  the  Lathi  word  cornu,  horn,  hi  allusion  to  its  toughness  and  com- 
pact texture. 

DIALLAGE  ROCK.  Syn.  Euphotide,  Gabbro,  and  some  Ophiolites.  Compounded  of 
felspar  and  diallage. 

DIORITE.  A  kind  of  Greenstone,  which  see.  Components,  felspar  and  hornblende 
in  grains.  According  to  Rose,  Ann.  des  Mines,  torn.  8,  p.  4,  diorite  consists 
of  albite  and  hornblende,  but  Delesse  has  shown  that  the  felspar  may 
be  Oligoclase  or  Labradorite.  (Ann.  des  Mines,  1849,  torn.  16,  p.  323.) 
Its  dark  color  is  due  to  disseminated  platefll^rfBiornblende.  See-  above, 
p.  599. 

DOLERITE.  According  to  Rose  (ibid.  p.  32),  its  composition  is  black  augite  and 
Labrador-felspar ;  according  to  Leonhard  (Mineralreich,  &c.,  p.  77),  augite, 
Labrador-felspar,  and  magnetic  iron.  See  above,  p.  598. 

DOMITE.    An  early  trachyte,  found  in  the  Puy  de  Dome,  in  Auvergne. 

EUPHOTIDE.  A  mixture  of  grains  of  Labrador-felspar  and  diallage.  (Rose,  ibid. 
p.  19.)  According  to  some,  this  rock  is  defined  to  be  a  mixture  of  augite 
or  hornblende  and  Saussurite,  a  mineral  allied  to  jade.  (Allan's  Alineral- 
°Vyi  P'  158.)  Haidinger  first  observed  that  in  this  rock  hornblende  sur- 
rounds the  crystals  of  diallage. 

FELSTONE.  Same  as  compact  felspar  (which  see).  When  crystals  of  felspar  occur 
in  it,  it  becomes  felstone  or  felspar-porphyry.  See  also  Hornstone. 

GABBRO,  see  Diallage  rock. 

GREENSTONE.     Syn.  A  mixture  of  felspar  and  hornblende.     See  above,  p.  599. 

GRAYSTONE.  (Graustein  of  Werner.)  Lead-gray  and  greenish  rock  composed  of 
felspar  and  augite,  the  felspar  being  more  than  seventy-five  per  cent.  (Scrope, 
Journ.  of  Sci.  No.  42,  p.  221.)  Graystone  lavas  are  intermediate  in  compo- 
sition between  basaltic  and  trachytic  lavas. 

HORNBLENDE  ROCK,  or  AMPHIBOLITE.  This  rock,  as  defined  by  Leonhard,  is  com- 
posed entirely  of  hornblende ;  but  such  a  rock  appears  to  be  exceptional, 
and  confined  to  mineral  veins.  Any  rocks  in  which  hornblende  plays  a  con- 
spicuous part,  constituting  the  "  roches  ampbiboliques  "  of  French  writers, 
may  be  called  hornblende  rock.  They  always  contain  more  or  less  felspar  in 
their  composition,  and  pass  into  basalt  or  greenstone,  or  aphanite.  See 
p.  597. 

HORNSTONE-PORPHYRY.  A  kind  of  felspar  porphyry  (Leonhard,  loc.  tit.),  with  a  base 
of  hornstone,  a  mineral  approaching  near  to  flint,  which  differs  from  com- 
pact felspar  in  being  infusible. 


606  MINERAL  COMPOSITION  [Oft.  XXVIII. 

HYPERSTHENE  ROCK,  a  mixture  of  grains  of  Labrador-felspar  and  hypersthene  (Rose, 
Ann.  des  Mines,  torn.  8,  p.  13),  having  the  structure  of  syenite  or  granite ; 
abundant  among  the  traps  of  Skye.  It  is  extremely  tough,  grayish,  and 
greenish  black.  Some  geologists  consider  it  a  greenstone,  in  which  hyper- 
sthene replaces  hornblende ;  and  this  opinion,  says  Delesse,  is  borne  out  by 
the  fact  that  hornblende  usually  occurs  in  hypersthene  rock,  often  envelop- 
ing the  crystals  of  hypersthene.  The  latter  have  a  pearly  or  metallic-pearly 
lustre. 

LATERITE.  A  red,  jaspery,  brick-like  rock,  composed  of  silicate  of  alumina  and 
oxide  of  iron,  or  sometimes  consisting  of  clay  colored  with  red  ochre.  See 
above,  p.  603. 

MELAPHYRE.  A  variety  of  black  porphyry  composed  of  Labrador-felspar  and  a 
small  quantity  of  augite.  Its  black  color  was  formerly  attributed  to  dissemi- 
nated microscopic  crystals  of  augite,  but  M.  Delesse  has  shown  that  the 
paste  is  discolored  by  hydrochloric  acid,  whereas  this  acid  does  not  attack 
the  crystals  of  augite,  which  are  seen  to  be  isolated,  and  few  in  num- 
ber. (Ann.  des  Mines,  4th.  ser.  torn.  xii.  p.  228.)  From  fj-ekag,  melas, 
black. 

OBSIDIAN.    Vitreous  lava  like  melted  glass,  nearly  allied  to  pitchstone. 
•  OPHIOLITE.    A  name  given  by  Alex.  Brongniart  to  serpentine. 

OPHITE.  A  name  given  by  Palassou  to  certain  trap  rocks  of  the  Pyrenees,  very 
variable  in  composition,  usually  composed  of  Labrador-felspar  and  horn- 
blende, and  sometimes  augite,  occasionally  of  a  green  color,  and  passing 
into  serpentine. 

PALAGONITE  TUFF.  An  altered  volcanic  tuff  containing  the  substance  termed  pala- 
gonite.  See  p.  603. 

PEARLSTONE.  A  volcanic  rock,  having  the  lustre  of  mother  of  pearl ;  usually 
having  a  nodular  structure ;  intimately  related  to  obsidian,  but  less 
glassy. 

PEPERINO.    A  form  of  volcanic  tuff,  composed  of  basaltic  scoriae.     See  p.  602. 

PETROSILEX.     See  Clinkstone  and  Compact  Felspar. 

PHONOLITE.     Syn.  of  Clinkstone,  which  see. 

PITCHSTONE,  or  RETINITE  of  the  French.  Vitreous  lava,  less  glassy  than  obsidian ; 
a  blackish  green  rock  resembling  glass,  having  a  resinous  lustre  and  appear- 
ance of  pitch  ;  composition  usually  of  glassy  felspar  (orthoclase)  with  a  little 
mica,  quartz,  and  hornblende ;  in  Arran  it  forms  a  dike  thirty  feet  wide, 
cutting  through  sandstone. 

PUMICE.    A  light,  spongy,  fibrous  form  of  trachyte.     See  p.  602. 

PYROXENIC-PORPHYRY,  same  as  augitic-porphyry,  pyroxene  being  Hatty's  name  for 
augite. 

SCORLE.  Syn.  volcanic  cinders  ;  reddish  brown  or  black  porous  form  of  lava.  See 
p.  602. 

SERPENTINE.  A  greenish  rock  in  which  there  is  much  magnesia.  Its  composition 
always  approaches  very  near  to  the  mineral  called  "  noble  serpentine  "  (see 
Table  of  Analyses,  p.  608),  which  forms  veins  in  this  rock.  The  minerals 
most  commonly  found  in  Serpentine  are  diallage,  garnet,  chlorite,  oxydulous 
iron,  and  chromate  of  iron.  The  diallage  and  garnet  occurring  in  serpen- 
tine are  richer  in  magnesia  than  when  they  are  crystallized  in  other  rocks. 
(Delesse,  Ann.  des  Mines,  1851,  torn,  xviii.  p.  309.)  Occurs  sometimes, 
I  though  rarely,  in  dikes,  altering  the  contiguous  strata ;  is  indifferently  a 

member  of  the  trappean  or  hypogene  series.  Its  absence  from  recent  vol- 


CH.  XXVIIL]  OF  VOLCANIC   ROCKS.  007 

canic  products  seems  to  imply  that  it  belongs  properly  to  the  metamorphic 
class ;  and,  even  when  it  is  found  in  dikes  cutting  through  aqueous  forma- 
tions, it  may  be  an  altered  basalt,  which  abounded  greatly  hi  olivine. 

TEPHRINE,  synonymous  with  lava.     Name  proposed  by  Alex.  Brongniart. 

TOADSTONE.     A  local  name  in  Derbyshire  for  a  kind  of  wacke,  which  see. 

TRACHYTE.  Chiefly  composed  of  glassy  felspar,  with  crystals  of  glassy  felspar. 
See  p.  699. 

TRAP  TUFF.    See  p.  602. 

TRASS.  A  kind  of  tuff  or  mud  poured  out  by  lake-craters  during  eruptions ;  com- 
mon hi  the  Eifel,  in  Germany. 

TUFF.     8yn.  Trap  tuff,  volcanic  tuff.     See  p.  602. 

VITREOUS  LAVA.     See  Pitchstone  and  Obsidian. 
VOLCANIC  TUFF.    See  p.  602. 

WACKE.    A  soft  and  earthy  variety  of  trap,  having  an  argillaceous  aspect.    It  re- 
sembles indurated  clay,  and  when  scratched,  exhibits  a  shining  streak. 
WHINSIONE.    A  Scotch  provincial  term  for  greenstone  and  other  hard  trap  rocks. 


608 


ANALYSIS  OF  MINERALS. 


[Cn.  XXVIII. 


ANALYSIS    OF   MINERALS   MOST    ABUNDANT   IN   THE    VOLCANIC    AND 
HYPO  GENE    ROCKS. 


Silica 

Alu- 

miua 

JSS" 

Lime. 

Potash. 

Soda. 

Iron 

Oiuie. 

Man- 
ganese. 

Remainder. 

Actinolite  (Bergman) 
Augite,  black,    of  volcanic  rocks 
(Klaproth). 

64- 

48-00 

5-00 

22- 

8-75 

24-00 
56-33 

:    _- 

:    - 

3- 
10-80 

i-oo 

43-05  C. 
0-27  W. 
12-20  W. 
11-55  W. 
8-96  W. 

0-85  W. 
0-30  Ch. 
0-22  W. 

0-5  W. 

1-5  F. 

1-50  loss. 

1-     W. 

9-83  W. 
12-30  W. 

1-63  T. 
2-00  F. 
1-58  F. 
0-90  loss. 
0-22  F. 
1-51  loss. 
3.59  L. 
3-28  F. 

o-ii  P. 

4-18  loss. 
4-12 

12-45  W. 
13'70  W. 
1070  W. 
5-22  W. 
5'     W. 
3-83  W. 

0-12  P. 
7-66  B. 
2  '09  loss. 
1-49  F. 
0-22  Ph. 
3-56  B. 
0-41  L. 
2-70  F. 
I  3-77  loss. 
4-02  B. 

Chiastolite  (Landgrabe)    - 
Chlorite  (Kobell)       -        -        -       - 

68-50 
31-14 
31-07 
26-37 

49-30 
56'81 

37- 
66-75 
6491 
68-84 
71-50 

58-91 

55-75 
53-20 

63-25 

62-87 
TV75 

30-11 
17-14 
15-47 

28'79 

5-50 
2'07 

2f- 

17-5 
19-16 
20-63 
15-50 

24-59 

265 
27  '31 

23-92 
22^91 

1-13 
34-40 
19'14 
17-09 

17-61 
29-68 

0-65 
0-50 
0*40 

1-01 
0-32 
traces 

0-46 

-    - 

.    . 

3-85 
19-99 
28-79 

9-43 
8-46 

24- 
0-75 
traces 

traces 
0-99 

1-25 
1-03 

traces 
1-89 

36" 
16' 
30- 
7-32 
16-15 

24-5 
8-53 

22- 
7' 
19-03  S. 
21-31  S. 
5-03  P. 
1-61 

3-48  S. 
11-72 
12- 
18-5 

1-17 
1-69 
7-39 
1-40 
3- 
1-70 
2.5 

9-33  S. 
6-19  P. 

17-44 

0-53 

traces 

0-51 
0-62 

1'5 

0-25 

0-25 
0-22 
traces 

a  trace 

V 

15-70 
^1-09 

o-io 

1-40 

traces 
0-43 

trac  a 

97'  S. 
1-89 

trapp). 
Diallage  of  euphotide  (Delesse) 

15-43 
2-20 

15- 
1-25 
0-78 
a  trace 
1*73 

4-01 

11- 
8-02 

3-23 
3'61 

12-" 
11-07 

3-16 
2-53 

3-40 
2-31 
1-39 

2-49 
9-12 
6-94 

7-59 

4- 

3-52 

6-88 
8-16 

(Kohler). 
Epidote  (Vauquelin) 
Felspar,  common  (Rose) 

the  Vosges  (Delesse). 

the  Vosges  (Delesse).  ' 
Labradorite  (Klaproth)      - 

(Delesse). 

from  Mont  Blanc  (Delesse). 

(Scheerer). 

(Phillips)        - 
Hornblende  (Klaproth)    - 

43- 
42- 
45-69 

47-88 

54'25 
5375 
53-42 

5  f64 
46-80 
42.5 
50- 

40-00 
41-22 
37-54 

49-06 

46-23 
40-86 
50- 
41-0 

43-07 
41-58 
40-83 
64-85 

16- 
12- 
12-18 
8-23 

2-25 
24-62 
1-38 

19-70 
23*50 
11-5 
35- 

12-67 
13*92 
19-80 

33-61 
33-03 

0-25 
0-42 
0-92 

2-25 
18-79 
18-40 

14- 

14-95 

9-" 

0-63 
4-70 
30-32 

0-41 

2-10 
47-35 
38-5 
38-6 

40-37 
42-61 
37-98 
28-53 

20- 
11- 
13-85 
7-05 

1-5 

21-72 

1-61 
9-87 

1-33 

2-58 
070 

0-25 

0-5 
1-50 

a  trace 
0-14 

21-35 

10-  ~ 

5k61 
6-05 
7-17 

4-19 

8-87 

0-65 

15-09 
5-40 

1-40^ 

i-oo 

1-45 

^    ousuor   ; 

from  Corsica  (Delesse). 
Hypersthene  (Klaproth) 
Leucite  (Klaproth)    .... 
Malacolite  or  Sahlite,  green  (De- 
lesse). 
Mesotype  (Gehlen)    .... 
•-  (Bcrzclius)    .... 

Mica  (Klaproth)  ""'   .... 
(Vauquelin)        - 

black  (H.  Rose) 
green,  of  protogine  (Delesse)   - 

reddish,    of  crystalline   lime- 
stone (Delesse). 

rose-colored,    of  granite    (C. 
Gmelin). 

white,  of  pegmatite  (Delesse)  - 
Olivine  (Berzelius)    .... 
(Klaproth)       .... 

roth). 
Serpentine  (Hisinger) 

common  (Delesse) 
Steatite  (Delesse)      .... 

Talc,  pure  (Delesse)         ... 
(Klaproth)         .... 

Tourmaline    or   Schorl,    black,   of 
granite   from  Devon  (Rammels- 
berg). 

61-75 
6175 

37-00 

41*16 
35-48 

33-09 

41-83 
34-75 

31-68 
30-5 

2-58 

0-61 
4'68 

0'50 

2'75 
0-65 

2'17 
0-48 

1-39^ 

1-37 
1-75 

ravia  (Rammelsberg). 
Tourmaline  (Gmelin)        ... 

In  the  last  column  of  the  above  Table,  the  following  signs  are  used  :  B  Boraclc  acid,  C.  Carbonic  acid 
Ch.  Oxide  of  Chrome,  F.  Fluoric  acid,  L.  Lithine,  P.  Phosphoric  acid,  T.  Oxide  of  Titanium,  W.  Water 
In  the  7th  column  of  numbers,  P.  means  Protoxide,  and  S.  Sesquioxide. 


CH.  XXIX.]  TRAP  DIKES.  609 


CHAPTER  XXIX. 
VOLCANIC  ROCKS,  continued. 

Trap  dikes— sometimes  project — sometimes  leave  fissures  vacant  by  decomposi- 
tion— Branches  and  veins  of  trap — Dikes  more  crystalline  in  the  centre — 
Strata  altered  at  or  near  the  contact — Obliteration  of  organic  remains — Con- 
version of  chalk  into  marble — Trap  interpoted  between  strata — Columnar  and 
globular  structure — Relation  of  trappean  rocks  to  the  products  of  active  vol- 
canoes— Form,  external  structure,  and  origin  of  volcanic  mountains — Craters 
and  Calderas — Sandwich  Islands — Lava  flowing  underground — Truncation  of 
cones — Javanese  calderas — Canary  Islands — Structure  and  origin  of  the  Cal- 
dera  of  Palma — Older  and  newer  volcanic  rocks  in,  unconformable — Aqueous 
conglomerate  in  Palma — Hypothesis  of  upheaval  considered — Slope  on  which 
stony  lavas  may  form — Extent  and  nature  of  aqueous  erosion  in  Palma — Island 
of  St.  Paul  in  the  Indian  Ocean — Peak  of  Tenerifle,  and  ruins  of  older  cone — 
Madeira — Its  volcanic  rocks,  partly  of  marine,  and  partly  of  subaerial  origin — 
Central  axis  of  eruptions — Varying  dip  of  solid  lavas  near  the  axis,  and  further 
from  it — Leaf-bed,  and  fossil  land-plants — Central  valleys  of  Madeira  not  craters, 
or  calderas. 

HAVING  in  the  last  chapter  spoken  of  the  composition  and  mineral 
characters  of  volcanic  rocks,  I  shall  next  describe  the  manner  and 
position  in  which  they  occur  in  the  earth's  crust,  and  their  external 
forms.  The  leading  varieties  both  of  the  basaltic  and  trachytic 
rocks,  as  well  as  of  greenstone  and  the  rest,  are  found  sometimes  in 
dikes  penetrating  stratified  and  unstratified  formations,  sometimes  in 
shapeless  masses  protruding  through  or  overlying  them,  or  in  hori- 
zontal sheets  intercalated  between  strata. 

Volcanic  or  Trap  Dikes. — Fissures  have  already  been  spoken  of  as 
occurring  in  all  kinds  of  rocks,  some  a  few  feet,  others  many  yards  in 
width,  and  often  filled  up  with  earth  or  angular  pieces  of  stone,  or 
with  sand  and  pebbles.  Instead  of  such  materials,  suppose  a  quan- 
tity of  melted  stone  to  be  driven  or  injected  into  an  open  rent,  and 
there  consolidated,  we  have  then  a  tabular  mass  resembling  a  wall, 
and  called  a  trap  dike.  It  is  not  uncommon  to  find  such  dikes  pass- 
ing through  strata  of  soft  materials,  such  as  tuff,  scoriae,  or  shale, 
which,  being  more  perishable  than  the  trap,  are  often  washed  away 
by  the  sea,  rivers,  or  rain,  in  which  case  the  dike  stands  prominently 
out  in  the  face  of  precipices,  or  on  the  level  surface  of  a  country  (see 
fig.  677). 

In  the  islands  of  Arran  and  Skye,  and  in  other  parts  of  Scotland, 
where  sandstone,  conglomerate,  and  other  hard  rocks  are  traversed  by 


610 


VARIOUS  FORMS  OF 


[Cn.  XXIX. 


dikes  of  trap,  the  converse  of  the  above  phenomenon  is  seen.  The 
dike,  having  decomposed  more  rapidly  than  the  containing  rock,  has 
once  more  left  open  the  original  fissure,  often  for  a  distance  of  many 
yards  inland  from  the  seacoast,  as  represented  in  the  annexed  view 
(fig.  678).  In  these  instances,  the  greenstone  of  the  dike  is  usually 


Fig.  677. 


Fig.  678. 


Dike  in  a  valley  near  Brazen  Head,  Madeira. 
(From  a  drawing  of  Capt  Basil  Hall,  E.  N.) 


Fissures  left  vacant  by  decomposed  trap. 
Strathaird,  Skye.    (MacCulloch.) 


Fig.  679. 


more  tough  and  hard  than  the  sandstone ;  but  chemical  action,  and 
chiefly  the  oxidation  of  the  iron,  has  given  rise  to  the  more  rapid 
decay. 

There  is  yet  another  case,  by  no  means  uncommon  in  Arran  and 
other  parts  of  Scotland,  where  the  strata  in  contact  with  the  dike, 
and  for  a  certain  distance  from  it,  have  been  hardened,  so  as  to  resist 
the  action  of  the  weather  more  than  the  dike  itself,  or  the  surround- 
ing rocks.  When  this  happens,  two  parallel  walls  of  indurated  strata 
are  seen  protruding  above  the  general  level  of  the  country  and  fol- 
lowing the  course  of  the  dike. 

As  fissures  sometimes  send  off  branches,  or  divide  into  two  or 
more  fissures  of  equal  size,  so  also  we  find 
trap  dikes  bifurcating  and  ramifying,  and 
sometimes  they  are  so  tortuous  as  to  be 
called  veins,  though  this  is  more  common 
in  granite  than  in  trap.  The  accompany- 
ing sketch  (fig.  679)  by  Dr.  MacCulloch 
represents  part  of  a  sea-cliff  in  Argyle- 
shire,  where  an  overlying  mass  of  trap,  b, 
sends  out  some  veins  which  terminate 
downwards.  Another  trap  vein,  a  a,  cuts 
through  both  the  limestone,  c,  and  the  trap,  b. 

In  fig.  680,  a  ground  plan  is  given  of  a  ramifying  dike  of 
greenstone,  which  I  observed  cutting  through  sandstone  on  the  beach 
near  Kildonan  Castle,  in  Arran.  The  larger  branch  varies  from  5 


Trap  veins  in  Airdnamurchan. 


CH.  XXIX.] 


TRAP  DIKES  AND  VEINS. 


611 


to  7  feet  in  width,  which  will  afford  a  scale  of  measurement  for  the 
whole. 

Fig.  680. 


Ground  plan  of  greenstone  dike  traversing  sandstone.    Arran. 

In  the  Hebrides  and  other  countries,  the  same  masses  of  trap 
which  occupy  the  surface  of  the  country  far  and  wide,  concealing 
the  subjacent  stratified  rocks,  are  seen  also  in  the  sea  cliffs,  pro- 
longed downwards  in  veins  or  dikes,  which  probably  unite  with 
other  masses  of  igneous  rock  at  a  greater  depth.  The  largest  of  the 
dikes  represented  in  the  annexed  diagram,  and  which  are  seen  in 
part  of  the  coast  of  Skye,  is  no  less  than  100  feet  in  width. 

Fig.  681. 


Trap  dividing  and  covering  sandstone  near  Suishnish  in  Skye.    (MacCulloch.) 

Every  variety  of  trap-rock  is  sometimes  found  in  dikes,  as  basalt, 
greenstone,  felspar-porphyry,  and  trachyte.  The  amygdaloidal  traps 
also  occur,  though  more  rarely,  and  even  tuff  and  breccia,  for  the 
materials  of  these  last  may  be  washed  down  into  open  fissures  at  the 
bottom  of  the  sea,  or  during  eruptions  on  the  land  may  be  showered 
into  them  from  the  air. 

Some  dikes  of  trap  may  be  followed  for  leagues  uninterruptedly 
in  nearly  a  straight  direction,  as  in  the  north  of  England,  showing 
that  the  fissures  which  they  fill  must  have  been  of  extraordinary 
length. 

In  many  cases  trap  at  the  edges  or  sides  of  a  dike  is  less  crystal- 
line or  more  earthy  than  in  the  centre,  in  consequence  of  the  melted 
matter  having  cooled  more  rapidly  by  coming  in  contact  with  the 
cold  sides  of  the  fissure  ;  whereas,  in  the  centre,  where  the  matter  of 
the  dike  is  kept  longer  in  a  fluid  or  soft  state,  crystals  are  slowly 
formed.  But  I  observed  the  converse  of  the  above  phenomena  in 
Teneriffe,  in  the  neighborhood  of  Santa  Cruz,  where  a  dike  is  seen 
cutting  through  horizontal  beds  of  scoriae  in  the  sea-cliff  near  the 
Barranco  de  Bufadero.  It  is  vertical  in  its  main  direction,  slightly 
flexuous,  and  about  one  foot  thick.  On  each  side  are  walls  of  com- 
pact basalt,  but  in  the  centre  the  rock  is  highly  vesicular  for  a  width 
of  about  4  inches.  In  this  instance,  the  fissure  may  have  become 


612 


TRAP  DIKES  AND  VEINS. 


[On.  XXIX. 


wider  after  the  lava  on  each  side  had  consolidated,  and  the  additional 
melted  matter  poured  into  the  middle  space  may  have  cooled  more 
rapidly  than  that  at  the  sides. 

In  the  ancient  part  of  Vesuvius,  called  Somma,  a  thin  band  of 
half-vitreous  lava  is  found  at  the  edge  of  some  dikes.  At  the  junc- 
tion of  greenstone  dikes  with  limestone,  a  sahlband,  or  selvage,  of 
serpentine  is  occasionally  observed.  On  the  left  shore  of  the  fiord  of 
Christiania,  in  Norway,  I  examined,  in  company  with  Professor  Keil- 
hau,  a  remarkable  dike  of  syenitic  greenstone,  which  is  traced  through 
Silurian  strata,  until  at  length,  in  the  promontory  of  Nsesodden,  it 
enters  mica-schist.  Fig.  682  represents  a  ground  plan,  where  the 
dike  appears  8  paces  in  width.  In  the  middle  it  is  highly  crystalline 
and  granitiform,-  of  a  purplish  color,  and  containing  a  few  crystals  of 
mica,  and  strongly  contrasted  with  the  whitish  mica-schist,  between 
which  and  the  syenitic  rock  there  is  usually  on  each  side  a  distinct 
black  band,  18  inches  wide,  of  dark  greenstone.  When  first  seen, 
these  bands  have  the  appearance  of  two  accompanying  dikes;  yet 
they  are,  in  fact,  only  the  different  form  which  the  syenitic  materials 
have  assumed  where  near  to  or  in  contact  with  the  mica-schist. 
At  one  point,  a,  one  of  the  sahlbands  terminates  for  a  space ;  but 
near  this  there  is  a  large  detached  block,  6,  having  a  gneiss-like  struc- 
ture, consisting  of  hornblende  and  felspar,  which  is  included  in  the 
midst  of  the  dike.  Round  this  a  smaller  encircling  zone  is  seen,  of 
dark  basalt,  or  fine-grained  greenstone,  nearly  corresponding  to  the 
larger  ones  which  border  the  dike,  but  only  1  inch  wide. 

It  seems,  therefore,  evident  that  the  fragment,  6,  has  acted  on  the 
matter  of  the  dike,  probably  by  causing  it  to  cool  more  rapidly,  in 
the  same  manner  as  the  walls  of  the  fissure  have  acted  on  a  larger 
scale.  The  facts,  also,  illustrate  the  facility  with  which  a  granitiform 
syenite  may  pass  into  ordinary  rocks  of  the  volcanic  family. 


Fig.  682. 
Syenitic  greenstone  dike  of  Nsesodden, 


Christiania. 


Fig.  683. 


Green-          Syenitic  Green- 

stone, rock.  stone. 

Z>.  Imbedded  fragment  of  crystalline  schist 
surrounded  by  a  band  of  greenstone. 


Greenstone  dike,  with  fragments  of  gneiss. 
*  Sorgenfri,  Christiania. 


The  fact  above  alluded  to,  of  a  foreign  fragment,  such  as  6,  fig. 
682,  included  in  the  midst  of  the  trap,  as  if  torn  off  from  some  sub- 


CH.  XXIX.]      ROCKS  ALTERED  BY  TRAP  DIKES.          613 

jacent  rock  or  the  walls  of  a  fissure,  is  by  no  means  uncommon.  A 
fine  example  is  seen  in  another  dike  of  greenstone,  10  feet  wide,  in 
the  northern  suburbs  of  Christiania,  in  Norway,  of  which  the  forego- 
ing figure  (683)  is  a  ground  plan.  The  dike  passes  through  shale, 
known  by  its  fossils  to  belong  to  the  Silurian  series.  In  the  black 
base  of  greenstone  are  angular  and  roundish  pieces  of  gneiss,  some 
white,  others  of  a  light  flesh-color ;  some  without  lamination,  like 
granite,  others  with  laminae,  which,  by  their  various  and  often  oppo- 
site directions,  show  that  they  have  been  scattered  at  random  through 
the  matrix.  These  imbedded  pieces  of  gneiss  measure  from  1  to 
about  8  inches  in  diameter. 

Rocks  altered  by  Volcanic  Dikes. — After  these  remarks  on  the  form 
and  composition  of  dikes  themselves,  I  shall  describe  the  alterations 
which  they  sometimes  produce  in  the  rocks  in  contact  with  them. 
The  changes  are  usually  such  as  the  intense  heat  of  melted  matter 
and  the  entangled  gases  might  be  expected  to  cause. 

PlaS'Newydd. — A  striking  example,  near  Plas-Newydd,  in  Angle- 
sea,  has  been  described  by  Professor  Henslow.*  The  dike  is  134 
feet  wide,  and  consists  of  a  rock  which  is  a  compound  of  felspar  and 
augite  (dolerite  of  some  authors).  Strata  of  shale  and  argillaceous 
limestone,  through  which  it  cuts  perpendicularly,  are  altered  to  a  dis- 
tance of  30,  or  even,  in  some  places,  to  35  feet  from  the  edge  of  the 
dike.  The  shale,  as  it  approaches  the  trap,  becomes  gradually  more 
compact,  and  is  most  indurated  where  nearest  the  junction.  Here  it 
loses  part  of  its  schistose  structure,  but  the  separation  into  parallel 
layers  is  still  discernible.  In  several  places  the  shale  is  converted  into 
hard  porcellanous  jasper.  In  the  most  hardened  part  of  the  mass  the 
fossil  shells,  principally  Producti,  are  nearly  obliterated ;  yet  even 
here  their  impressions  may  frequently  be  traced.  The  argillaceous 
limestone  undergoes  analogous  mutations,  losing  its  earthy  texture  as 
it  approaches  the  dike,  and  becoming  granular  and  crystalline.  But 
the  most  extraordinary  phenomenon  is  the  appearance  in  the  shale  of 
numerous  crystals  of  analcime  and  garnet,  which  are  distinctly  con- 
fined to  those  portions  of  the  rock  affected  by  the  dike.f  Some  gar- 
nets contain  as  much  as  20  per  cent,  of  lime,  which  they  may  have 
derived  from  the  decomposition  of  the  fossil  shells  or  Producti.  The 
same  mineral  has  been  observed,  under  very  analogous  circumstances, 
in  High  Teesdale,  by  Professor  Sedgwick,  where  it  also  occurs  in 
shale  and  limestone,  altered  by  basalt. £ 

Antrim. — In  several  parts  of  the  county  of  Antrim,  in  the  north 
of  Ireland,  chalk  with  flints  is  traversed  by  basaltic  dikes.  The  chalk 
is  there  converted  into  granular  marble  near  the  basalt,  the  change 
sometimes  extending  8  or  10  feet  from  the  wall  of  the  dike,  being 
greatest  near  the  point  of  contact,  and  thence  gradually  decreasing 


*  Cambridge  Transactions,  vol.  i.  p.  402. 

f  Ibid.,  vol.  i.  p.  410.  \  Ibid.,  vol.  ii.  p.  175. 


614: 


ROCKS  ALTERED  BY  TRAP  DIKES. 


[On.  XXIX. 


till  it  becomes  evanescent.  "  The  extreme  effect,"  says  Dr.  Berger, 
"  presents  a  dark  brown  crystalline  limestone,  the  crystals  running  in 
flakes  as  large  as  those  of  coarse  primitive  (metamorphic)  limestone ; 
the  next  state  is  saccharine,  then  fine  grained  and  arenaceous ;  a  com- 
pact variety,  having  a  porcellanous  aspect  and  a  bluish-gray  color, 
succeeds  :  this,  towards  the  outer  edge,  becomes  yellowish-white,  and 
insensibly  graduates  into  the  unaltered  chalk.  The  flints  in  the 
altered  chalk  usually  assume  a  gray  yellowish  color."  *  All  traces  of 
organic  remains  are  effaced  in  that  part  of  the  limestone  which  is 
most  crystalline. 

The  annexed  drawing   (fig.   684)  represents  three  basaltic   dikes 

Fig.  684. 


Dike  35  feet.    Dike 
1  foot. 


Dike  20  feet. 


Basaltic  dikes  in  chalk  in  island  of  Bath! in,  Antrim. 
Ground  plan,  as  seen  on  the  beach.    (Conybeare  and  Buckland.t) 

traversing  the  chalk,  all  within  the  distance  of  90  feet.  The  chalk 
contiguous  to  the  two  outer  dikes  is  converted  into  a  finely  granular 
marble,  m  ra,  as  are  the  whole  of  the  masses  between  the  outer  dikes 
and  the  central  one.  The  entire  contrast  in  the  composition  and 
color  of  the  intrusive  and  invaded  rocks,  in  these  cases,  renders  the 
phenomena  peculiarly  clear  and  interesting. 

Another  of  the  dikes  of  the  northeast  of  Ireland  has  converted  a 
mass  of  red  sandstone  into  hornstone.  By  another,  the  shale  of  the 
coal-measures  has  been  indurated,  assuming  the  character  of  flinty 
slate ;  and  in  another  place  the  slate-clay  of  the  Has  has  been 
changed  into  flinty  slate,  which  still  retains  numerous  impressions  of 
ammonites.! 

It  might  have  been  anticipated  that  beds  of  coal  would,  from  their 
combustible  nature,  be  affected  in  an  extraordinary  degree  by  the 
contact  of  melted  rock.  Accordingly,  one  of  the  greenstone  dikes  of 
Antrim,  on  passing  through  a  bed  of  coal,  reduces  it  to  a  cinder  for 
the  space  of  9  feet  on  each  side. 

At  Cockfield  Fell,  in  the  north  of  England,  a  similar  change  is 
observed.  Specimens  taken  at  the  distance  of  about  30  yards  from 
the  trap  are  not  distinguishable  from  ordinary  pit-coal ;  those  nearer 
the  dike  are  like  cinders,  and  have  all  the  character  of  coke ; 


*  Dr.  Berger,  Geol.  Trans.,  First  Series,  vol.  iii.  p.  172. 

f  Geol.  Trans.,  First  Series,  vol.  iii.  p.  210,  and  plate  10. 

\  Ibid.,  p.  213 ;  and  Playfair,  Illust.  of  Hutt.  Theory,  s.  258. 


CH.  XXIX.]  STRUCTURE  OF  VOLCANIC  ROCKS. 

while  those  close  to  it  are  converted  into  a  substance  resembling 
soot.* 

As  examples  might  be  multiplied  without  end,  I  shall  merely  select 
one  or  two  others,  and  then  conclude.  The  rock  of  Stirling  Castle  is 
a  calcareous  sandstone,  fractured  and  forcibly  displaced  by  a  mass  of 
greenstone  which  has  evidently  invaded  the  strata  in  a  melted  state. 
The  sandstone  has  been  indurated,  and  has  assumed  a  texture  ap- 
proaching to  hornstone  near  the  junction.  In  Arthur's  Seat  and 
Salisbury  Craig,  near  Edinburgh,  a  sandstone  which  comes  in  contact 
with  greenstone  is  converted  into  a  jaspideous  rock. 

The  secondary  sandstones  in  Skye  are  converted  into  solid  quartz 
in  several  places,  where  they  come  in  contact  with  veins  or  masses  of 
trap ;  and  a  bed  of  quartz,  says  Dr.  MacCulloch,  found  near  a  mass 
of  trap,  among  the  coal  strata  of  Fife,  was  in  all  probability  a  stratum 
of  ordinary  sandstone,  having  been  subsequently  indurated  and  turned 
into  quartzite  by  the  action  of  heat.f 

But  although  strata  in  the  neighborhood  of  dikes  are  thus  altered 
in  a  variety  of  cases,  shale  being  turned  into  flinty  slate  or  jasper, 
limestone  into  crystalline  marble,  sandstone  into  quartz,  coal  into 
coke,  and  the  fossil  remains  of  all  such  strata  wholly  and  in  part 
obliterated,  it  is  by  no  means  uncommon  to  meet  with  the  same 
rocks,  even  in  the  same  districts,  absolutely  unchanged  in  the  prox- 
imity of  volcanic  dikes. 

This  great  inequality  in  the  effects  of  the  igneous  rocks  may  often 
arise  from  an  original  difference  in  their  temperature,  and  in  that  of 
the  entangled  gases,  such  as  is  ascertained  to  prevail  in  different  lavas, 
or  in  the  same  lava  near  its  source  and  at  a  distance  from  it.  The 
power  also  of  the  invaded  rocks  to  conduct  heat  may  vary,  according 
to  their  composition,  structure,  and  the  fractures  which  they  may 
have  experienced,  and  perhaps,  also,  according  to  the  quantity  of 
water  (so  capable  of  being  heated)  which  they  contain.  It  must  hap- 
pen in  some  cases  that  the  component  materials  are  mixed  in  such 
proportions  as  prepare  them  readily  to  enter  into  chemical  union,  and 
form  new  minerals ;  while  in  other  cases  the  mass  may  be  more 
homogeneous,  or  the  proportions  less  adapted  for  such  union. 

We  must  also  take  into  consideration,  that  one  fissure  may  be  sim- 
ply filled  with  lava,  which  may  begin  to  cool  from  the  first ;  whereas 
in  other  cases  the  fissure  may  give  passage  to  a  current  of  melted 
matter,  which  may  ascend  for  days  or  months,  feeding  streams  which 
are  overflowing  the  country  above,  or  are  ejected  in  the  shape  of  sco- 
riae from  some  crater.  If  the  walls  of  a  rent,  moreover,  are  heated 
by  hot  vapor  before  the  lava  rises,  as  we  know  may  happen  on  the 
flanks  of  a  volcano,  the  additional  caloric  supplied  by  the  dike  and  its 
gases  will  act  more  powerfully. 


*  Sedgwick,  Camb.  Trans.,  vol.  ii.  p.  37. 
f  Syst.  of  Geol.,  vol.  i.  p.  206. 


616 


INTRUSION  OF  TRAP  BETWEEN  STRATA.         [Cn.  XXIX. 


Intrusion  of  Trap  between  Strata. — In  proof  of  the  mechanical 
force  which  the  fluid  trap  has  sometimes  exerted  on  the  rocks  into 
which  it  has  intruded  itself,  I  may  refer  to  the  Whin-Sill,  where  a 
mass  of  basalt,  from  60  to  80  feet  in  height,  represented  by  a,  fig. 
685,  is  in  part  wedged  in  between  the  rocks  of  limestone,  6,  and 
shale,  Cj  which  have  been  separated  from  the  great  mass  of  limestone 
and  shale,  d,  with  which  they  were  united. 

Fig.  685. 


Trap  interposed  between  displaced  beds  of  limestone  and  shale,  at  White  Force, 
High  Teesdale,  Durham.    (Sedgwick.*) 

The  shale  in  this  place  is  indurated ;  and  the  limestone,  which  at 
a  distance  from  the  trap  is  blue,  and  contains  fossil  corals,  is  here 
converted  into  white  granular  marble  without  fossils. 

Masses  of  trap  are  not  unfrequently  met  with  intercalated  between 
strata,  and  maintaining  their  parallelism  to  the  planes  of  stratification 
throughout  large  areas.  They  must  in  some  places  have  forced  their 
way  laterally  between  the  divisions  of  the  strata,  a  direction  in  which 
there  would  be  the  least  resistance  to  an  advancing  fluid,  if  no  verti- 
cal rents  communicated  with  the  surface,  and  a  powerful  hydrostatic 
pressure  were  caused  by  gases  propelling  the  lava  upwards. 

Columnar  and  Globular  Structure.  —  One  of  the  characteristic 
forms  of  volcanic  rocks,  especially  of  basalt,  is  the  columnar,  where 
large  masses  are  divided  into  regular  prisms,  sometimes  easily  sepa- 
rable, but  in  other  cases  adhering  firmly  together.  The  columns  vary 
in  the  number  of  angles,  from  three  to  twelve ;  but  they  have  most 
commonly  from  five  to  seven  sides.  They  are  often  divided  trans- 
versely, at  nearly  equal  distances,  like  the  joints  in  a  vertebral  column, 
as  in  the  Giant's  Causeway,  in  Ireland.  They  vary  exceedingly  in 
respect  to  length  and  diameter.  Dr.  MacCulloch  mentions  some  in 
Skye  which  are  about  400  feet  long ;  others,  in  Morven,  not  exceed- 
ing an  inch.  In  regard  to  diameter,  those  of  Ailsa  measure  9  feet, 
and  those  of  Morven  an  inch  or  less.f  They  are  usually  straight,  but 
sometimes  curved ;  and  examples  of  both  these  occur  in  the  island 
of  Staffa.  In  a  horizontal  bed  or  sheet  of  trap  the  columns  are  ver- 


*  Camb.  Trans.,  vol.  ii.  p.  180. 

f  MacCul.,  Syst.  of  Geol.,  vol.  ii.  p.  137. 


CH.  XXIX.] 


STRUCTURE  OF  VOLCANIC  ROCKS. 


617 


tical ;  in  a  vertical  dike  they  are  horizontal.  Among  other  examples 
of  the  last-mentioned  phenomenon  is  the  mass  of  basalt,  called  the 
Chimney,  in  St.  Helena  (see  fig.  686),  a  pile  of  hexagonal  prisms,  64 


Fig.  686. 


Fig.  68T. 


Small  portion  of  the  dike 
in  fig.  686. 


Volcanic  dike  composed  of  hori- 
zontal prisms.    St.  Helena. 

feet  high,  evidently  the  remainder  of  a  narrow  dike,  the  walls  of  rock 
which  the  dike  originally  traversed  having  been  removed  down  to  the 
level  of  the  sea.  In  fig.  687,  a  small  portion  of  this  dike  is  repre- 
sented on  a  less  reduced  scale.* 

It  being  assumed  that  columnar  trap  has  consolidated  from  a  fluid 
state,  the  prisms  are  said  to  be  always  at  right  angles  to  the  cooling 
surfaces.  If  these  surfaces,  therefore,  instead  of  being  either  per- 
pendicular or  horizontal,  are  curved,  the  columns  ought  to  be  inclined 
at  every  angle  to  the  horizon  ;  and  there  is  a  beautiful  exemplification 
of  this  phenomenon  in  one  of  the  valleys  of  the  Vivarais,  a  moun- 
tainous district  in  the  south  of  France,  where,  in  the  midst  of  a 
region  of  gneiss,  a  geologist  encounters  unexpectedly  several  volcanic 

Fig.  688. 


Lava  of  La  Coupe  d'Ayzac,  near  Antraigues,  in  the  Department  of  Ardeche. 

cones  of  loose  sand  and  scoriae.     From  the  crater  of  one  of  these 
cones,  called  La  Coupe  d'Ayzac,  a  stream  of  lava  descends  and  occu- 


*  Seale's  Geognosy  of  St.  Helena,  plate  9. 


618  STRUCTURE  OF  VOLCANIC  ROCKS.  [Cn.  YYTY. 

pies  the  bottom  of  a  narrow  valley,  except  at  those  points  where  the 
river  Volant,  or  the  torrents  which  join  it,  have  cut  away  portions  of 
the  solid  lava.  The  foregoing  sketch  (fig.  688)  represents  the  rem- 
nant of  the  lava  at  one  of  the  points  where  a  lateral  torrent  joins  the 
main  valley  of  the  Volant.  It  is  clear  that  the  lava  once  filled  the 
whole  valley  up  to  the  dotted  line  d  a ;  but  the  river  has  gradually 
swept  away  all  below  that  line,  while  the  tributary  torrent  has  laid 
open  a  transverse  section ;  by  which  we  perceive,  in  the  first  place, 
that  the  lava  is  composed,  as  usual  in  this  country,  of  three  parts : 
the  uppermost,  at  a,  being  scoriaceous ;  the  second,  6,  presenting 
irregular  prisms ;  and  the  third,  c,  with  regular  columns,  which  are 
vertical  on  the  banks  of  the  Volant,  where  they  rest  on  a  horizontal 
base  of  gneiss,  but  which  are  inclined  at  an  angle  of  45°  at  g,  and 
are  horizontal  at  /,  their  position  having  been  everywhere  determined, 
according  to  the  law  before  mentioned,  by  the  concave  form  of  the 
original  valley. 

In  the  annexed  figure  (689)  a  view  is 
given  of  some  of  the  inclined  and  curved 
columns  which  present  themselves  on  the 
sides  of  the  valleys  in  the  hilly  region 
north  of  Vicenza,  in  Italy,  and  at  the 
foot  of  the  higher  Alps.*  Unlike  those 
of  the  Vivarais,  last  mentioned,  the  ba- 
salt of  this  country  was  evidently  sub- 
marine, and  the  present  valleys  have 
since  been  hollowed  out  by  denudation. 

The  columnar  structure  is  by  no  means 
peculiar  to  the  trap  rocks  in  which  augite 
abounds ;  it  is  also  observed  in  clink- 
stone, trachyte,  and  other  felspathic 

Columnar  basalt  in  the  Vicentin.         rocks    of     the    IgneOUS     class,    although 

in  these  it  is  rarely  exhibited  in  such 
regular  polygonal  forms. 

It  has  been  already  stated  that  basaltic  columns  are  often  divided 
by  cross  joints.  Sometimes  each  segment,  instead  of  an  angular, 
assumes  a  spheroidal  form,  so  that  a  pillar  is  made  up  of  a  pile  of 
balls,  usually  flattened,  as  in  the  Cheese-grotto  at  Bertrich-Baden,  in 
the  Eifel,  near  the  Moselle  (fig.  690).  The  basalt  there  is  part  of  a 
small  stream  of  lava,  from  30  to  40  feet  thick,  which  has  proceeded 
from  one  of  several  volcanic  craters,  still  extant,  on  the  neighboring 
heights.  The  position  of  the  lava  bordering  the  river  in  this  valley 
might  be  represented  by  a  section  like  that  already  given  at  fig.  635, 
if  we  merely  supposed  inclined  strata  of  slate  and  the  argillaceous 
sandstone  called  graywacke  to  be  substituted  for  gneiss. 

In  some  masses  of  decomposing  greenstone,  basalt,  and  other  trap 

*  Fortis.  Mem.  sur  1'Hist.  Nat.  de  Tltalie,  torn.  i.  p.  233,  plate  7. 


CH.  XXIX.] 


STRUCTURE   OF  VOLCANIC  ROCKS. 

Fig.  690. 


619 


Fig.  691. 


Basaltic  pillars  of  the  Kasegrotte,  Bertrich-Baden,  halfway  between  Treves  and  Coblentz. 
Height  of  grotto,  from  7  to  8  feet. 

rocks  the  globular  structure  is  so  conspicuous  that  the  rock  has  the 
appearance  of  a  heap  of  large  cannon  balls.  According  to  the  theory 
of  M.  Delesse,  the  centre  of  each  spheroid  has  been  a  centre  of  crys- 
tallization, around  which  the  different  minerals  of  the  rock  arranged 
themselves  symmetrically  during  the  process  of  cooling.  But  it  was 
also,  he  says,  a  centre  of  contraction,  produced  by  the  same  cooling. 
The  globular  form,  therefore,  of  such  spheroids  is  the  combined  result 
of  crystallization  and  contraction.* 

A  striking  example  of  this  structure 
occurs  in  a  resinous  trachyte  or  pitch- 
stone-porphyry  in  one  of  the  Ponza 
islands,  which  rise  from  the  Mediter- 
ranean, off  the  coast  of  Terracina  and 
Gaeta.  The  globes  vary  from  a  few 
inches  to  three  feet  in  diameter,  and  are 
of  an  ellipsoidal  form  (see  fig.  691).  The 
whole  rock  is  in  a  state  of  decomposition, 
"  and  when  the  balls,"  says  Mr.  Scrope, 
"  have  been  exposed  a  short  time  to  the 
weather,  they  scale  off  at  a  touch  into 
numerous  concentric  coats,  like  those  of 
a  bulbous  root,  inclosing  a  compact  nu- 
cleus. The  lamina  of  this  nucleus  have 
not  been  so  much  loosened  by  decompo- 
sition ;  but  the  application  of  a  ruder 
blow  will  produce  a  still  further  exfolia- 
tion." f 


Globiform  pitchstone.    Chiaja  di 
Luna,  Isle  of  Ponza.    (Scrope.) 


*  Delesse,  sur  les  Roches  Globuleuses,  Mem.  de  la  Soc.  Geol.  de  France,  2  s6r. 
torn.  iv. 

f  Scrope,  Geol.  Trans.,  Second  Series,  vol.  ii.  p.  205. 


620  RELATION  OF  TRAP,  LATA,  AND  SCORIA.        [On.  XXIX. 

A  fissile  texture  is  occasionally  assumed  by  clinkstone  and  other 
trap  rocks,  so  that  they  have  been  used  for  roofing  houses.  Some- 
times the  prismatic  and  slaty  structure  is  found  in  the  same 
mass.  The  causes  which  give  rise  to  such  arrangements  are  very 
obscure,  but  are  supposed  to  be  connected  with  changes  of  tempera- 
ture during  the  cooling  of  the  mass,  as  will  be  pointed  out  in  the 
sequel.  (See  Chaps.  XXXV.  and  XXXVI.) 


Relation  of  Trappean  Rocks  to  the  products  of  active  Volcanoes. 

When  we  reflect  on  the  changes  above  described  in  the  strata  near 
their  contact  with  trap  dikes,  and  consider  how  complete  is  the  anal- 
ogy or  often  identity  in  composition  and  structure  of  the  rocks  called 
trappean  and  the  lavas  of  active  volcanoes,  it  seems  difficult  at  first  to 
understand  how  so  much  doubt  could  have  prevailed  for  half  a  cen- 
tury as  to  whether  trap  was  of  igneous  or  aqueous  origin.  To  a  cer- 
tain extent,  however,  there  was  a  real  distinction  between  the  trap- 
pean formations  and  those  to  which  the  term  volcanic  was  almost 
exclusively  confined.  A  large  portion  of  the  trappean  rocks  first 
studied  in  the  north  of  Germany,  and  in  Norway,  France,  Scotland, 
and  other  countries,  were  such  as  had  been  formed  entirely  under 
water,  or  had  been  injected  into  fissures  and  intruded  between  strata, 
and  which  had  never  flowed  out  in  the  air,  or  over  the  bottom  of  a 
shallow  sea.  When  these  products,  therefore,  of  submarine  or  sub- 
terranean igneous  action  were  contrasted  with  loose  cones  of  scoriae, 
tuff,  and  lava,  or  with  narrow  streams  of  lava  in  great  part  scoria- 
ceous  and  porous,  such  as  were  observed  to  have  proceeded  from 
Vesuvius  and  Etna,  the  resemblance  seemed  remote  and  equivocal. 
It  was,  in  truth,  like  comparing  the  roots  of  a  tree  with  its  leaves 
and  branches,  which,  although  they  belong  to  the  same  plant,  differ 
in  form,  texture,  color,  mode  of  growth,  and  position.  The  external 
cone,  with  its  loose  ashes  and  porous  lava,  may  be  likened  to  the 
light  foliage  and  branches,  and  the  rocks  concealed  far  below,  to  the 
roots.  But  it  is  not  enough  to  say  of  the  volcano, 

"  quantum  vertice  in  auras 
^Etherias,  tantum  radice  in  Tartara  tendit," 

for  its  roots  do  literally  reach  downwards  to  Tartarus,  or  to  the  re- 
gions of  subterranean  fire  ;  and  what  is  concealed  far  below  is  proba- 
bly always  more  important  in  volume  and  extent  than  what  is  visible 
above  ground. 

We  have  already  stated  how  frequently  dense  masses  of  strata 
have  been  removed  by  denudation  from  wide  areas  (see  Chap.  VI.) ; 
and  this  fact  prepares  us  to  expect  a  similar  destruction  of  whatever 
may  once  have  formed  the  uppermost  part  of  ancient  submarine  or 
subaerial  volcanoes,  more  especially  as  those  superficial  parts  are 


CH.  XXIX.]       RELATION  OF  TRAP,  LAVA,  AND  SCORLE. 

always  of  the  lightest  and  most  perish-  Fig.  692. 

able  materials.  The  abrupt  manner  in 
which  dikes  of  trap  usually  terminate  at 
the  surface  (see  fig.  692),  and  the  water- 
worn  pebbles  of  trap  in  the  alluvium 
which  covers  the  dike,  prove  incontesta- 
bly  that  whatever  was  uppermost  in  these 
formations  has  been  swept  away.  It  is 
easy,  therefore,  to  conceive  that  what  is 


gone  in  regions  of  trap  may  have  corre-      strata  intercepted  by  a  trap  dike, 
sponded  to  what  is  now  visible  in  active         S31^  covered  with  alluvium, 
volcanoes. 

It  will  be  seen  in  the  following  chapters,  that  in  the  earth's  crust 
there  are  volcanic  tuffs  of  all  ages,  containing  marine  shells,  which 
bear  witness  to  eruptions  at  many  successive  geological  periods. 
These  tuffs,  and  the  associated  trappean  rocks,  must  not  be  compared 
to  lava  and  scoriae  which  had  cooled  in  the  open  air.  Their  counter- 
parts must  be  sought  in  the  products  of  modern  submarine  volcanic 
eruptions.  If  it  be  objected  that  we  have  no  opportunity  of  studying 
these  last,  it  may  be  answered,  that  subterranean  movements  have 
caused,  almost  everywhere  in  regions  of  active  volcanoes,  great  changes 
in  the  relative  level  of  land  and  sea,  in  times  comparatively  modern, 
so  as  to  expose  to  view  the  effects  of  volcanic  operations  at  the  bottom 
of  the  sea. 

Thus,  for  example,  the  examination  of  the  igneous  rocks  of  Sicily, 
especially  those  of  the  Val  di  Noto,  has  proved  that  all  the  more 
ordinary  varieties  of  European  trap  have  been  there  produced  under 
the  waters  of  the  sea,  at  a  modern  period ;  that  is  to  say,  since  the 
Mediterranean  has  been  inhabited  by  a  great  proportion  of  the  exist- 
ing species  of  testacea. 

These  igneous  rocks  of  the  Val  di  Noto,  and  the  more  ancient 
trappean  rocks  of  Scotland  and  other  countries,  differ  from  subaerial 
volcanic  formations  in  being  more  compact  and  heavy,  and  in  forming 
sometimes  extensive  sheets  of  matter  intercalated  between  marine 
strata,  and  sometimes  stratified  conglomerates,  of  which  the  rounded 
pebbles  are  all  trap.  They  differ  also  in  the  absence  of  regular  cones 
and  craters,  and  in  the  want  of  conformity  of  the  lava  to  the  lowest 
levels  of  existing  valleys. 

It  is  highly  probable,  however,  that  insular  cones  did  exist  in  some 
parts  of  the  Val  di  Noto ;  and  that  they  were  removed  by  the  waves, 
in  the  same  manner  as  the  cone  of  Graham  Island,  in  the  Mediterra- 
nean, was  swept  away  in  1831,  and  that  of  Nyoe,  off  Iceland,  in  1783.* 
All  that  would  remain  in  such  cases,  after  the  bed  of  the  sea  has  been 
upheaved  and  laid  dry,  would  be  dikes  and  shapeless  masses  of  igne- 

.*  SeePrinc.  of  Geol.,  Index,  "Graham  Island,"  "Nyoe,"  "Conglomerates,  vol- 
canic," &c. 


622  RELATION  OF  TRAP,  LAVA,  AND  SCORIA.        [On.  XXIX. 

ous  rock,  cutting  through,  sheets  of  lava  which  may  have  spread  over 
the  level  bottom  of  the  sea,  and  strata  of  tuff,  formed  of  materials  first 
scattered  far  and  wide  by  the  winds  and  waves,  and  then  deposited. 
Conglomerates  also,  with  pebbles  of  trap,  to  which  the  action  of  the 
waves  must  give  rise  during  the  denudation  of  such  volcanic  islands, 
will  emerge  from  the  deep  whenever  the  bottom  of  the  sea  becomes 
land.  The  proportion  of  volcanic  matter  which  is  originally  submarine 
must  always  be  very  great,  as  those  volcanic  vents  which  are  not  en- 
tirely beneath  the  sea  are  almost  all  of  them  in  islands,  or,  if  on  con- 
tinents, near  the  shore. 

As  to  the  absence  of  porosity  in  the  trappean  formations,  the 
appearances  are  in  a  great  degree  deceptive,  for  all  amygdaloids  are, 
as  already  explained,  porous  rocks,  into  the  cells  of  which  mineral 
matter,  such  as  silex,  carbonate  of  lime,  and  other  ingredients,  have 
been  subsequently  introduced  (see  p.  601) ;  sometimes,  perhaps,  by 
secretion  during  the  cooling  and  consolidation  of  lavas. 

In  the  Little  Cumbray,  one  of  the  Western  Islands,  near  Arran,  the 
amygdaloid  sometimes  contains  elongated  cavities  filled  with  brown 
spar ;  and  when  the  nodules  have  been  washed  out,  the  interior  of  the 
cavities  is  glazed  with  the  vitreous  varnish  so  characteristic  of  the 
pores  of  slaggy  lavas.  Even  in  some  parts  of  this  rock  which  are  ex- 
cluded from  air  and  water,  the  cells  are  empty,  and  seem  to  have 
always  remained  in  this  state,  and  are  therefore  undistinguishable  from 
some  modern  lavas.* 

Dr.  MacCulloch,  after  examining  with  great  attention  these  and  the 
other  igneous  rocks  of  Scotland,  observes,  "  that  it  is  a  mere  dispute 
about  terms,  to  refuse  to  the  ancient  eruptions  of  trap  the  name  of 
submarine  volcanoes;  for  they  are  such  in  every  essential  point, 
although  they  no  longer  eject  fire  and  smoke."  f  The  same  author 
also  considers  it  not  improbable  that  some  of  the  volcanic  rocks  of 
the  same  country  may  have  been  poured  out  in  the  open  air.]; 

Although  the  principal  component  minerals  of  subaerial  lavas  are 
the  same  as  those  of  intrusive  trap,  and  both  the  columnar  and  glob- 
ular structure  are  common  to  both,  there  are,  nevertheless,  some  vol- 
canic rocks  which  never  occur  in  currents  of  lava,  such  as  greenstone, 
the  more  crystalline  porphyries,  and  those  traps  in  which  quartz  and 
mica  appear  as  constituent  parts.  In  short,  the  intrusive  trap  rocks, 
forming  the  intermediate  step  between  lava  and  the  plutonic  rocks, 
depart  in  their  characters  from  lava  in  proportion  as  they  approximate 
to  granite. 

These  views  respecting  the  relations  of  the  volcanic  and  trap  rocks 
will  be  better  understood  when  the  reader  has  studied,  in  the  33d 
chapter,  what  is  said  of  the  plutonic  formations. 

*  MacCulloch,  West.  Islands,  vol.  ii.  p.  487. 
f  Syst.  of  Geol.,  vol.  ii.  p.  114. 
4  Ibid. 


CH.  XXIX.]  VOLCANIC  MOUNTAINS.  623 

EXTERNAL   FORM,    STRUCTURE,    AND    ORIGIN    OF   VOLCANIC    MOUNTAINS. 

The  origin  of  volcanic  cones  with  crater-shaped  summits  has  been 
alluded  to  in  the  last  chapter  (p.  593),  and  more  fully  explained  in 
the  "  Principles  of  Geology  "  (chaps,  xxiv.  to  xxvii.),  where  Vesuvius, 
Etna,  Santorin,  and  Barren  Island  are  described.  The  more  ancient 
portions  of  those  mountains  or  islands,  formed  long  before  the  times 
of  history,  exhibit  the  same  external  features  and  internal  structure 
which  belong  to  most  of  the  extinct  volcanoes  of  still  higher  antiquity ; 
and  these  last  have  evidently  been  due  to  a  complicated  series  of 
operations,  varied  in  kind  according  to  circumstances ;  as,  for  example, 
whether  the  accumulation  took  place  above  or  below  the  level  of  the 
sea,  whether  the  lava  issued  from  one  or  several  contiguous  vents,  and, 
lastly,  whether  the  rocks  reduced  to  fusion  in  the  subterranean  regions 
happen  to  have  contained  more  or  less  silica,  potash,  soda,  lime,  iron, 
and  other  ingredients. 

We  are  best  acquainted  with  the  effects  of  eruptions  above  water, 
or  those  called  subaerial  or  supramarine ;  yet  the  products  even  of 
these  are  arranged  in  so  many  ways  that  their  interpretation  has  given 
rise  to  a  variety  of  contradictory  opinions,  some  of  which  will  have  to 
be  considered  in  this  chapter. 

Craters  and  Colder  as,  Sandwich  Islands. — We  learn  from  Mr. 
Dana's  valuable  work  on  the  geology  of  the  United  States  Exploring 
Expedition,  published  in  1849,  that  two  of  the  principal  volcanoes  of 
Sandwich  Islands,  Mounts  Loa  and  Kea  in  Owyhee,  are  huge  flattened 
volcanic  cones,  about  14,000  feet  high  (see  fig.  693),  each  equalling 
two  and  a  half  Etnas  in  their  dimensions. 

Fig.  693. 


Mount  Loa,  in  the  Sandwich  Islands.    (Dana.) 

a.  Crater  at  the  summit  6.  The  lateral  crater  at  Kilauea. 

The  dotted  lines  indicate  a  supposed  column  of  solid  rock  caused  by  the  lava  consolidating 

after  eruptions. 

From  the  summits  of  these  lofty  though  featureless  hills,  and  from 
vents  not  far  below  their  summits,  successive  streams  of  lava,  often 
2  miles  or  more  in  width,  and  sometimes  26  miles  long,  have  flowed. 
They  have  been  poured  out  one  after  the  other,  some  of  them  in 
recent  times,  in  every  direction  from  the  apex  of  the  cone,  down 
slopes  varying  on  an  average  from  4  degrees  to  8  degrees ;  but  in  some 
places  considerably  steeper.  Sometimes  deep  rents  are  formed  on  the 
sides  of  those  conical  mountains,  which  are  afterwards  filled  from 
above  by  streams  of  lava  passing  over  them,  the  liquid  matter  in  such 
cases  consolidating  in  the  fissures  and  forming  dikes. 

The  lateral  crater  of  Kilauea,  b,  fig.  693,  is  between  3000  and  4000 
feet  above  the  sea-level,  or  about  the  height  of  Vesuvius.  It  is  an 


624:  EXTERNAL  FORM,  STRUCTURE,  AND  ORIGIN       [Gn.  XXIX. 

immense  chasm,  1000  feet  deep,  and  its  outer  circuit  no  less  than 
from  two  to  three  miles  in  diameter.  Lava  is  usually  seen  to  boil 
up  at  the  bottom  in  a  lake,  the  level  of  which  varies  continually,  for 
the  liquid  rises  and  falls  several  hundred  feet  according  to  the  active 
or  quiescent  state  of  the  volcano.  But  instead  of  overflowing  the 
rim  of  the  crater,  as  commonly  happens  in  other  vents,  the  column  of 
melted  rock,  when  its  pressure  becomes  excessive,  forces  a  passage 
through  some  subterranean  galleries  or  rents  leading  towards  the  sea. 
Mr.  Coan,  an  American  missionary,  has  described  an  eruption  which 
took  place  in  June  1840,  when  the  lava  which  had  risen  high  in  the 
great  chasm  began  to  escape  from  it.  Its  direction  was  first  recog- 
nized by  the  emission  of  a  vivid  light  from  the  bottom  of  an  ancient 
wooded  crater,  called  Arare,  400  feet  deep  and  6  miles  to  the  east- 
ward of  Kilauea.  The  connection  of  this  light  with  the  discharge  or 
tapping  of  the  great  reservoir  was  proved  by  a  change  in  the  level  of 
the  lava  in  Kilauea,  which  sank  gradually  for  three  weeks,  or  until  the 
eruption  ceased,  when  the  lake  stood  400  feet  lower  than  at  the  com- 
mencement of  the  outbreak.  The  passage,  therefore,  of  the  fluid 
matter  from  Kilauea  to  Arare  was  underground,  and  it  is  supposed  by 
Mr.  Coan  to  have  been  at  its  first  outflow  1000  feet  deep  below  the 
surface.  The  next  indication  of  the  subterranean  progress  of  the  same 
lava  was  observed  a  mile  or  two  from  Arare,  where  the  fiery  flood 
broke  out  and  spread  itself  superficially  over  50  acres  of  land,  and 
then  again  found  its  way  underground  for  several  miles  farther  towards 
the  sea,  to  reappear  at  the  bottom  of  a  second  ancient  and  wooded 
crater,  which  it  partly  filled  up.  The  course  of  the  fluid  then  became 
again  invisible  for  several  miles,  until  it  broke  out  for  the  last  time  at 
a  point  ascertained  by  Captain  Wilkes  to  be  1244  feet  above  the  sea, 
and  27  miles  distant  from  Kilauea.  From  thence  it  poured  along  for 
12  miles  in  the  open  air,  and  then  leapt  over  a  cliff  50  feet  high,  and 
ran  for  three  weeks  into  the  sea.  Its  termination  was  at  a  place  about 
40  miles  distant  from  Kilauea.  The  crust  of  the  earth  overlying  the 
subterranean  course  of  the  lava  was  often  traversed  by  innumerable 
fissures,  which  emitted  steam,  and  in  some  places  the  incumbent  rocks 
were  uplifted  20  or  30  feet. 

Thus  in  the  same  volcano  examples  are  afforded  of  the  overflowing 
of  lava  from  the  summit  of  a  cone  2-J  miles  high,  and  of  the  under- 
flowing  of  melted  matter.  Whether  this  last  has  formed  sheets  inter- 
calated between  the  stratified  products  of  previous  eruptions,  or 
whether  it  has  penetrated  through  oblique  or  vertical  fissures,  cannot 
be  determined.  In  one  instance,  however,  for  a  certain  space,  it  is 
said  to  have  spread  laterally,  uplifting  the  incumbent  soil. 

The  annexed  section  of  the  crater  of  Kilauea,  as  given  by  Mr.  Dana, 
follows  the  line  of  its  shortest  diameter,  a,  6,  which  is  about  7500  feet 
long.  The  boundary  cliffs,  a,  c,  and  6,  d,  are  for  the  most  part  quite 
vertical  and  650  feet  high.  They  are  composed  of  compact  rock  in 
layers,  not  divided  by  scoriae,  some  a  few  inches,  others  30  feet  in 


CH.  XXIX.]  OF  VOLCANIC  ROCKS.  625 

a  Fig.  694.  6 


JT 


Section  of  the  crater  of  Kilauea  in  the  Sandwich  Islands.    (Dana.) 
a,  6.  External  boundaries  of  the  chasm  in  the  line  of  its  shortest  diameter 
c,  e,  /,  d.  Black  ledge.  ff,  h.  Lake  of  lava. 

thickness,  and  nearly  horizontal.  Before  this,  we  come  to  what  is 
called  the  "  black  ledge,"  c,  e,  and  /,  c?,  composed  of  similar  stratified 
materials.  This  ledge  is  three  hundred  and  forty-two  feet  in  height 
above  the  lake  of  lava,  </,  A,  which  it  encircles.  The  chasm,  a,  6, 
and  its  walls  have  probably  been  due  to  a  former  sinking  down  of 
the  incumbent  rocks  undermined  for  a  space  by  the  fusion  of  their 
foundations.  The  lower  ledge,  c,  e,  and  /,  e?,  may  consist  in  part  of 
the  mass  which  sank  vertically,  but  part  -of  it  at  least  must  be  made 
up  of  layers  of  lava,  which  have  been  seen  to  pour  one  after  the  other 
over  the  "black  ledge."  If  at  any  future  period  the  heated  fluid, 
ascending  from  the  volcanic  focus  to  the  bottom  of  the  great  chasm, 
should  augment  in  volume,  and,  before  it  can  obtain  relief,  should 
spread  itself  subterraneously,  it  may  melt  still  farther  the  subjacent 
masses,  and,  causing  a  failure  of  support,  may  enlarge  still  more  the 
limits  of  the  amphitheatre  of  Kilauea.  There  are  distinct  signs  of 
subsidences,  from  100  to  200  feet  perpendicular,  which  have  occurred 
in  the  neighborhood  of  Kilauea  at  various  points,  and  they  are  each 
bounded  by  vertical  walls.  If  all  of  them  were  united,  they  would 
constitute  a  sunken  area  equal  to  eight  square  miles,  or  twice  the  ex- 
tent of  Kilauea  itself.  Similar  accidents  are  also  likely  to  occur  near 
the  summit  of  a  dome  like  Mount  Loa,  for  the  hydrostatic  pressure  of 
the  lava,  after  it  has  risen  to  the  edge  or  lip  of  the  highest  crater,  «, 
fig.  693,  must  be  great  and  must  create  a  tendency  to  lateral  fis- 
suring,  in  which  case  lava  will  be  injected  into  every  opening,  and 
may  begin  to  undermine.  If,  then,  some  of  the  melted  matter  be 
drawn  off  by  escaping  at  a  lower  level,  where  the  pressure  would  be 
still  greater,  the  whole  top  of  the  mountain,  or  a  large  part  of  it, 
might  fall  in. 

Instances  of  such  truncations,  however  caused,  have  occurred  in 
Java  and  in  the  Andes  within  the  times  of  history,  and  to  such  events 
we  may  perhaps  refer  a  very  common  feature  in  the  configuration  of 
volcanic  mountains, — namely,  that  the  present  active  cone  of  eruption 
is  surrounded  by  the  ruins  of  a  larger  and  older  cone,  usually  present- 
ing a  crescent-shaped  precipice  towards  the  newer  cone.  In  volcanoes 
long  since  extinct,  the  erosive  power  of  running  water,  or,  in  certain 
cases,  of  the  sea,  may  have  greatly  modified  the  shape  of  the  "  atrium," 
or  space  between  the  older  and  newer  cone,  and  the  cavity  may 
thereby  be  prolonged  downwards,  and  end  in  a  ravine.  In  such 
cases  it  may  be  impossible  to  determine  how  much  of  the  missing 
rocks  has  been  removed  by  explosion  at  the  time  when  the  original 
40 


626  JAVA.  [On.  XXIX. 

crater  was  active,  or  how  much  by  subsequent  engulphment  and  de- 
nudation. 

Java. — One  of  the  latest  contributions  to  our  knowledge  of  vol- 
canoes will  be  found  in  Dr.  Junghuhn's  work  on  Java,  where  forty- 
six  conical  eminences  of  volcanic  origin,  varying  in  elevation  from 
4000  to  nearly  12,000  feet  above  the  sea,  constitute  the  highest 
peaks  of  a  mountain  range,  running  through  the  island  from  east  to 
west.  All  of  them,  with  one  exception,  did  this  indefatigable  traveller 
survey  and  map.  In  none  of  them  could  he  discover  any  marine  re- 
mains, whether  adhering  to  their  flanks  or  entering  into  their  internal 
structure,  although  strata  of  marine  origin  are  met  with  nearer  the  sea 
at  lower  levels.  Dr.  Junghuhn  ascribes  the  origin  of  each  volcano  to 
a  succession  of  subaerial  eruptions  from  one  or  more  central  vents, 
whence  scoriae,  pumice,  and  fragments  of  rock  were  thrown  out,  and 
whence  have  flowed  streams  .of  trachytic  or  basaltic  lava.  Such  over- 
flowings have  been  witnessed  in  modern  times  from  the  highest  sum- 
mits of  several  of  the  peaks.  The  external  slope  of  each  cone  is  gene- 
rally greatest  near  its  apex,  where  the  volcanic  strata  have  also  the 
steepest  dip,  sometimes  attaining  angles  of  20,  30,  and  35  degrees, 
but  becoming  less  and  less  inclined  as  they  recede  from  the  summit, 
until,  near  their  base,  the  dip  is  reduced  to  10  and  often  to  4  or  5 
degrees.*  The  interference  of  the  lavas  of  adjoining  volcanoes  some- 
times produces  elevated  platforms,  or  "  saddles,"  in  which  the  layers 
of  rock  may  be  very  slightly  inclined.  At  the  top  of  many  of  the 
loftiest  mountains  the  active  cone  and  crater  are  of  small  size,  and 
surrounded  by  a  plain  of  ashes  and  sand,  this  plain  being  encircled  in 
its  turn  by  what  Dr.  Junghuhn  calls  "  the  old  crater-wall,"  which  is 
often  1000  feet  and  more  in  vertical  height.  There  is  sometimes  a 
terrace  of  intermediate  height  (as  in  the  mountain  called  Tengger), 
comparable  to  the  "black  ledge"  of  Kilauea  (fig.  694).  .  Most  of  the 
spaces  thus  bounded  by  semicircular  or  more  than  semicircular  ranges 
of  cliffs  are  vastly  superior  in  dimensions  to  the  area  of  any  known 
crater  or  hollow  which  has  been  observed  in  any  part  of  the  world  to 
be  occupied  by  a  lake  of  liquid  lava.  As  the  Spaniards  have  given  to 
such  large  cavities  the  name  of  Caldera  (or  cauldron),  it  may  be  use- 
ful to  use  this  term  in  a  technical  sense,  whatever  views  we  may 
entertain  as  to  their  origin.  Many  of  them  in  Java  are  no  less  than 
four  geographical  miles  in  diameter,  and  they  are  attributed  by  Jung- 
huhn to  the  truncation  by  explosion  and  subsidence  of  ancient  cones 
of  eruption.  Unfortunately,  although  several  lofty  cones  have  lost  a 
portion  of  their  height  within  the  memory  of  man,  neither  the  inhab- 
itants of  Java  nor  their  Dutch  rulers  have  transmitted  to  us  any  reli- 
able accounts  of  the  order  of  events  which  occurred.f 

Dr.  Junghuhn  believes  that  Papandayang  lost  some  portion  of  its 

*  Java,  deszelfe  gedaante,  bekleeding  en  invendige  structuur,  door  F.  Junghuhn. 
(German  translation  of  2d  edit,  by  Hasskarl,  Leipzig,  1852.) 
\  See  Principles  of  Geol.,  9th  edit.,  p.  493. 


CH.  XXIX.]  JAVANESE  CALDERAS.  627 

summit  in  1772  ;  but  affirms  that  most  of  the  towns  on  its  sides  said 
to  have  been  engulfed  were  in  reality  overflowed  by  lava. 

From  the  highest  parts  of  many  Javanese  calderas  rivers  flow,  which 
in  the  course  of  ages  have  cut  out  deep  valleys  in  the  mountain's  side. 
As  a  general  rule,  the  outer  slopes  of  each  cone  are  furrowed  by 
straight  and  narrow  ravines  from  200  to  600  feet  deep,  radiating  in  all 
directions  from  the  top,  and  increasing  the  number  as  we  descend  to 
lower  zones.  The  ridges  or  "  ribs  "  intervening  between  these  furrows 
are  very  conspicuous,  and  compared  to  the  spokes  of  an  umbrella.  In 
a  mountain  above  10,000  feet  high,  no  furrows  or  intervening  ribs  are 
met  with  in  the  upper  300  or  400  feet.  At  the  height  of  10,000  feet 
there  may  be  no  more  than  10  in  number,  whereas  500  feet  lower  32 
of  them  may  be  counted.  They  are  all  ascribed  to  the  action  of 
running  water ;  and  if  they  ever  cut  through  the  rim  of  a  caldera,  it  is 
only  because  the  cone  has  been  truncated  so  low  down  as  to  cause  the 
summit  to  intersect  a  middle  region,  where  the  torrents  once  exerted 
sufficient  power  to  cause  a  series  of  such  indentations.  It  appears 
from  such  facts,  that,  if  a  cone  escapes  destruction  by  explosion  or 
engulfment,  it  may  remain  uninjured  in  its  upper  portion,  while 
there  is  time  for  the  excavation  of  deep  ravines  by  lateral  torrents. 

It  is  remarked  by  Dr.  Junghuhn,  as  also  by  Mr.  Dana,  in  regard  to 
the  Pacific  Islands,  that  volcanic  mountains,  however  large  and  how- 
ever much  exposed  to  heavy  falls  of  rain,  support  no  rivers  so  long  as 
they  are  in  the  process  of  growth,  or  while  the  highest  crater  emits 
from  time  to  time  showers  of  scoriae  and  floods  of  lava.  Such  ejecta- 
menta  and  such  currents  of  melted  rock  fill  up  each  superficial  inequal- 
ity or  depression  where  water  might  otherwise  collect,  and  are  more- 
over so  porous  that  no  rill  of  water,  however  small,  can  be  generated. 
But  where  the  subterranean  fires  have  been  long  since  spent,  or  are 
nearly  exhausted,  and  where  the  superficial  scoriae  and  lavas  decom- 
pose and  become  covered  with  clayey  soils,  the  erosive  action  of  water 
begins  to  operate  with  a  prodigious  force,  proportionate  to  the  steep- 
ness of  the  declivities  and  the  incoherent  nature  of  the  sand  and 
ashes.  Even  the  more  solid  lavas  are  occasionally  cavernous,  and 
almost  always  alternate  with  scoriae  and  perishable  tuffs,  so  as  to  be 
readily  undermined,  and  most  of  them  are  speedily  reduced  to  frag- 
ments of  a  transportable  size  because  they  are  divided  by  vertical 
joints  or  split  into  columns. 

Canary  Islands — Palma. — I  have  enlarged  so  fully  in  the  "  Prin- 
ciples of  Geology"  on  the  different  views  entertained  by  eminent 
authorities  respecting  the  origin  of  volcanic  cones,  and  the  laws  gov- 
erning the  flow  of  lava,  and  its  consolidation,  that,  in  order  not  to 
repeat  here  what  I  have  elsewhere  published,  I  shall  confine  myself 
in  the  remainder  of  this  chapter  to  the  description  of  facts  observed 
by  me  during  an  exploration  of  Madeira  and  some  of  the  Canary 
Islands  in  1853-'4.  In  these  excursions,  made  in  the  winter  of 
1853-'4,  I  was  accompanied  by  an  active  fellow-laborer,  Mr.  Hartung, 


628 


CANARY  ISLANDS— PALMA. 


[On.  XXIX. 


Tig.  695. 


JSrtercePfc- 


of  Konigsberg.*  We  visited,  among  other  places,  the  beautiful  island 
of  Palma,  a  spot  rendered  classical  by  the  description  given  of  it  in 
1825  by  the  late  Leopold  Yon  Buch,  who  regarded  it  as  a  type  of 
what  he  called  a  "  crater  of  elevation." 

Palma  is  46  geographical  miles  west  of  Teneriffe.  Seen  from  the 
channel  which  divides  the  two  islands,  Palma  appears  to  consist  of 

two  principal  mountain  masses, 
the  depression  between  them 
being  at  the  pass  of  Tacanda,  or 
at  a  (map,  fig.  695),  which  is 
about  4600  feet  above  the  sea- 
level.  The  most  northern  of 
these  masses  makes,  notwith- 
standing certain  irregularities 
hereafter  to  be  mentioned,  a  con- 
siderable approach  in  general 
form  to  a  great  truncated  cone, 
having  in  the  centre  a  huge  and 
deep  cavity  called  by  the  inhab- 
itants "  La  Caldera,"  This  cav- 
ity (b,  c,  d,  e,  fig.  695)  is  from  3 
to  4  geographical  miles  in  diame- 
ter, and  the  range  of  precipices 
surrounding  it  vary  from  about 
1500  to  2500  feet  in  vertical 
height.  From  their  base  a  steep 

slope,  clothed  by  a  splendid  forest  of  pines,  descends  for  a  thousand 
and  sometimes  two  thousand  feet  lower,  the  centre  of  the  Caldera 
being  about  2000  feet  above  the  sea.  The  northern  half  of  the 
encircling  ridge  is  more  than  7000  English  feet  above  the  sea  in  its 
highest  peaks,  and  is  annually  white  with  snow  during  the  winter 
months. 

Externally  the  flanks  of  this  truncated  cone  incline  outwards  in 
every  direction,  the  slopes  being  steepest  near  the  crest,  and  lessening 
as  they  approach  the  lower  country.  A  great  number  of  ravines 
commence  on  the  flanks  of  the  mountain,  a  short  distance  below  the 
summit,  shallow  at  first,  but  getting  deeper  as  they  descend,  and  be- 
coming at  the  same  time  more  numerous,  as  in  the  cones  of  Java 
before  mentioned. 

So  unbroken  is  the  precipitous  boundary-wall  of  the  Caldera,  ex- 
cept at  its  southwestern  end,  where  the  torrent  which  drains  it 
through  a  deep  gorge  (6,  &',  fig.  696)  issues,  that  there  is  not  even  a 
footpath  by  which  one  can  descend  into  it  save  at  one  place  called 
the  Cumbrecito  (e,  map,  fig.  695).  This  Cumbrecito  is  a  narrow 
col  or  watershed  at  the  height  of  about  2000  feet  above  the  bot- 


Fw&ncaliente  Pt. 


Map  of  Palma,  from  Survey  of 
Capt.Vidal,K.N. 


*  See  Hartung,  Geology  of  Madeira  and  Porto  Santo.     Leipzig, 


CH.  XXIX.] 


CALDERA  OF  PALMA. 

Fig.  696. 


629 


Map  of  the  Caldera  of  Palma  and  the  great  ravine,  called  "  Barranco  de  las  Angnstias."    From 
the  Survey  of  Capt.  Vidal,  E.  N.,  1837.    Scale,  two  geographical  miles  to  an  inch. 

torn  of  the  Caldera,  and  4000  above  the  sea,  and  situated  at  the  pre- 
cise limit  of  two  geological  formations  presently  to  be  mentioned. 
This  col  also  occurs  at  the  level  where,  in  other  parts  of  the  Caldera, 
the  vertical  precipices  join  the  talus-like,  rocky  slope,  covered  with 
pines.  The  other  or  principal  entrance  by  which  the  Caldera  is 
drained  is  the  great  ravine  or  barr-anco,  as  it  is  called  (see  6,  b',  fig. 
696),  which  extends  from  the  southwestern  extremity  of  the  Caldera 
to  the  sea,  a  distance  of  4^  geographical  miles,  in  which  space  the 
water  of  the  torrent  falls  about  1500  feet. 

This  sketch  (fig.  697)  was  taken  by  Yon  Buch  from  a  point  at  sea 
not  visited  by  us,  but  we  saw  enough  to  convince  us  that  several  late- 
ral cones  ought  to  have  been  introduced  on  the  great  slope  to  the 
left,  besides  numerous  deep  furrows  radiating  from  near  the  summit 
to  the  sea  (see  the  map,  fig.  696).  The  sea  does  not  enter  the  great 
Barranco,  as  might  be  inferred  from  this  sketch. 


630 


ISLAND  OF  PALMA. 

Fig.  697. 


[OH.  XXIX. 


Yiew  of  the  Isle  of  Palma,  and  of  the  entrance  into  the  central  cavity  or  Caldera. 
From  Von  Buch's  "  Canary  Islands." 

The  annexed  section  (fig.  698)  passes  through  the  island  from 
Santa  Cruz  de  Palrna  to  Briera  Point,  or  from  southeast  to  northwest 
(see  map,  p.  628).  It  has  been  drawn  up  on  a  true  scale  of  heights 
and  horizontal  distances  from  the  observations  of  Mr.  Hartung  and 
my  own. 

Fig.  698. 


Section  of  the  Island  of  Palma,  from  Point  Briera,  on  the  northwest,  to  Santa  Cruz  de  Palma, 

on  the  southeast.    See  map,  fig.  695,  p.  628. 
a,  &.  The  Caldera  (height  of  a,  6000  feet). 

c.  Commencement  of  steeper  dip. 

d.  Santa  Cruz  de  Palma  or  Tedote. 

e.  Lateral  cone,  3940  feet  above  the  sea  (Vidal's  Map). 
/  Briera  Point. 

g.  One  of  several  outliers  of  the  upper  formation  in  centre  of  Caldera. 
8.  P.  Half-buried  cone  and  crater  of  San  Pedro. 

The  lavas  are  seen  to  be  slightly  inclined  near  the  sea  at  Santa 
Cruz,  where  we  observed  them  flowing  round  the  cone  of  San  Pedro, 
which  they  have  more  than  half  buried  without  entering  the  crater. 
On  starting  from  the  same  part  of  the  seacoast,  and  ascending  the 
deep  Barranco  de  la  Madera,  we  saw  just  below  c  the  basaltic  lavas 
dipping  at  an  angle  of  5  degrees,  there  being  no  dikes  in  that  region. 
Farther  up,  where  the  dikes  were  still  scarce,  the  dip  of  the  beds 
increases  to  10  and  15  degrees,  and  they  become  still  steeper  as  they 
approach  the  Caldera  at  6,  where  dikes  abound. 

The  section  (fig.  699)  is  at  right  angles  to  the  preceding,  and  cuts 
through  the  cone  in  the  direction  of  the  great  Barranco,  or  from  north- 
east to  southwest. 

The  lowest  of  the  two  slanting  lines,  m,  «",  descending  from  the 
Caldera  to  the  sea  along  the  bottom  of  the  Barranco,  represents  the 
present  bed  of  the  torrent ;  the  upper  line,  &,  Z,  the  height  at  which 
beds  of  gravel,  elevated  high  above  the  present  river-channel,  are  visi- 
ble in  detached  patches,  shown  by  dotted  spaces  at  &,  and  to  the  south- 
west of  it,  on  the  same  slope.  These,  and  the  continuous  stratified 


CH.  XXIX,] 


SECTION  OF  ISLAND  OF  PALMA. 


631 


632  CALDERA  OF  PALMA.  [Cn.  XXIX. 

gravel  and  conglomerate  lower  down  at  I  and  i,  are  newer  than  all  the 
volcanic  rocks  seen  in  this  section. 

The  upper  volcanic  formation,  to  be  described  in  the  sequel,  is 
traversed  by  numerous  dikes,  which  could  not  be  expressed  on  this 
small  scale.  The  vertical  lines  in  the  lower  formation  represent  a  few 
of  the  perpendicular  dikes  which  abound  there.  Countless  others, 
inclined  and  tortuous,  are  found  penetrating  the  same  rocks.  The  five 
outliers  of  somewhat  pyramidal  shape,  at  the  bottom  of  the  Caldera 
(on  each  side  of  m),  agree  in  structure  and  composition  with  the  upper 
formation,  and  may  have  subsided  into  their  present  position,  if  the 
Caldera  was  caused  by  engulfment,  or  may  have  slid  down  in  the 
form  of  land-slips,  if  the  cavity  be  attributed  chiefly  to  aqueous 
erosion. 

In  the  description  above  given  of  the-  section1  (fig..  699),  the  cliffs 
which  wall  in  the  Caldera  are  spoken  of  as  consisting  of  two  forma- 
tions. Of  these  the  uppermost  alone  gives  rise  to  vertical  precipices, 
from  the  base  of  which  the  lower  descends  in  steep  slopes,  which, 
although  they  have  the  external  aspect  of  taluses,  are  not  in  fact  made 
up  of  broken  materials,  or  of  ruins  detached  from  the  higher  rocks,  but 
consist  of  rocks  in  place.  Both  formations  are  of  volcanic  origin,  but 
they  differ  in  composition  and  structure.  In  the  upper,  the  beds  con- 
sist of  agglomerate,  scoriae,  lapilli,  and  lava,  chiefly  basaltic,  the  whole 
dipping  outwards,  as  if  from  the  axis  of  the  original  cone,  at  angles 
varying  from  10  to  28  degrees.  The  solid  lavas  do  not  constitute 
more  than  a  fourth  of  the  entire  mass,  and  are  divided  into  beds  of 
very  variable  thickness,  some  scoriaceous  and  vesicular,  others  more 
compact,  and  even  in  some  cases  rudely  columnar.  All  these  more 
stony  masses  are  seen  to  thin  out  and  come  to  an  end  wherever  they 
can  be  traced  horizontally  for  a  distance  of  half  or  a  quarter  of  a  mile, 
and  usually  sooner.  Coarse  breccias  or  agglomerates  predominate  in 
the  lower  part,  as  if  the  commencement  of  the  second  series  of  rocks 
marked  an  era  of  violent  gaseous  explosions.  Single  beds  of  this 
aggregate  of  angular  stones  and  scoriae  attain  a  thickness  of  from  200 
to  300  feet.  They  are  united  together  by  a  paste  of  volcanic  dust  or 
spongiform  scoriae. 

At  one  point  on  the  right  side  of  the  great  Barranco,  near  its  exit 
from  the  Caldera,  we  observed  in  the  boundary  precipice  a  lofty 
column  of  amorphous  and  scoriaceous  rock  in  which  the  red  or  rust- 
colored  scoriae  are  as  twisted  and  ropy  as  any  to  be  seen  on  the  slopes 
of  Vesuvius ;  seeming  to  imply  that  there  was  here  an  ancient  vent  or 
channel  of  discharge  subsequently  buried  under  the  products  of  newer 
eruptions.  Countless  dikes,  more  or  less  vertical,  consisting  chiefly  of 
basaltic  lava,  traverse  the  walls  of  the  Caldera,  some  of  them  terminat- 
ing upwards,  but  a  great  number  reaching  the  very  crest  of  the  ridge, 
and  therefore  having  been  posterior  in  origin  to  the  whole  precipice. 

We  could  not  discover  in  any  one  of  the  fallen  masses  of  agglom- 
erate which  strewed  the  base  of  the  cliffs  a  single  pebble  or  water-worn 


CH.  XXIX.]  CALDERA  OF  PALMA.  633 

fragment.  Each  imbedded  stone  is  either  angular,  or,  if  globular,  con- 
sists of  scoriae  more  or  less  spongy,  and  evidently  not  owing  its  shape 
to  attrition.  It  would  be  impossible  to  account  for  the  absence  of 
water-worn  pebbles  if  the  coarse  breccia  in  question  had  been  spread 
by  aqueous  agency  over  a  horizontal  area  coextensive  with  the  Caldera 
and  the  volcanic  rocks  which  surround  it.  The  only  cause  known  to 
us  capable  of  dispersing  such  heavy  fragments,  some  of  them  3,  4,  or 
or  6  feet  in  diameter,  without  blunting  their  edges,  is  the  power  of 
steam,  unless  indeed  we  could  suppose  that  ice  had  cooperated  with 
water  in  motion ;  and  the  interference  of  ice  cannot  be  suspected  in 
this  latitude  (28°  40'),  especially  as  I  looked  in  vain  for  signs  of 
glacial  action  here  and  in  the  other  mountainous  regions  of  the 
Canary  Islands. 

The  lower  formation  of  the  Caldera  is,  as  before  stated,  equally  of 
igneous  origin.  It  differs  in  its  prevailing  color  from  the  upper,  ex- 
hibiting a  tea-green  and  in  parts  a  light  yellow  tint,  instead  of  the 
usual  brown,  lead-colored,  or  reddish  hues  of  basalt  and  its  associated 
seorice.  Beds  of  a  light  greenish  tuff  are  common,  together  with  tra- 
chytic  and  greenstone  rocks,  the  whole  so  reticulated  by  dikes,  some 
vertical,  others  oblique,  others  tortuous,  that  we  found  it  impossible 
to  determine  the  general  dip  of  the  beds,  although  at  the  head  of  the 
great  gorge  or  Barranco  they  certainly  dip  outwards,  or  to  the  south, 
as  stated  by  Von  Bach.  But  in  following  the  section  down  the  same 
ravine,  where  the  mountain  called  Alejanado  (d,  figs.  pp.  628  and  631) 
is  cut  through,  and  where  the  rocks  of  the  lower  formation  are  very 
crystalline,  we  found  what  is  not  alluded  to  by  the  Prussian  geologist, 
that  the  beds  e-xposed  to  view  in  cliffs  1500  feet  high  have  an  anticli- 
nal arrangement,  exhibiting  first  a  southerly  and  then  a  northerly  dip 
at  angles  varying  from  20  to  40  degrees  (see  section,  fig.  699,  at  k). 
Hence  we  may  presume  that  the  older  strata  must  have  undergone 
great  movements  before  the  upper  formation  was  superimposed.  No 
organic  remains  having  been  discovered  in  the  older  series,  we  can- 
not positively  decide  whether  it  was  of  subaerial  or  submarine  origin. 
We  can  only  affirm  that  it  has  been  produced  by  successive  eruptions, 
chiefly  of  felspathic  lavas  and  tuffs.  Many  beds  which  probably  con- 
sisted at  first  of  soft  tuffs  have  been  much  hardened  by  the  contact  of 
dikes  and  apparently  much  altered  by  other  plutonic  influence,  so  that 
they  have  acquired  a  semicrystalline  and  almost  metamorphic  char- 
acter. 

The  existence  of  so  great  a  mass  of  volcanic  rocks  of  ancient  date 
on  the  exact  site  of  an  equally  vast  accumulation  of  comparatively 
modern  lavas  and  scoriae  is  peculiarly  worthy  of  notice  as  a  general 
phenomenon  observed  in  very  different  parts  of  the  globe.  It  proves 
that,  notwithstanding  the  fact  in  the  past  history  of  volcanoes  that 
one  region  after  another  has  been  for  ages  and  has  then  ceased  to  be 
the  chief  theatre  of  igneous  action,  still  the  activity  of  subterranean 
heat  may  often  be  persistent  for  more  than  one  geological  period  in 


634:  CALDERA   OF  PALMA.  [Cn.  XXIX. 

the  same  place,  relaxing  perhaps  its  energies  for  a  while,  but  then 
breaking  out  afresh  with  an  intensity  as  great  as  ever. 

We  have  still  to  consider  the  mode  of  origin  of  the  higher  volcanic 
mass,  or  the  upper  series  of  rocks  with  which  the  peculiar  form  of  the 
Caldera  is  more  intimately  connected.  The  principal  question  here 
arising  is  this,  whether  the  mass  was  dome-shaped  from  the  beginning, 
having  grown  by  the  superposition  of  one  conical  envelope  of  lava 
and  ashes  formed  over  another,  or  whether,  as  Von  Buch  and  his  fol- 
lowers imagine,  its  component  materials  were  first  spread  out  in  hori- 
zontal or  nearly  horizontal  deposits  and  then  upheaved  at  once  into  a 
dome-shaped  mountain  with  a  caldera  in  its  centre.  According  to  the 
first  hypothesis  the  cone  was  built  up  gradually,  and  completed  with 
all  its  beds  dipping  as  now,  and  traversed  by  all  its  dikes,  before  the 
Caldera  originated.  According  to  the  other,  the  Caldera  was  the 
result  of  the  same  movements  which  gave  a  dome-shaped  structure  to 
the  mass,  and  which  caused  the  beds  to  be  highly  inclined ;  in  other 
words,  the  cone  and  the  Caldera  were  produced  simultaneously.  So 
singularly  opposite  are  these  views,  that  the  principal  agency  intro- 
duced by  the  one  theory  is  upheaval,  by  the  other  the  fall  of  matter 
from  the  air.  The  very  name  of  "  Elevation  Craters  "  points  to  the 
kind  of  movement  to  which  one  school  attributes  the  origin  of  a  cone 
and  caldera ;  whereas  the  chief  agencies  appealed  to  by  the  other  are 
gaseous  explosions,  engulfment,  and  aqueous  denudation. 

The  favorable  reception  of  the  doctrine  of  upheaval  has  arisen  from 
the  following  circumstances :  Streams  of  lava,  it  i&  said,  which  run 
down  a  declivity  of  more  than  three  degrees,  are  never  stony ;  and, 
if  the  slope  exceed  five  or  six  degrees,  they  are  mere  shallow  and 
narrow  strings  of  vesicular  or  fragmentary  slag.  Whenever,  therefore, 
we  find  parallel  layers  of  stony  lava,  especially  if  they  be  of  some  thick- 
ness, high  up  in  the  walls  of  a  caldera,  we  may  be  sure  that  they  were 
solidified  originally  on  a  very  gentle  slope ;  and  if  they  are  now  in- 
clined at  angles  of  10°,  20°,  or  30°,  not  only  they,,  but  all  the  inter- 
stratified  beds  of  lapilli,  scoriae,  tuff,  and  agglomerate,  must  have 
been  at  first  nearly  flat,  and  must  have  been  afterwards  lifted  up  with 
the  solid  beds  into  their  present  position.  It  is  supposed  that  such 
a  derangement  of  the  strata  could  scarcely  fail  to  give  rise  to  a  wide 
opening  near  the  centre  of  upheaval,  and  in  the  case  of  Palma,  the 
Caldera  (which  Von  Buch  called  "  the  hollow  axis  of  the  cone  ")  may 
represent  this  breach  of  continuity. 

Among  other  objections  to  the  elevation-crater  theory  often  ad- 
vanced and  never  yet  answered  are  the  following:  First,  in  most 
calderas,  as  in  Palma,  the  rim  of  the  great  cavity  and  the  circular 
range  of  precipices  surrounding  it  remain  entire  and  unbroken  on 
three  sides,  whereas  it  is  difficult  to  conceive  that  a  series  of  volcanic 
strata  2000  or  3000  feet  thick  could  have  once  extended  over  an  area 
six  or  seven  miles  in  its  shortest  diameter  and  then  have  been  upraised 
bodily,  so  that  the  beds  should  dip  at  steep  angles  towards  all  points 


CH.  XXIX.]  HYPOTHESIS  OF  UPHEAVAL.  635 

of  the  compass  from  a  centre,  and  yet  that  no  great  fractures  should 
have  been  produced.  We  should  expect  to  see  some  open  fissures  on 
every  side,  widening  as  they  approach  the  Caldera.  The  dikes,  it  is 
true,  do  undoubtedly  attest  many  dislocations  of  the  mass,  which  have 
taken  place  at  successive  and  often  distant  periods.  But  none  of  them 
can  have  belonged  to  the  supposed  period  of  terminal  and  paroxysmal 
upheaval,  for,  had  the  caldera  existed  when  they  originated,  the  melt- 
ed matter  now  solidified  in  each  dike  must,  instead  of  filling  a  rent, 
have  flowed  down  into  the  Caldera,  tending  so  far  to  obliterate  the 
great  cavity. 

The  second  objection  is  the  impossibility  of  imagining  that  so  vast 
a  series  of  agglomerates,  tuffs,  stratified  lapilli,  and  highly  scoriaceous 
lavas  could  have  been  poured  out  with  a  limited  area  without  soon 
giving  rise  to  a  hill,  and  eventually  to  a  lofty  mountain.  Such  heavy 
angular  fragments  as  are  seen  in  the  agglomerates,  single  beds  of  which 
are  sometimes  200  or  300  feet  thick,  must,  when  hurled  into  the  air 
have  fallen  down  again  near  the  vent,  and  would  be  arranged  in  in- 
clined layers  dipping  outwards  from  the  central  axis  of  eruption.  It 
is  in  perfect  accordance  with  this  hypothesis  that  we  should  behold 
agglomerate,  lapilli,  and  scoriae  predominating  in  the  walls  of  the  Cal- 
dera ;  whereas  in  the  ravines  nearer  the  sea,  where  the  inclination  of 
the  beds  has  diminished  to  10  and  even  to  5  degrees,  the  proportion 
of  stony  as  compared  to  fragmentary  materials  is  precisely  reversed. 
It  is  also  natural  that  the  dikes  should  be  most  numerous  where  the 
ejectamenta  are  to  the  more  solid  beds  in  the  proportion  of  3  to  1,  as 
at  6,  fig.  698,  p.  630 ;  while  the  dikes  are  few  in  number  where  the 
stony  lavas  predominate  (as  at  c,  ibid.).  Many  of  the  scoriaceous  beds 
at  b  may  be  the  upper  extremities  of  currents  which  became  stony 
and  compact  when  they  reached  c,  and  flowed  over  a  more  level  coun- 
try ;  but  this  suggestion  cannot  be  assented  to  by  the  advocates  of  the 
upheaval  theory,  for  it  assumes  the  existence  of  a  cone  long  before  the 
time  had  arrived  for  the  catastrophe  which  according  to  their  views 
gave  rise  to  a  conical  mountain. 

If,  however,  we  reject  the  doctrine  that  the  beds  were  tilted  by  a 
movement  posterior  to  the  accumulation  of  all  the  compact  and  frag- 
mentary rocks,  how  are  we  to  account  for  the  steepness  of  the  dip  of 
some  stony  lavas  high  up  in  the  walls  of  the  Caldera  ?  These  masses 
are  occasionally  50  or  100  feet  thick,  of  lenticular  shape,  as  seen  in 
the  cliffs  from  below,  and  to  all  appearance  parallel  to  the  associated 
layers  of  scoriae  and  lapilli.  But  unfortunately  no  one  can  climb  up 
and  determine  how  far  the  supposed  parallelism  may  be  deceptive. 
The  solid  beds  extend  in  general  over  small  horizontal  spaces,  and 
some  of  them  may  possibly  be  no  other  than  intrusive  lavas,  in  the 
nature  of  dikes,  more  or  less  parallel  to  the  layers  of  ejectamenta. 
Such  lavas,  when  the  crater  was  full,  may  have  forced  their  way 
between  highly  inclined  beds  of  scoriae  and  lapilli.  We  know  that 
lava  often  breaks  out  from  the  side  or  base  of  a  cone,  instead  of  rising 


636  STONY  LAVAS  FORMED   ON  SLOPES.  [On.  XXIX. 

to  the  rim  of  the  crater.  Nevertheless  one  or  two  of  the  stony  masses 
alluded  to  seemed  to  me  to  resemble  lavas  which  had  flowed  out 
superficially.  They  may  have  solidified  on  a  broad  ledge  formed  by 
the  rim  of  a  crater.  Such  a  rim  might  be  of  considerable  breadth  after 
a  partial  truncation  of  the  cone.  And  some  lavas  may  now  and  then 
have  entirely  filled  up  the  atrium,  or  what  in  the  case  of  Somma  and 
Vesuvius  is  called  the  atrio  del  cavallo,  that  is  to  say,  the  interspace 
between  the  old  and  new  cone.  When  by  the  products  of  new  erup- 
tions a  uniform  slope  has  been  restored,  and  the  two  cones  have  blend- 
ed into  one  (see  e,  d,  c,  fig.  p.  645),  the  next  breaking  down  of  the  side 
of  the  mountain  may  display  a  mass  of  compact  rock  of  great  thickness 
in  the  walls  of  a  caldera,  resting  upon  and  covered  by  ejectamenta. 
Other  extensive  wedges  of  solid  lava  will  be  formed  on  the  flanks  of 
every  volcanic  mountain  by  the  Interference  of  lateral,  or,  as  they  are 
often  termed,  parasitic  cones,  which  check  or  stop  the  downward  flow 
of  lava,  and  occasionally  offer  deep  craters  into  which  the  melted  mat- 
ter is  poured. 

By  aid  of  one  or  all  the  processes  above  enumerated  we  may  cer- 
tainly explain  a  few  exceptional  cases  of  intercalated  stony  beds,  in 
the  midst  of  others  of  a  loose  and  scoriaceous  nature,  the  whole  being 
highly  inclined.  But  to  account  for  a  succession  of  compact  and  truly 
parallel  lavas,  having  a  steep  dip,  we  may  suppose  that  they  flowed 
originally  down  the  flanks  of  a  cone  sloping  at  angles  of  from  10  to 
15  degrees,  or  even  much  more,  as  in  many  active  volcanoes.  They 
may  also  have  acquired  subsequently  a  still  steeper  inclination,  for  it 
would  be  rash  to  assume  the  entire  absence  of  local  disturbances 
during  the  growth  of  a  volcanic  mountain.  Some  dikes  are  seen 
crossing  others  of  a  different  composition,  marking  a  distinctness  in 
the  periods  of  their  origin.  The  volume  of  rock  filling  such  a  multi- 
tude of  fissures  as  we  see  indicated  by  the  dikes  in  Palm  a  must  be 
enormous ;  so  that,  could  it  be  withdrawn,  the  mass  of  ejectamenta 
would  collapse  and  lose  both  in  height  and  bulk.  The  injection, 
therefore,  of  all  this  matter  in  a  liquid  state  must  have  been  attended 
by  the  gradual  distension  of  the  cone,  the  increase  of  which  I  have 
elsewhere  compared  both  to  the  exogenous  and  endogenous  growth 
of  a  tree,  as  it  has  been  affected  alike  by  external  and  internal  acces- 
sions. 

But  the  acquisition  of  a  steeper  dip  by  such  reiterated  rendings  and 
injections  of  a  cone  is  altogether  opposed  to  the  views  of  those  who 
defend  the  upheaval  hypothesis,  because  it  draws  with  it  the  conclu- 
sion that  the  slopes  were  always  growing  steeper  and  steeper  in  pro- 
portion as  the  cone  waxed  older  and  loftier.  Once  admit  this,  and  it 
follows  that  the  upper  layers  of  solid  lava  must  have  conformed  to 
surfaces  already  inclined  at  angles  of  20,  or,  in  the  case  of  the  Caldera 
of  Palma,  28  degrees. 

For  this  reason  the  defenders  of  the  upheaval  hypothesis  are  con- 
sistent with  themselves  in  assigning  the  whole  movement  by  which 


Gn.  XXIX.]  AQUEOUS  EROSION  IN  PALMA.  Qtf 

the  strata,  whether  solid  or  incoherent,  have  been  tilted,  exclusively  to 
one  terminal  catastrophe.  The  whole  development  of  subterranean 
force  is  represented  as  the  last  incident  in  every  series  of  volcanic 
operations,  the  closing  scene  of  the  drama ;  and  the  sudden  and  par- 
oxysmal nature  of  the  catastrophe  is  inferred  from  the  absence  of  all 
signs  of  successive  and  intermittent  action  so  characteristic  of  the  ante- 
cedent volcanic  phenomena. 

I  have  alluded  to  an  opinion  entertained  by  some  able  geologists, 
that  no  lava  can  acquire  any  degree  of  solidity  if  it  flows  down  a 
declivity  of  more  than  three  degrees.  This  doctrine  I  have,  I  think, 
proved  in  my  memoir  on  Mount  Etna  *  to  be  entirely  erroneous.  I 
have  there  shown,  from  observations  made  by  me  in  1857,  that  mod- 
ern lavas,  several  of  them  of  known  date,  have  formed  continuous 
beds  of  compact  stone  on  slopes  of  15,  36,  and  38  degrees,  and,  in  the 
case  of  the  lava  of  1852,  more  than  40  degrees.  The  thickness  of 
these  tabular  layers  varies  from  1-J  foot  to  26  feet ;  and  their  planes  of 
stratification  are  parallel  to  those  of  the  overlying  and  underlying 
scoriae  which  form  part  of  the  same  currents. 

There  are  some  lavas  northeast  of  Fuencaliente,  at  the  southern 
extremity  of  Palma,  so  modern  as  to  be  still  black  and  uncovered 
with  vegetation,  which  descend  slopes  of  no  less  than  22  degrees,  and 
yet  contain  large  masses  of  compact  stone,  formed  chiefly  on  the  sides 
of  tunnel-shaped  cavities,  15  or  20  feet  deep,  in  which  one  layer  has 
solidified  within  another  on  the  walls  of  these  channels,  while  in  the 
central  part  the  lava  seems  to  have  remained  fluid  so  as  to  run  out 
of  the  tunnel,  leaving  an  arched  cavity,  the  roof  of  which  has  in  most 
cases  fallen  in.  The  strength  of  the  enveloping  crust  of  scoriae  at  the. 
lower  end  of  a  lava-current  in  which  one  of  these  tunnels  existed,  may 
have  been  sufficient  to  arrest  the  progress  of  the  stream  for  hours  or 
days,  and  during  that  time  solidification  may  have  occurred  under 
great  hydrostatic  pressure. 

Before  taking  leave  of  Palma,  we  have  yet  to  consider  another  dis- 
tinct point,  namely,  what  amount  of  denudation  has  taken  place  in  the 
Caldera  and  its  environs.  Assuming  that  the  great  cavity  or  some 
part  of  it  may  have  originated  in  the  truncation  of  a  cone  in  the  man- 
ner before  suggested,  to  what  extent  has  its  shape  been  subsequently 
enlarged  or  modified  by  aqueous  erosion?  It  will  be  remembered 
that  a  conglomerate  of  well-rounded  pebbles,  no  less  than  800  feet 
thick,  was  spoken  of  as  visible  in  the  great  Barranco  (see  description 
of  section,  pp.  630-632).  That  conspicuous  deposit,  3  or  4  miles  in 
length,  was  evidently  derived  from  the  destruction  of  rocks  like  those 
in  the  Caldera,  for  the  present  torrent  brings  down  annually  similar 
stones  of  every  size,  some  very  large,  and  rounds  them  by  attrition  in 
its  channel.  By  what  changes  in  the  configuration  of  the  island  after 
the  old  volcano  and  its  Caldera  were  formed  was  so  vast  a  thickness  of 

*  Phil.  Trans.  1858. 


638  AQUEOUS  EROSION   IN  PALMA.  [On.  XXIX. 

gravel  formed,  to  be  afterwards  cut  through  to  a  depth  of  800  feet  ? 
The  ravine  through  which  the  torrent  now  flows  has  been  excavated 
to  that  depth  through  the  old  conglomerate.  The  occurrence  of  two 
or  three  layers  of  contemporaneous  lava,  intercalated  between  the  strata 
of  puddingstone,  ought  not  to  surprise  us ;  for  even  in  historical  times 
eruptions  have  been  witnessed  in  the  southern  half  of  Palma.  Such 
basaltic  lavas,  one  of  them  columnar  in  structure,  had  not  come  down 
from  the  Caldera,  but  from  cones  much  nearer  the  sea,  and  immediately 
adjoining  the  Barranco,  like  the  cone  of  Argual  (see  map,  p.  629)  and 
others.  These  lavas,  of  the  same  age  as  the  conglomerate,  consist  of 
three  or  four  currents  of  limited  extent,  for  in  many  parts  of  the  river- 
cliffs  no  volcanic  formation  is  visible  on  either  bank.  On  the  right 
bank  of  the  Barranco,  the  conglomerate,  when  traced  westward,  is  soon 
found  to  come  to  an  end  as  it  abuts  against  the  lofty  precipice  E  (fig. 

Fig.  TOO. 
West 


A.  Eavine  or  Barranco  de  las  Angustias,  near  its  termination  in  Palma. 

&,  &',  6".  Conglomerata,  800  feet  thick  in  parts. 

c,  c'.  Lava  intercalated  between  the  beds  of  conglomerate. 

<?,  df.  Another  and  older  current  of  basaltic  lava,  columnar  in  parts. 

E.  Cliff  of  ancient  volcanic  rocks  of  the  Upper  Formation  (p.  634),  a  prolongation  of 

the  western  wall  of  the  Caldera. 

F.  Platform  on  which  the  town  of  Argual  stands. 

700),  which  is  a  prolongation  of  the  western  wall  of  the  Caldera.  Its 
extent  eastward  from  6,  may  be  more  considerable,  but  cannot  be 
ascertained,  as  it  is  concealed  under  modern  scoriae  and  lava  spread 
over  the  great  platform,  r. 

As  we  could  find  no  organic  remains  in  the  old  gravel,  we  have  no 
positive  means  of  deciding  whether  it  be  fluviatile  or  marine.  The 
height  of  its  base  above  the  sea,  where  it  is  800  feet  thick,  may  be 
about  350  feet,  but  patches  of  it  ascend  to  elevations  of  1000  and 
1500  feet  near  the  top  of  the  Barranco,  as  shown  at  &,  &c.,  in  section, 
fig.  699  p.  631.  Such  a  mass  of  gravel,  therefore,  bears  testimony 
to  the  removal  of  a  prodigious  amount  of  materials  from  the  Caldera 
by  the  action  of  water.  Whatever  may  have  been  the  mode  of 
transportation,  it  is  obvious  that  a  large  portion  of  the  volcanic  mate- 
rials, consisting  of  sand,  lapilli,  and  scoriae,  before  described  (p.  632) 
as  belonging  to  the  upper  formation  in  the  Caldera,  would  leave 
behind  them  few  pebbles.  Nearly  all  of  these  perishable  deposits 


CH.  XXIX.]  AQUEOUS   EROSION  IN  PALMA.  639 

would  be  swept  down  in  the  shape  of  mud  into  the  Atlantic.  Even 
the  hard  rounded  stones,  since  they  were  once  angular  and  are  now 
ground  down  into  pebbles,  must  have  lost  more  than  half  their  original 
bulk,  and  bear  witness  to  large  quantities  of  sedimentary  matter  con- 
signed to  the  bed  of  the  ocean.  We  saw  in  the  Caldera  blocks  of 
huge  size  thrown  down  by  cascades  from  the  upper  precipices  during 
the  melting  of  the  snows,  a  fortnight  before  our  visit,  and  much  de- 
struction was  likewise  going  on  in  the  lower  set  of  rocks  by  the  same 
agency.  We  also  learned  that  a  great  flood  rushed  down  the  Barranco 
in  the  spring  of  1854,  shortly  before  our  arrival,  damaging  several 
houses  and  farms,  and  I  have  therefore  no  doubt  that  the  erosive 
power  even  of  rain  and  river  water,  aided  by  earthquakes,  might  in 
the  course  of  ages  empty  out  a  valley  as  large  as  the  Caldera,  although 
probably  not  of  the  same  shape.  I  am  disposed  to  attribute  the  cir- 
cular range  of  cliffs  surrounding  the  Caldera  to  volcanic  action,  be- 
cause they  forcibly  reminded  me  of  the  precipices  encircling  three 
sides  of  the  Val  del  Bove,  on  Etna ;  and  because  they  agree  so  well 
with  Junghuhn's  description  of  the  "  old  crater-walls  "  of  active  vol- 
canoes in  Java,  some  of  which  equal  or  surpass  in  dimensions  even 
the  Caldera  of  Palma.  The  latter  may  have  consisted  at  first  of  a  true 
crater,  enlarged  afterwards  into  a  caldera  by  the  partial  destruction  of 
a  great  cone ;  but,  if  so,  it  has  certainly  been  since  modified  by  denu- 
dation. Nor  can  any  geologist  now  define  how  much  of  the  work  has 
been  accomplished  by  aqueous,  and  how  much  by  volcanic  agency.  The 
phenomenon  of  a  river  cutting  its  channel  through  a  dense  mass  of 
ancient  alluvium  formed  during  oscillations  in  the  level  of  the  land  is 
not  confined  to  volcanic  countries,  and  I  need  not  dwell  here  on  its 
interpretation,  but  refer  to  what  was  said  in  the  seventh  chapter. 
(See  p.  84.) 

There  remains,  however,  another  question  of  high  theoretical 
interest;  namely,  whether  the  denudation  was  marine  or  fluviatile. 
It  was  stated  that  the  materials  of  the  great  cone  or  assemblage  of 
cones  in  the  north  of  Palma  are  of  subaerial  origin,  as  proved  by  the 
angularity  of  the  fragments  of  rock  in  the  agglomerates ;  but  it  may 
be  asked,  whether,  when  the  Caldera  was  formed  long  afterwards,  it 
may  not,  like  the  crater  of  St.  Paul's  (fig.  702,  p.  643),  have  had  a 
communication  with  the  sea,  which  may  have  entered  by  the  great 
Barranco,  and  if,  after  a  period  of  partial  submergence,  the  island  may 
not  then  have  risen  again  to  its  original  altitude.  In  such  a  case  the 
retiring  waters  might  leave  behind  them  a  conglomerate,  partly  of 
river-pebbles,  collected  at  the  points  where  the  torrent  successively 
entered  the  sea,  and  partly  of  stones  rounded  by  the  waves.  The 
torrent  may  have  finally  cut  a  deep  ravine  in  the  gravel  and  associated 
lavas  when  the  land  was  rising  again.  Such  oscillations  of  level, 
amounting  to  more  than  2000  feet,  would  not  be  deemed  improbable 
by  any  geologists,  provided  they  enable  us  to  explain  more  naturally 
than  by  any  other  causation,  the  origin  of  the  physical  outlines  of  the 


640  AQUEOUS  EROSION  IN  PALMA.  [On.  XXIX. 

country.  As  to  the  fact  that  no  marine  shells  have  yet  been  dis- 
covered in  the  conglomerate,  sufficient  search  has  not  yet  been  made 
for  them  to  entitle  us  to  found  an  argument  on  such  negative  evidence. 
At  the  same  time  I  confess  that,  having  found  sea-shells  and  bryozoa 
abundantly  in  certain  elevated  marine  conglomerates  in  the  Grand 
Canary,  before  I  visited  Palma,  and  being  unable  to  meet  with  any  in 
the  Barranco  de  las  Angustias,  I  regarded  the  old  gravel  when  I  was 
on  the  spot  as  of  fluviatile  origin.  Such  inferences  are  always  doubt- 
ful in  the  absence  of  more  positive  data,  and  the  intervention  of  the 
sea  might  perhaps  account  for  some  phenomena  in  the  configuration 
of  the  Caldera  and  Barranco  more  naturally  than  river  action.  For 
example,  we  have  the  lofty  cliff  E,  fig.  TOO,  p.  638,  already  mentioned, 
and  c,/,  map,  p.  628,  extending  four  or  five  miles  from  the  Caldera  to 
the  sea  on  the  right  bank  of  the  Barranco,  and  no  cliff  of  correspond- 
ing height  or  structure  on  the  other  bank,  where  for  miles  towards 
the  southeast  there  is  the  platform  r,  fig.  700,  p.  638,  supporting  sev- 
eral minor  volcanic  cones.  The  sea  might  be  supposed  to  leave  just 
such  a  cliif  as  E,  after  cutting  away  a  portion  of  the  southwestern  ex- 
tremity of  the  old  dome-shaped  mountain  in  the  north  of  Palma, 
whereas  a  torrent  or  river  might  be  expected  to  leave  a  cliff  of  similar 
structure  and  nearly  equal  height  on  both.  As  to  the  fact  of  the  old 
conglomerate  ascending  an  inclined  plane,  z,  Z,  &,  p.  631,  from  the  sea- 
level  to  an  elevation  of  about  1500  feet,  near  the  entrance  of  the  Cal- 
dera, this  is  by  no  means  conclusive  in  favor  of  fluviatile  action, 
although  some  elevated  patches  of  the  same  may  in  truth  belong  to 
an  old  river-bed ;  but  in  South  America  gravel-beds  of  marine  origin 
have  a  similar  upward  slope,  when  followed  inland,  and  the  cause  of 
such  an  arrangement  has  been  explained  in  a  satisfactory  manner  by 
Mr.  Darwin.* 

Another  argument  in  favor  of  marine  denudation  may  be  derived 
from  that  peculiar  feature  in  the  configuration  of  Palma,  before  alluded 
to,  called  the  pass  of  the  Cumbrecito  (e,  fig.  699,  p.  631),  forming  a 
notch  in  the  uppermost  line  of  precipices  surrounding  the  Caldera. 
This  break  divides  the  mountain  called  Alejenado,  c?,  p.  631,  from  the 
eastern  wall,  e,  /,  and  cuts  quite  through  the  upper  formation  ;  yet  the 
range  of  precipice,  /,  e,  on  the  eastern  side  of  the  Caldera  is  continued 
uninterruptedly,  and  retains  its  full  height  of  1500  or  2000  feet  above 
its  base,  to  the  southward  of  the  Cumbrecito,  or  from  e  towards  a, 
map,  fig.  695,  p.  628.  In  this  prolongation  of  the  cliff  for  half  a  mile 
southward,  beds  of  volcanic  matter  and  dikes  are  seen,  as  in  the  walls 
of  the  Caldera. 

The  indentation  forming  the  pass  of  the  Cumbrecito,  e,  p.  631,  has 
more  the  appearance  of  an  old  channel,  such  as  a  current  of  water  may 
have  excavated,  than  of  a  rent  or  a  chasm  caused  by  a  fault.  In  case 
of  a  fault  the  lower  formation  would  not  be  persistent  and  uninter- 

*  Geolog.  Observ.,  South  America,  p.  43. 


CH.  XXIX.]  AQUEOUS  EROSION  IN  PALMA. 

rupted  across  the  Cumbrecito,  constituting  the  watershed ;  but  would 
have  sunk  down  and  have  been  replaced  by  the  upper  basaltic  rocks. 
If  we  could  assume  that  the  sea  once  entered  the  Caldera  here  as  well 
as  by  the  great  Barranco,  it  might  have  produced  such  a  breach  as  e, 
and  such  an  extension  of  the  line  of  cliffs  as  that  now  observable  be- 
tween e  and  «,  map,  p.  628,  without  any  corresponding  cliff  to  the 
westward  of  e,  a. 

Yet  we  could  discover  no  elevated  outliers  of  conglomerate  to  attest 
the  supposed  erosion  at  the  Cumbrecito,  which  is  about  3500  feet 
above  the  level  of  the  sea.  It  might  also  be  objected  to  the  hypothesis 
of  marine  denudation  in  Palm  a,  that  there  are  no  ranges  of  ancient 
sea-cliffs  on  the  external  slopes  of  the  island.  The  flanks  of  the 
mountain,  except  where  it  is  furrowed  by  ravines  or  broken  by  lateral 
cones,  descend  to  the  sea  with  a  uniform  inclination.  In  reply  to 
such  a  remark,  I  may  observe  that  we  do  not  require  the  submergence 
of  the  uppermost  3000  feet  of  the  old  cone  in  order  to  allow  the  sea 
to  enter  both  the  great  Barranco  and  the  Cumbrecito  and  to  flow  into 
the  Caldera.  It  would  be  enough  to  suppose  the  land  to  sink  down 
so  as  to  permit  the  waves  to  wash  the  base  of  the  basaltic  cliffs  in  the 
interior  of  the  Caldera,  and  to  wear  a  passage  through  the  Cumbrecito 
where  there  may  have  been  always  a  considerable  depression  in  the 
outline  of  the  upper  formation.  But  would  not  the  same  waves  which 
had  power  to  form  in  the  Barranco  a  mass  of  conglomerate  800  feet 
thick  have  left  memorials  of  their  beach-action  on  the  external  slope 
of  the  island?  No  such  monuments  are  to  be  seen,  and  their  absence 
raises  an  objection  of  no  small  weight  against  the  supposition  of  the 
sea  having  ever  entered  the  Caldera.  It  may,  however,  be  said,  in 
explanation,  first,  that  cliffs  are  not  so  easily  cut  on  the  side  of  an 
island  towards  which  the  beds  dip  as  on  the  side  from  which  they 
dip ;  secondly,  if  some  small  cliffs  and  sea-beaches  had  existed,  they 
may  have  been  subsequently  buried  under  showers  of  ashes  and 
currents  of  lava  proceeding  from  lateral  cones  during  eruptions  of  the 
same  date  as  those  which  were  certainly  contemporaneous  with  the 
conglomerate  of  the  great  Barranco. 

On  the  eastern  coast  of  Palma,  about  half  a  mile  from  the  sea,  in 
the  ravine  of  Las  Nieves,  not  far  from  Santa  Cruz,  we  observed  a  con- 
glomerate of  well-rounded  pebbles  having  a  thickness  of  100  feet,  cov- 
ered by  successive  beds  of  lava,  also  about  100  feet  thick.  In  this 
instance  the  ancient  gravel  beds  occupy  a  position  very  analogous  to 
the  buried  cone,  s,  p,  fig.  698,  p.  630.  When  in  Palma,  I  conceived 
them  to  be  of  fluviatile  origin ;  but,  whether  marine  or  freshwater,  it 
must  be  admitted  that  the  superposition  of  so  dense  an  accumulation 
of  lavas  to  a  mass  of  conglomerate  100  feet  thick  shows  how  easily 
the  outer  slopes  of  the  island  may  have  been  denuded  by  the  sea  and 
yet  display  no  superficial  signs  of  marine  denudation,  every  old  beach 
or  delta  once  at  the  mouth  of  a  torrent  being  concealed  under  newer 
volcanic  outpourings.  At  the  same  time  I  should  state  that  M. 
41 


642 


ISLAND   OF  ST.   PAUL. 


[Cn.  XXIX 


Hartung  and  I,  when  in  Palma,  came  to  the  conclusion  that  the  waves 
of  the  sea  had  never  reached  the  Caldera,  although  they  may  have 
penetrated  for  some  distance  into  the  Barranco  de  laa  Angustias,  and 
may  have  overflowed  the  space  now  overspread  by  certain  strata  of 
conglomerate  to  the  east  of  the  Barranco. 

Since  the  cessation  of  volcanic  action  in  the  north  of  Palma,  the 
most  frequent  eruptions  appear  to  have  taken  place  in  a  line  running 
north  and  south,  from  a  to  Fuencaliente,  map,  p.  628  ;  one  of  the 
volcanoes  in  this  range,  called  Yerigojo,  g,  being  no  less  than  6565 
English  feet  high.  The  lavas  descending  from  several  vents  in  this 
chain  reach  the  sea  both  on  the  east  and  west  coast,  and  are  many 
of  them  nearly  as  naked  and  barren  of  vegetation  as  when  they  first 
flowed.  The  tendency  in  volcanic  vents  to  assume  a  linear  arrange- 
ment, as  seen  in  the  volcanoes  of  the  Andes  and  Java  on  a  grand 
scale,  is  exemplified  by  the  cones  and  craters  of  this  small  range  in 
Palma.  It  has  been  conjectured  that  such  linearity  in  the  direction 
of  superficial  outbreaks  is  connected  with  deep  fissures  in  the  earth's 
crust  communicating  with  a  subjacent  focus  of  subterranean  heat. 

By  discussing  at  so  much  length  the  question  whether  the  sea  may 
or  may  not  have  played  an  important  part  in  enlarging  the  Caldera 


Fig.  701. 


Nine-pin 
Eock. 


Entrance  nearly  dry 
at  low  water. 


Map  of  the  Island  of  St  Paul,  in  the  Indian  Ocean,  lat.  83°  44'  S.,  long.  77°  3V  E., 
surveyed  by  Capt.  Blackwood,  E.  N.,  1842. 

of  Palma,  I  have  been  desirous  at  least  to  show  how  many  facts  and 
observations  are  required  to  explain  the  structure  and  configuration 


CH.  XXIX.] 


ISLAND   OF  ST.   PAUL— TENERIFFE. 


643 


of  such,  volcanic  islands.  It  may  be  useful  to  cite,  in  illustration  of 
the  same  subject,  the  present  geographical  condition  of  St.  Paul's  or 
Amsterdam  Island,  in  the  Indian  Ocean,  midway  between  the  Cape 
of  Good  Hope  and  Australia. 

In  this  case  the  crater  is  only  a  mile  in  diameter,  and  180  feet 
deep,  and  the  surrounding  cliffs  were  loftiest  about  800  feet  high,  so 
that  in  regard  to  size  such  a  cone  and  crater  are  insignificant  when 
compared  to  the  cone  and  Caldera  of  Palma  or  to  such  volcanic 
domes  as  Mounts  Loa  and  Kea  in  the  Sandwich  Islands.  But  the 
Island  of  St.  Paul  exemplifies  a  class  of  insular  volcanoes  into  which 
the  ocean  now  enters  by  a  single  passage.  Every  crater  must  almost 


Fig.  702. 


View  of  the  Crater  of  the  Island  of  St.  Paul. 
Fig.  703. 


Side  view  of  the  Island  of  St.  Paul  (N.  E.  side).    Nine-pin  Eocks  two  miles  distant 
(Captain  Blackwood.) 

invariably  have  one  side  much  lower  than  all  the  others,  namely,  that 
side  towards  which  the  prevailing  winds  never  blow,  and  to  which, 
therefore,  showers  of  dust  and  scoriae  are  rarely  carried  during  erup- 
tions. There  will  also  be  one  point  on  this  windward  or  lowest  side 
more  depressed  than  all  the  rest,  by  which,  in  the  event  of  a  partial 
submergence,  the  sea  may  enter  as  often  as  the  tide  rises,  or  as  often 
as  the  wind  blows  from  that  quarter.  For  the  same  reason  that  the 
sea  continues  to  keep  open  a  single  entrance  into  the  lagoon  of  an 
atoll  or  annular  coral  reef,  it  will  not  allow  this  passage  into  the  cra- 
ter to  be  stopped  up,  but  will  scour  it  out  at  low  tide,  or  as  often  as 
the  wind  changes.  The  channel,  therefore,  will  always  be  deepened 
in  proportion  as  the  island  rises  above  the  level  of  the  sea,  at  the  rate 
perhaps  of  a  few  feet  or  yards  in  a  century. 


6M- 


VIEW  OF  PEAK  or  TENERIFFE. 


[Cn.  XXIX. 


CH.  XXIX.  1  PEAK  OF  TENERIFFE. 

The  crater  of  Vesuvius  in  1822  was  2000  feet  deep;  and,  if  it 
were  a  half-submerged  cone  like  St.  Paul,  the  excavating  power  of 
the  ocean  might,  in  conjunction  with  a  gradual  upheaving  force,  give 
rise  to  a  large  caldera.  Whatever,  therefore,  may  have  been  the 
nature  of  the  forces,  igneous  or  aqueous,  which  have  shaped  out  the 
Val  del  Bove  on  Etna,  or  the  deep  abyss  called  the  Caldera  in  the 
north  of  Palma,  we  may  well  conceive  that  some  craters  may  have 
been  enlarged  into  calderas  by  the  denuding  power  of  the  ocean, 
whenever  considerable  oscillations  in  the  relative  level  of  land  and  sea 
have  occurred. 

Peak  of  Teneriffe.  —  The  accompanying  view  of  the  Peak,  taken 
from  sketches  made  by  M.  Hartung  and  myself  during  our  visit  to 
Teneriffe  in  1854,  will  show  the  manner  in  which  that  lofty  cone  is 
encircled  on  more  than  two  sides  by  what  I  consider  as  the  ruins  of 
an  older  cone,  chiefly  formed  by  eruptions  from  a  summit  which  has 
disappeared.  That  ancient  culminating  point  from  which  one  or 
more  craters  probably  poured  forth  their  lavas  and  ejectamenta  may 
not  have  been  placed  precisely  where  the  present  peak  now  rises,  and 
may  not  have  had  the  same  form,  but  its  position  was  probably  not 
materially  different.  The  great  wall  or  semicircular  range  of  preci- 
pices, c,  c,  surrounding  the  atrium,  6,  6,  is  obviously  analogous  to  the 
walls  of  a  Caldera  like  that  of  Palma  ;  but  here  the  cliffs  are  insig- 
nificant in  dimensions  when  compared  to  those  in  Palma,  being  in 
general  no  more  than  500  feet  high  and  rarely  exceeding  1000  feet. 
The  plain  or  atrium,  6,  6,  figs.  704  and  705,  lying  at  the  base  of  the 
cliffs,  is  here  called  Las  Canadas,  and  is  covered  with  sand  and  pum- 
ice thrown  out  from  the  Peak  or  from  craters  on  its  flanks.  Copious 
streams  of  lava,  d,  d,  have  also  flowed  down  from  lateral  openings, 
especially  from  a  crater  called  the  Chahorra,  /,  fig.  705,  which  is  not 
seen  in  the  view,  fig.  704,  as  it  is  hidden  by  the  Peak.  The  last 
eruption  was  as  late  as  the  year  1798. 

Fig.  705. 

• 

***V. 
Guia. 


Section  through  part  of  Teneriffe,  from  N.E.  to  S.W.    On  a  true  scale  ;  as  given  in 

Von  Buch's  "  Canary  Islands." 

a.  Peak  of  Teneriffe.  d.  Modern  lavas. 

&.  The  Canadas  or  atrium.  /.  Cone  and  crater  of  Chahorra. 

c.  Cliff  bounding  the  atrium. 

To  what  extent  the  lavas,  d,  d,  figs.  704  and  705,  may  have  nar- 
rowed the  circus  or  atrium,  b,  or  taken  away  from  the  height  of  the 
cliff,  0,  no  geologist  can  determine  for  want  of  sections  ;  but  should 
the  Peak  and  the  Chahorra  continue  to  be  active  volcanoes  for  ages, 
the  new  cone,  a,  might  become  united  with  the  old  one,  and  the  lava 


646  ISLAND  OF  MADEIRA.  [Cn.  XXIX. 

might  flow  first  from  e  to  c,  and  then  from  a  to  c,  fig.  705,  so  that  the 
slope  might  begin  to  resemble  that  formed  by  lavas  and  ejectamenta 
from  the  summit  a  to  Guia,  on  the  southwestern  side  of  the  cone. 

Madeira. — Every  volcanic  island,  so  far  as  I  have  examined  them, 
varies  from  every  other  one  in  the  details  of  its  geographical  and 
geological  structure  so  greatly  that  I  have  no  expectation  of  finding 
any  simple  hypothesis,  like  that  of  "  elevation  craters,"  applicable  to 
all,  or  capable  of  explaining  their  origin  and  mode  of  growth.  Few 
islands,  for  example,  resemble  each  other  more  than  Madeira  and 
Palma,  inasmuch  as  both  consist  mainly  of  basaltic  rocks  of  subaerial 
origin,  but,  when  we  compare  them  closely  together,  there  is  no  end 
to  the  points  in  which  they  differ. 

The  oldest  formation  known  in  Madeira  is  of  submarine  volcanic 
origin,  and  referable  to  the  Upper  Miocene  tertiary  epoch,  as  will  be 
explained  in  Chap.  XXXI.,  p.  665.  To  this  formation  belong  the  tuffs 
and  limestones  containing  marine  shells  and  corals  which  occur  at  S. 
Vicente  on  the  northern  coast,  where  they  rise  to  the  height  of  more 
than  1300  feet  above  the  sea.  They  bear  testimony  to  an  upheaval  to 
that  amount,  at  least  since  the  commencement  of  volcanic  action  in 
those  parts. 

The  pebbles  in  these  marine  beds  are  well  rounded  and  polished, 
strongly  contrasting  in  that  respect  with  the  angular  fragments  of 
similar  varieties  of  volcanic  rocks  so  frequent  in  the  superimposed  tuffs 
and  agglomerates  formed  above  the  level  of  the  sea. 

The  length  of  Madeira  from  east  to  west  is  about  30  miles,  its 
greatest  breadth  from  north  to  south  being  12  miles.  The  annexed 
section,  fig.  705,  drawn  upon  a  true  scale  of  heights  and  horizontal 
distances  from  the  observations  of  M.  Hartung  and  myself,  will  enable 
the  reader  to  comprehend  some  of  the  points  in  which,  geologically 
considered,  Madeira  resembles  or  varies  from  Palma.  In  the  central 
region,  at  A,  as  well  as  in  the  adjoining  region  on  each  side  of  it,  are 
seen,  as  in  the  centre  of  Palma,  a  great  number  of  dikes  penetrating 
through  a  vast  accumulation  of  ejectamenta,  c.  Here  also,  as  in 
Palma,  we  observe  as  we  recede  from  the  centre,  that  the  dikes 
decrease  in  number,  and  beds  of  scoriae,  lapilli,  agglomerate,  and  tuff 
begin  to  alternate  with  stony  lavas,  d,  d,  until  at  the  distance  of  a  mile 
or  more  from  the  central  axis  the  volcanic  mass,  below/,  A,  and  e,  g, 
consists  almost  exclusively  of  streams  or  sheets  of  basalt,  with  many 
red  partings  of  laterite  or  red  ochreous  clay.  These  red  beds  vary  in 
thickness  from  a  few  inches  to  two  or  three  feet,  and  consist  sometimes 
of  layers  of  tuff,  sometimes  of  ancient  soils  derived  from  decomposed 
lava,  both  of  them  burnt  to  a  brick-red  color,  and  altered  by  the  contact 
of  melted  matter  which  has  flowed  over  them.  Some  of  these  bands 

are  represented  in  fig.  706,  by  interrupted  lines, .  The  darker 

divisions  with  vertical  cross-bars  ||||!l|j|||lH!ii||  indicate  lavas  which  originally 
flowed  on  the  surface.  Had  there  been  room,  many  more  alternations 
of  such  lavas  would  have  been  introduced.  They  consist  chiefly  of 


CH.  XXIX.]  ISLAND   OF  MADEIRA.  64t 

basalts  more  or  less  vesicular,  and  in  some  places  of  trachyte.  The 
lighter  tint,  c,  expresses  an  accumulation  of  scoriae,  agglomerate,  and 
other  materials,  such  as  may  have  been  piled  up  in  the  open  air,  in  or 
around  the  chief  orifices  of  eruption,  and  between  volcanic  cones.  This 
older  formation,  though  represented  by  an  uniform  tint,  is  by  no  means 
an  amorphous  mass,  but  is  separated  into  innumerable  layers  which 
dip  towards  all  points  of  the  compass,  so  that  their  mode  of  arrange- 
ment could  not  be  expressed  in  a  small  diagram. 

The  Pico  Torres,  A,  more  than  6000  feet  high,  is  one  of  many 
central  peaks,  composed  of  ejected  materials.  By  the  union  of  the 
foundations  of  many  similar  peaks,  ridges  or  mountain  crests  are 
formed,  from  which  the  tops  of  vertical  dikes  project  like  turrets  above 
the  weathered  surface  of  the  softer  beds  of  tuff  and  scoriae.  Hence 
the  broken  and  picturesque  outline,  giving  a  singular  and  romantic 
character  to  the  scenery  of  the  highest  part  of  Madeira.  North  of  A 
is  seen  Pico  Ruivo  (B),  the  most  elevated  peak  in  the  island,  yet  ex- 
ceeding by  a  few  feet  only  the  height  of  Pico  Torres.  It  is  similar  in 
composition,  but  its  uppermost  part,  300  feet  high,  retains  a  more 
perfectly  conical  form,  and  has  a  dike  of  basalt  with  olivene  at  its 
summit,  with  streams  of  scoriaceous  lava  adhering  to  its  steep  flanks. 
There  are  a  great  many  such  peaks  east  and  west  of  A,  which  seem  to 
be  the  ruins  of  cones  of  eruption,  the  materials  of  some  at  least  having 
been  arranged  with  a  qua-quaversal  dip.  Among  these  is  Pico 
Grande,  c,  fig.  708,  now  half-buried  under  more  modern  lavas  which 
have  flowed  round  it. 

It  will  be  seen  that  the  beds  of  lava  in  the  central  region  between 
e  and  /  (fig.  706,  p.  648)  are  nearly  horizontal,  or  have  a  dip  of  no 
more  than  from  three  to  five  degrees,  whereas  the  angle  of  slope  of 
the  beds  between  /  and  h  is  often  seventeen  degrees  on  the  southern 
flank,  and  usually  as  much  as  ten  on  the  northern,  or  between  e  and  g. 
The  moderate  inclination  of  the  lavas  between  B,  A,  and  R  has  been 
caused  by  the  juxtaposition  of  a  multitude  of  cones  which  have  pre- 
vented the  streams  of  melted  matter  from  flowing  freely  from  the  main 
axis  or  lava-shed  towards  the  sea,  whether  in  a  north  or  south  direc- 
tion. The  marked  prolongation  of  this  gentle  slope  on  both  sides  of 
K,  and  from  R  to/,  may  be  attributed  to  the  fact  that  below /there  is 
a  very  ancient  ridge  of  erupted  materials,  c,  which  has  formed  a  bar- 
rier intercepting  the  free  passage  of  the  central  lavas  to  the  sea.  Be- 
tween this  secondary  buried  chain  above  c  or  below/,  and  the  higher 
central  chain  of  scoriae  below  A,  the  valley  or  cavity,  d,  s,  was  filed 
up  with  horizontal  beds  of  lava,  over  which  an  enormous  mass  of 
other  sheets  of  basalt  and  deposits  of  tuff,  from  d  to  R  and  from  R  to 
/,  were  afterwards  accumulated,  until  at  last  an  aggregate  thickness 
of  3500  feet  of  stratified  materials  was  formed.  Sections  of  this  vast 
accumulation  are  exposed  to  view  in  nearly  vertical  precipices  in  the 
deep  valley  called  the  Curral.  But  when  the  lavas  had  surmounted 
the  ancient  ndge  below/,  and  were  no  more  obstructed  in  their  sea- 


648 


SECTION  OF  MADEIRA. 


[Cn.  XXIX. 


CH.  XXIX.]  FOSSIL  PLANTS  OF  MADEIRA.  640 

ward  course,  they  flowed  with  a  steep  inclination,  often  at  an  angle  of 
17  degrees,  towards  the  south.  Nearer  the  sea,  as  at  i  and  L,  on  both 
sides  of  the  island,  where  the  most  modern  lavas  occur,  the  dip  dimin- 
ishes to  5  degrees,  and  even  to  3j,  as  at  K,  near  Funchal.  In  this 
latter  characteristic  (the  smaller  inclination  of  the  lavas  near  the  sea, 
and  their  association  there  with  modern  cones  of  eruption,  such  as  M, 
N,  o)  there  is  a  strict  analogy  between  Madeira  and  Palma.  Distinct 
buried  cones  of  eruption  also  occur  at  many  points,  as  at  p  and  <?,  fig. 
706,  which  have  been  overwhelmed  by  lavas  flowing  from  the  central 
region. 

As  a  'general  rule,  the  lavas  of  Madeira,  whether  vesicular  or  com- 
pact, do  not  constitute  continuous  sheets  parallel  to  each  other. 
When  viewed  in  the  sea-cliffs  in  sections  transverse  to  the  direction  in 
which  they  flowed,  they  vary  greatly  in  thickness,  even  if  followed  for 
a  few  hundred  feet  or  yards,  and  they  usually  thin  out  entirely  in  less 
than  a  quarter  of  a  mile.  In  the  ravines  which  radiate  from  the  centre 
of  the  island,  the  beds  are  more  persistent,  but  even  here  they  usually 
are  seen  to  terminate,  if  followed  for  a  few  miles ;  their  thickness  also 
being  very  variable,  and  sometimes  increasing  suddenly  from  a  few 
feet  to  many  yards. 

We  saw  no  remains  of  fossil  plants  in  any  of  the  red  partings  or 
laterites  above  alluded  to ;  but  Mr.  Smith,  of  Jordanhill,  was  more 
fortunate  in  1840,  having  met  with  the  carbonized  branches  and  roots 
of  shrubs  in  some  red  clays  under  basalt  near  Funchal.  Nevertheless,  M, 
Hartung  and  I  obtained  satisfactory  evidence  in  the  northern  part  of  the 
island,  in  the  ravine  of  S.  Jorge,  of  the,  former  existence  of  terrestrial 
vegetation,  and  consequently  of  the  subaerial  origin  of  a  large  portion  of 
the  lavas  of  Madeira.  At  q  in  the  section  (fig.  706)  the  occurrence  of  a 
bed  of  impure  lignite,  covered  by  basalt,  had  long  been  known.  Asso- 
ciated with  it  we  observed  several  layers  of  tuff  and  clay  or  hardened 
mud,  in  one  of  which  leaves  of  dicotyledonous  plants  and  of  ferns  abound. 
Sir  Charles  J.  F.  Bunbury,  who  was  with  me  in  Madeira  during  the 
winter  of  1853-'4,  at  once  pronounced  one  of  the  fossil  ferns  to  agree 
in  its  peculiar  vernation  with  Woodwardia  radicans,  a  species  now 
common  in  Madeira ;  and  he  afterwards  discovered  the  common  Ma- 
deira fern,  Davallia  Canariensis,  and  a  Nephrodium,  and  other  ferns 
among  the  fossil  remains.  He  also  pointed  out  that,  among  the  dico- 
tyledonous leaves,  some  were  of  the  myrtle  family,  the  larger  propor 
tion  having  their  surfaces  smooth  and  unwrinkled,  with  a  somewhat 
rigid  and  coriaceous  texture,  and  with  undivided  or  entire  margins. 
"  These  characters,"  observed  Sir  C.  Bunbury,  "  belong  to  the  laurel- 
type,  and  indicate  a  certain  analogy  between  the  ancient  vegetable  re- 
mains and  the  modern  forests  of  Madeira,  in  which  laurels  and  other 
evergreens  abound,  with  glossy  coriaceous  and  entire-edged  leaves, 
while  below  them  there  is  an  undergrowth  of  ferns  and  various  other 
plants."  * 

*  Bunbury,  Quart.  Geol.  Journ.,  1854,  vol.  x.  p.  326. 


650  CRATER  OF  LAGOA.  [Cn.  XXIX. 

Professor  Heer,  of  Zurich,  has  since  published  (1855)  an  account 
of  some  additional  fossils  collected  by  M.  Hartung  from  the  tuff  of 
San  Jorge,  enumerating  twenty-seven  forms,  referable  to  ferns  and 
phenogamous  plants,  most  of  them  agreeing  with  species  now  inhabit- 
ing Madeira,  such  as  Pteris  aguilina,  Trichomanes  radicans,  &c.,  and 
leaves  like  those  of  Osmunda  regalis  (?),  no  longer  found  in  the  island. 
Among  the  dicotyledonous  plants  the  Professor  describes  Myrica 
Faya,  Oreodaphne  fcetens,  Erica  arborea,  &c.?  also  a  few  genera,  such 
as  Corylus  and  Ulmus,  now  foreign  to  Madeira.  The  botanical  de- 
terminations both  of  Prof.  Heer  and  Sir  C.  Bunbury  would  lead  us  to 
refer  the  leaf-bed  to  a  period  as  modern  as  the  Newer  Pliocene,  if  not 
the  Post-pliocene.* 

The  lignite  above  mentioned  and  the  leaf-bed  occur  at  the  height 
of  1000  feet  above  the  level  of  the  sea,  and  are  overlaid  by  super- 
imposed basalts  and  scoriae,  1100  feet  thick,  implying  the  existence 
of  an  ancient  terrestrial  vegetation  long  before  a  large  part  of  Ma- 
deira had  been  built  up.  The  nature  of  the  tuffs  accompanying  the 
lignite,  together  with  some  agglomerates  in  the  vicinity,  entitles  us  to 
presume  that  near  this  spot  a  series  of  eruptions  once  broke  out. 
Nor  is  it  improbable  that  there  may  have  been  here  the  crater  of 
some  lateral  cone  in  which  the  lignite  and  leaf-bed  accumulated ;  for, 
although  craters  are  remarkably  rare  in  Madeira,  when  we  consider 
how  great  is  the  number  of  cones  of  eruption,  yet  on  the  mountain 
called  Lagoa,  2-J-  miles  west  of  Machico,  a  crater  as  perfect  as  that  of 
Astroni  near  Naples  may  be  seen. 

At  the  bottom  of  this  circular  cavity  (fig.  70 7),  which  is  about 

Fig.  707. 


Crater  of  Lagoa,  2£  miles  west  of  Machico,  Madeira. 

In  this  cut,  taken  from  a  sketch  of  my  own,  the  depth  of  the  crater  may  appear 
too  great,  unless  it  is  borne  in  mind  that  there  are  no  trees  visible,  and  most  of  the 
bushes  are  of  the  Madeira  whortleberry  ( Vaccinium  Madeirense),  five  or  six  feet 
high.  Immediately  behind  the  foreground  an  artificial  mound  is  seen  thrown  up  as 
a  fence. 

*  Heer,  Schweiz.  Gesellschaft  fiir  Naturwissenschaften,  Band  XV. 


CH.  XXIX.]  CENTRAL  VALLEYS.  651 

150  feet  deep,  is  a  plain  about  500  feet  in  diameter,  having  a  pond 
in  the  middle,  towards  which  the  plain  slopes  gently  from  all  sides. 
Such  ponds  are  often  seen  in  the  interior  of  extinct  craters.  Except 
in  the  middle  it  is  shallow,  and  supports  aquatic  plants.  Many  leaves 
must  also  be  blown  into  it  from  the  surrounding  heights  when  high 
winds  prevail,  so  that  a  mass  of  peaty  matter  convertible  into  lignite 
may  collect  here. 

Had  streams  of  lava  descending  from  greater  heights  entered  this 
Lagoa  crater,  they  would  have  formed  dense  masses  of  compact  rock 
cooling  slowly  under  great  pressure,  like  those  now  incumbent  on  the 
impure  lignite  of  S.  Jorge.  The  dip  of  the  latter  cannot  be  clearly 
determined,  since  it  is  exposed  to  view  for  too  short  a  distance  ;  and 
the  same  may  be  said  of  the  leaf-bed,  part  of  which  may  be  traced 
lower  down  the  ravine.  It  seems,  however,  to  dip  to  the  north  or 
towards  the  sea  conformably  with  the  general  inclination  of  the  ba- 
saltic and  tufaceous  strata. 

A  deep  valley,  called  the  Curral  (B,  fig.  708),  surrounded  by  preci- 
pices from  1500  to  2500  feet  high,  and  by  peaks  of  still  greater  ele- 
vation, occurs  in  the  middle  of  Madeira.  It  has  been  compared  by 
some  to  a  crater  or  caldera,  for  its  upper  portion  is  situated  in  the 
region  where  dikes  and  ejectamenta  abound.  The  Curral,  however, 
extends,  without  diminishing  in  depth,  to  below  the  region  of  numer- 
ous dikes,  and  it  lays  open  to  view  all  the  beds  R,  s,  fig.  706.  Nor 
do  the  volcanic  masses  dip  away  in  all  directions  from  the  Curral,  as 
from  a  central  point,  or  from  the  hollow  axis  of  a  cone.  The  Curral 
is  in  fact  one  only  of  three  great  valleys  which  radiate  from  the  most 
mountainous  district,  a  second  depression,  called  the  Serra  d'Agoa 
(D,  fig.  708),  being  almost  as  deep.  This  cavity  is  also  drained  by  a 
river  flowing  to  the  south  ;  while  a  third  valley,  namely,  that  of  the 
Janella,  sends  its  waters  to  the  north.  The  section  alluded  to  (fig. 
708),  passing  through  part  of  the  axis  of  the  island  in  an  east  and 
west  direction,  shows  how  the  Curral  and  Serra  d'Agoa,  B  and  D,  are 


East. 


Section  through  the  central  region  of  Madeira,  from  East  to  "West. 

A.  Part  of  the  platform,  called  the  Paul  de  Serra.          B.   Curral ;  a  valley,  3000  feet  deep. 
0.  Pico  Grande.  D.  The  valley  of  the  Serra  d'Agoa. 

separated  by  a  narrow  and  lofty  ridge,  c,  part  of  which  is  surmount- 
ed by  the  Pico  Grande,  before  mentioned,  nearly  5400  feet  high. 
There  is  no  essential  difference  between  the  shape  of  these  three  great 
valleys  and  many  of  those  in  the  Alps  and  Pyrenees,  where  the  val- 
ley-making process  can  have  had  no  connection  with  any  superficial 
volcanic  action. 


652  TRACHYTIC  ROCKS.  [Cn.  XXIX. 

In  the  Alps,  no  doubt,  as  in  other  lofty  chains,  the  formation  of 
valleys  has  been  greatly  aided  by  subterranean  movements,  both 
gradual  and  violent,  and  by  the  dislocation  of  rocks.  The  same  may 
be  true  of  Madeira  and  of  almost  every  lofty  volcanic  region ;  but, 
when  we  reflect  that  the  central  heights  A  and  B,  fig.  706,  are  more 
than  6000  feet  above  the  sea,  and  that  the  waters  flowing  from  them, 
swollen  by  melted  snows,  reach  the  sea  by  a  course  of  not  much 
more  than  6  miles  in  the  case  of  those  draining  the  Curral,  and  by 
nearly  as  short  a  route  in  the  Serra  d'Agoa,  we  shall  be  prepared 
for  almost  any  amount  of  denudation  effected  simply  by  subaerial 
erosion. 

The  general  absence  of  water-worn  pebbles  in  the  tuffs  underlying 
the  Madeira  lavas  is  very  striking,  and  contrasts  with  the  frequent 
occurrence  of  gravel-beds  under  so  many  of  the  Auvergne  lavas.  It 
simply  proves  that  Madeira,  like  the  volcanic  mountains  of  Java,  or 
like  Mount  Etna  or  Mona  Loa  in  the  Sandwich  Islands,  could  not, 
so  long  as  eruptions  were  frequent,  and  while  the  porous  lavas  ab- 
sorbed all  the  rain-water,  support  a'  single  torrent  on  its  slopes.* 
The  period,  therefore,  of  fluviatile  erosion  must  have  been  almost 
entirely  subsequent  in  date  to  the  formation  of  the  central  nucleus 
of  ejectamenta,  c,  fig.,  p.  648,  and  of  the  lavas  d,  ibid.  When  we 
infer  that  these  were  of  supramarine  origin  as  far  down  as  the  line 
PJ  s,  t,  and  perhaps  lower,  it  follows  that  a  lofty  island,  4000  feet  or 
more  in  height,  must  have  resulted,  even  if  no  upheaval  had  ever 
occurred. 

The  movements  which  upraised  the  marine  deposits  of  San  Vicente 
may  or  may  not  have  extended  over  a  wide  area.  How  far,  when 
they  occurred,  they  modified  the  form  of  the  island,  or  added  to  its 
height,  is  a  fair  subject  of  speculation  ;  and  whether  the  steep  dip  of 
the  lavas  seen  in  the  ravines  intersecting  the  slopes  of  the  mountain, 
f  h  and  e  g  (ng.  706,  p.  648),  may  be  ascribable  in  part  to  such 
movements.  The  lavas  of  more  modern  date,  near  Funchal,  may  be 
imagined  to  remain  comparatively  horizontal,  because  they  have 
escaped  the  influence  of  disturbing  forces  to  which  the  older  nucleus 
was  exposed.  Without  discussing  this  point  (so  fully  treated  of  in 
reference  to  Palma),  I  may  observe  that  unquestionably  different 
parts  of  Madeira  have  been  formed  in  succession.  Near  Porto  da 
Cruz,  for  example,  on  the  northern  coast,  trachytes  of  a  gray  and  yel- 
low, and  trachytic  tuffs  almost  of  a  white  color,  in  slightly  inclined 
or  almost  horizontal  beds,  have  partially  filled  up  deep  valleys  previ- 
ously excavated  through  the  older  and  inclined  basaltic  rocks  (dip- 
ping at  an  angle  of  10°  to  the  north),  under  which  the  leaf-bed  and 
lignite  before  mentioned  (fig.  706,  p.  648)  lie  buried.  During  the 
convulsions  which  accompanied  the  outpouring  of  every  newer  series 

*  See  remarks  on  Etna,  Lyell's  Principles  of  Geology,  chapter  xxv.  (9th  ed., 
p.  405). 


CH.  XXIX.]  LAVAS  OF  MADEIRA.  653 

of  lavas  the  older  rocks  may  have  been  more  or  less  disturbed  and 
tilted,  without  destroying  the  general  form  of  the  old  dome-shaped 
mountain  supposed  by  us  to  have  been  the  result  of  repeated  erup- 
tions from  the  central  vents. 

The  locality  just  referred  to  of  Porto  da  Cruz  exemplifies  not  only 
the  long  intervals  of  time  which  separated  the  outflowing  of  distinct 
sets  of  lavas,  but  also  the  precedence  of  the  basaltic  to  the  trachytic 
outpourings.  So  also  on  the  southern  slope  of  Madeira,  we  observed 
between  the  Jardim  and  Pico  Bodes,  situated  in  a  direct  line  about  6 
miles  northwest  of  Funchal,  a  well-marked  series  of  trachytic  rocks 
of  considerable  thickness  occupying  the  highest  geological  position. 
They  consist  of  white  and  gray  trachytes,  occurring  at  points  varying 
from  2500  to  3500  feet  above  the  sea.  Their  position  may  be  under- 
stood by  supposing  them  to  constitute  the  uppermost  beds  repre- 
sented at  h  in  the  section  (fig.  706,  p.  648),  and  on  the  slope  above 
h.  The  doctrine,  therefore,  that  in  each  series  of  volcanic  eruptions 
the  trachytic  lavas  flow  out  first,  and  after  them  the  basaltic  (see  p. 
657),  is  by  no  means  borne  out  in  Madeira,  although  some  of  the 
newest  currents,  like  those  at  the  foot  of  the  cones  M,  N,  o  (fig.  706), 
are  basaltic. 

Several  of  the  latest  and  most  powerful  streams  of  lava  which 
have  issued  from  the  central  axis  of  Madeira  are  composed  of  a 
felspathic  rock  of  a  mixed  character,  on  the  whole  more  trachytic 
than  basaltic.  It  divides  into  spheroidal  masses,  often  several  feet  in 
diameter,  which  are  very  conspicuous  when  the  contained  iron  has 
become  more  highly  oxidated.  M.  Delesse,  who  had  the  kindness  to 
analyze  for  me  several  of  our  specimens,  found  certain  varieties  of 
this  rock  to  be  without  augite,  and  simply  a  mixture  of  blackish- 
green  felspar  with  olivine.  These  would,  according  to  him,  be 
classed  by  most  of  the  French  geologists  under  the  general  designa- 
tion of  basalt.  Whatever  name  we  assign  to  this  product  it  indi- 
cates a  change  in  the  mineral  nature  of  the  materials  last  emitted 
from  the  central  axis.  Where  the  island  is  narrow  this  spheroidal 
trap  often  reaches  the  sea,  but  in  the  broadest  and  loftiest  part  of 
Madeira  it  forms  a  superficial  envelope,  which  extends  for  a  certain 
distance  only  from  the  central  heights,  as,  for  example,  to  near  o  (fig. 
706,  p.  648).  Hence,  near  Funchal,  we  must  ascend  to  a  height  of 
1100  or  1200  feet  before  we  meet  with  this  felspathic  formation,  the 
lower  grounds  along  the  coast  being  occupied  by  true  basalts,  which 
never  exhibit  a  spheroidal  structure. 

Among  other  contrasts  of  character  in  the  superficial  volcanic  for- 
mations of  Madeira,  I  may  remark  that  many  of  the  central  peaks, 
such  as  A,  fig.  706,  seem  to  be  the  mere  skeletons  of  cones  of  erup- 
tion, whereas  other  cones  of  like  origin,  such  as  M,  N,  o,  met  with  at 
lower  levels  and  nearer  the  sea,  are  more  regular,  and  have  no  pro- 
truding dikes  on  their  summits  or  flanks.  This  difference  in  form 
may  imply  that  the  more  degraded  hills  are  of  higher  antiquity ;  but 


654 


LAVAS  OF  MADEIRA. 


[Cn.  XXIX. 


it  may  quite  as  often  arise  from  the  circumstance  that  such  accumu- 
lations of  loose  ejected  materials  have  been  exposed  from  the  first  to 
greater  waste  in  regions  where  the  snows  melt  suddenly,  and  where 
the  winds  are  most  violent.  A  dense  covering  of  turf  and  shrubs, 
the  most  effective  of  all  preservatives  against  pluvial  degradation, 
cannot  readily  be  formed  in  such  mountainous  and  stormy  regions. 

Some  few  lavas  in  Madeira  have  a  singularly  recent  aspect  as  com- 
pared to  others  which  are  covered  with  a  considerable  depth  of  vege- 
table soil.  I  allude  particularly  to  the  lava  currents  near  Port  Moniz, 
one  of  which  is  as  rough  and  bristling  as  are  some  streams  before 
alluded  to  in  Palma  (p.  641)  of  historical  date.  I  am  indebted  to  M, 
Hartung  for  the  annexed  drawing  of  lava  at  Port  Moniz,  which  I  did 

Fig.  709. 


Surface  of  lava  ne 


Port  Moniz,  K  "W.  point  of  Madeira ;  from  a  drawing  by  M.  Hartung. 
a.  Channel  traversing  the  lava. 


not  visit  myself.  It  is  traversed  by  a  channel,  a,  like  one  of  those 
already  described  (p.  637).  For  how  long  a  period  such  characters 
may  be  retained  is  uncertain,  so  much  does  this  depend  on  the  min- 
eral composition  of  the  rock.  Some  of  the  lavas  of  Auvergne,  of 
prehistorical  date  and  certainly  of  high  antiquity,  are  almost  as  rug- 
ged ;  so  that  this  freshness  of  aspect  is  only  a  probable  indication  of 
a  relatively  modern  origin. 


CH.  XXX.]  RELATIVE  AGE  OF  VOLCANIC  ROCKS.  655 


CHAPTER  XXX. 

ON  THE  DIFFERENT  AGES  OF  THE  VOLCANIC  ROCKS. 

Tests  of  relative  age  of  volcanic  rocks — Tests  by  superposition  and  intrusion — 
Test  by  alteration  of  rocks  in  contact — Test  by  organic  remains — Test  of  age 
by  mineral  character— Test  by  included  fragments — Volcanic  rocks  of  the  Post- 
Pliocene  period — Basalt  of  the  Bay  of  Trezza  in  Sicily — Post-Pliocene  volcanic 
rocks  near  Naples — Dikes  of  Somma. 

HAVING  referred  the  sedimentary  strata  to  a  long  succession  of 
geological  periods,  we  have  now  to  consider  how  far  the  volcanic  for- 
mations can  be  classed  in  a  similar  chronological  order.  The  tests 
of  relative  age  in  this  class  of  rocks  are  four :  1st,  superposition  and 
intrusion,  with  or  without  alteration  of  the  rocks  in  contact ;  2d, 
organic  remains ;  3d,  mineral  characters  ;  4th,  included  fragments  of 
older  rocks. 

Tests  by  Superposition,  &c. — If  a  .volcanic  rock  rest  upon  an  aque- 
ous deposit,  the  former  must  be  the  newest  of  the  two ;  but  the  like 
rule  does  not  hold  good  where  the  aqueous  formation  rests  upon  the 
volcanic,  lor  melted  matter,  rising  from  below,  may  penetrate  a  sedi- 
mentary mass  without  reaching  the  surface,  or  may  be  forced  in  con- 
formably between  two  strata,  as  b  at  D  in  the  annexed  figure  (fig. 
710),  after  which  it  may  cool  down  and  consolidate.  Superposition, 

Fig.  710. 


therefore,  is  not  of  the  same  value  as  a  test  of  age  in  the  unstratified 
volcanic  rocks  as  in  fossiliferous  formations.  We  can  only  rely  im- 
plicitly on  this  test  where  the  volcanic  rocks  are  contemporaneous, 
not  where  they  are  intrusive.  Now,  they  are  said  to  be  contempora- 
neous if  produced  by  volcanic  action  which  was  going  on  simultane- 
ously with  the  deposition  of  the  strata  with  which  they  are  asso- 
ciated. Thus  in  the  section  at  D  (fig.  710),  we  may  perhaps  ascertain 
that  the  trap  6  flowed  over  the  fossiliferous  bed  c,  and  that,  after  its 
consolidation,  a  was  deposited  upon  it,  a  and  c  both  belonging  to  the 
same  geological  period.  But  if  the  stratum  a  be  altered  by  b  at  the 
point  of  contact,  we  must  then  conclude  the  trap  to  have  been  intru- 


056         RELATIVE  AGE  OF  VOLCANIC  ROCKS.     [Cn.  XXX. 

sive,  or  if,  in  pursuing  b  for  some  distance,  we  find  at  length  that  it 
cuts  through  the  stratum  a,  and  then  overlies  it  as  at  E. 

We  may,  however,  be  easily  deceived  in  supposing  the  volcanic 
rock  to  be  intrusive,  when  in  reality  it  is  contemporaneous ;  for  a 
sheet  of  lava,  as  it  spreads  over  the  bottom  of  the  sea,  cannot  rest 
everywhere  upon  the  same  stratum,  either  because  these  have  been 
denuded,  or  because,  if  newly  thrown  down,  they  thin  out  in  certain 
places,  thus  allowing  the  lava  to  cross  their  edges.  Besides  the 
heavy  igneous  fluid  will  often,  as  it  moves  along,  cut  a  channel  into 

beds  of  soft  mud  and  sand.  Suppose 
the  submarine  lava  F  (fig.  711)  to  have 
come  in  contact  in  this  manner  with 
the  strata,  a,  b,  c,  and  that  after  its 
consolidation  the  strata,  d,  e,  are  thrown 
down  in  a  nearly  horizontal  position, 
yet  so  as  to  lie  unconformably  to  F,  the 
appearance  of  subsequent  intrusion  will 
here  be  complete,  although  the  trap  is  in  fact  contemporaneous.  We 
must  not,  therefore,  hastily  infer  that  the  rock  F  is  intrusive,  unless 
we  find  the  strata,  d,  e,  or  c,  to  have  been  altered  at  their  junction, 
as  if  by  heat. 

The  test  of  age  by  superposition  is  strictly  applicable  to  all  stratified 
volcanic  tuffs,  according  to  the  rules  already  explained  in  the  case  of 
other  sedimentary  deposits  (see  p.  93). 

Test  of  Age  by  Organic  Remains. — We  have  seen  how,  in  the  vicinity 
of  active  volcanoes,  scoriae,  pumice,  fine  sand,  and  fragments  of  rock 
are  thrown  up  into  the  air,  and  then  showered  down  upon  the  land, 
or  into  neighboring  lakes  or  seas.  In  the  tuffs  so  formed,  shells,  corals, 
or  any  other  durable  organic  bodies  which  may  happen  to  be  strewed 
over  the  bottom  of  a  lake  or  sea  will  be  imbedded,  and  thus  continue 
as  permanent  memorials  of  the  geological  period  when  the  volcanic 
eruption  occurred.  Tufaceous  strata  thus  formed  in  the  neighborhood 
of  Vesuvius,  Etna,  Stromboli,  and  other  volcanoes  now  active  in 
islands  or  near  the  sea,  may  give  information  of  the  relative  age  of 
these  tuffs  at  some  remote  future  period  when  the  fires  of  these  moun- 
tains are  extinguished.  By  evidence  of  this  kind  we  can  establish  a 
coincidence  in  age  between  volcanic  rocks  and  the  different  primary, 
secondary,  and  tertiary  fossiliferous  strata. 

The  tuffs  alluded  to  may  not  always  be  marine,  but  may  include, 
in  some  places,  freshwater  shells ;  in  others,  the  bones  of  terrestrial  quad- 
rupeds. The  diversity  of  organic  remains  in  formations  of  this  nature 
is  perfectly  intelligible,  if  we  reflect  on  the  wide  dispersion  of  ejected 
matter  during  late  eruptions,  such  as  that  of  the  volcano  of  Coseguina, 
in  the  province  of  Nicaragua,  January  19, 1835.  Hot  cinders  and  fine 
scoriae  were  then  cast  up  to  a  vast  height,  and  covered  the  ground  as 
they  fell  to  the  depth  of  more  than  10  feet  and  for  a  distance  of  8 
leagues  from  the  crater  in  a  southerly  direction.  Birds,  cattle,  and 


CH.  XXX.]     RELATIVE  AGE  OF  VOLCANIC  ROCKS.         $57 

wild  animals  were  scorched  to  death  in  great  numbers,  and  buried  in 
ashes.  Some  volcanic  dust  fell  at  Cbiapa,  upwards  of  1200  miles,  not 
to  leeward  of  the  volcano  as  might  have  been  anticipated,  but  to 
windward,  a  striking  proof  of  a  counter-current  in  the  upper  region  of 
the  atmosphere,  and  some  on  Jamaica,  about  TOO  miles  distant  to  the 
northeast.  In  the  sea,  also,  at  the  distance  of  1100  miles  from  the  point 
of  eruption,  Captain  Eden,  of  the  "  Conway,"  sailed  40  miles  through 
floating  pumice,  among  which  were  some  pieces  of  considerable  size.* 

Test  of  Age  by  Mineral  Composition. — As  sediment  of  homogeneous 
composition,  when  discharged  from  the  mouth  of  a  large  river,  is 
often  deposited  simultaneously  over  a  wide  space,  so  a  particular  kind 
of  lava  flowing  from  a  crater  during  one  eruption,  may  spread  over  an 
extensive  area;  as  in  Iceland  in  1783,  when  the  melted  matter,  pour- 
ing from  Skaptar  Jokul,  flowed  in  streams  in  opposite  directions,  and 
caused  a  continuous  mass  the  extreme  points  of  which  were  90  miles 
distant  from  each  other.  This  enormous  current  of  lava  varied  in 
thickness  from  100  feet  to  600  feet,  and  in  breadth  from  that  of  a 
narrow  river  gorge  to  15  miles.f  Now,  if  such  a  mass  should  after- 
wards be  divided  into  separate  fragments  by  denudation,  we  might 
still  perhaps  identify  the  detached  portions  by  their  similarity  in 
mineral  composition.  Nevertheless,  this  test  will  not  always  avail  the 
geologist ;  for,  although  there  is  usually  a  prevailing  character  in  lava 
emitted  during  the  same  eruption,  and  even  in  the  successive  currents 
flowing  from  the  same  volcano,  still,  in  many  cases,  the  different  parts 
even  of  one  lava-stream,  or,  as  before  stated,  of  one  continuous  mass 
of  trap,  vary  much  in  mineral  composition  and  texture. 

In  Auvergne,  the  Eifel,  and  other  countries  where  trachyte  and 
basalt  are  both  present,  the  trachytic  rocks  are  for  the  most  part 
older  than  the  basaltic.  These  rocks  do,  indeed,  sometimes  alternate 
partially,  as  in  the  volcano  of  Mont  Dor,  in  Auvergne ;  and  we  have 
seen  that  in  Madeira  trachytic  rocks  may  overlie  an  older  basaltic  se- 
ries (p.  653) ;  but  the  great  mass  of  trachyte  occupies  more  generally 
perhaps  an  inferior  position,  and  is  cut  through  and  overflowed  by 
basalt.  It  can  by  no  means  be  inferred  that  trachyte  predominated  at 
one  period  of  the  earth's  history  and  basalt  at  another,  for  we  know 
that  trachytic  lavas  have  been  formed  at  many  successive  periods,  and 
are  still  emitted  from  many  active  craters ;  but  it  seems  that  in  each 
region,  where  a  long  series  of  eruptions  have  occurred,  the  more  fel- 
spathic  lavas  have  been  first  emitted,  and  the  escape  of  the  more 
augitic  kinds  has  followed.  The  hypothesis  suggested  by  Mr.  Scrope 
may,  perhaps,  afford  a  solution  of  this  problem.  The  minerals,  he 
observes,  which  abound  in  basalt  are  of  greater  specific  gravity  than 
those  composing  the  felspathic  lavas;  thus,  for  example,  hornblende, 
augite,  and  olivine  are  each  more  than  three  times  the  weight  of 


*  Caldcleugh,  Phil.  Trans.,  1836,  p.  27. 
f  See  Principles,  Index,  "  Skaptar  Jokul." 
42 


658         KELATIVE  AGE  OF  VOLCANIC  ROCKS.     [Cn.  XXX. 

water ;  whereas  common  felspar,  albite,  and  Labrador  felspar  have  each 
scarcely  more  than  2 -J  times  the  specific  gravity  of  water ;  and  the 
difference  is  increased  in  consequence  of  there  being  much  more  iron 
in  a  metallic  state  in  basalt  and  greenstone  than  in  trachyte  and  other 
felspathic  lavas  and  trap  rocks.  If,  therefore,  a  large  quantity  of  rock 
be  melted  up  in  the  bowels  of  the  earth  by  volcanic  heat,  the  denser 
ingredients  of  the  boiling  fluid  may  sink  to  the  bottom,  and  the 
lighter  remaining  above  would  in  that  case  be  first  propelled  upwards 
to  the  surface  by  the  expansive  power  of  gases.  Those  materials, 
therefore, 'which  occupy  the  lowest  place  in  the  subterranean  reservoir 
will  always  be  emitted  last,  and  take  the  uppermost  place  on  the 
exterior  of  the  earth's  crust. 

Test  by  Included  Fragments. — We  may  sometimes  discover  the 
relative  age  of  two  trap  rocks,  or  of  an  aqueous  deposit  and  the  trap 
on  which  it  rests,  by  finding  fragments  of  one  included  in  the  other  in 
cases  such  as  those  before  alluded  to,  where  the  evidence  of  super- 
position alone  would  be  insufficient.  It  is  also  not  uncommon  to  find 
a  conglomerate  almost  exclusively  composed  of  rolled  pebbles  of  trap, 
associated  with  some  fossiliferous  stratified  formation  in  the  neighbor- 
hood of  massive  trap.  If  the  pebbles  agree  generally  in  mineral  char- 
acter with  the  latter,  we  are  then  enabled  to  determine  its  relative  age 
by  knowing  that  of  the  fossiliferous  strata  associated  with  the  con- 
glomerate. The  origin  of  such  conglomerates  is  explained  by  observ- 
ing the  shingle  beaches  composed  of  trap  pebbles  in  modern  volcanic 
islands,  or  at  the  base  of  Etna. 

Newer  Tertiary  Pliocene  Periods. — I  shall  now  select  examples  of 
contemporaneous  volcanic  rocks  of  successive  geological  periods,  to 
show  that  igneous  causes  have  been  in  activity  in  all  past  ages  of  the 
world,  and  that  they  have  been  ever  shifting  the  places  where  they 
have  broken  out  at  the  earth's  surface. 

One  portion  of  the  lavas,  tuffs,  and  trap-dikes  of  Etna,  Vesuvius, 
and  the  island  of  Ischia  has  been  produced  within  the  historical  era ; 
another  and  a  far  more  considerable  part  originated  at  times  imme- 
diately antecedent,  when  the  waters  of  the  Mediterranean  were  already 
inhabited  by  the  existing  testacea,  but  when  certain  species  of 
elephant,  rhinoceros,  and  other  quadrupeds  now  extinct,  inhabited 
Europe.  A  third  and  more  ancient  portion  again  of  these  volcanoes 
originated  at  the  close  of  the  Newer  Pliocene  period,  when  less  than 
ten,  sometimes  only  one,  in  a  hundred  of  the  shells  differed  from  those 
now  living  (see  p.  190). 

It  has  already  been  stated  that  in  the  case  of  Etna,  Post-pliocene 
formations  occur  in  the  neighborhood  of  Catania,  while  the  oldest 
lavas  of  the  great  volcano  are  Pliocene.  These  are  seen  associated 
with  sedimentary  deposits  at  Trezza  and  other  places  on  the  southern 
and  eastern  flanks  of  the  great  cone  (see  above,  p.  190). 

The  Cyclopian  Islands,  called  by  the  Sicilians  Del  Farraglioni,  in 
the  sea-cliffs  of  which  these  beds  of  clay,  tuff,  and  associated  lava  are 


OH.  XXX.]  POST-PLIOCENE  VOLCANIC  ROCKS. 

Fig.  712. 


659 


Fig.  713. 


View  of  the  Isle  of  Cyclops  in  the  Bay  of  Trezza.* 

laid  open  to  view,  are  situated  in  the  Bay  of  Trezza,  and  may  be  re 
garded  as  the  extremity  of  a  promontory  severed  from  the  main  land. 
Here  numerous  proofs  are  seen  of  submarine  eruptions,  by  which  the 
argillaceous  and  sandy  strata 
were  invaded  and  cut  through, 
and  tufaceous  breccias  formed. 
Enclosed  in  these  breccias  are 
many  angular  and  hardened 
fragments  of  laminated  clay  in 
different  states  of  alteration  by 
heat,  and  intermixed  with  vol- 
canic sands. 

The  loftiest  of  the  Cyclopian 
islets,  or  rather  rocks,  is  about 
200  feet  in  height,  the  summit 
being  formed  of  a  mass  of 
stratified  clay,  the  laminae  of 
which  are  occasionally  subdi- 
vided by  thin  arenaceous  lay- 
ers. These  strata  dip  to  the 
N.W.,  and  rest  on  a  mass  of 
columnar  lava  (see  fig.  712)  in 
which  the  tops  of  the  pillars 
are  weathered,  and  so  rounded 
as  to  be  often  hemispherical. 
tn  some  places  in  the  adjoining 
and  largest  islet  of  the  group, 
which  lies  to  the  northeastward 

/,  . ,     .  ,     -,  •      ,  i        •.  Contortions  of  strata  in  the  largest  of  the 

of  that  represented  m  the  draw-  Cyclopian  islands. 


*  This  view  of  the  Isle  of  Cyclops  is  from  an  original  drawing  by  my  friend  the 
late  Captain  Basil  Hall,  R.N. 


660 


VOLCANIC  ROCKS  OF 


[Cii.  XXX. 


ing  (fig.  712),  the  overlying  clay  has  been  greatly  altered  and  hard- 
ened by  the  igneous  rock,  and  occasionally  contorted  in  the  most 
extraordinary  manner ;  yet  the  lamination  has  not  been  obliterated, 
but,  on  the  contrary,  rendered  much  more  conspicuous,  by  the  indu- 
rating process. 

In  the  foregoing  woodcut  (fig.  713)  I  have  represented  a  portion 
of  the  altered  rock,  a  few  feet  square,  where  the  alternating  thin 
laminae  of  sand  and  clay  have  put  on  the  appearance  which  we  often 
observe  in  some  of  the  most  contorted  of  the  metamorphic  schists. 

A  great  fissure,  running  from  east  to  west,  nearly  divides  this 
larger  island  into  two  parts,  and  lays  open  its  internal  structure.  In 
the  section  thus  exhibited,  a  dike  of  lava  is  seen,  first  cutting  through 
an  older  mass  of  lava,  and  then  penetrating  the  superincumbent  ter- 
tiary strata.  In  one  place  the  lava  ramifies  and  terminates  in  thin 
veins,  from  a  few  feet  to  a  few  inches  in  thickness  (see  fig.  714). 

Fig.  714. 


a  5  c  a  & 

Clay.    Lava.    Clay.     Altered.    Lava    Clay,  &c. 

Newer  Pliocene  strata  invaded  by  lava,  Isle  of  Cyclops  (horizontal  section). 
a.  Lava.  Z>.  Laminated  clay  and  sand.  e.  The  same  altered. 

The  arenaceous  laminae  are  much  hardened  at  the  point  of  contact, 
and  the  clays  are  converted  into  siliceous  schist.  In  this  island  the 
altered  rocks  assume  a  honeycomb  structure  on  their  weathered  surface, 
singularly  contrasted  with  the  smooth  and  even  outline  which  the 
same  beds  present  in  their  usual  soft  and  yielding  state. 

The  pores  of  the  lava  are  sometimes  coated,  or  entirely  filled,  with 
carbonate  of  lime,  and  with  a  zeolite  resembling  analcime,  which  has 
been  called  cyclopite.  The  latter  mineral  has  also  been  found  in  small 
fissures  traversing  the  altered  marl,  showing  that  the  same  cause  which 
introduced  the  minerals  into  the  cavities  of  the  lava,  whether  we  sup- 
pose sublimation  or  aqueous  infiltration,  conveyed  it  also  into  the  open 
rents  of  the  contiguous  sedimentary  strata. 


CH.  XXX.]  THE  POST-PLIOCENE  PERIOD.  661 

Post-Pliocene  Formations  near  Naples. — I  have  traced  in  the 
"  Principles  of  Geology  "  the  history  of  the  changes  which  the  vol- 
canic region  of  Campania  is  known  to  have  undergone  during  the  last 
2000  years.  The  aggregate  effect  of  igneous  operations  during  that 
period  is  far  from  insignificant,  comprising  as  it  does  the  formation  of 
the  modern  cone  of  Vesuvius  since  the  year  79,  and  the  production  of 
several  minor  cones  in  Ischia,  together  with  that  of  Monte  Nuovo  in 
the  year  1538.  Lava-currents  have  also  flowed  upon  the  land  and 
along  the  bottom  of  the  sea — volcanic  sand,  pumice,  and  scoriae  have 
been  showered  down  so  abundantly  that  whole  cities  were  buried — 
tracts  of  the  sea  have  been  filled  up  or  converted  into  shoals — and 
tufaceous  sediment  has  been  transported  by  rivers  and  land-floods  to 
•the  sea.  There  are  also  proofs,  during  the  same  recent  period,  of  a 
permanent  alteration  of  the  relative  levels  of  the  land  and  sea  in  sev- 
eral places,  and  of  the  same  tract  having,  near  Puzzuoli,  been  alter- 
nately upheaved  and  depressed  to  the  amount  of  more  than  20  feet. 
In  connection  with  these  convulsions,  there  are  found,  on  the  shores 
of  the  Bay  of  Baiae,  recent  tufaceous  strata,  filled  with  articles  fabri- 
cated by  the  hands  of  man,  and  mingled  with  marine  shells. 

It  was  also  stated  in  this  work  (p.  189),  that  when  we  examine  this 
same  region,  it  is  found  to  consist  largely  of  tufaceous  strata,  of  a  date 
anterior  to  human  history  or  tradition,  which  are  of  such  thickness 
as  to  constitute  hills  from  500  to  more  than  2000  feet  in  height. 
Some  of  these  strata  contain  marine  shells  which  are  exclusively  of 
living  species,  others  contain  a  slight  mixture,  one  or  two  per  cent., 
of  extinct  species.  Of  the  latter  class  is  the  ancient  cone  of  Vesuvius, 
called  Somma,  which  is  of  far  greater  volume  than  the  modern  cone, 
and  is  intersected  by  a  far  greater  number  of  dikes.  In  contrasting 
this  ancient  part  of  the  mountain  with  that  of  modern  date,  one  prin- 
cipal point  of  difference  is  observed :  namely,  the  greater  frequency  in 
the  older  cone  of  fragments  of  altered  sedimentary  rocks  ejected 
during  eruptions.  We  may  easily  conceive  that  the  first  explosions 
would  act  with  the  greatest  violence,  rending  and  shattering  whatever 
solid  masses  obstructed  the  escape  of  lava  and  the  accompanying 
gases,  so  that  great  heaps  of  ejected  pieces  of  rock  would  naturally 
occur  in  the  tufaceous  breccias  formed  by  the  earliest  eruptions.  But 
when  a  passage  had  once  been  opened  and  an  habitual  vent  established, 
the  materials  thrown  out  would  consist  of  liquid  lava,  which  would 
take  the  form  of  sand  and  scoriae,  or  of  angular  fragments  of  such 
solid  lavas  as  may  have  choked  up  the  vent. 

Among  the  fragments  which  abound  in  the  tufaceous  breccias  of 
Somma,  none  are  more  common  than  a  saccharoid  dolomite,  supposed 
to  have  been  derived  from  an  ordinary  limestone  altered  by  heat  and 
volcanic  vapors. 

Carbonate  of  lime  enters  into  the  composition  of  so  many  of  the 
simple  minerals  found  in  Somma,  that  M.  Mitscherlich,  with  much 
probability,  ascribes  their  great  variety  to  the  action  of  the  volcanic 
beat;  on  subjacent  masses  of  limestone. 


662  VOLCANIC  ROCKS  OF  [Cn.  XXX. 

Dikes  of  Somma. — The  dikes  seen  in  the  great  escarpment  which 
Somma  presents  towards  the  modern  cone  of  Vesuvius  are  very 
numerous.  They  are  for  the  most  part  vertical,  and  traverse  at  right 
angles  the  beds  of  lava,  scoriae,  volcanic  breccia,  and  sand,  of  which 
the  ancient  cone  is  composed.  They  project  in  relief  several  inches 
or  sometimes  feet,  from  the  face  of  the  cliff,  being  extremely  compact, 
and  less  destructible  than  the  intersected  tuffs  and  porous  lavas.  In 
vertical  extent  they  differ  from  a  few  yards  to  500  feet,  and  in  breadth 
from  1  to  12  feet.  Many  of  them  cut  all  the  inclined  beds  in  the 
escarpment  of  Somma  from  top  to  bottom,  others  stop  short  before 
they  ascend  above  half  way,  and  a  few  terminate  at  both  ends,  either 
in  a  point  or  abruptly.  In  mineral  composition  they  scarcely  differ 
from  the  lavas  of  Somma,  the  rock  consisting  of  a  base  of  leucite  and 
augite,  through  which  large  crystals  of  augite  and  some  of  leucite 
are  scattered.*  Examples  are  not  rare  of  one  dike  cutting  through 
another,  and  in  one  instance  a  shift  or  fault  is  seen  at  the  point  of 
intersection. 

In  some  cases,  however,  the  rents  seem  to  have  been  filled  laterally, 
when  the  walls  of  the  crater  had  been  broken  by  star-shaped  cracks, 
as  seen  in  the  accompanying  wood-cut  (fig.  715).  But  the  shape  of 

Fig.  715. 


Dikea  or  veins  at  the  Punto  del  JNasone  on  Somma.    (Necker.  t) 

these  rents  is  an  exception  to  the  general  rule ;  for  nothing  is  more 
remarkable  than  the  usual  parallelism  of  the  opposite  sides  of  the 
dikes,  which  correspond  almost  as  regularly  as  the  two  opposite  faces 
of  a  wall  of  masonry.  This  character  appears  at  first  the  more  inex- 
plicable, when  we  consider  how  jagged  and  uneven  are  the  rents  caused 
be  earthquakes  in  masses  of  heterogeneous  composition,  like  those 
composing  the  cone  of  Somma.  In  explanation  of  this  phenomenon, 

*  L.  A.  Necker,  Mem.  de  la  Soc.  de  Phys.  et  d'Hist.  Nat.  de  Geneve,  torn,  ii., 
part  i.,  Nov.  1822. 

f  From  a  drawing  of  M.  Necker,  in  Mem.  above  cited. 


CH.  XXX.]  THE  POST-PLIOCENE  PERIOD.  663 

M.  Necker  refers  us  to  Sir  W.  Hamilton's  account  of  an  eruption  of 
Vesuvius  in  the  year  1779,  who  records  the  following  facts :  "The 
lavas,  when  they  either  boiled  over  the  crater,  or  broke  out  from  the 
conical  parts  of  the  volcano,  constantly  formed  channels  as  regular  as 
if  they  had  been  cut  by  art  down  the  steep  part  of  the  mountain ;  and, 
whilst  in  a  state  of  perfect  fusion,  continued  their  course  in  those 
channels,  which  were  sometimes  full  to  the  brim,  and  at  other  times 
more  or  less  so,  according  to  the  quantity  of  matter  in  motion. 

"  These  channels,  upon  examination  after  an  eruption,  I  have  found 
to  be  in  general  from  two  to  five  or  six  feet  wide,  and  seven  or  eight 
feet  deep.  They  were  often  hid  from  the  sight  by  a  quantity  of 
scoriae  that  had  formed  a  crust  over  them ;  and  the  lava,  having  been 
conveyed  in  a  covered  way  for  some  yards,  came  out  fresh  again  into 
an  open  channel.  After  an  eruption,  I  have  walked  in  some  of  those 
subterraneous  or  covered  galleries,  which  were  exceedingly  curious,  the 
sides,  top,  and  bottom  being  worn  perfectly  smooth  and  even  in  most 
parts,  by  the  violence  of  the  currents  of  the  red-hot  lavas  which  they 
had  conveyed  for  many  weeks  successively."  * 

Now,  the  walls  of  a  vertical  fissure,  through  which  lava  has  ascended 
in  its  way  to  a  volcanic  vent,  must  have  been  exposed  to  the  same 
erosion  as  the  sides  of  the  channels  before  adverted  to.  The  pro- 
longed and  uniform  friction  of  the  heavy  fluid,  as  it  is  forced  and 
made  to  flow  upwards,  cannot  fail  to  wear  and  smooth  down  the 
surfaces  on  which  it  rubs,  and  the  intense  heat  must  melt  all  such 
masses  as  project  and  obstruct  the  passage  of  the  incandescent  fluid. 

The  texture  of  the  Yesuvian  dikes  is  different  at  the  edges  and  in 
the  middle.  Towards  the  centre,  observes  M.  Necker,  the  rock  is 
larger  grained,  the  component  elements  being  in  a  far  more  crystalline 
state ;  while  at  the  edge  the  lava  is  sometimes  vitreous,  and  always 
finer  grained.  A  thin  parting  band,  approaching  in  its  character  to 
pitchstone,  occasionally  intervenes,  at  the  contact  of  the  vertical  dike 
and  intersected  beds.  M.  Necker  mentions  one  of  these  at  the  place 
called  Primo  Monte,  in  the  Atrio  del  Cavallo ;  and  when  I  examined 
Somma,  in  1828,  I  saw  three  or  four  others  in  different  parts  of  the 
great  escarpment.  These  phenomena  are  in  perfect  harmony  with  the 
results  of  the  experiments  of  Sir  James  Hall  and  Mr.  Gregory  Watt, 
which  have  shown  that  a  glassy  texture  is  the  effect  of  sudden  cooling, 
while,  on  the  contrary,  a  crystalline  grain  is  produced  where  fused 
minerals  are  allowed  to  consolidate  slowly  and  tranquilly  under  high 
pressure. 

It  is  evident  that  the  central  portion  of  the  lava  in  a  fissure  would, 
during  consolidation,  part  with  its  heat  more  slowly  than  the  sides, 
although  the  contrast  of  circumstances  would  not  be  so  great  as  when 
we  compare  the  lava  near  the  bottom  and  at  the  surface  of  a  current 
flowing  in  the  open  air.  In  this  case  the  uppermost  part,  where  it 

*  Phil.  Trans.,  vol.  Ixx.,  1780. 


664:  POST-PLIOCENE  VOLCANIC  ROCKS.  [Cn.  XXX. 

has  been  in  contact  with  the  atmosphere,  and  where  refrigeration  has 
been  most  rapid,  is  always  found  to  consist  of  scoriform,  vitreous,  and 
porous  lava ;  while  at  the  greater  depth  the  mass  assumes  a  more 
lithoidal  structure,  and  then  becomes  more  and  more  stony  as  we  de- 
scend, until  at  length  we  are  able  to  recognize  with  a  magnifying  glass 
the  simple  minerals  of  which  the  rock  is  composed.  On  penetrating 
still  deeper,  we  can  detect  the  constituent  parts  by  the  naked  eye,  and 
in  the  Yesuvian  currents  distinct  crystals  of  augite  and  leucite  become 
apparent. 

The  same  phenomenon,  observes  M.  Necker,  may  readily  be  exhib- 
ited on  a  smaller  scale,  if  we  detach  a  piece  of  liquid  lava  from  a 
moving  current.  The  fragment  cools  instantly,  and  we  find  the  sur- 
face covered  with  a  vitreous  coat ;  while  the  interior,  although  ex- 
tremely fine-grained,  has  a  more  stony  appearance. 

It  must,  however,  be  observed,  that  although  the  lateral  portions  of 
the  dikes  are  finer  grained  than  the  central,  yet  the  vitreous  parting 
layer  before  alluded  to  is  rare  in  Yesuvius.  This  may,  perhaps,  be 
accounted  for,  as  the  above-mentioned  author  suggests,  by  the  great 
heat  which  the  walls  of  a  fissure  may  acquire  before  the  fluid  mass 
begins  to  consolidate,  in  which  case  the  lava,  even  at  the  sides,  would 
cool  very  slowly.  Some  fissures,  also,  may  be  filled  from  above,  as 
frequently  happens  in  the  volcanoes  of  the  Sandwich  Islands,  accord- 
ing to  the  observations  of  Mr.  Dana ;  and  in  this  case  the  refrigera- 
tion at  the  sides  would  be  more  rapid  than  when  the  melted  matter 
flowed  upwards  from  the  volcanic  foci,  in  an  intensely  heated  state. 
Mr.  Darwin  informs  me  that  in  St.  Helena  almost  every  dike  has  a 
vitreous  selvage. 

The  rock  composing  the  dikes  both  in  the  modern  and  ancient 
part  of  Yesuvius  is  far  more  compact  than  that  of  ordinary  lava,  for 
the  pressure  of  a  column  of  melted  matter  in  a  fissure  greatly  exceeds 
that  in  an  ordinary  stream  of  lava ;  and  pressure  checks  the  expan- 
sion of  those  gases  which  give  rise  to  vesicles  in  lava. 

There  is  a  tendency  in  almost  all  the  Yesuvian  dikes  to  divide  into 
horizontal  prisms,  a  phenomenon  in  accordance  with  the  formation  of 
vertical  columns  in  horizontal  beds  of  lava ;  for  in  both  cases  the 
divisions  which  give  rise  to  the  prismatic  structure  are  at  right  angles 
to  the  cooling  surfaces.  (See  above,  p.  617.) 


CH.  XXXI.]  NEWER  PLIOCENE  VOLCANIC  ROCKS.  665 


CHAPTER  XXXI. 

ON    THE    DIFFERENT   AGES    OF   THE    VOLCANIC    ROCKS,    Continued. 

Volcanic  rocks  of  the  Newer  Pliocene  period — Val  di  Noto — Sicilian  dikes — Region 
of  Olot  in  Catalonia — Volcanic  rocks  of  the  Older  Pliocene  period — Tuscany — 
Rome — Volcanic  region  of  Olot  in  Catalonia — Cones  and  lava-currents — Ravines 
and  ancient  gravel-beds — Jets  of  air  called  Bufadors — Age  of  the  Catalonian 
volcanoes — Upper  Miocene  period — Volcanic  archipelagoes  of  Madeira,  the  Ca- 
naries, and  the  Azores — Lower  Miocene  period — Brown-coal  of  the  Eifel  and 
contemporaneous  trachytic  breccias — Age  of  the  brown-coal — Peculiar  characters 
of  the  volcanoes  of  the  upper  and  lower  Eifel — Lake  Craters — Trass — Hungarian 
volcanoes. 

VOLCANIC    ROCKS    OF   THE    NEWER   PLIOCENE    PERIOD. 

Val  di  Noto. — I  have  already  alluded  (see  p.  192)  to  the  igneous 
rocks  which  are  associated  with  a  great  marine  formation  of  lime- 
stone, sand,  and  marl  in  the  southern  part  of  Sicily,  as  at  Vizzini 
and  other  places.  In  this  formation,  which  was  shown  to  belong  to 
the  Newer  Pliocene  period,  large  beds  of  oysters  and  corals  repose 
upon  lava,  and  are  unaltered  at  the  point  of  contact.  In  other  places 
we  find  dikes  of  igneous  rock  intersecting  the  fossiliferous  beds,  and 
converting  the  clays  into  siliceous  schist,  the  laminae  being  contorted 
and  shivered  into  innumerable  fragments  at  the  junction,  as  near  the 
town  of  Vizzini. 

The  volcanic  formations  of  the  Val  di  Noto  usually  consist  of  the 
most  ordinary  variety  of  basalt,  with  or  without  olivine.  The  rock 
is  sometimes  compact,  often  very  vesicular.  The  vesicles  are  occa- 
sionally empty,  both  in  dikes  and  currents,  and  are  in  some  localities 
filled  with  calcareous  spar,  arragonite,  and  zeolites.  The  structure 
is,  in  some  places,  spheroidal ;  in  others,  though  rarely,  columnar.  I 
found  dikes  of  amygdaloid,  wacke,  and  prismatic  basalt,  intersecting 
the  limestone  at  the  bottom  of  the  hollow  called  Gozzo  degli  Martiri, 
below  Melilli. 

Dikes  in  Sicily. — Dikes  of  vesicular  and  amygdaloidal  lava  are  also 
seen  traversing  marine  tuff  or  peperino,  west  of  Palagonia,  some  of 
the  pores  of  the  lava  being  empty,  while  others  are  filled  with  carbon- 
ate of  lime.  In  such  cases  we  may  suppose  the  peperino  to  have 
resulted  from  showers  of  volcanic  sand  and  scoriae,  together  with 
fragments  of  limestone,  thrown  out  by  a  submarine  explosion,  similar 
to  that  which  gave  rise  to  Graham  Island  in  1831.  When  the  mass 


666 


DIKES  OF  LAVA. 


[On.  XXXI. 


was,  to  a  certain  degree,  consolidated,  it  may  have  been  rent  open,  so 
that  the  lava  ascended  through  fissures,  the  walls  of  which  were  per- 
fectly even  and  parallel.  After  the  melted  matter  that  filled  the  rent 
(fig.  716)  had  cooled  down,  it  must  have  been  fractured  and  shifted 
horizontally  by  a  lateral  movement. 

In  the  second  figure  (fig.  7 17)  the  lava  has  more  the  appearance  of 

Fig.  716. 


•   0 


*    0 

Ground-plan  of  dikes  near  Palagonia. 
a.  Lava. 

&.  Peperino,  consisting  of  volcanic  sand,  mixed  with  fragments  of 
lava  and  limestone. 

a  vein  which  forced  its  way  through  the  peperino.  It  is  highly 
probable  that  similar  appearances  would  be  seen,  if  we  could  examine 
the  floor  of  the  sea  in  that  part  of  the  Mediterranean  where  the  waves 
have  recently  washed  away  the  new  volcanic  island ;  for  when  a  super- 
incumbent mass  of  ejected  fragments  has  been  removed  by  denuda- 
tion, we  may  expect  to  see  sections  of  dikes  traversing  tuff,  or,  in 
other  words,  sections  of  the  channels  of  communication  by  which  the 
subterranean  lavas  reached  the  surface. 

Volcanic  Rocks  of  Olot  in  Catalonia. — Geologists  are  far  from  being 
able,  as  yet,  to  assign  to  each  of  the  volcanic  groups  scattered  over 
Europe  a  precise  chronological  place  in  the  tertiary  series ;  but  I  shall 
describe  here,  as  probably  referable  in  part  to  the  Post-pliocene  and 
in  part  to  the  Newer  Pliocene  period,  a  district  of  extinct  volcanoes 
near  Olot  in  the  north  of  Spain,  which  is  little  known,  and  which  I 
visited  in  the  summer  of  1830. 

The  whole  extent  of  country  occupied  by  volcanic  products  in 
Catalonia  is  not  more  than  fifteen  geographical  miles  from  north  to 
south,  and  about  six  from  east  to  west.  The  vents  of  eruption  range 
entirely  within  a  narrow  band  running  north  and  south ;  and  the 
branches,  which  are  represented  as  extending  eastward  in  the  map, 
are  formed  simply  of  two  lava-streams — those  of  Castell  Follit  and 
Cellent. 

Dr.  Maclure,  the  American  geologist,  was  the  first  who  made 
known  the  existence  of  these  volcanoes ;  *  and,  according  to  his  do- 


*  Maclure,  Journ.  de  Phys.,  vol.  Ixvi.  p.  219,  1808  ;   cited  by  Daubeny,  Descrip- 
tion of  Volcanoes. 


CH.  XXXI.] 


PLIOCENE  VOLCANOES. 


667 


scription,  the  volcanic  region  extended  over  twenty  square  leagues, 
from  Amer  to  Massanet.  I  searched  in  vain  in  the  environs  of  Mas- 
sanet  in  the  Pyrenees  for  traces  of  a  lava-current ;  and  I  can  say  with 
confidence,  that  the  adjoining  map  gives  a  correct  view  of  the  true 
area  of  the  volcanic  action. 

Fig.  718. 


Volcanic  district  of  Catalonia. 

Geological  Structure  of  the  District. — The  eruptions  have  burst  en- 
tirely through  fossiliferous  rocks,  composed  in  great  part  of  gray  and 
greenish  sandstone  and  conglomerate,  with  some  thick  beds  of  num- 
mulitic  limestone.  The  conglomerate  contains  pebbles  of  quartz, 
limestone,  and  Lydian  stone.  This  system  of  rocks  is  very  exten- 
sively spread  throughout  Catalonia ;  one  of  its  members  being  a  red 
sandstone,  to  which  the  celebrated  salt-rock  of  Cardona,  usually  con- 
sidered as  of  the  cretaceous  era,  is  subordinate. 

Near  Amer,  in  the  Valley  of  the  Ter,  on  the  southern  borders  of 
the  region  delineated  in  the  map,  crystalline  rocks  are  seen,  consisting 
of  gneiss,  mica-schist,  and  clay-slate.  They  run  in  a  line  nearly 
parallel  to  the  Pyrenees,  and  throw  off  the  fossiliferous  strata  from 
their  flanks,  causing  them  to  dip  to  the  north  and  northwest.  This 
dip,  which  is  towards  the  Pyrenees,  is  connected  with  a  distinct  axis 
of  elevation,  and  prevails  through  the  whole  area  described  in  the 


VOLCANOES  OF  CATALONIA. 


[Cn.  XXXI. 


map,  the  inclination  of  the  beds  being  sometimes  at  an  angle  of  be- 
tween 40  and  50  degrees. 

It  is  evident  that  the  physical  geography  of  the  country  has  under- 
gone no  material  change  since  the  commencement  of  the  era  of  the 
volcanic  eruptions,  except  such  as  has  resulted  from  the  introduction 
of  new  hills  of  scorias,  and  currents  of  lava  upon  the  surface.  If  the 
lavas  could  be  remelted  and  poured  out  again  from  their  respective 
craters,  they  would  descend  the  same  valleys  in  which  they  are  now 
seen,  and  reoccupy  the  spaces  which  they  at  present  fill.  The  only 
difference  in  the  external  configuration  of  the  fresh  lavas  would  con- 
sist in  this,  that  they  would  nowhere  be  intersected  by  ravines,  or 
exhibit  marks  of  erosion  by  running  water. 

Volcanic  Cones  and  Lavas. — There  are  about  fourteen  distinct 
cones  with  craters  in  this  part  of  Spain,  besides  several  points 
whence  lavas  may  have  issued ;  all  of  them  arranged  along  a  narrow 
line  running  north  and  south,  as  will  be  seen  in  the  map.  The 
greatest  number  of  perfect  cones  are  in  the  immediate  neighborhood 
of  Olot,  some  of  which  (fig.  719,  Nos.  2,  3,  and  5)  are  represented  in 

Fig.  T19. 


Yiew  of  the  volcanoes  around  Olot  in  Catalonia. 

the  annexed  woodcut ;  and  the  level  plain  on  which  that  town  stands 
has  clearly  been  produced  by  the  flowing  down  of  many  lava-streams 
from  those  hills  into  the  bottom  of  a  valley,  probably  once  of  con- 
siderable depth,  like  those  of  the  surrounding  country. 

In  this  drawing  an  attempt  is  made  to  represent,  by  the  shading 
of  the  landscape,  the  different  geological  formations  of  which  the 
country  is  composed.*  The  white  line  of  mountains  (No.  1)  in  the 

*  This  view  is  taken  from  a  sketch  which  I  made  on  the  spot  in  1830. 


CH.  XXXI.]  PLIOCENE  VOLCANOES.  669 

distance  is  the  Pyrenees,  which  are  to  the  north  of  the  spectator, 
and  consist  of  hypogene  and  ancient  fossiliferous  rocks.  In  front  of 
these  are  the  fossiliferous  formations  (No.  4),  which  are  in  shade. 
Still  nearer  to  us  the  hills  2,  3,  5,  are  volcanic  cones,  and  the  rest  of 
the  ground  on  which  the  sunshine  falls  is  strewed  over  with  volcanic 
ashes  and  lava. 

The  Fluvia,  which  flows  near  the  town  of  Olot,  has  cut  to  the 
depth  of  only  40  feet  through  the  lavas  of  the  plain  before  men- 
tioned. The  bed  of  the  river  is  hard  basalt;  and  at  the  bridge  of 
Santa  Madelina  are  seen  two  distinct  lava-currents,  one  above  the 
other,  separated  by  a  horizontal  bed  of  scoria3  8  feet  thick. 

In  one  place,  to  the  south  of  Olot,  the  even  surface  of  the  plain  is 
broken  by  a  mound  of  lava  called  the  "  Bosque  de  Tosca,"  the  upper 
part  of  which  is  scoriaceous,  and  covered  with  enormous  heaps  of 
fragments  of  basalt,  more  or  less  porous.  Between  the  numerous 
hummocks  thus  formed  are  deep  cavities,  having  the  appearance  of 
small  craters.  The  whole  precisely  resembles  some  of  the  modern 
currents  of  the  Etna,  or  that  of  Come,  near  Clermont ;  the  last  of 
which,  like  the  Bosque  de  Tosca,  supports  only  a  scanty  vegetation. 

Most  of  the  Catalonian  volcanoes  are  as  entire  as  those  in  the 
neighborhood  of  Naples,  or  on  the  flanks  of  Etna.  One  of  these, 
called  Montsacopa  (No.  3,  fig.  719),  is  of  a  very  regular  form,  and 
has  a  circular  depression  or  crater  at  the  summit.  It  is  chiefly  made 
up  of  red  scoria3,  undistinguishable  from  those  of  the  minor  cones  of 
Etna.  The  neighboring  hills  of  Olivet  (No.  2)  and  Garrinada  (No.  5) 
are  of  similar  composition  and  shape.  The  largest  crater  of  the 
whole  district  occurs  farther  to  the  east  of  Olot,  and  is  called  Santa 
Margarita.  It  is  455  feet  deep,  and  about  a  mile  in  circumference. 
Like  Astroni,  near  Naples,  it 'is  richly  covered  with  wood,  wherein 
game  of  various  kinds  abounds. 

Although  the  volcanoes  of  Catalonia  have  broken  out  through 
sandstone,  shale,  and  limestone,  as  have  those  of  the  Eifel,  in  Ger- 
many, to  be  described  in  the  sequel,  there  is  a  remarkable  difference 
in  the  nature  of  the  ejections  composing  the  cones  in  these  two 
regions.  In  the  Eifel,  the  quantity  of  pieces  of  sandstone  and  shale 
thrown  out  from  the  vents  is  often  so  immense  as  far  to  exceed  in 
volume  the  scoriae,  pumice,  and  lava ;  but  I  sought  in  vain  in  the 
cones  near  Olot  for  a  single  fragment  of  any  extraneous  rock ;  and 
Don  Francisco  Bolos,  an  eminent  botanist  of  Olot,  informed  me  that 
he  had  never  been  able  to  detect  any. 

Volcanic  sand  and  ashes  are  not  confined  to  the  cones,  but  have 
been  sometimes  scattered  by  the  wind  over  the  country,  and  drifted 
into  narrow  valleys,  as  is  seen  between  Olot  and  Cellent,  where  the 
annexed  section  (fig.  720,  p.  670)  is  exposed.  The  light  cindery 
volcanic  matter  rests  in  thin  regular  layers,  just  as  it  alighted  on  the 
slope  formed  of  the  solid  conglomerate.  No  flood  could  have  passed 
through  the  valley  since  the  scoriae  fell,  or  these  would  have  been  for 


6TO 


VOLCANOES  OF  CATALONIA. 


[Cn.  XXXL 


720. 


a.  Conglomerate. 

&.  Thin  seams  of  volcanic  sand  and  scoriae. 


the  most  part  removed.  The  cur- 
rents of  lava  in  Catalonia,  like 
those  of  Auvergne,  the  Vivarais, 
Iceland,  and  all  mountainous  coun- 
tries, are  of  considerable  depth  in 
narrow  defiles,  but  spread  out  into 
comparatively  thin  sheets  in  places 
where  the  valleys  widen.  If  a 
river  has  flowed  on  nearly  level 
ground,  as  in  the  great  plain  near  Clot,  the  water  has  only  excavated 
a  channel  of  slight  depth;  but  where  the  declivity  is  great,  the 
stream  has  cut  a  deep  section,  sometimes  by  penetrating  directly 
through  the  central  part  of  a  lava-current,  but  more  frequently  by 
passing  between  the  lava  and  the  secondary  or  tertiary  rock  which 
bounds  the  valley.  Thus,  in  the  accompanying  section  (fig.  721),  at 


Fig.  721. 


Section  above  the  bridge  of  Cellent. 

a.  Scoriaceous  lava.  d.  Scoriae,  vegetable  soil,  and  alluvium. 

&.  Schistose  basalt.  e.  Nummulitic  limestone. 

c.  Columnar  basalt.  /.  Micaceous  gray  sandstone. 

the  bridge  of  Cellent,  six  miles  east  of  Olot,  we  see  the  lava  on  one 
side  of  the  small  stream ;  while  the  inclined  stratified  rocks  consti- 
tute the  channel  and  opposite  bank.  The  upper  part  of  the  lava  at 
that  place,  as  is  usual  in  the  currents  of  Etna  and  Vesuvius,  is  scoria- 
ceous  ;  farther  down  it  becomes  less  porous,  and  assumes  a  spheroidal 
structure;  still  lower  it  divides  in  horizontal  plates,  each  about  2 
inches  in  thickness,  and  is  more  compact.  Lastly,  at  the  bottom  is  a 
mass  of  prismatic  basalt  about  5  feet  thick.  The  vertical  columns 
often  rest  immediately  on  the  subjacent  stratified  rocks  ;  but  there  is 
sometimes  an  intervention  of  sand  and  scoria?  such  as  cover  the  coun- 
try during  volcanic  eruptions,  and  which,  unless  protected,  as  here,  by 
superincumbent  lava,  is  washed  away  from  the  surface  of  the  land. 
Sometimes  the  bed  d  contains  a  few  pebbles  and  angular  fragments 
of  rock ;  in  other  places  fine  earth,  which  may  have  constituted  an 
ancient  vegetable  soil. 


CH.  XXXI.] 


PLIOCENE  VOLCANOES. 


671 


In  several  localities,  beds  of  sand  and  ashes  are  interposed  between 
the  lava  and  subjacent  stratified  rock,  as  may  be  seen  if  we  follow 
the  course  of  the  lava-current  which  descends  from  Las  Planas 
towards  Amer,  and  stops  two  miles  short  of  that  town.  The  river 
there  has  often  cut  through  the  lava,  and  through  18  feet  of  under- 
lying limestone.  Occasionally  an  alluvium,  several  feet  thick,  is 
interposed  between  the  igneous  and  marine  formations ;  and  it  is 
interesting  to  remark  that  in  this,  as  in  other  beds  of  pebbles  occu- 
pying a  similar  position,  there  are  no  rounded  fragments  of  lava; 
whereas  in  the  most  modern  gravel-beds  of  the  rivers  of  this  country 
volcanic  pebbles  are  abundant. 

The  deepest  excavation  made  by  a  river  through  lava,  which  I 
observed  in  this  part  of  Spain,  is  seen  in  the  bottom  of  a  valley  near 
San  Feliu  de  Pallerols,  opposite  the  Castell  de  Stolles.  The  lava 
there  has  filled  up  the  bottom  of  a  valley,  and  a  narrow  ravine  has 
been  cut  through  it  to  the  depth  of  100  feet.  In  the  lower  part  the 
lava  has  a  columnar  structure.  A  great  number  of  ages  were  proba- 
bly required  for  the  erosion  of  so  deep  a  ravine  ;  but  we  have  no  rea- 
son to  infer  that  this  current  is  of  higher  antiquity  than  those  of  the 
plain  near  Olot.  The  fall  of  the  ground,  and  consequent  velocity  of 
the  stream,  being  in  this  case  greater,  a  more  considerable  volume  of 
rock  may  have  been  removed  in  the  same  time. 

I  shall  describe  one  more  section  (fig.  722)  to  elucidate  the  phe- 
nomena of  this  district.  A  lava-stream,  flowing  from  a  ridge  of  hills 

Fig.  722. 


Section  at  Castell  Follit. 

A.  Church  and  town  of  Castell  Follit,  overlooking  precipices  of  basalt. 

B.  Small  island,  on  each  side  of  which  branches  of  the  river  Teronel  flow  to  meet  the 

Fluvia. 

c.  Precipice  of  basaltic  lava,  chiefly  columnar,  about  130  feet  in  height. 

d.  Ancient  alluvium,  underlying  the  lava-current, 
ft,  Inclined  strata  of  sandstone. 

on  the  east  of  Olot,  descends  a  considerable  slope,  until  it  reaches 
the  valley  of  the  river  Fluvia.  Here,  for  the  first  time,  it  comes  in 
contact  with  running  water,  which  has  removed  a  portion,  and  laid 


672  VOLCANOES  OF  CATALONIA.        [Cn.  XXXI 

open  its  internal  structure  in  a  precipice  about  130  feet  in  height, 
at  the  edge  of  which  stands  the  town  of  Castell  Follit. 

By  the  junction  of  the  rivers  Fluvia  and  Teronel,  the  mass  of  lava 
has  been  cut  away  on  two  sides ;  and  the  insular  rock  B  (fig.  722) 
has  been  left,  which  was  probably  never  so  high  as  the  cliff  A,  as  it 
may  have  constituted  the  lower  part  of  the  sloping  side  of  the  origi- 
nal current. 

From  an  examination  of  the  vertical  cliffs,  it  appears  that  the 
upper  part  of  the  lava  on  which  the  town  is  built  is  scoriaceous,  pass- 
ing downwards  into  a  spheroidal  basalt ;  some  of  the  huge  spheroids 
being  no  less  than  6  feet  in  diameter.  Below  this  is  a  more  compact 
basalt,  with  crystals  of  olivine.  There  are  in  all  five  distinct  ranges 
of  basalt,  the  uppermost  spheroidal,  and  the  rest  prismatic,  separated 
by  thinner  beds  not  columnar,  and  some  of  which  are  schistose. 
These  were  probably  formed  by  successive  flows  of  lava,  whether 
during  the  same  eruption  or  at  different  periods.  The  whole  mass 
rests  on  alluvium,  10  or  12  feet  in  thickness,  composed  of  pebbles  of 
limestone  and  quartz,  but  without  any  intermixture  of  igneous  rocks ; 
in  which  circumstance  alone  it  appears  to  differ  from  the  modern 
gravel  of  the  Fluvia. 

Bufadors. — The  volcanic  rocks  near  Olot  have  often  a  cavernous 
structure,  like  some  of  the  lavas  of  Etna ;  and  in  many  parts  of  the 
hill  of  Batet,  in  the  environs  of  the  town,  the  sound  returned  by  the 
earth,  when  struck,  is  like  that  of  an  archway.  At  the  base  of  the 
same  hill  are  the  mouths  of  several  subterranean  caverns,  about  twelve 
in  number,  called  in  the  country  "  bufadors,"  from  which  a  current  of 
cold  air  issues  during  summer,  but  in  winter  it  is  said  to  be  scarcely 
perceptible.  I  visited  one  of  these  bufadors  in  the  beginning  of 
August,  1830,  when  the  heat  of  the  season  was  unusually  intense,  and 
found  a  cold  wind  blowing  from  it,  which  may  easily  be  explained ; 
for  as  the  external  air,  when  rarefied  by  heat,  ascends,  the  pressure  of 
the  colder  and  heavier  air  of  the  caverns  in  the  interior  of  the  moun- 
tain causes  it  to  rush  out  to  supply  its  place. 

In  regard  to  the  age  of  these  Spanish  volcanoes,  attempts  have  been 
made  to  prove,  that  in  this  country,  as  well  as  in  Auvergne  and  the 
Eifel,  the  earliest  inhabitants  were  eye-witnesses  to  the  volcanic 
action.  In  the  year  1421,  it  is  said,  when  Olot  was  destroyed  by  an 
earthquake,  an  eruption  broke  out  near  Amer,  and  consumed  the 
town.  The  researches  of  Don  Francisco  Bolos  have,  I  think,  shown, 
in  the  most  satisfactory  manner,  that  there  is  no  good  historical  foun- 
dation for  the  latter  part  of  this  story ;  and  any  geologist  who  has  visit- 
ed Amer  must  be  convinced  that  there  never  was  any  eruption  on  that 
spot.  It  is  true  that  in  the  year  above  mentioned,  the  whole  of  Olot, 
with  the  exception  of  a  single  house,  was  cast  down  by  an  earthquake ; 
one  of  those  shocks  which,  at  distant  intervals  during  the  last  five 
centuries,  have  shaken  the  Pyrenees,  and  particularly  the  country  be- 
tween Perpignan  and  Olot,  where  the  movements,  at  the  period  alluded 
to,  were  most  violent. 


CH.  XXXI.]  PLIOCEXE   VOLCANOES. 

The  annihilation  of  the  town  may,  perhaps,  have  been  due  to  the 
cavernous  nature  of  the  subjacent  rocks ;  for  Catalonia  is  beyond  the 
line  of  those  European  earthquakes  which  have,  within  the  period  of 
history,  destroyed  towns  throughout  extensive  areas. 

As  we  have  no  historical  records,  then,  to  guide  us  in  regard  to  the 
extinct  volcanoes,  we  must  appeal  to  geological  monuments.  The  an- 
nexed diagram  (fig.  723)  will  present  to  the  reader,  in  a  synoptical 
form,  the  results  obtained  from  numerous  sections. 

Fig.  723. 


Superposition  of  rocks  in  the  volcanic  district  of  Catalonia. 

a.  Sandstone  and  nummulitic  limestone.  c.  Cones  of  scoriae  and  lava. 

&.  Older  alluvium  without  volcanic  pebbles.  d.  Newer  alluvium. 

The  more  modern  alluvium  (d)  is  partial,  and  has  been  formed  by 
the  action  of  rivers  and  floods  upon  the  lava;  whereas  the  older  gravel 
(6)  was  strewed  over  the  country  before  the  volcanic  eruptions.  In 
neither  have  any  organic  remains  been  discovered ;  so  that  we  can 
merely  affirm,  as  yet,  that  the  volcanoes  broke  out  after  the  elevation 
of  some  of  the  newest  rocks  of  the  nummulitic  (Eocene)  series  of 
Catalonia,  and  before  the  formation  of  an  alluvium  (d)  of  unknown 
date.  The  integrity  of  the  cones  merely  shows  that  the  country  has 
not  been  agitated  by  violent  earthquakes,  or  subjected  to  the  action  of 
any  great  flood  since  their  origin. 

East  of  Olot,  on  the  Catalonian  coast,  marine  tertiary  strata  occur, 
which,  near  Barcelona,  attain  the  height  of  about  500  feet.  From  the 
shells  which  I  collected,  these  strata  appear  to  correspond  in  age  with 
the  Subapennine  beds ;  and  it  is  not  improbable  that  their  upheaval 
from  beneath  the  sea  took  place  during  the  period  of  volcanic  erup- 
tion round  Olot.  In  that  case  these  eruptions  may  have  occurred 
partly  during  the  Newer  Pliocene,  and  partly  during  the  Post-pliocene 
period,  but  their  exact  age  is  at  present  uncertain. 

Older  Pliocene  Period. — Italy. — In  Tuscany,  as  at  Radicofani, 
Viterbo,  and  Aquapendente,  and  in  the  Campagna  di  Roma,  sub- 
marine volcanic  tuffs  are  interstratified  with  the  Older  Pliocene  strata 
of  the  Subapennine  hills  in  such  a  manner  as  to  leave  no  doubt  that 
they  were  the  products  of  eruptions  which  occurred  when  the  shelly 
marls  and  sands  of  the  Subapennine  hills  were  in  the  course  of  depo- 
sition. This  opinion  I  expressed*  after  my  visit  to  Italy  in  1828, 

*  See  first  edition  of  Principles  of  Geology,  vol.  iii.  chaps,  xiii.  and  xir.,  1833 ; 
and  former  editions  of  this  work,  chap.  xxxi. 
43 


UPPER  MIOCENE  VOLCANOES.  [Cn.  XXXI. 

and  it  has  recently  (1850)  been  confirmed  by  the  arguments  adduced 
by  Sir  R.  Murchison  in  favor  of  the  submarine  origin  of  the  earlier 
volcanic  rocks  of  Italy.*  These  rocks  are  well  known  to  rest  con- 
formably on  the  Subapennine  marls,  even  as  far  south  as  Monte  Mario 
in  the  suburbs  of  Rome.  On  the  exact  age  of  the  deposits  of  Monte 
Mario  new  light  has  recently  been  thrown  by  a  careful  study  of  their 
marine  fossil  shells,  undertaken  by  MM.  Rayneval,  Vanden  Hecke,  and 
Ponzi.  They  have  compared  no  less  than  160  species  f  with  the  shells 
of  the  Coralline  Crag  of  Suffolk,  so  well  described  by  Mr.  Searles 
Wood ;  and  the  specific  agreement  between  the  British  and  Italian 
fossils  is  so  great,  if  we  make  due  allowance  for  geographical  distance 
and  the  difference  of  latitude,  that  we  can  have  little  hesitation  in 
referring  both  to  the  same  period  or  to  the  Older  Pliocene  of  this 
work.  It  is  highly  probable  that,  between  the  oldest  trachytes  of 
Tuscany  and  the  newest  rocks  in  the  neighborhood  of  Naples,  a  series 
of  volcanic  products  might  be  detected  of  every  age  from  the  Older 
Pliocene  to  the  historical  epoch. 

VOLCANIC    ROCKS    OF    THE    UPPER   MIOCENE    PERIOD. 

Madeira  and  Porto  Santo. — When  treating  generally  of  the  origin 
and  structure  of  volcanic  mountains,  I  have  described  (p.  646)  at  some 
length  the  volcanic  tuffs  and  other  igneous  rocks  of  Tertiary  and  Post- 
tertiary  date  in  the  island  of  Madeira.  Among  the  submarine  de- 
posits, it  was  stated  that  some  were  as  old  as  the  Upper  Miocene 
period,  as  shown  by  the  fossil  shells  included  in  the  tuffs  which  have 
been  upraised  at  San  Vicente  in  the  northern  part  of  the  island  to  the 
height  of  1300  feet  above  the  level  of  the  sea.  A  similar  formation 
constitutes  the  fundamental  portion  of  the  neighboring  island  of  Porto 
Santo,  forty  miles  distant  from  Madeira.  The  marine  beds  are  there 
elevated  to  an  equal  height,  and  covered,  as  in  Madeira,  with  lavas  of 
supramarine  origin. 

The  largest  number  of  fossils  have  been  collected  from  tuffs  and 
conglomerates  and  some  beds  of  limestone  in  the  island  of  Baixo,  off 
the  southern  extremity  of  Porto  Santo.  They  amount  in  this  single 
locality  to  more  than  sixty  in  number,  of  which  about  fifty  are  mol- 
lusca,  many  of  them  in  the  state  of  casts  only. 

Some  of  the  shells  probably  lived  on  the  spot  in  the  intervals  be- 
tween eruptions ;  some  may  have  been  cast  up  into  the  water  or  air 
together  with  muddy  ejections,  and,  falling  down  again,  were  de- 
posited on  the  bottom  of  the  sea.  The  hollows  in  some  fragments  of 
vesicular  lava,  entering  into  the  composition  of  the  breccias  and  con- 
glomerates, are  partially  filled  with  calc-sinter,  being  thus  half  con- 
verted into  amygdaloids. 

*  Geol.  Quart.  Journ.,  vol.  vi.  p.  281. 

•j-  Catalogue  des  Fossiles  de  Monte  Mario,  Rome,  1854. 


CH.  XXXI.]  UPPER  MIOCENE  VOLCANOES.  675 

Among  the  fossil  shells  common  to  Madeira  and  Porto  Santo,  large 
cones,  strombs,  and  cowries  are  conspicuous  among  the  univalves,  and 
Cardium,  Spondylus,  and  Lithodomus  among  the  lamellibranchiate 
bivalves.  Among  the  Echinoderms  the  large  Clypeaster,  C.  altus,  an 
extinct  European  Miocene  fossil,  is  seen. 

The  largest  list  of  fossils  has  been  published  by  M.  Karl  Meyer,  in 
Hartung's  "  Madeira ; "  but  in  the  collection  made  by  myself,  and  in  a 
still  larger  one  formed  by  Mr.  J.  Yate  Johnson,  several  remarkable 
forms  not  in  Meyer's  list  occur,  as,  for  example,  Pholadomya,  and  a 
large  Terebra.  Mr.  Johnson  also  found  a  fine  specimen  of  Nautilus 
(Atruria)  zigzag,  a  well-known  Falunian  fossil  of  Europe ;  and  in 
the  same  volcanic  tuff  of  Baixo,  the  Echinoderm  Brissus  Scillce,  a 
living  Mediterranean  species,  found  fossil  in  the  Miocene  strata  of 
Malta.  M.  Meyer  identifies  one-third  of  the  Madeira  shells  with 
known  European  Miocene  (or  Falunian)  forms.  The  huge  Strombus 
of  San  Vicente  and  Porto  Santo,  S.  Italicus,  is  an  extinct  shell  of  the 
Subapennine  or  Older  Pliocene  formations. 

The  mollusca  already  obtained  from  various  localities  of  Madeira 
and  Porto  Santo  are  not  less  than  one  hundred  in  number,  and,  accord- 
ing to  Dr.  S.  P.  Woodward,  rather  more  than  a  third  are  of  species 
still  living,  but  many  of  these  are  not  now  inhabitants  of  the  neighbor- 
ing sea. 

It  has  been  remarked  (p.  213)  that  in  the  Older  Pliocene  and 
Upper  Miocene  deposits  of  Europe,  many  forms  occur  of  a  more 
southern  aspect  than  those  now  inhabiting  the  nearest  sea.  In  like 
manner  the  fossil  corals,  or  Zoantharia,  six  in  number,  which  I  ob- 
tained from  Madeira,  of  the  genera  Astrcea,  Sarcinula,  flydnophora, 
&c.,  were  pronounced  by  Mr.  Lonsdale  to  be  forms  foreign  to  the  ad- 
jacent coasts,  and  to  agree  with  those  of  more  tropical  latitudes  and 
parts  of  the  Red  Sea.  So  the  Miocene  shells  of  the  Madeiras  seem  to 
belong  to  the  fauna  of  a  sea  warmer  than  that  now  separating  Madeira 
from  the  nearest  part  of  the  African  coast.  We  learn,  indeed,  from 
the  observations  made  in  1859,  by  the  Rev.  R.  T.  Lowe,  that  more 
than  one-half,  or  fifty-three  in  ninety,  of  the  marine  mollusks  collected 
by  him  from  the  sandy  beach  of  Mogador  are  common  British  species, 
although  Mogador  is  18-J-  degrees  south  of  the  nearest  shores  of  Eng- 
land. The  living  shells  of  Madeira  and  Porto  Santo  are  in  like  man- 
ner those  of  a  temperate  climate,  although  in  great  part  differing  spe- 
cifically from  those  of  Mogador.* 

Grand  Canary. — In  the  Canaries,  especially  in  the  Grand  Canary, 
the  same  marine  Upper  Miocene  formation  is  found.  Stratified  tuffs, 
with  intercalated  conglomerates  and  lavas,  are  there  seen  in  nearly 
horizontal  layers  in  sea-cliffs  about  300  feet  high,  near  Las  Palmas. 
M.  Hartung  and  I  were  unable  to  find  marine  shells  in  these  tuffs  at  a 
greater  elevation  than  400  feet  above  the  sea ;  but  as  the  deposit  to 

*  Linnaean  Proceedings ;  Zoology,  1860. 


676  UPPER  MIOCENE  VOLCANOES.  [On.  XXXI. 

which  they  belong  reaches  to  the  height  of  1100  feet  or  more  in  the 
interior,  we  conceive  that  an  upheaval  of  at  least  that  amount  has 
taken  place.  The  Clypeaster  altus,  Spondylus  gcederopus,  Pectunculus 
pilosus,  Cardita  calyculata,  and  several  other  shells,  serve  to  identify 
this  formation  with  that  of  the  Madeiras,  and  Ancillaria  glandiformis, 
which  is  not  rare,  and  some  other  fossils,  remind  us  of  the  faluns  of 
Touraine. 

The  sixty-two  Miocene  species  which  I  collected  in  the  Grand 
Canary  are  referred,  by  Dr.  S.  P.  Woodward,  to  forty-seven  genera, 
ten  of  which  are  no  longer  represented  in  the  neighboring  sea,  namely, 
Corbis,  an  African  form,  Hinnites,  now  living  in  Oregon,  Thecidium 
(T.  Mediterranean,  identical  with  the  Miocene  fossil  of  St.  Juvat,  in 
Brittany),  Calyptrcea,  Hipponyx,  Nerita,  Erato,  Oliva,  Ancillaria,  and 
Fasciolaria. 

These  tuffs  of  the  southern  shores  of  the  Grand  Canary,  containing 
the  Upper  Miocene  shells,  appear  to  be  about  the  same  age  as  the 
most  ancient  volcanic  rocks  of  the  island,  composed  of  slaty  diabase, 
phonolite,  and  trachyte.  Over  the  marine  lavas  and  tuffs  trachytic  and 
basaltic  products  of  subaerial  volcanic  origin,  between  4000  and  5000 
feet  in  thickness,  have  been  piled,  the  central  parts  of  the  Grand 
Canary  reaching  the  heights  of  about  6000  feet  above  the  level  of  the 
sea.  Some  lavas  have  a  very  fresh  aspect,  and  have  been  poured  out 
since  the  time  when  the  vaDeys  were  already  excavated  to  within  a 
few  feet  of  their  present  depth.  They  must  be  very  modern,  geo- 
logically speaking,  but  being  anterior  to  the  European  colonization  of 
the  Grand  Canary,  their  date  is  unknown. 

A  raised  beach  occurs  at  San  Catalina,  about  a  quarter  of  a  mile 
north  of  Las  Palmas,  which  is  situated  in  the  northeastern  part  of  the 
island.  It  intervenes  between  the  base  of  the  high  cliff  formed  of  the 
tuffs  with  Miocene  shells  and  the  sea-shore.  From  this  beach,  elevated 
twenty-five  feet  above  high-water  mark,  and  at  a  distance  of  about  1 50 
feet  from  the  shore,  I  obtained,  with  the  assistance  of  Don  Pedro 
Maffiotte,  more  than  fifty  species  of  living  marine  shells.  Many  of 
them,  according  to  Dr.  S.  P.  Woodward,  are  no  longer  inhabitants  of 
the  contiguous  sea,  as,  for  example,  S  trombus  bubonius,  which  is  still 
living  on  the  West  coast  of  Africa,  and  Cerithium  procerum,  found  at 
Mozambique :  others  are  Mediterranean  species,  as  Pecten  Jacobceus 
and  P.  polymorphus.  Some  of  these  testacea,  such  as  Cardita 
squamosa,  are  inhabitants  of  deep  water,  and  the  deposit  on  the  whole 
seems  to  indicate  a  depth  of  water  exceeding  a  hundred  feet. 

Azores. — In  the  island  of  St.  Mary's,  one  of  the  Azores,  marine 
fossil  shells  have  long  been  known.  They  are  found  in  the  northeast 
coast  in  a  small  projecting  promontory  called  Ponta  do  Papagaio  (or 
Point-Part-ot),  chiefly  in  a  limestone  about  20  feet  thick,  which  rests 
upon,  and  is  again  covered  by,  basaltic  lavas,  scoriae,  and  conglom- 
erates. The  pebbles  in  the  conglomerate  are  cemented  together  with 
carbonate  of  lime. 


CH.  XXXI.]  LOWER  MIOCENE  VOLCANIC  ROCKS.  677 

M.  Hartung,  in  his  account  of  the  Azores,  published  in  1860,  de- 
scribes twenty-three  shells  from  St.  Mary's,*  of  which  eight  perhaps 
are  identical  with  living  species,  and  twelve  are  with  more  or  less  cer- 
tainty referred  to  European  Tertiary  forms,  chiefly  Upper  Miocene. 
One  of  the  most  characteristic  and  abundant  of  the  new  species,  Car- 
dium  Hartungi,  not  known  as  fossil  in  Europe,  is  very  common  in 
Porto  Santo  and  Baixo,  and  serves  to  connect  the  Miocene  fauna  of 
the  Azores  and  the  Madeiras. 

It  appears  from  what  has  been  said  in  the  twenty-ninth  and  in  the 
present  chapter,  that  the  volcanic  eruptions  of  Madeira,  the  Canaries, 
and  the  Azores,  commenced  in  the  Upper  Miocene  period,  and  con- 
tinued down  to  Post-pliocene  times :  in  some  islands  of  the  Canarian 
and  Azorian  groups,  the  volcanic  fires  are  not  yet  extinct,  as  the  re- 
corded eruptions  of  Lanzerote,  Teneriffe,  Palma,  St.  Michaels,  and 
others  attest. 

In  each  of  the  three  archipelagoes  there  are  proofs  of  Miocene  sub- 
marine formations  having  been  gradually  uplifted  during  the  outpour- 
ing of  successive  lavas,  in  the  same  manner  as  the  Pliocene  marine 
strata  of  the  oldest  parts  of  Vesuvius  and  Etna  have  been  upraised 
during  eruptions  of  Post-tertiary  date.  In  the  Grand  Canary,  in 
Teneriffe,  and  in  Porto  Santo,  I  observed  raised  beaches,  showing  that 
movements  of  elevation  have  in  each  of  them  been  continued  down  to 
the  Post-tertiary  period. 


LOWER   MIOCENE    VOLCANIC    ROCKS. 

The  Eifel. — A  large  portion  of  the  volcanic  rocks  of  the  Lower 
Rhine  and  the  Eifel  are  coeval  with  the  Lower  Miocene  deposits  to 
which  most  of  the  "Brown-Coal"  of  Germany  belongs.  The  Ter- 
tiary strata  of  that  age  are  seen  on  both  sides  of  the  Rhine,  in  the 
neighborhood'of  Bonn,  resting  unconformably  on  highly  inclined  and 
vertical  strata  of  Silurian  and  Devonian  rocks.  Its  geographical 
position,  and  the  space  occupied  by  the  volcanic  rocks,  both  of  the 
Westerwald  and  Eifel,  will  be  seen  by  referring  to  the  map  (fig.  724), 
for  which  I  am  indebted  to  the  late  Mr.  Horner,  whose  residence  for 
some  years  in  the  country  enabled  him  to  verify  the  maps  of  MM. 
Noeggerath  and  Yon  Oeynhausen,  from  which  that  now  given  has 
been  principally  compiled.f 

The  Brown-Coal  formation  of  that  region  consists  of  beds  of  loose 
sand,  sandstone,  and  conglomerate,  clay  with  nodules  of  clay-iron- 
stone, and  occasionally  silex.  Layers  of  light  brown  and  sometimes 
black  lignite  are  interstratified  with  the  clays  and  sands,  and  often 

*  Hartung,  Die  Azoren,  1860 ;  also  Insel  Gran  Canaria,  Madeira,  und  Porto 
Santo,  1864,  Leipsig. 

f  Horner,  Trans,  of  Geol.  Soc.,  Second  Series,  vol.  v. 


6T8 


AGE  OF  THE  BROWN-COAL. 
Fig.  724. 


[Cn.  XXXI. 


Map  of  the  volcanic  region  of  the  Upper  and  Lower  Eifel. 
12345  English  Miles. 


Volcanic     j  A.  Of  the  Upper  Eifel. 
District.      |  R  Of  the  Lower  Eifel. 

Trachyte. 


Points  of  eruption,  with  craters 
and  scorise. 

BaSalt 
Brown-coal. 


Jf  B.  The  country  in  that  part  of  the  map  which  is  left  blank  is  composed  of  inclined 
Silurian  and  Devonian  rocks. 

irregularly  diffused  through  them.  They  contain  numerous  impres- 
sions of  leaves  and  stems  of  trees,  and  are  extensively  worked  for 
fuel,  whence  the  name  of  the  formation. 

In  several  places,  layers  of  trachytic  tuff  are  interstratified,  and  in 
these  tuffs  are  leaves  of  plants  identical  with  those  found  in  the  brown- 
coal,  showing  that,  during  the  period  of  the  accumulation  of  the  latter, 
some  volcanic  products  were  ejected. 

M.  Von  Dechen,  in  his  work  on  the  Siebengebirge,*  has  given  a 
copious  list  of  the  animal  and  vegetable  remains  of  the  freshwater 
strata  associated  with  the  brown-coal.  Plants  of  the  genera  Flabel- 
laria,  Ceanothus,  and  Daphnogene,  including  D.  cinnamomifolia  (fig. 
204,  p.  264),  occur  in  these  beds,  with  nearly  150  other  plants. 

The  fishes  of  the  brown-coal  near  Bonn  are  found  in  a  bituminous 


*  Geognost.  Beschreib.  des  Siebengebirges  am  Rhein.     Bonn,  1852. 


CH.  XXXI.]  LAKE-CRATERS  OF  THE  EIFEL.  679 

shale,  called  paper-coal,  from  being  divisible  into  extremely  thin 
leaves.  The  individuals  are  very  numerous;  but  they  appear  to 
belong  to  a  small  number  of  species,  some  of  which  were  referred  by 
Agassiz  to  the  genera  Leuciscus,  Aspius,  and  Perca.  The  remains  of 
frogs  also,  of  extinct  species,  have  been  discovered  in  the  paper-coal ; 
and  a  complete  series  may  be  seen  in  the  museum  at  Bonn,  from  the 
most  imperfect  state  of  the  tadpole  to  that  of  the  full-grown  animal. 
With  these  a  salamander,  scarcely  distinguishable  from  the  recent 
species,  has  been  found,  and  the  remains  of  many  insects. 

A  vast  deposit  of  gravel,  chiefly  composed  of  pebbles  of  white 
quartz,  but  containing  also  a  few  fragments  of  other  rocks,  lies  over 
the  brown-coal,  forming  sometimes  only  a  thin  covering,  at  others 
attaining  a  thickness  of  more  than  100  feet.  The  gravel  is  very  dis- 
tinct in  character  from  that  now  forming  the  bed  of  the  Rhine.  It  is 
called  "  Kiesel-gerdlle  "  by  the  Germans,  often  reaches  great  elevations, 
and  is  covered  in  several  places  with  volcanic  ejections.  It  is  evident 
that  the  country  has  undergone  great  changes  in  its  physical  geogra- 
phy since  this  gravel  was  formed ;  for  its  position  has  scarcely  any 
relation  to  the  existing  drainage,  and  the  great  valley  of  the  Rhine 
and  all  the  more  modern  volcanic  rocks  of  the  same  region  are  posterior 
to  it  in  date. 

Some  of  the  newest  beds  of  volcanic  sand,  pumice,  and  scoriae  are 
interstratified  near  Andernach  and  elsewhere  with  the  loam  called 
loess,  which  was  before  described  as  being  full  of  land  and  freshwater 
shells  of  recent  species,  and  referable  to  the  Post-pliocene  period. 
But  this  intercalation  of  volcanic  matter  between  beds  of  loess  may 
possibly  be  explained  without  supposing  the  last  eruptions  of  the 
Lower  Eifel  to  have  taken  place  so  recently  as  the  era  of  the  depo- 
sition of  the  loess. 

The  igneous  rocks  of  the  Westerwald,  and  of  the  mountains  called 
the  Siebengebirge,  consist  partly  of  basaltic  and  partly  of  trachytic 
lavas,  the  latter  being  in  general  the  more  ancient  of  the  two.  There 
are  many  varieties  of  trachyte,  some  of  which  are  highly  crystalline, 
resembling  a  coarse-grained  granite,  with  large  separate  crystals  of 
felspar.  Trachytic  tuff  is  also  very  abundant.  These  formations, 
some  of  which  were  certainly  contemporaneous  with  the  origin  of  the 
brown-coal,  were  the  first  of  a  long  series  of  eruptions,  the  more  recent 
of  which  happened  when  the  country  had  acquired  nearly  all  its  pres- 
ent geographical  features. 

Newer  Volcanoes  of  the  Eifel. — Lake-Craters. — As  I  recognized 
in  the  more  modern  volcanoes  of  the  Eifel  characters  distinct  from 
any  previously  observed  by  me  in  those  of  France,  Italy,  or  Spain,  I 
shall  briefly  describe  them.  The  fundamental  rocks  of  the  district 
are  gray  and  red  sandstones  and  shales,  with  some  associated  lime- 
stones, replete  with  fossils  of  the  Devonian  or  Old  Red  Sandstone 
group.  The  volcanoes  broke  out  in  the  midst  of  these  inclined  strata, 
and  when  the  present  systems  of  hills  and  valleys  had  already  been 


680 


TERTIARY  VOLCANIC  ROCKS. 


[Ca 


formed.  The  eruptions  occurred  sometimes  at  the  bottom  of  deep 
valleys,  sometimes  on  the  summit  of  hills,  and  frequently  on  inter- 
vening platforms.  In  travelling  through  this  district  we  often  fall 
upon  them  most  unexpectedly,  and  may  find  ourselves  on  the  very 
edge  of  a  crater  before  we  had  been  led  to  suspect  that  we  were  ap- 
proaching the  site  of  any  igneous  outburst.  Thus,  for  example,  on 
arriving  at  the  village  of  Gemund,  immediately  south  of  Daun,  we 
leave  the  stream,  which  flows  at  the  bottom  of  a  deep  valley  in  which 
strata  of  sandstone  and  shale  crop  out.  We  then  climb  a  steep  hill, 
on  the  surface  of  which  we  see  the  edges  of  the  same  strata  dipping 
inwards  towards  the  mountain.  When  we  have  ascended  to  a  con- 
siderable height,  we  see  fragments  of  scoriae  sparingly  scattered  over 
the  surface ;  until,  at  length,  on  reaching  the  summit,  we  find  ourselves 
suddenly  on  the  edge  of  a  tarn,  or  deep  circular  lake-basin  (see  fig. 
725). 

Fig.  726. 


The  Gemunder  Maar. 

This,  which  is  called  the  Gemunder  Maar,  is  one  of  three  lakes 
which  are  in  immediate  contact,  the  same  ridge  forming  the  barrier 
of  two  neighboring  cavities.  On  viewing  the  first  of  these  (fig.  725), 
we  recognize  the  ordinary  form  of  a  crater,  for  which  we  have  been 
prepared  by  the  occurrence  of  scoria?,  scattered  over  the  surface  of 
the  soil.  But  on  examining  the  walls  of  the  crater  we  find  precipices 
of  sandstone  and  shale  which  exhibit  no  signs  of  the  action  of  heat ; 
and  we  look  in  vain  for  those  beds  of  lava  and  scorise,  dipping  out- 
wards on  every  side,  which  we  have  been  accustomed  to  consider  as 
characteristic  of  volcanic  vents.  As  we  proceed,  however,  to  the 
opposite  side  of  the  lake,  and  afterwards  visit  the  craters  c  and  d  (fig. 
726),  we  find  a  considerable  quantity  of  scoria?  and  some  lava,  and  see 

Fig.  726. 


a.  Village  of  Gemund. 
&.  Gemunder  Maar. 


c.  Weinfelder  Maar. 

d.  Schalkenmehren  Maar. 


CH.  XXXI.]  LAKE-CRATERS  OF  THE  EIFEL. 

the  whole  surface  of  the  soil  sparkling  with  volcanic  sand,  and  strewed 
with  ejected  fragments  of  half-fused  shale,  which  preserves  its  lami- 
nated texture  in  the  interior,  while  it  has  a  vitrified  or  scoriform 
coating. 

A  few  miles  to  the  south  of  the  lakes  above  mentioned  occurs  the 
Pulvermaar  of  Gillenfeld,  an  oval  lake  of  very  regular  form,  and  sur- 
rounded by  an  unbroken  ridge  of  fragmentary  materials  consisting  of 
ejected  shale  and  sandstone,  and  preserving  a  uniform  height  of  about 
150  feet  above  the  water.  The  slope  in  the  interior  is  at  an  angle  of 
about  45  degrees ;  on  the  exterior,  of  35  degrees.  Volcanic  substances 
are  intermixed  very  sparingly  with  the  ejections,  which  in  this  place 
entirely  conceal  from  view  the  stratified  rocks  of  the  country.* 

The  Meerfelder  Maar  is  a  cavity  of  far  greater  size  and  depth,  hol- 
lowed out  of  similar  strata ;  the  sides  presenting  some  abrupt  sections 
of  inclined  secondary  rocks,  which  in  other  places  are  buried  under 
vast  heaps  of  pulverized  shale.  I  could  discover  no  scoriae  amongst 
the  ejected  materials,  but  balls  of  olivine  and  other  volcanic  substances 
are  mentioned  as  having  been  found.f  This  cavity,  which  we  must 
suppose  to  have  discharged  an  immense  volume  of  gas,  is  nearly  a 
mile  in  diameter,  and  is  said  to  be  more  than  one  hundred  fathoms 
deep.  In  the  neighborhood  is  a  mountain  called  the  Mosenberg, 
which  consists  of  red  sandstone  and  shale  in  its  lower  parts,  but  sup- 
ports on  its  summit  a  triple  volcanic  cone,  while  a  distinct  current  of 
lava  is  seen  descending  the  flanks  of  the  mountain.  The  edge  of  the 
crater  of  the  largest  cone  reminded  me  much  of  the  form  and  charac- 
ters of  that  Vesuvius ;  but  I  was  much  struck  with  the  precipitous  and 
almost  overhanging  wall  or  parapet  which  the  scoriae  presented 
towards  the  exterior,  as  at  a  b  (fig.  727) ;  which  I  can  only  explain  by 

Fig.  727. 


Stratified  rocks.  v.  Volcanic. 

Outline  of  the  Mosenberg,  Upper  Eifel. 

supposing  that  fragments  of  red-hot  lava,  as  they  fell  round  the  vent, 
were  cemented  together  into  one  compact  mass,  in  consequence  of 
continuing  to  be  in  a  half-melted  state. 

If  we  pass  from  the  Upper  to  the  Lower  Eifel,  from  A  to  B  (see 
Map,  p.  678),  we  find  that  celebrated  lake-crater  of  Laach,  which  has 
a  greater  resemblance  than  any  of  those  before  mentioned  to  the  Lago 

*  Scrope,  Edin.  Journ.  of  Science,  June,  1826,  p.  145. 
f  Hibbert,  Extinct  Volcanoes  of  the  Rhine,  p.  24. 


TERTIARY  VOLCANIC  ROCKS.  [Cn.  XXXI. 

di  Bolsena,  and  others  in  Italy,  being  surrounded  by  a  ridge  of, gently 
sloping  hills,  composed  of  loose  tuffs,  scoriae,  and  blocks  of  a  variety 
of  lavas. 

One  of  the  most  interesting  volcanoes  on  the  left  bank  of  the  Rhine 
near  Bonn  is  called  the  Roderberg.  It  forms  a  circular  crater  nearly 
a  quarter  of  a  mile  in  diameter,  and  100  feet  deep,  now  covered  with 
fields  of  corn.  The  highly  inclined  strata  of  ancient  sandstone  and 
shale  rise  even  to  the  rim  of  one  side  of  the  crater ;  but  they  are  over- 
spread by  quartzose  gravel,  and  this  again  is  covered  by  volcanic 
scoriae  and  tufaceous  sand.  The  opposite  wall  of  the  crater  is  com- 
posed of  cinders  and  scorified  rock,  like  that  at  the  summit  of  Vesu- 
vius. It  is  quite  evident  that  the  eruption  in  this  case  burst  through 
the  sandstone  and  alluvium  which  immediately  overlies  it ;  and  I 
observed  some  of  the  quartz  pebbles  mixed  with  scoriae  on  the  flanks 
of  the  mountain,  as  if  they  had  been  cast  up  into  the  air,  and  had 
fallen  again  with  the  volcanic  ashes.  I  have  already  observed,  that  a 
large  part  of  this  crater  has  been  filled  up  with  the  loess. 

The  most  striking  peculiarity  of  a  great  many  of  the  craters  above 
described,  is  the  absence  of  any  signs  of  alteration  or  torrefaction  in 
their  walls,  when  these  are  composed  of  regular  strata  of  ancient 
sandstone  and  shale.  It  is  evident  that  the  summits  of  hills  formed 
of  the  above-mentioned  stratified  rocks  have,  in  some  cases,  been 
carried  away  by  gaseous  explosions,  while  at  the  same  time  no  lava, 
and  often  a  very  small  quantity  only  of  scoriae,  has  escaped  from  the 
newly-formed  cavity.  There  is,  indeed,  no  feature  in  the  Eifel  volca- 
noes more  worthy  of  note,  than  the  proofs  they  afford  of  very  copi- 
ous aeriform  discharges,  unaccompanied  by  the  pouring  out  of  melted 
matter,  except,  here  and  there,  in  very  insignificant  volume.  I  kno^r 
of  no  other  extinct  volcanoes  where  gaseous  explosions  of  such  mag- 
nitude have  been  attended  by  the  emission  of  so  small  a  quantity 
of  lava.  Yet  I  looked  in  vain  in  the  Eifel  for  any  appearances 
which  could  lend  support  to  the  hypothesis,  that  the  sudden  rushing 
out  of  such  enormous  volumes  of  gas  had  ever  lifted  up  the  stratified 
rocks  immediately  around  the  vent,  so  as  to  form  conical  masses, 
having  their  strata  dipping  outwards  on  all  sides  from  a  central  axis, 
as  is  assumed  in  the  theory  of  elevation  craters,  alluded  to  in  Chapter 
XXIX. 

Trass. — In  the  Lower  Eifel,  eruptions  of  trachytic  lava  preceded 
the  emission  of  currents  of  basalt,  and  immense  quantities  of  pumice 
were  thrown  out  wherever  trachyte  issued.  The  tufaceous  alluvium 
called  trass,  which  has  covered  large  areas  in  this  region  and  choked 
up  some  valleys  now  partially  reexcavated,  is  unstratified.  Its  base 
consists  almost  entirely  of  pumice,  in  which  are  included  fragments 
of  basalt  and  other  lavas,  pieces  of  burnt  shale,  slate,  and  sandstone, 
and  numerous  trunks  and  branches  of  trees.  If,  as  is  probable,  this 
trass  was  formed  during  the  period  of  volcanic  eruptions,  it  may  have 
originated  in  the  manner  of  the  moya  of  the  Andes. 


CH.  XXXI.]  HUNGARIAN  VOLCANOES.  683 

We  may  easily  conceive  that  a  similar  mass  might  now  be  pro 
duced,  if  a  copious  evolution  of  gases  should  occur  in  one  of  the 
lake-basins.  The  water  might  remain  for  weeks  in  a  state  of  violent 
ebullition,  until  it  became  of  the  consistency  of  mud,  just  as  the  sea 
continued  to  be  charged  with  red  mud  round  Graham's  Island,  in  the 
Mediterranean,  in  the  year  1831.  If  a  breach  should  then  be  made 
in  the  side  of  the  cone,  the  flood  would  sweep  away  great  heaps  of 
ejected  fragments  of  shale  and  sandstone,  which  would  be  borne 
down  into  the  adjoining  valleys.  Forests  might  be  torn  by  such 
a  flood,  and  thus  the  occurrence  of  the  numerous  trunks  of  trees  dis- 
persed irregularly  through  the  trass, 'can  be  explained. 

The  manner  in  which  this  trass  conforms  to  the  shape  of  the  pres- 
ent valleys  implies  its  comparatively  modern  origin,  probably  not 
dating  farther  back  than  the  Post-pliocene,  or,  at  farthest,  the  Newer 
Pliocene  period.  Of  like  modern  date  are  numerous  perfect  cones 
of  scorise  and  some  streams  of  lava  which  occur  in  the  Eifel,  as,  for 
example,  the  small  cones  with  craters  near  Andernach,  on  the  left 
bank  of  the  Rhine,  and  the  columnar  lava  of  Bertrich-Baden,  be- 
tween Treves  and  Coblentz,  of  which  I  have  given  a  figure  at  p.  619. 

Hungary. — M.  Beudant,  in  his  elaborate  work  on  Hungary,  de- 
scribes five  distinct  groups  of  volcanic  rocks,  which,  although  no- 
where of  great  extent,  form  striking  features  in  the  physical  geogra- 
phy of  that  country,  rising  as  they  do  abruptly  from  extensive  plains 
composed  of  tertiary  strata.  They  may  have  constituted  islan.ds  in 
the  ancient  sea,  as  Santorin  and  Milo  now  do  in  the  Grecian  Archi- 
pelago ;  and  M.  Beudant  has  remarked  that  the  mineral  products  of 
the  last-mentioned  islands  resemble  remarkably  those  of  the  Hunga- 
rian extinct  volcanoes,  where  many  of  the  same  minerals,  as  opal, 
chalcedony,  resinous  silex  (silex  resinite),  pearlite,  obsidian,  and  pitch- 
stone  abound. 

The  Hungarian  lavas  are  chiefly  felspathic,  consisting  of  different 
varieties  of  trachyte ;  many  are  cellular,  and  used  as  millstones ;  some 
so  porous  and  even  scoriform  as  to  resemble  those  which  have  issued 
in  the  open  air.  Pumice  occurs  in  great  quantity ;  and  there  are 
conglomerates,  or  rather  breccias,  wherein  fragments  of  trachyte  are 
bound  together  by  pumiceous  tuff",  or  sometimes  by  silex. 

It  is  probable  that  these  rocks  were  permeated  by  the  waters  of  hot 
springs,  impregnated,  like  the  Geysers,  with  silica ;  or,  in  some  in- 
stances, perhaps  by  aqueous  vapors,  which,  like  those  of  Lancerote, 
may  have  precipitated  hydrate  of  silica. 

By  the  influence  of  such  springs  or  vapors  the  trunks  and  branches 
of  trees  washed  clown  during  floods,  and  buried  in  tuffs  on  the  flanks 
of  the  mountains,  are  supposed  to  have  become  silicified.  It  is 
scarcely  possible,  says  M.  Beudant,  to  dig  into  any  of  the  pumiceous 
deposits  of  these  mountains  without  meeting  with  opalized  wood, 
and  sometimes  entire  silicified  trunks  of  trees  of  great  size  and 
weight. 


684  TERTIARY  VOLCANIC  ROCKS.  [Cn.  XXXII. 

It  appears  from  the  species  of  shells  collected  principally  by  M. 
Boue,  and  examined  by  M.  Deshayes,  that  the  fossil  remains  imbed- 
ded in  the  volcanic  tuffs,  and  in  strata  alternating  with  them  in  Hun- 
gary, are  of  the  Miocene  type,  and  not  identical,  as  was  formerly  sup- 
posed, with  the  fossils  of  the  Paris  basin. 


CHAPTER  XXXII. 

ON   THE    DIFFERENT    AGES    OF    THE    VOLCANIC    ROCKS,    Continued. 

Volcanic  rocks  of  the  Tertiary  period,  continued — Extinct  volcanoes  of  Auvergne — 
Mont  Dor — Breccias  and  alluviums  of  Mont  Perrier,  with  bones  of  quadrupeds — 
River  dammed  up  by  lava-current — Range  of  minor  cones  from  Auvergne  to  the 
Vivarais — Monts  Dome — Puy  de  Come — Puy  de  Pariou — Cones  not  denuded  by 
general  flood — Lower  Miocene  volcanic  rocks  near  Clermont — Hill  of  Gergovia — 
Eocene  volcanic  rocks  of  Monte  Bolca — Trap  of  Cretaceous  period — Oolitic  pe- 
riod— New  Red  Sandstone  period — Carboniferous  period — "Rock  and  Spindle" 
near  St.  Andrew's — Old  Red  Sandstone  period— Silurian  period — Cambrian  pe- 
riod— Laurentian  volcanic  rocks. 

Volcanic  RocJcs  of  Auvergne. — The  extinct  volcanoes  of  Auvergne 
and  Cantal,  in  Central  France,  seem  to  have  commenced  their  erup- 
tions in  the  Lower  Miocene  period,  but  to  have  been  most  active 
during  the  Upper  Miocene  and  Pliocene  eras.  I  have  already  alluded 
to  the  grand  succession  of  events,  of  which  there  is  evidence  in  Au- 
vergne since  the  last  retreat  of  the  sea  (see  p.  228). 

The  earliest  monuments  of  the  tertiary  period  in  that  region  are 
lacustrine  deposits  of  great  thickness  (2,  fig.  728,  p.  686),  in  the  low- 
est conglomerates  of  which  are  rounded  pebbles  of  quartz,  mica- 
schist,  granite,  and  other  non-volcanic  rocks,  without  the  slightest 
intermixture  of  igneous  products.  To  these  conglomerates  succeed 
argillaceous  and  calcareous  marls  and  limestones  (3,  fig.  728),  con- 
taining Lower  Miocene  shells  and  bones  of  mammalia,  the  higher 
beds  of  which  sometimes  alternate  with  volcanic  tuff  of  contempora- 
neous origin.  After  the  filling  up  or  drainage  of  the  ancient  lakes, 
huge  piles  of  trachytic  and  basaltic  rocks,  with  volcanic  breccias, 
accumulated  to  a  thickness  of  several  thousand  feet,  and  were  super- 
imposed upon  granite,  or  the  contiguous  lacustrine  strata.  The 
greater  portion  of  these  igneous  rocks  appear  to  have  originated  dur- 
ing the  Upper  Miocene  and  Pliocene  periods ;  and  extinct  quadru- 
peds of  those  eras,  belonging  to  the  genera  Mastodon,  Khinoceros, 
and  others,  were  buried  in  ashes  and  beds  of  alluvial  sand  and  gravel, 
which  owe  their  preservation  to  overspreading  sheets  of  lava. 


OH.  XXXIL]         MONT  DOR,  AUVERGNE.  685 

In  Auvergne,  tlie  most  ancient  and  conspicuous  of  the  volcanic 
masses  is  Mont  Dor,  which  rests  immediately  on  the  granitic  rocks 
standing  apart  from  the  freshwater  strata.*  This  great  mountain 
rises  suddenly  to  the  height  of  several  thousand  feet  above  the  sur- 
rounding platform,  and  retains  the  shape  of  a  flattened  and  somewhat 
irregular  cone,  all  the  sides  sloping  more  or  less  rapidly,  until  their 
inclination  is  gradually  lost  in  the  high  plain  around.  This  cone  is 
composed  of  layers  of  scoriae,  pumice-stones,  and  their  fine  detritus, 
with  interposed  beds  of  trachyte  and  basalt,  which  descend  often  in 
uninterrupted  sheets  until  they  reach  and  spread  themselves  round 
the  base  of  the  mountain,  f  Conglomerates,  also,  composed  of  angu- 
lar and  rounded  fragments  of  igneous  rocks,  are  observed  to  alter- 
nate with  the  above ;  and  the  various  masses  are  seen  to  dip  off 
from  the  central  axis,  and  to  lie  parallel  to  the  sloping  flanks  of  the 
mountain. 

The  summit  of  Mont  Dor  terminates  in  seven  or  eight  rocky  peaks, 
where  no  regular  crater  can  now  be  traced,  but  where  we  may  easily 
imagine  one  to  have  existed,  which  may  have  been  shattered  by 
earthquakes,  and  have  suffered  degradation  by  aqueous  agents.  Orig- 
inally, perhaps,  like  the  highest  crater  of  Etna,  it  may  have  formed 
an  insignificant  feature  in  the  great  pile,  and  may  frequently  have 
been  destroyed  and  renovated. 

According  to  some  geologists,  this  mountain,  as  well  as  Vesuvius, 
Etna,  and  all  large  volcanoes,  has  derived  its  dome-like  form  not  from 
the  preponderance  of  eruptions  from  one  or  more  central  points,  but 
from  the  upheaval  of  horizontal  beds  of  lava  and  scoriae.  I  have  ex- 
plained my  reasons  for  objecting  to  this  view  in  Chapter  XXIX., 
when  speaking  of  Palma,  and  in  the  "  Principles  of  Geology."  J  The 
average  inclination  of  the  dome-shaped  mass  of  Mont  Dor  is  8°  6', 
whereas  in  Mounts  Loa  and  Kea,  before  mentioned,  in  the  Sandwich 
Islands  (see  fig.  693,  p.  623),  the  flanks  of  which  have  been  raised  by 
recent  lavas,  we  find  from  Mr.  Dana's  description  that  the  one  has  a 
slope  of  6°  30',  the  other  of  7°  46'.  There  is  therefore  no  reason 
whatever  for  imagining,  as  some  have  supposed,  that  the  basaltic  cur- 
rents of  the  ancient  French  volcano  were  at  first  more  horizontal  than 
they  are  now.  Nevertheless  it  is  possible  that  during  the  long  series 
of  eruptions  required  to  give  rise  to  so  vast  a  pile  of  volcanic  matter, 
which  is  thickest  at  the  summit  or  centre  of  the  dome,  some  disloca- 
tion and  upheaval  took  place  ;  and  during  the  distension  of  the  mass, 
beds  of  lava  and  scoriae  may,  in  some  places,  have  acquired  a  greater, 
in  others  a  less  inclination,  than  that  which  at  first  belonged  to  them. 

Respecting  the  age  of  the  great  mass  of  Mont  Dor,  we  cannot  come 
at  present  to  any  positive  decision,  because  no  organic  remains  have 


*  See  the  Map,  p.  221. 

f  Scrope's  Central  France,  p.  98, 

j  See  chaps,  xxiv.,  xxv.,  and  xxvi.,  7th,  8th,  and  9th  editions. 


686  TERTIARY  VOLCANIC  ROCKS.  [Cn.  XXXII. 

yet  been  found  in  the  tuffs,  except  impressions  of  the  leaves  of  trees 
of  species  not  yet  determined.  We  may  confidently  assume  that  the 
earliest  eruptions  were  posterior  in  origin  to  those  grits  and  conglom- 
erates of  the  freshwater  formation  of  the  Limagne  which  contain  no 
pebbles  of  volcanic  rocks  ;  while,  on  the  other  hand,  some  eruptions 
took  place  before- the  great  lakes  were  drained,  and  others  occurred 
after  the  desiccation  of  those  lakes,  and  when  deep  valleys  had 
already  been  excavated  through  freshwater  strata. 

Fig.  728. 
Mont  Perrier. 

.t 

ttrazeR. 

'*i*f*§^^^^ 

"121  2  1 

Section  from  the  valley  of  the  Couze  at  Neehers,  through  Mont  Perrier  and  Issoire,  to  the 
Valley  of  the  Allier  and  the  Tour  de  Boulade,  Auvergne. 

10.  Lava-current  of  Tartaret  near  its  termi-  angular  masses  of  trachyte,  quartz,  peb- 

nation  at  Nechers.  bles,  &c. 

9.  Bone-bed,  red  sandy  clay  under  the  lava  5.  Lower  bone-bed  of  Perrier,  ochreous  sand 

of  Tartaret.  and  gravel. 

8.  Bone-bed  of  the  Tour  de  Boulade.  4  a.  Basaltic  dike. 

7.  Alluvium  newer  than  No.  6.  4.  Basaltic  platform. 

6.  Alluvium  with  bones  of  hippopotamus.  3.  Upper  freshwater  beds,  limestone,  marl, 
5  c.  Trachytic  breccia  resembling  5  a.  gypsum,  &c. 

5  &.  Upper  bone-bed  of  Perrier,  gravel,  &c.  2.  Lower  freshwater  formation,  red  clay,  green 
5  a.  Pumiceous  breccia  and  conglomerate,  sand,  &c. 

1.  Granite. 

In  the  above  section  I  have  endeavored  to  explain  the  geological 
structure  of  a  portion  of  Auvergne,  which  I  reexamined  in  1843.* 
It  may  convey  some  idea  to  the  reader  of  the  long  and  complicated 
series  of  events  which  have  occurred  in  that  country,  since  the  first 
lacustrine  strata  (No.  2)  were  deposited  on  the  granite  (No.  1).  The 
changes  of  which  we  have  evidence  are  the  more  striking,  because 
they  imply  great  denudation,  without  there  being  any  proofs  of  the 
intervention  of  the  sea  during  the  whole  period.  It  will  be  seen  that 
the  upper  freshwater  beds  (No.  3),  once  formed  in  a  lake,  must  have 
suffered  great  destruction  before  the  excavation  of  the  valleys  of  the 
Couze  and  Allier  had  begun.  In  these  freshwater  beds,  Lower  Mio- 
cene fossils,  as  described  in  Chapter  XV.,  have  been  found.  The  ba- 
saltic dike,  4',  is  one  of  many  examples  of  the  intrusion  of  volcanic 
matter  through  the  ancient  freshwater  beds,  and  may  have  been  of 
Miocene  or  Pliocene  date,  giving  rise,  when  it  reached  the  surface  and 
overflowed,  to  such  platforms  of  basalt  as  often  cap  the  tertiary  hills 
in  Auvergne,  and  one  of  which  (4)  is  seen  on  Mont  Perrier. 

It  not  unfrequently  happens  that  beds  of  gravel  containing  bones 
of  extinct  mammalia  are  detected  under  these  very  ancient  sheets  of 
basalt,  as  between  No.  4  and  the  freshwater  strata,  No.  3,  at  A,  from 

*  See  Quart.  Geol.  Journ.,  vol.  ii.  p.  77.  » 


CH.  XXXII.]  VOLCANOES  OF  AUVERGNE.  687 

which  it  is  clear  that  the  surface  of  No.  3  formed  at  that  period  the 
lowest  level  at  which  the  waters  then  draining  the  country  flowed. 
Next  in  age  to  this  basaltic  platform  comes  a  patch  of  ochreous  sand 
and  gravel  (No.  5),  containing  many  bones  of  quadrupeds.  Upon 
this  rests  a  pumiceous  breccia  or  conglomerate,  with  angular  masses 
of  trachyte  and  some  quartz  pebbles.  This  deposit  is  followed  by  5  b 
(which  is  similar  to  5)  and  5  c  similar  to  the  trachytic  breccia  5  a. 
These  two  breccias  are  supposed,  from  their  similarity  to  others  found 
on  Mont  Dor,  to  have  descended  from  the  flanks  of  that  mountain 
during  eruptions  ;  and  the  interstratified  alluvial  deposits  contain  the 
remains  of  mastodon,  rhinoceros,  tapir,  deer,  beaver,  and  quadrupeds 
of  other  genera,  referable  to  about  forty  species,  all  of  which  are  ex- 
tinct. I  formerly  supposed  them  to  belong  to  the  same  era  as  the 
Miocene  faluns  of  Touraine ;  but  more  recent  researches  seem  to  show 
that  they  ought  rather  to  be  ascribed  to  the  older  Pliocene  epoch. 

Whatever  be  their  date  in  the  tertiary  series,  they  are  quadrupeds 
which  inhabited  the  country  when  the  formations  5  and  5  c  orig- 
inated. Probably  they  were  drowned  during  floods,  such  as  rush 
down  the  flanks  of  volcanoes  during  eruptions,  when  great  bodies  of 
steam  are  emitted  from  the  crater,  or  when,  as  we  have  seen,  both  on 
Etna  and  in  Iceland  in  modern  times,  large  masses  of  snow  are  sud- 
denly melted  by  lava,  causing  a  deluge  of  water  to  bear  down  frag- 
ments of  igneous  rocks  mixed  with  mud  to  the  valleys  and  plains 
below. 

It  will  be  seen  that  the  valley  of  the  Issoire,  down  which  these 
ancient  inundations  swept,  was  first  excavated  at  the  expense  of  the 
formations  2,  3,  and  4,  and  then  filled  up  by  the  masses  5  and  5  c, 
after  which  it  was  reexcavated  before  the  more  modern  alluviums 
(Nos.  6  and  V)  were  formed.  In  these  again  other  fossil  mammalia 
of  distinct  species  have  been  detected  by  M.  Bravard,  the  bones  of 
an  hippopotamus  having  been  found  among  the  rest. 

At  length,  when  the  valley  of  the  Allier  was  eroded  at  Issoire 
down  to  its  lowest  level,  a  talus  of  angular  fragments  of  basalt  and 
freshwater  limestone  (No.  8)  was  formed,  called  the  bone-bed  of  the 
Tour  de  Boulade,  from  which  a  great  many  other  Newer  Pliocene 
mammalia  have  been  collected  by  MM.  Bravard  and  Pomel.  Among 
these,  the  Elephas  primigenius,  Rhinoceros  tichorinus,  Deer  (including 
reindeer),  Equus,  Bos,  Antelope,  Felis,  and  Canis  were  included. 
Even  this  deposit  seems  hardly  to  be  the  newest  in  the  neighborhood, 
for  if  we  cross  from  the  town  of  Issoire  (see  fig.  728)  over  Mont  Per- 
rier  to  the  adjoining  valley  of  the  Couze,  we  find  another  bone-bed 
(No.  9)  overlaid  by  a  current  of  lava. 

The  history  of  this  .lava-current,  which  terminates  a  few  hundred 
yards  below  the  point,  No.  10,  in  the  suburbs  of  the  village  of 
Nechers,  is  interesting.  It  forms  a  long  narrow  stripe  more  than  13 
miles  in  length,  at  the  bottom  of  the  valley  of  the  Couze,  which  flows 
out  of  a  lake  at  the  foot  of  Mont  Dor.  This  lake  is  caused  by  a  bar- 


TERTIARY  VOLCANIC   ROCKS.  [Cn.  XXXII. 

rier  thrown  across  the  ancient  channel  of  the  Couze,  consisting  partly 
of  the  volcanic  cone  called  the  Puy  de  Tartaret,  formed  of  loose  sco- 
riae, from  the  base  of  which  has  issued  the  lava-current  before  men- 
tioned. The  materials  of  the  dam  which  blocked  up  the  river,  and 
caused  the  Lac  de  Chambon,  are  also,  in  part,  derived  from  a  landslip 
which  may  have  happened  at  the  time  of  the  great  eruption  which 
formed  the  cone. 

This  cone  of  Tartaret  affords  an  impressive  monument  of  the  very 
different  dates  at  which  the  igneous  eruptions  of  Auvergne  have  hap- 
pened ;  for  it  was  evidently  thrown  up  at  the  bottom  of  the  existing 
valley,  which  is  bounded  by  lofty  precipices  composed  of  sheets  of 
ancient  columnar  trachyte  and  basalt,  which  once  flowed  at  very  high 
levels  from  Mont  Dor.* 

When  we  follow  the  course  of  the  river  Couze,  from  its  source  in 
the  lake  of  Chambon  to  the  termination  of  the  lava-current  at 
Nechers,  a  distance  of  thirteen  miles,  we  find  that  the  torrent  has  in 
most  places  cut  a  deep  channel  through  the  lava,  the  lower  portion  of 
which  is  columnar.  In  some  narrow  gorges  the  water  has  even  had 
power  to  remove  the  entire  mass  of  basaltic  rock,  though  the  work 
of  erosion  must  have  been  very  slow,  as  the  basalt  is  tough  and  hard, 
and  one  column  after  another  must  have  been  undermined  and  re- 
duced to  pebbles,  and  then  to  sand.  During  the  time  required  for 
this  operation,  the  perishable  cone  of  Tartaret,  composed  of  sand  and 
ashes,  has  stood  uninjured,  proving  that  no  great  flood  or  deluge  can 
have  passed  over  this  region  in  the  interval  between  the  eruption  of 
Tartaret  and  our  own  times. 

If  we  now  return  to  the  section  (fig.  *728),  I  may  observe  that  the 
lava-current  of  Tartaret,  which  has  diminished  greatly  in  height  and 
volume  near  its  termination,  presents  here  a  steep  and  perpendicular 
face  25  feet  in  height  towards  the  river.  Beneath  it  is  the  alluvium 
No.  9,  consisting  of  a  red  sandy  clay,  which  must  have  covered  the 
bottom  of  the  valley  when  the  current  of  melted  rock  flowed  down. 
The  bones  found  in  this  alluvium,  which  I  obtained  myself,  consisted 
of  a  species  of  field-mouse,  Arvicola,  and  the  molar  tooth  of  an  ex- 
tinct horse,  JEquus  fossilis.  The  other  species,  obtained  from  the 
same  bed,  are  referable  to  the  genera  Sus,  J3os,  Cervus,  Felis,  Canis, 
Maries,  Talpa,  Sorex,  Lepus,  Sciurus,  Mus,  and  Lagomys,  in  all  no 
less  than  forty-three  species,  all  closely  allied  to  recent  animals,  yet 
nearly  all  of  them,  according  to  M.  Bravard,  showing  some  points  of 
difference,  like  those  which  Mr.  Owen  discovered  in  the  case  of  the 
horse  above  alluded  to.  The  bones  also  of  a  frog,  snake,  and  lizard, 
and  of  several  birds,  were  associated  with  the  fossils  before  enumer- 
ated, and  several  recent  land-shells,  such  as  Cyclostoma  elegans,  Helix 
hortensis,  H.  nemoralis,  H.  lapicida,  and  Clausilia  rugosa.  If  the 

*  For  a  view  of  Puy  de  Tartaret  and  Mont  Dor,  see  Scrope's  Volcanoes  of  Cen- 
tral France. 


CH.  XXXII.J  PUY  DE   COME.  689 

animals  were  drowned  by  floods,  which  accompanied  the  eruptions  of 
the  Puy  de  Tartaret,  .they  would  give  an  exceedingly  modern  geologi- 
cal date  to  that  event,  which  must,  in  that  case,  have  belonged  to  the 
end  of  the  Newer  Pliocene,  or,  perhaps,  to  the  Post-pliocene  period. 
That  the  current  which  has  issued  from  the  Puy  de  Tartaret  may,  never- 
theless, be  very  ancient  in  reference  to  the  events  of  human  history, 
we  may  conclude,  not  only  from  the  divergence  of  the  mammiferous 
fauna  from  that  of  our  day,  but  from  the  fact  that  a  Roman  bridge  of 
such  form  and  construction  as  continued  in  use  down  to  the  fifth  cen- 
tury, but  which  may  be  older,  is  now  seen  at  a  place  about  a  mile  and 
a  half  from  St.  Nectaire.  This  ancient  bridge  spans  the  river  Couze 
with  two  arches,  each  about  14  feet  wide.  These  arches  spring  from 
the  lava  of  Tartaret,  on  both  banks,  showing  that  a  ravine  precisely 
like  that  now  existing,  had  already  been  excavated  by  the  river  through 
that  lava  thirteen  or  fourteen  centuries  ago. 

In  Central  France  there  are  several  hundred  minor  cones  like  that 
of  Tartaret,  a  great  number  of  which,  like  Monte  Nuovo,  near  Naples, 
may  have  been  principally  due  to  a  single  eruption.  Most  of  these 
cones  range  in  a  linear  direction  from  Auvergne  to  the  Vivarais,  and 
they  were  faithfully  described  so  early  as  the  year  1802,  by  M.  de 
Montlosier.  They  have  given  rise  chiefly  to  currents  of  basaltic  lava. 
Those  of  Auvergne  called  the  Monts  Dome,  placed  on  a  granitic  plat- 
form, form  an  irregular  ridge  (see  fig.  624,  p.  594),  about  18  miles  in 
length  and  2  in  breadth.  They  are  usually  truncated  at  the  summit, 
where  the  crater  is  often  preserved  entire,  the  lava  having  issued  from 
the  base  of  the  hill.  But  frequently  the  crater  is  broken  down  on  one 
side,  where  the  lava  has  flowed  out.  The  hills  are  composed  of  loose 
scoriae,  blocks  of  lava,  lapilli,  and  pozzuolana,  with  fragments  of  tra- 
chyte and  granite. 

Puy  de  Come. — The  Puy  de  Come  and  its  lava-current,  near  Cler- 
mont,  may  be  mentioned  as  one  of  these  minor  volcanoes.  This  con- 
ical hill  rises  from  the  granitic  platform,  at  an  angle  of  between  30° 
and  40,°  to  the  height  of  more  than  900  feet.  Its  summit  presents 
two  distinct  craters,  one  of  them  with  a  vertical  depth  of  250  feet. 
A  stream  of  lava  takes  its  rise  at  the  western  base  of  the  hill  instead 
of  issuing  from  either  crater,  and  descends  the  granitic  slope  towards 
the  present  site  of  the  town  of  Pont  Gibaud.  Thence  it  pours  in  a 
broad  sheet  down  a  steep  declivity  into  the  valley  of  the  Sioule,  filling 
the  ancient  river-channel  for  the  distance  of  more  than  a  mile.  The 
Sioule,  thus  dispossessed  of  its  bed,  has  worked  out  a  fresh  one 
between  the  lava  and  the  granite  of  its  western  bank ;  and  the  excava- 
tion has  disclosed,  in  one  spot,  a  wall  of  columnar  basalt  about  50  feet 
high.* 

The  excavation  of  the  ravine  is  still  in  progress,  every  winter  some 
columns  of  basalt  being  undermined  and  carried  down  the  channel  of 

*  Scrope's  Central  France,  p.  60,  and  plate. 
44 


690 


TERTIARY  VOLCANIC  ROCKS. 


[Cn.  XXXII. 


the  river,  and  in  the  course  of  a  few  miles  rolled  to  sand  and  pebbles. 
Meanwhile  the  cone  of  Come  remains  unimpaired,  its  loose  materials 
being  protected  by  a  dense  vegetation,  and  the  hill  standing  on  a 
ridge  not  commanded  by  any  higher  ground,  so  that  no  floods  of 
rain-water  can  descend  upon  it.  There  is  no  end  to  the  waste  which 
the  hard  basalt  may  undergo  in  future,  if  the  physical  geography  of 
the  country  continue  unchanged,  no  limit  to  the  number  of  years 
during  which  the  heap  of  incoherent  and  transportable  materials  called 
the  Puy  de  Come  may  remain  in  a  stationary  condition.  In  this  place, 
therefore,  we  behold  in  the  results  of  aqueous  and  atmospheric  agency 
in  past  times,  a  counterpart  of  what  we  must  expect  to  recur  in  future 


Lava  of  Chaluzet. — At  another  point,  farther  down  the  course  of 
the  Sioule,  we  find  a  second  illustration  of  the  same  phenomenon  in 
the  Puy  Rouge,  a  conical  hill  to  the  north  of  the  village  of  Pranal. 
The  cone  is  composed  entirely  of  red  and  black  scoriae,  tuff,  and  vol- 
canic bombs.  On  its  western  side,  towards  the  village  of  Chaluzet, 
there  is  a  worn-down  crater,  whence  a  powerful  stream  of  lava  has 
issued,  and  flowed  into  the  valley  of  the  Sioule.  The  river  has  since 
excavated  a  ravine  through  the  lava  and  subjacent  gneiss,  to  the  depth 
in  some  places  of  400  feet. 

Fig.  729. 


a.  S  coriaceous  lava. 
6.  Columnar  basalt. 
c.  Gravel. 

D.  Ancient   mining 

gallery. 

E.  Pathway. 
/.  Gneiss. 


Lava-current  of  Chaluzet,  Auvergne,  near  its  termination.* 

On  the  upper  part  of  the  precipice  forming  the  left  side  of  this 
ravine,  we  see  a  great  mass  of  black  and  red  scoriaceous  lava  becoming 
more  and  more  columnar  towards  its  base.  (See  fig.  729.)  Below 


*  Lyell  and  Murchison,  Ed.  New  Phil.  Journ.,  1829. 


CH.  XXXIL]  PUY  DE  PARIOU.  691 

this  is  a  bed  of  sand  and  gravel  3  feet  thick,  evidently  an  ancient 
river-bed,  now  at  an  elevation  of  25  feet  above  the  channel  of  the 
Sioule.  This  gravel,  from  which  water  gushes  out,  rests  upon  gneiss, 
/,  which  has  been  eroded  to  the  depth  of  25  feet  at  the  point  where 
the  annexed  view  is  taken.  At  D,  close  to  the  village  of  Les  Combres, 
the  entrance  of  a  gallery  is  seen,  in  which  lead  has  been  worked  in 
the  gneiss.  This  mine  shows  that  the  pebble-bed  is  continuous,  in  a 
horizontal  direction,  between  the  gneiss  and  the  volcanic  mass.  Here 
again  it  is  quite  evident,  that,  while  the  basalt  was  gradually  under- 
mined and  carried  away  by  the  force  of  running  water,  the  cone 
whence  the  lava  issued  escaped  destruction,  because  it  stood  upon  a 
platform  of  gneiss  several  hundred  feet  above  the  level  of  the  valley  in 
which  the  force  of  running  water  was  exerted. 

Puy  de  Pariou. — The  brim  of  the  crater  of  the  Puy  de  Pariou,  near 
Clermont,  is  so  sharp,  and  has  been  so  little  blunted  by  time,  that  it 
scarcely  affords  room  to  stand  upon.  This  and  other  cones  in  an 
equally  remarkable  state  of  integrity  have  stood,  I  conceive,  uninjured, 
not  in  spite  of  their  loose  porous  nature,  as  might  at  first  be  naturally 
supposed,  but  in  consequence  of  it.  No  rills  can  collect  where  all  the 
rain  is  instantly  absorbed  by  the  sand  and  scoriae,  as  is  remarkably 
the  case  on  Etna ;  and  nothing  but  a  waterspout  breaking  directly 
upon  the  Puy  de  Pariou  could  carry  away  a  portion  of  the  hill,  so  long 
as  it  is  not  rent  or  engulfed  by  earthquakes. 

Hence  it  is  conceivable  that  even  those  cones  which  have  the  fresh- 
est aspect  and  most  perfect  shape  may  lay  claim  to  very  high  an- 
tiquity. Dr.  Daubeny  has  justly  observed,  that  had  any  of  these  vol- 
canoes been  in  a  state  of  activity  in  the  age  of  Julius  Caesar,  that  gen- 
eral, who  encamped  upon  the  plains  of  Auvergne,  and  laid  siege  to  its 
principal  city  (Gergovia,  near  Clermont),  could  hardly  have  failed  to 
notice  them.  Had  there  been  any  record  of  their  eruptions  in  the 
time  of  Pliny  or  Sidonius  Apollinaris,  the  one  would  scarcely  have 
omitted  to  make  mention  of  it  in  his  Natural  History,  nor  the  other 
to  introduce  some  allusion  to  it  among  the  descriptions  of  this  his 
native  province.  This  poet's  residence  was  on  the  borders  of  the  Lake 
Aidat,  which  owed  its  very  existence  to  the  damming  up  of  a  river  by 
one  of  the  most  modern  lava-currents.* 

Plomb  du  Cantal. — In  regard  to  the  age  of  the  igneous  rocks  of 
the  Cantal,  we  can  at  present  merely  affirm,  that  they  overlie  the 
Lower  Miocene  lacustrine  strata  of  that  country,  which  may  be  partly 
Upper  Eocene  and  partly  Lower  Miocene  (see  Map,  p.  221).  They 
form  a  great  dome-shaped  mass,  having  an  average  slope  of  only  4°, 
which  has  evidently  been  accumulated,  like  the  cone  of  Etna,  during  a 
long  series  of  eruptions.  It  is  composed  of  trachytic,  phonolitic,  and 
basaltic  lavas,  tuffs,  and  conglomerates,  or  breccias,  forming  a  moun- 
tain several  thousand  feet  in  height.  Dikes  also  of  phonolite,  trachyte, 

*  Daubeny  on  Volcanoes,  p.  14. 


692  PLOMB  DU  CANTAL.  [On.  XXXII 

and  basalt  are  numerous,  especially  in  the  neighborhood  of  the  largi 
cavity,  probably  once  a  crater,  around  which  the  loftiest  summits  oi 
the  Cantal  are  ranged  circularly,  few  of  them,  except  the  Plomb  di 
Cantal,  rising  far  above  the  border  or  ridge  of  this  supposed  crater 
A  pyramidal  hill,  called  the  Puy  Griou,  occupies  the  middle  of  th< 
cavity.*  It  is  clear  that  the  volcano  of  the  Cantal  broke  out  precisely 
on  the  site  of  the  lacustrine  deposit  before  described  (p.  229),  whicl 
had  accumulated  in  a  depression  of  a  tract  composed  of  micaceou 
schist.  In  the  breccias,  even  to  the  very  summit  of  the  mountain,  w< 
find  ejected  masses  of  the  freshwater  beds,  and  sometimes  fragment! 
of  flint,  containing  Lower  Miocene  shells.  Valleys  radiate  in  al 
directions  from  the  central  heights  of  the  mountain,  increasing  in  sizi 
as  they  recede  from  those  heights.  Those  of  the  Cer  and  Jourdanne 
which  are  more  than  20  miles  in  length,  are  of  great  depth,  and  la^ 
open  the  geological  structure  of  the  mountain.  No  alternation  of  lava 
with  undisturbed  lacustrine  strata  has  been  observed,  nor  any  tuff 
containing  freshwater  shells,  although  some  of  these  tuffs  include  fossi 
remains  of  terrestrial  plants,  said  to  imply  several  distinct  restoration 
of  the  vegetation  of  the  mountain  in  the  intervals  between  great  erup 
tions.  On  the  northern  side  of  the  Plomb  du  Cantal,  at  La  Vissiere 
near  Murat,  is  a  spot,  pointed  out  on  the  Map  (p.  221),  where  fresh 
water  limestone  and  marl  are  seen  covered  by  a  thickness  of  about  80( 
feet  of  volcanic  rock.  Shifts  are  here  seen  of  the  strata  of  limestone 
and  marl.f 

In  treating  of  the  lacustrine  deposits  of  Central  France,  in  th< 
fifteenth  chapter,  it  was  stated  that,  in  the  arenaceous  and  pebbb 
group  of  the  lacustrine  basins  of  Auvergne,  Cantal,  and  Velay,  no  vol 
canic  pebbles  had  ever  been  detected,  although  massive  piles  of  igne 
ous  rocks  are  now  found  in  the  immediate  vicinity.  As  this  observa 
tiou  has  been  confirmed  by  minute  research,  we  are  warranted  ii 
inferring  that  the  volcanic  eruptions  had  not  commenced  when  th< 
older  subdivisions  of  the  freshwater  groups  originated. 

In  Cantal  and  Velay  no  decisive  proofs  have  yet  been  brought  t( 
light  that  any  of  the  igneous  outbursts  happened  during  the  depo 
sition  of  the  freshwater  strata ;  but  there  can  be  no  doubt  that  ii 
Auvergne  some  volcanic  explosions  took  place  before  the  drainage  oi 
the  lakes,  and  at  a  time  when  the  Lower  Miocene  species  of  animals 
and  plants  still  flourished.  Thus,  for  example,  at  Pont  du  Chateau 
near  Clermont,  a  section  is  seen  in  a  precipice  on  the  right  bank  oi 
the  river  Allier,  in  which  beds  of  volcanic  tuff  alternate  with  a  fresh 
water  limestone,  which  is  in  some  places  pure,  but  in  others  spottec 
with  fragments  of  volcanic  matter,  as  if  it  were  deposited  whil( 
showers  of  sand  and  scoria3  were  projected  from  a  neighboring  vent.]; 

Another  example  occurs  in  the  Puy  de  Marmont,  near  Veyres 

*  Mem.  de  la  Soc.  Geol.  de  France,  torn.  i.  p.  175. 

f  See  Lyell  and  Murchison,  Ann.  de  Sci.  Nat.,  Oct.  1829. 

\  See  Scrope's  Central  France,  p.  21. 


CH.  XXXII.] 


GERGOVIA. 


693 


where  a  freshwater  marl  alternates  with  volcanic  tuff  containing 
Miocene  shells.  The  tuff  or  breccia  in  this  locality  is  precisely  such 
as  is  known  to  result  from  volcanic  ashes  falling  into  water,  and  sub- 
siding together  with  ejected  fragments  of  marl  and  other  stratified 
rocks.  These  tuffs  and  marls  are  highly  inclined,  and  traversed  by 
a  thick  vein  of  basalt,  which,  as  it  rises  in  the  hill,  divides  into  two 
branches. 

Gergovia. — The  hill  of  Gergovia,  near  Clermont,  affords  a  third 
example.  I  agree  with  MM.  Dufrenoy  and  Jobert  that  there  is  no 
alternation  here  of  a  contemporaneous  sheet  of  lava  with  freshwater 
strata,  in  the  manner  supposed  by  some  other  observers ;  *  but  the 
position  and  contents  of  some  of  the  associated  tuffs  prove  them  to 
have  been  derived  from  volcanic  eruptions  which  occurred  during  the 
deposition  of  the  lacustrine  strata. 

The  bottom  of  the  hill  consists  of  slightly  inclined  beds  of  white 
and  greenish  marls,  more  than  300  feet  in  thickness,  intersected  by  a 
dike  of  basalt,  which  may  be  studied  in  the  ravine  above  the  village 
of  Merdogne.  The  dike  here  cuts  through  the  marly  strata  at  a  con- 
siderable angle,  producing,  in  general,  great  alteration  and  confusion 
in  them  for  some  distance  from  the  point  of  contact.  Above  the 
white  and  green  marls,  a  series  of  beds  of  limestone  and  marl,  con- 
taining freshwater  shells,  are  seen  to  alternate  with  volcanic  tuff.  In 
the  lowest  part  of  this  division,  beds  of  pure  marl  alternate  with  com- 
pact fissile  tuff,  resembling  some  of  the  subaqueous  tuffs  of  Italy  and 
Sicily  called  peperinos.  Occasionally  fragments  of  scoriae  are  visible 
in  this  rock.  Still  higher  is  seen  another  group  of  some  thickness 
consisting  exclusively  of  tuff,  upon  which  lie  other  marly  strata  inter- 


rig.  730. 


Basaltic 


White 
and  green 
marls. 


Hill  of  Gergovia. 


mixed  with  volcanic  matter.     Among  the  species  of  fossil  shells  which 
I  found  in  these  strata  were  Melania  inquinata,  a  Unio,  and  a  Mela- 


*  See  Scrope's  Central  France,  p.  7. 


694:  EOCENE  VOLCANIC  KOCKS.  [Cn.  XXXII. 

nopsis,  but  they  were  not  sufficient  to  enable  me  to  determine  with 
precision  the  age  of  the  formation. 

There  are  many  points  in  Auvergne  where  igneous  rocks  have  been 
forced  by  subsequent  injection  through  clays  and  marly  limestones, 
in  such  a  manner  that  the  whole  has  become  blended  in  one  confused 
and  brecciated  mass,  between  which  and  the  basalt  there  is  sometimes 
no  very  distinct  line  of  demarcation.  In  the  cavities  of  such  mixed 
rocks  we  often  find  chalcedony,  and  crystals  of  mesotype,  stilbite,  and 
arragonite.  To  formations  of  this  class  may  belong  some  of  the 
breccias  immediately  adjoining  the  dike  in  the  hill  of  Gergovia ;  but 
it  cannot  be  contended  that  the  volcanic  sand  and  scoriae  interstratified 
with  the  marls  and  limestones  in  the  upper  part  of  that  hill  were  intro- 
duced, like  the  dike,  subsequently,  by  intrusion  from  below.  They 
must  have  been  thrown  down  like  sediment  from  water,  and  can  only 
have  resulted  from  igneous  action,  which  was  going  on  contempo- 
raneously with  the  deposition  of  the  lacustrine  strata. 

The  reader  will  bear  in  mind  that  this  conclusion  agrees  well  with 
the  proofs,  adverted  to  in  the  fifteenth  chapter,  of  the  abundance  of 
silex,  travertin,  and  gypsum  precipitated  when  the  upper  lacustrine 
strata  were  formed ;  for  these  rocks  are  such  as  the  waters  of  mineral 
and  thermal  springs  might  generate. 

Eocene  Volcanic  Rocks. — The  fissile  limestone  of  Monte  BolcaT 
near  Verona,  has  for  many  centuries  been  celebrated  in  Italy  for  the 
number  of  perfect  Ichthyolites  which  it  contains.  Agassiz  has  de- 
scribed no  less  than  133  species  of  fossil  fish  from  this  single  deposit, 
and  the  multitude  of  individuals  by  which  many  of  the  species  are 
represented,  is  attested  by  the  variety  of  specimens  treasured  up  in 
the  principal  museums  of  Europe.  They  have  been  all  obtained  from 
quarries  worked  exclusively  by  lovers  of  natural  history,  for  the  sake 
of  the  fossils.  Had  the  lithographic  stone  of  Solenhofen,  now  re- 
garded as  so  rich  in  fossils,  been  in  like  manner  quarried  solely  for 
scientific  objects,  it  would  have  remained  almost  a  sealed  book  to 
palaeontologists,  so  sparsely  are  the  organic  remains  scattered  through 
it.  I  visited  Monte  Bolca  in  company  with  Sir  Roderick  Murchison 
in  1828,  and  we  then  satisfied  ourselves  that  the  fish-bearing  strata 
formed  part  of  the  Eocene  rocks  of  the  adjacent  Vicentine  :  we  also 
ascertained  that  the  associated  volcanic  products,  consisting  chiefly 
of  peperino  or  brown  basaltic  tuff,  were  contemporaneous  and  inter- 
stratified  with  marine  deposits  charged  with  the  same  fossils  as  those 
which  characterize  the  Middle  Eocene  group  of  Monte  Bolca.  In 
some  of  the  tuffs  nummulites  are  met  with,  and  two  species,  Num- 
mulites  globulus  and  N.  mille-caput,  were  obtained  by  Sir  R.  Murchi- 
son  in  a  subsequent  visit  from  beds  intervening  between  those  which 
yield  the  chief  supply  of  fossil  fish.  We  observed  dikes  of  basalt 
cutting  through  vast  masses  of  the  peperino  in  Monte  Postale,  which 

*  Murchison  on  the  Structure  of  the  Alps,  Quart.  Geol.  Journ.,  vol.  v.  p.  225. 


CH.  XXXII.]  EOCENE  VOLCANIC  ROCKS.  695 

adjoins  Monte  Bolca.  There  is  evidence  here  of  a  long  series  of 
submarine  volcanic  eruptions  of  Eocene  date,  and  during  some  of 
them,  as  Sir  R.  Murchison  has  suggested,  shoals  of  fish  were  probably 
destroyed  by  the  evolution  of  heat,  noxious  gases,  and  tufaceous  mud, 
just  as  happened  when  Graham's  Island  was  thrown  up  between 
Sicily  and  Africa  in  1831,  at  which  time  the  waters  of  the  Mediter- 
ranean were  seen  to  be  charged  with  red  mud,  and  covered  with  dead 
fish  over  a  wide  area.* 

Associated  with  the  marls  and  limestones  of  Monte  Bolca  are  beds 
containing  lignite  and  shale  with  numerous  plants,  which  have  been 
described  by  linger  and  Massalongo,  and  referred  by  them  to  the 
Eocene  period.  I  have  already  cited  (p.  291)  Professor  Heer's  re- 
mark, that  several  of  the  species  are  common  to  Monte  Bolca  and 
the  white  clay  of  Alum  Bay,  a  Middle  Eocene  deposit ;  and  the  same 
botanist  dwells  on  the  tropical  character  of  the  flora  of  Monte  Bolca 
and  its  distinctness  from  the  subtropical  flora  of  the  Lower  Miocene 
of  Switzerland  and  Italy,  in  which  last  there  is  a  far  more  consider- 
able mixture  of  forms  of  a  temperate  climate,  such  as  the  willow, 
poplar,  birch,  elm,  and  others.  All  these  are  wanting  at  Monte 
Bolca,  while  on  the  other  hand  the  coniferae  are  represented  by  five 
species  of  Podocarpus,  the  Dicotyledons  by  the  fig  and  sandal-wood 
tribe,  and  by  some  Proteacece.  There  are  also  many  tropical  forms 
of  Leguminosce,  together  with  fan-palms,  and  a  palm  allied  to  the 
cocoa-nut  with  its  fruit ;  also,  according  to  Massalongo,  an  orchideous 
epiphyte.  That  scarcely  any  one  of  the  Monte  Bolca  fish  should 
have  been  found  in  any  other  locality  in  Europe,  is  a  striking  illustra- 
tion of  the  extreme  imperfection  of  the  palseontological  record.  We 
are  in  the  habit  of  imagining  that  our  insight  into  the  geology  of  the 
Eocene  period  is  more  than  usually  perfect,  and  we  are  certainly  ac- 
quainted with  an  almost  unbroken  succession  of  assemblages  of  shells 
passing  one  into  the  other  from  the  era  of  the  Thanet  sands  to  that 
of  the  Bembridge  beds  or  Paris  gypsum.  The  general  dearth,  there- 
fore, of  fish  might  induce  a  hasty  reason er  to  conclude  that  there  was 
a  poverty  of  ichthyic  forirls  during  this  long  period ;  but  when  a  local 
accident,  like  the  volcanic  eruptions  of  Monte  Bolca,  occurs,  proofs 
are  suddenly  revealed  to  us  of  the  richness  and  variety  of  this  great 
class  of  vertebrata  in  the  Eocene  sea.  The  number  of  genera  of 
Monte  Bolca  fish  is,  according  to  Agassiz,  no  less  than  seventy- five, 
twenty  of  them  peculiar  to  that  locality,  and  only  eight  common  to 
the  antecedent  Cretaceous  period.  No  less  than  forty-seven  out  of 
the  seventy-five  genera  make  their  appearance  for  the  first  time  in  the 
Monte  Bolca  rocks,  none  of  them  having  been  met  with  as  yet  in  the 
antecedent  formations.  They  form  a  great  contrast  to  the  fish  of  the 
secondary  period,  as,  with  the  exception  of  the  Placoids,  they  are  all 
Teleosteans,  only  one  genus,  Pycnodus,  belonging  to  the  order  of 

*  Principles  of  Geology,  chap,  xxvi.,  9th  ed.,  p.  432. 


696  CRETACEOUS  VOLCANIC  ROCKS.  [On.  XXXII. 

Ganoids,  which  form,  as  before  stated,  the  vast  majority  of  the  ich- 
thyolites  entombed  in  the  secondary  rocks. 

Cretaceous  Period. — Although  we  have  no  proof  of  volcanic  rocks 
erupted  in  England  during  the  deposition  of  the  chalk  and  greensand, 
it  would  be  an  error  to  suppose  that  no  theatres  of  igneous  action 
existed  in  the  Cretaceous  period.  M.  Virlet,  in  his  account  of  the 
geology  of  the  Morea,  p.  205,  has  clearly  shown  that  certain  traps  in 
Greece,  called  by  him  ophiolites,  are  of  this  date ;  as  those,  for  ex- 
ample, which  alternate  conformably  with  cretaceous  limestone  and 
greensand  between  Kastri  and  Damala  in  the  Morea.  They  consist 
in  great  part  of  diallage  rocks  and  serpentine,  and  of  an  amygdaloid 
with  calcareous  kernels,  and  a  base  of  serpentine. 

In  certain  parts  of  the  Morea,  the  age  of  these  volcanic  rocks  is 
established  by  the  following  proofs  :  first,  the  lithographic  limestones 
of  the  Cretaceous  era  are  cut  through  by  trap,  and  then  a  conglomer- 
ate occurs,  at  Naupila  and  other  places,  containing  in  its  calcareous 
cement  many  well-known  fossils  of  the  chalk  and  greensand,  together 
with  pebbles  formed  of  rolled  pieces  of  the  same  ophiolite,  which 
appear  in  the  dikes  above  alluded  to. 

Period  of  Oolite  and  Lias. — Although  the  green  and  serpentinous 
trap  rocks  of  the  Morea  belong  chiefly  to  the  Cretaceous  era,  as 
before  mentioned,  yet  it  seems  that  some  eruptions  of  similar  rocks 
began  during  the  Oolitic  period ;  *  and  it  is  probable  that  a  large 
part  of  the  trappean  masses,  called  ophiolites  in  the  Apennines,  and 
associated  with  the  limestone  of  that  chain,  are  of  corresponding  age. 

That  some  part  of  the  volcanic  rocks  of  the  Hebrides,  in  our  own 
country,  originated  contemporaneously  with  the  Oolite  which  they 
traverse  and  overlie,  has  been  ascertained  by  Professor  E.  Forbes,  in 
1850.  Some  of  the  eruptions  in  Skye,  for  example,  occurred  at  the 
close  of  the  Middle  and  before  the  commencement  of  the  Upper 
Oolitic  period.f 

Trap  of  the  New  Red  Sandstone  Period. — In  the  southern  part  of 
Devonshire,  trappean  rocks  are  associated  with  New  Red  Sandstone, 
and,  according  to  Sir  H.  de  la  Beche,  have  Hot  been  intruded  subse- 
quently into  the  sandstone,  but  were  produced  by  contemporaneous 
volcanic  action.  Some  beds  of  grit,  mingled  with  ordinary  red  marl, 
resemble  sands  ejected  from  a  crater ;  and  in  the  stratified  conglom- 
erates occurring  near  Tiverton  are  many  angular  fragments  of  trap 
porphyry,  some  of  them  one  or  two  tons  in  weight,  intermingled  with 
pebbles  of  other  rocks.  These  angular  fragments  were  probably 
thrown  out  from  volcanic  vents,  and  fell  upon  sedimentary  matter 
then  in  the  course  of  deposition.]; 

Carboniferous  Period. — Two  classes  of  contemporaneous  trap  rocks 
were  ascertained  by  Dr.  Fleming  to  occur  in  the  coal-field  of  the 

*  Boblaye  and  Virlet,  Morea,  p.  23. 

f  Geol.  Quart.  Journ.,  1851,  vol.  vii.  p.  108. 

i  De  la  Beche,  Geol.  Proceedings,  vol.  ii.  p.  198. 


CH.  XXXIL]  CARBONIFEROUS  VOLCANIC  ROCKS. 


69Y 


Forth  in  Scotland.  The  newest  of  these,  connected  with  the  higher 
series  of  coal-measures,  is  well  exhibited  along  the  shores  of  the 
Forth,  in  Fifeshire,  where  they  consist  of  basalt  with  olivine,  amyg- 
daloid, greenstone,  wacke,  and  tuff.  They  appear  to  have  been 
erupted  while  the  sedimentary  strata  were  in  a  horizontal  position, 
and  to  have  suffered  the  same  dislocations  which  those  strata  have 
subsequently  undergone.  In  the  volcanic  tuffs  of  this  age  are  found 
not  only  fragments  of  limestone,  shale,  flinty  slate,  and  sandstone,  but 
also  pieces  of  coal. 

Fig.  781. 


Eock  and  Spindle,  St.  Andrew's,  as  seen  in  1888. 
a.  Unstratified  tuff.  &.  Columnar  greenstone.  c.  Stratified  tuff. 


698  CARBONIFEROUS  VOLCANIC  ROCKS.  [Cn.  XXXII. 

The  other  or  older  class  of  carboniferous  traps  are  traced  along  the 
south  margin  of  Stratheden,  and  constitute  a  ridge  parallel  with  the 
Ochils,  and  extending  from  Stirling  to  near  St.  Andrew's.  They  con- 
sist almost  exclusively  of  greenstone,  becoming,  in  a  few  instances, 
earthy  and  amygdaloidal.  They  are  regularly  interstratified  with 
the  sandstone,  shale,  and  ironstone  of  the  lower  Coal-measures,  and, 
on  the  East  Lomond,  with  Mountain  Limestone. 

I  examined  these  trap  rocks  in  1838,  in  the  cliffs  south  of  St.  An- 
drew's, where  they  consist  in  great  part  of  stratified  tuffs,  which  are 
curved,  vertical,  and  contorted,  like  the  associated  coal-measures.     In 
the  tuff  I  found  fragments  of  carboniferous  shale  and  limestone,  and 
intersecting  veins  of  greenstone.     At  one  spot,  about  two  miles  from 
St.  Andrew's,  the  encroachment  of  the  sea  on  the  cliff's  has  isolated 
several  masses  of  trap,  one  of  which  (fig.  731)  is  aptly  called  the 
"rock  and  spindle,"*  for  it  consists  of  a  pinnacle 
Fig.  732.  of  tuff,  which  may  be  compared  to  a  distaff,  and 

near  the  base  is  a  mass  of  columnar  greenstone,  in 
which  the  pillars  radiate  from  a  centre  and  appear  at 
a  distance  like  the  spokes  of  a  wheel.  The  largest 
diameter  of  this  wheel  is  about  twelve  feet,  and  the 
polygonal  terminations  of  the  columns  are  seen 
round  the  circumference  (or  tire,  as  it  were,  of  the 
wheel),  as  in  the  accompanying  figure.  I  conceive 
at  5,  fig.  731.  this  mass  to  be  the  extremity  of  a  string  or  vein  of 

greenstone,  which  penetrated  the  tuff.  The  prisms 
point  in  every  direction,  because  they  were  surrounded  on  all  sides 
by  cooling  surfaces,  to  which  they  always  arrange  themselves  at  right 
angles,  as  before  explained  (p.  617). 

A  trap  dike  was  pointed  out  to  me  by  Dr.  Fleming,  in  the  parish 
of  Flisk,  in  the  northern  part  of  Fifeshire,  which  cuts  through  the 
gray  sandstone  and  shale,  forming  the  lowest  part  of  the  Old  Red 
Sandstone,  but  which  may  probably  be  of  carboniferous  date.  It 
may  be  traced  for  many  miles,  passing  through  the  amygdaloidal 
and  other  traps  of  the  hill  called  Norman's  Law.  In  its  course  it 
affords  a  good  exemplification  of  the  passage  from  the  trappean  into 
the  plutonic,  or  highly  crystalline  texture.  Professor  Gustavus  Rose, 
to  whom  I  submitted  specimens  of  this  dike,  finds  the  rock,  which 
he  calls  dolerite,  to  consist  of  greenish  black  augite  and  Labrador 
felspar,  the  latter  being  the  most  abundant  ingredient.  A  small 
quantity  of  magnetic  iron,  perhaps  titaniferous,  is  also  present.  The 
result  of  this  analysis  is  interesting,  because  both  the  ancient  and 
modern  lavas  of  Etna  consist  in  like  manner  of  augite,  Labradorite, 
and  titaniferous  iron. 

Trap  of  the  Old  Red  Sandstone  Period.— By  referring  to  the  sec- 

*  "  The  Rock,"  as  English  readers  of  Burns'  poems  may  remember,  is  a  Scotch 
term  for  a  distaff. 


CH.  XXXII.]  DEVONIAN  VOLCANIC  ROCKS.  699 

tion  explanatory  of  the  structure  of  Forfarshire,  already  given  (p.  48), 
the  reader  will  perceive  that  beds  of  conglomerate,  No.  3,  occur  in 
the  middle  of  the  Old  Red  Sandstone  system,  1,  2,  3,  4.  The  peb- 
bles in  these  conglomerates  are  sometimes  composed  of  granitic  and 
quartzose  rocks,  sometimes  exclusively  of  different  varieties  of  trap, 
which  last,  although  purposely  omitted  in  the  section  referred  to,  is 
often  found  either  intruding  itself  in  amorphous  masses  and  dikes 
into  the  old  fossiliferous  tilestones,  No.  4,  or  alternating  with  them  in 
conformable  beds.  All  the  different  divisions  of  the  red  sandstone, 
1,  2,  3,  4,  are  occasionally  intersected  by  dikes,  but  they  are  very 
rare  in  Nos.  1  and  2,  the  upper  members  of  the  group  consisting  of 
red  shale  and  red  sandstone.  These  phenomena,  which  occur  at  the 
foot  of  the  Grampians,  are  repeated  in  the  Sidlaw  Hills ;  and  it 
appears  that  in  this  part  of  Scotland  volcanic  eruptions  were  most 
frequent  in  the  earlier  part  of  the  Old  Red  Sandstone  period. 

The  trap  rocks  alluded  to  consist  chiefly  of  felspathic  porphyry 
and  amygdaloid,  the  kernels  of  the  latter  being  sometimes  calcareous, 
often  chalcedonic,  and  forming  beautiful  agates.  We  meet  also  with 
claystone,  clinkstone,  greenstone,  compact  felspar,  and  tuff.  Some  of 
these  rocks  flowed  as  lavas  over  the  bottom  of  the  sea,  and  enveloped 
quartz  pebbles  which  were  lying  there,  so  as  to  form  conglomerates 
with  a  base  of  greenstone,  as  is  seen  in  Lumley  Den,  in  the  Sidlaw 
Hills.  On  either  side  of  the  axis  of  this  chain  of  hills  (see  section, 
p.  48),  the  beds  of  massive  trap,  and  the  tuffs  composed  of  volcanic 
sand  and  ashes,  dip  regularly  to  the  southeast  or  northwest,  conform- 
ably with  the  shales  and  sandstones.  But  the  geological  structure  of 
the  Pentland  Hills,  near  Edinburgh,  shows  that  igneous  rocks  were 
there  formed  during  the  newer  part  of  the  Devonian  or  "  Old  Red" 
period.  These  hills  are  1900  feet  high  above  the  sea,  and  consist  of 
conglomerates  and  sandstones  of  Upper  Devonian  age,  resting  on  the 
inclined  edges  of  grits  and  slates  of  Lower  Devonian  and  Upper  Silu- 
rian date.  The  contemporaneous  volcanic  rocks  intercalated  in  this 
Upper  Old  Red  consist  of  felspathic  lavas,  or  felstones,  with  asso- 
ciated tuffs  or  ashy  beds.  The  lavas  were  some  of  them  originally 
compact,  others  vesicular,  and  these  last  have  been  converted  into 
amygdaloids.  They  consist  chiefly  of  felstone  or  compact  felspar. 
The  Pentland  Hills,  say  Messrs.  Maclaren  and  Geikie,  afford  evidence 
that  at  the  time  of  the  Upper  Old  Red  Sandstone,  the  district  to  the 
southwest  of  Edinburgh  was  for  a  long  while  the  seat  of  a  powerful 
volcano,  which  sent  out  massive  streams  of  lava  and  showers  of  ash, 
and  continued  active  until  well-nigh  the  dawn  of  the  Carboniferous 
period.* 

Silurian  Period. — It  appears  from  the  investigations  of  Sir  R. 
Murchison  in  Shropshire,  that  when  the  lower  Silurian  strata  of 

*  Maclaren,  Geology  of  Fife  and  Lothians.  Geikie,  Trans.  Royal  Soc.  Edin- 
burgh, 1860-1861. 


700  SILURIAN  VOLCANIC  ROCKS.  [Cn.  XXXII. 

that  country  were  accumulating,  there  were  frequent  volcanic  erup- 
tions beneath  the  sea ;  and  the  ashes  and  scoriae  then  ejected  gave 
rise  to  a  peculiar  Mud  of  tufaceeus  sandstone  or  grit,  dissimilar  to 
the  other  rocks  of  the  Silurian  series,  and  only  observable  in  places 
where  syenitic  and  other  trap  rocks  protrude.  These  tuffs  occur  on 
the  franks  of  the  Wrekin  and  Caer  Caradoc,  and  contain  Silurian 
fossils,  such  as  casts  of  encrinites,  trilobites,  and  mollusca.  Although 
fossiliferous,  the  stone  resembles  a  sandy  claystone  of  the  trap 
family.* 

Thin  layers  of  trap,  only  a  few  inches  thick,  alternate  in  some 
parts  of  Shropshire  and  Montgomeryshire  with  sedimentary  strata  of 
the  lower  Silurian  system.  This  trap  consists  of  slaty  porphyry  and 
granular  felspar  rock,  the  beds  being  traversed  by  joints  like  those  in 
the  associated  sandstone,  limestone,  and  shale,  and  haying  the  same 
strike  and  dip.f 

In  Radnorshire  there  is  an  example  of  twelve  bands  of  stratified 
trap,  alternating  with  Silurian  schists  and  flagstones,  in  a  thickness  of 
350  feet.  The  bedded  traps  consist  of  felspar  porphyry,  clinkstone, 
and  other  varieties ;  and  the  interposed  Llandeilo  flags  are  of  sand- 
stone and  shale,  with  trilobites  and  graptolites.J 

The  Snowdonian  hills  in  Caernarvonshire  consist  in  great  part  of 
volcanic  tuffs,  the  oldest  of  which  are  interstratified  with  the  Bala 
limestone  and  slate.  There  are  some  contemporaneous  felspathic 
lavas  of  this  era,  which,  says  Professor  Eamsay,  alter  the  slates  on 
which  they  repose,  having  doubtless  been  poured  out  over  them  in  a 
melted  state,  whereas  the  slates  which  overlie  them  having  been  sub- 
sequently deposited  after  the  lava  had  cooled  and  consolidated,  have 
entirely  escaped  alteration.  But  there  are  greenstones  associated 
with  the  same  formation,  which,  although  they  are  often  conformable 
to  the  slates,  are  in  reality  intrusive  rocks.  They  alter  the  stratified 
deposits  both  above  and  below  them,  and  when  traced  to  great  dis- 
tances, are  sometimes  seen  to  cut  through  the  slates,  and  to  send  off 
branches.  Nevertheless,  these  greenstones  appear  to  belong,  like  the 
lavas,  to  the  Lower  Silurian  period. 

Cambrian  Volcanic  Rocks. — The  Lingula  beds  in  North  Wales 
have  been  described  as  7000  feet  in  thickness.  In  the  upper  portion 
of  these  deposits,  volcanic  tuffs  or  ashy  materials  are  interstratified 
with  ordinary  muddy  sediment,  and  here  and  there  associated  with 
thick  beds  of  felspathic  lava.  These  rocks  form  the  mountains  called 
the  Arans  and  the  Arenigs ;  numerous  greenstones  are  associated 
with  them,  which  are  intrusive,  although  they  often  run  in  the  lines 
of  bedding  for  a  space.  "  Much  of  the  ash,"  says  Professor  Ramsay, 
"  seems  to  have  been  subaerial.  Islands,  like  Graham's  Island,  may 
have  sometimes  raised  their  craters  for  various  periods  above  the 


*  Murchison,  Silurian  System,  &c.,  p.  230. 
f  Ibid.,  p.  212.  J  Ibid.,  p.  325. 


CH.  XXXII.]  LAURENTIAN  VOLCANIC  ROCKS.  YOl 

water,  and  by  the  waste  of  such  islands  some  of  the  ashy  matter  be- 
came waterworn,  whence  the  ashy  conglomerate.  Viscous  matter 
seems  also  to  have  been  shot  into  the  air  as  volcanic  bombs,  which 
fell  among  the  dust  and  broken  crystals  (that  often  form  the  ashes) 
before  perfect  cooling  and  consolidation  had  taken  place."  * 

Laurentian  Volcanic  Rocks. — The  Laurentian  rocks  in  Canada, 
especially  in  Ottawa  and  Argenteuil,  are  the  oldest  intrusive  masses 
yet  known.  They  form  a  set  of  dikes  of  a  fine-grained  dark  green- 
stone or  dolerite,  composed  of  felspar  and  pyroxene,  with  occasional 
scales  of  mica  and  grains  of  pyrites.  Their  width  varies  from  a  few 
feet  to  a  hundred  yards,  and  they  have  a  columnar  structure,  the 
columns  being  truly  at  right  angles  to  the  plane  of  the  dike.  Some 
of  the  dikes  send  off  branches.  These  dolerites  are  cut  through  by 
intrusive  syenite,  and  this  syenite,  in  its  turn,  is  again  cut  and 
penetrated  by  felspar  porphyry,  the  base  of  which  consists  of  petro- 
silex,  or  a  mixture  of  orthoclase  and  quartz.  All  these  trap  rocks 
appear  to  be  of  Laurentian  date,  for  the  lowest  fossiliferous  rocks, 
such  as  the  Cambrian  or  Potsdam  sandstone,  overlie  eroded  portions 
of  them.f  Whether  some  of  the  various  conformable  crystalline 
rocks  of  the  Laurentian  series,  such  as  the  coarse-grained  granitoid 
and  porphyritic  varieties  of  gneiss,  exhibiting  scarcely  any  signs  of 
stratification,  some  of  the  serpentines,  may  not  also  be  of  volcanic 
origin,  is  a  point  very  difficult  to  determine  in  a  region  which  has 
undergone  so  much  metamorphic  action. 

*  Geol.  Quart.  Journ.,  vol.  ix.  p.  170,  1853. 
f  Logan,  Geology  of  Canada,  1862. 


702  PLUTONIC  ROCKS.  [Cn.  XXXIH. 


CHAPTER  XXXIII. 

PLUTONIC      ROCKS GRANITE. 

General  aspect  of  granite — Decomposing  into  spherical  masses — Rude  columnar 
structure — Analogy  and  difference  of  volcanic  and  plutonic  formations — Minerals 
in  granite,  and  their  arrangement — Graphic  and  porphyritic  granite — Mutual 
penetration  of  crystals  of  quartz  and  felspar — Occasional  minerals — Syenite— 
Syenitic,  talcose,  and  schorly  granites — Eurite — Passage  of  granite  into  trap — 
Examples  near  Christiania  and  ill  Aberdeenshire — Analogy  in  composition  of 
trachyte  and  granite — Granite  veins  in  Glen  Tilt,  Cornwall,  the  Valorsine,  and 
other  countries — Different  composition  of  veins  from  main  body  of  granite — 
Metalliferous  veins  in  strata  near  their  junction  with  granite — Apparent  isolation 
of  nodules  of  granite — Quartz  veins — Whether  plutonic  rocks  are  ever  overlying 
— Their  exposure  at  the  surface  due  to  denudation. 

THE  plutonic  rocks  may  be  treated  of  next  in  order,  as  they  are 
most  nearly  allied  to  the  volcanic  class  already  considered.  I  have 
described,  in  the  first  chapter,  these  plutonic  rocks  as  the  unstratified 
division  of  the  crystalline  or  hypogene  formations,  and  have  stated 
that  they  differ  from  the  volcanic  rocks,  not  only  by  their  more  crys- 
talline texture,  bnt  also  by  the  absence  of  tuffs  and  breccias,  which 
are  the  products  of  eruptions  at  the  earth's  surface,  or  beneath  seas 
of  inconsiderable  depth.  They  differ  also  by  the  absence  of  pores 
or  cellular  cavities,  to  which  the  expansion  of  the  entangled  gases 
gives  rise  in  ordinary  lava.  From  these  and  other  peculiarities  it  has 
been  inferred,  that  the  granites  have  been  formed  at  considerable 
depths  in  the  earth,  and  have  cooled  and  crystallized  slowly  under 
great  pressure,  where  the  contained  gases  could  not  expand.  The 
volcanic  rocks,  on  the  contrary,  although  they  also  have  risen  up 
from  below,  have  cooled  from  a  melted  state  more  rapidly  upon  or 
near  the  surface.  From  this  hypothesis  of  the  great  depth  at  which 
the  granites  originated,  has  been  derived  the  name  of  "  Plutonic 
rocks."  The  beginner  will  easily  conceive  that  the  influence  of  sub- 
terranean heat  may  extend  downwards  from  the  crater  of  every  active 
volcano  to  a  great  depth  below,  perhaps  several  miles  or  leagues,  and 
the  effects  which  are  produced  deep  in  the  bowels  of  the  earth  may, 
or  rather  must,  be  distinct ;  so  that  volcanic  and  plutonic  rocks,  each 
different  in  texture,  and  sometimes  even  in  composition,  may  origi- 
nate simultaneously,  the  one  at  the  surface,  the  other  far  beneath  it. 

By  some  writers,  all  the  rocks  jiow  under  consideration  have  been 


OH.  XXXIIL]  GENERAL  ASPECT  OF  GRANITE.  703 

comprehended  under  the  name  of  granite,  which  is,  then,  understood 
to  embrace  a  large  family  of  crystalline  and  compound  rocks,  usually 
found  underlying  all  other  formations ;  whereas  we  have  seen  that 
trap  very  commonly  overlies  strata  of  different  ages.  Granite  often 
preserves  a  very  uniform  character  throughout  a  wide  range  of  terri- 
tory, forming  hills  of  a  peculiar  rounded  form,  usually  clad  with  a 
scanty  vegetation.  The  surface  of  the  rock  is  for  the  most  part  in  a 
crumbling  state,  and  the  hills  are  often  surmounted  by  piles  of  stones 
like  the  remains  of  a  stratified  mass,  as  in  the  annexed  figure,  and 

Fig.  733. 


Mass  of  granite  near  the  Sharp  Tor,  Cornwall. 

sometimes  like  heaps  of  boulders,  for  which  they  have  been  mistaken. 
The  exterior  of  these  stones,  originally  quadrangular,  acquires  a 
rounded  form  by  the  action  of  air  and  water,  for  the  edges  and  angles 
waste  away  more  rapidly  than  the  sides.  A  similar  spherical  struc- 
ture has  already  been  described  as  characteristic  of  basalt  and  other 
volcanic  formations,  and  it  must  be  referred  to  analogous  causes,  as 
yet  but  imperfectly  understood. 

Although  it  is  the  general  peculiarity  of  granite  to  assume  no  defi- 
nite shapes,  it  is  nevertheless  occasionally  subdivided  by  fissures,  so  as 
to  assume  a  cuboidal,  and  even  a  columnar  structure.  Examples  of 
these  appearances  may  be  seen  near  the  Land's  End,  in  Cornwall. 
(See  fig.  734.) 

The  plutonic  formations  also  agree  with  the  volcanic  in  having  veins 
or  ramifications  proceeding  from  central  masses  into  the  adjoining 
rocks,  and  causing  alterations  in  these  last,  which  will  be  presently 
described.  They  also  resemble  trap  in  containing  no  organic  remains ; 
but  they  differ  in  being  more  uniform  in  texture,  whole  mountain 
masses  of  indefinite  extent  appearing  to  have  originated  under  con- 
ditions precisely  similar.  They  also  differ  in  never  being  scoriaceous 
or  amygdaloidal,  and  never  forming  a  porphyry  with  an  uncrystalline 
base,  or  alternating  with  tuffs.  Nor  do  they  form  conglomerates, 
although  there  is  sometimes  an  insensible  passage  from  a  fine  to  a 
coarse-grained  granite,  and  occasionally  patches  of  a  fine  texture  are 
imbedded  in  a  coarser  variety. 

Felspar,  quartz,  and  mica  are  usually  considered  as  the  minerals 
essential  to  granite,  the  felspar  being  most  abundant  in  quantity,  and 
the  proportion  of  quartz  exceeding  that  of  mica.  These  minerals  are 


704: 


MINERAL  COMPOSITION  OP  GRANITE.        [On.  XXXIII. 
Fig.  734. 


Granite  having  a  cuboidal  and  rude  columnar  structure,  Land's  End,  Cornwall. 

united  in  what  is  termed  a  confused  crystallization ;  that  is  to  say, 
there  is  no  regular  arrangement  of  the  crystals  in  granite,  as  in  gneiss 
(see  fig.  756,  p.  733),  except  in  the  variety  termed  graphic  granite, 
which  occurs  mostly  in  granitic  veins.  This  variety  is  a  compound 
of  felspar  and  quartz,  so  arranged  as  to  produce  an  imperfect  laminar 
structure.  The  crystals  of  felspar  appear  to  have  been  first  formed, 
leaving  between  them  the  space  now  occupied  by  the  darker-colored 
quartz.  This  mineral,  when  a  section  is  made  at  right  angles  to  the 


Fig.  735. 


Fig.  736. 


Graphic  granite. 

Fig.  735.    Section  parallel  to  the  laminae. 
Fig.  786.    Section  transverse  to  the  laminae. 


alternate  plates  of  felspar  and  quartz,  presents  broken  lines,  which 
have  been  compared  to  Hebrew  characters.  The  variety  of  granite 
called  by  the  French  Pegmatite,  which  is  a  mixture  of  quartz  and 
common  felspar,  usually  with  some  small  admixture  of  white  silvery 
mica,  often  passes  into  graphic  granite. 


CH.  XXXIII.]        MINERAL  COMPOSITION  OF  GRANITE.  YQ5 

Ordinary  granite,  as  well  as  syenite  and  eurite,  usually  contains  two 
kinds  of  felspar:  1st,  the  common,  or  orthoclase,  in  which  potash  is 
the  prevailing  alkali,  and  this  generally  occurs  in  large  crystals  of  a 
white  or  flesh  color;  and  2 dly,  felspar  in  smaller  crystals,  in  which, 
soda  predominates,  usually  of  a  dead  white  or  spotted,  and  striated 
like  albite,  but  not  the  same  in  composition.* 

As  a  general  rule,  quartz,  in  a  compact  or  amorphous  state,  forms  a 
vitreous  mass,  serving  as  the  base  in  which  felspar  and  mica  have 
crystallized  ;  for  although  these  minerals  are  much  more  fusible 
than  silex,  they  have  often  imprinted  their  shapes  upon  the  quartz. 
This  fact,  apparently  so  paradoxical,  has  given  rise  to  much  ingenious 
speculation.  We  should  naturally  have  anticipated  that,  during  the 
cooling  of  the  mass,  the  flinty  portion  would  be  the  first  to  consoli- 
date ;  and  that  the  different  varieties  of  felspar,  as  well  as  garnets  and 
tourmalines,  being  more  easily  liquefied  by  heat,  would  be  the  last. 
Precisely  the  reverse  has  taken  place  in  the  passage  of  most  granite 
aggregates  from  a  fluid  to  a  solid  state,  crystals  of  the  more  fusible 
minerals  being  found  enveloped  in  hard,  transparent,  glassy  quartz, 
which  has  often  taken  very  faithful  casts  of  each,  so  as  to  preserve 
even  the  microscopically  minute  striations  on  the  surface  of  prisms 
of  tourmaline.  Various  explanations  of  this  phenomenon  have  been 
proposed  by  MM.  de  Beaumont,  Fournet,  and  Durocher.  They  refer 
to  M.  Gaudin's  experiments  on  the  fusion  of  quartz,  which  shows  that 
silex,  as  it  cools,  has  the  property  of  remaining  in  a  viscous  state, 
whereas  alumina  never  does.  This  "  gelatinous  flint "  is  supposed  to 
retain  a  considerable  degree  of  plasticity  long  after  the  granitic  mix- 
ture has  acquired  a  low  temperature ;  and  M.  E.  de  Beaumont  suggests 
that  electric  action  may  prolong  the  duration  of  the  viscosity  of  silex. 
Occasionally,  however,  we  find  the  quartz  and  felspar  mutually  im- 
printing their  forms  on  each  other,  affording  evidence  of  the  simul- 
taneous crystallization  of  both.f 

According  to  the  experiments  and  observations  of  Gustave  Rose, 
the  quartz  of  granite  has  the  specific  gravity  of  2*6,  which  charac- 
terizes silica  when  it  is  precipitated  from  a  liquid  solvent,  and  not 
that  inferior  density,  namely,  2 '3,  which  belongs  to  it  when  it  cools 
in  the  laboratory,  in  what  is  called  the  dry  way,  or  from  a  state  of 
fusion.  It  has  been,  therefore,  inferred,  perhaps  somewhat  rashly, 
that  the  manner  in  which  the  consolidation  of  granite  takes  place  is 
exceedingly  different  from  the  cooling  of  lavas,  even  of  those  which 
are  the  most  crystalline.  It  has  also  been  still  more  hastily  inferred, 
that  the  intense  heat  formerly  supposed  to  be  necessary  for  the  pro- 
duction of  mountain  masses  of  plutonic  rocks  may  be  dispensed  with. 
The  first  question  to  be  decided  is,  whether  or  not  silica  can  be  ob- 


*  Delesse,  Ann.  des  Mines,  1852,  t.  iii.  p.  409,  and  1848,  t.  xiii.  p.  675. 
f  Bulletin,  2e  serie,  iv.  1304 ;  and  D'Archiac,  Hist,  des  Progres  de  la  Geol., 
i.  38. 

45 


706  GLASS-CAVITIES  IN  GRANITE.  [On.  XXXIII. 

tained  even  in  the  laboratory  in  a  crystalline  state  by  fusion.  Mr. 
Sorby,  who  has  devoted  much  time  and  talent  to  the  solution  of  this 
and  kindred  problems,  has  come  to  the  conclusion  that  it  can  be  so 
obtained.  He  informs  me  that  he  is  convinced,  by  the  examination 
of  quartz  fused  by  Mr.  David  Forbes,  that  silica  can  crystallize  in  the 
dry  way,  and  he  has  found  in  quartz  forming  a  constituent  part  of 
some  trachytes,  both  from  Guadaloupe  and  Iceland,  glass-cavities* 
quite  similar  to  those  met  with  in  genuine  volcanic  minerals,  which 
prove  most  conclusively  that  this  quartz  crystallized  out  from  a  fused 
material  like  obsidian. 

By  "  glass-cavities  "  are  meant  those  in  which  a  liquid,  on  cooling, 
has  become  first  viscous  and  then  solid  without  crystallizing  or  under- 
going a  definite  change  in  its  physical  structure.  Other  cavities 
which,  like  those  just  mentioned,  are  frequently  discernible  under  the 
microscope  in  the  minerals  composing  granitic  rocks,  are  filled  some 
of  them  with  gas  or  vapor,  others  with  liquid,  and  by  the  movements 
of  the  bubbles  thus  included  the  distinctness  of  such  cavities  from 
those  filled  with  a  glassy  substance  can  be  tested. 

Mr.  Sorby  admits  that  the  frequent  occurrence  of  fluid  cavities  in 
the  quartz  of  granite  implies  that  water  was  almost  always  present  in 
the  formation  of  this  rock ;  but  the  same  may  be  said  of  almost  all 
lavas,  and  it  is  now  more  than  forty  years  since  Mr.  Scrope  insisted  on 
the  important  part  which  water  plays  in  volcanic  eruptions,  being  so 
intimately  mixed  up  with  the  materials  of  the  lava  that  he  supposed 
it  to  aid  it  in  giving  mobility  to  the  fluid  mass.  It  is  well  known  that 
steam  escapes  for  months,  sometimes  for  years,  from  the  cavities  of 
lava  when  it  is  cooling  and  consolidating. 

As  to  the  result  of  Mr.  Sorby's  experiments  and  speculations  on 
this  difficult  subject,  they  may  be  stated  in  a  few  words.  He  con- 
cludes that  the  physical  conditions  under  which  the  volcanic  and 
granitic  rocks  originate  are  so  far  similar  that  in  both  cases  they  com- 
bine igneous  fusion,  aqueous  solution,  and  gaseous  sublimation — the 
proof,  he  says,  of  the  operation  of  water  in  the  formation  of  granite 
being  quite  as  strong  as  that  of  heat.f 

When  rocks  are  melted  at  great  depths  water  must  be  present,  for 
two  reasons:  First,  because  in  a  state  of  solid  combination  water 
enters  largely  into  the  composition  of  some  of  the  most  common 
minerals,  especially  those  of  the  aluminous  class ;  and,  secondly,  be- 
cause rain-water  and  sea-water  are  always  descending  through  fissured 
and  porous  rocks,  and  must  at  length  find  their  way  into  the  regions 
of  subterranean  heat.  But  the  existence  of  water  under  great  pres- 
sure affords  no  argument  against  our  attributing  an  excessively  high 
temperature  to  the  mass  with  which  it  is  mixed  up. 

Bunsen,  indeed,  imagines  that  in  Iceland  it  attains  a  white  heat  at 


*  See  Quart.  Geol.  Journ.,  vol.  xiv.  p.  465. 
f  Ibid.,  p.  488. 


CH.  XXXIII.]  PORPHYRITIC  GRANITE.  707 

a  very  moderate  depth.  Still  less  does  the  point  to  which  the  ma- 
terials of  granite  or  lava  must  be  cooled  down  before  they  crystallize  or 
consolidate  afford  any  test  of  the  degree  of  heat  which  the  same  ma- 
terials acquired  before  they  could  be  made  to  form  lakes  and  seas  of 
molten  rock  in  the  interior  of  the  earth's  crust. 

To  what  extent  some  of  the  metamorphic  rocks  containing  the 
same  minerals  as  the  granites  may  have  been  formed  by  hydro- 
thermal  action  without  the  intervention  of  intense  heat  comparable 
to  that  brought  into  play  in  a  volcanic  eruption,  will  be  considered 
when  we  treat  of  the  metamorphic  rocks,  in  the  thirty-fifth  chapter, 
p.  736. 

Porphyritic  Granite. — This  name  has  been  sometimes  given  to  that 
variety  in  which  large  crystals  of  common  felspar,  sometimes  more  than 
3  inches  in  length,  are  scattered  through  an  ordinary  base  of  granite. 
An  example  of  this  texture  may  be  seen  in  the  granite  of  the  Land's  End, 
in  Cornwall  (fig.  737).  The  two  larger  prismatic  crystals  in  this  draw- 
rig.  787. 


Porphyritic  granite.    Land's  End,  Cornwall. 

ing  represent  felspar,  smaller  crystals  of  which  are  also  seen,  similar 
in  form,  scattered  through  the  base.  In  this  base  also  appear  black 
specks  of  mica,  the  crystals  of  which  have  a  more  or  less  perfect 
hexagonal  outline.  The  remainder  of  the  mass  is  quartz,  the  trans- 
lucency  of  which  is  strongly  contrasted  to  the  opaqueness  of  the  white 
felspar  and  black  mica.  But  neither  the  transparency  of  the  quartz 
nor  the  silvery  lustre  of  the  mica  can  be  expressed  in  the  engraving. 

The  uniform  mineral  character  of  large  masses  of  granite  seems  to 
indicate  that  large  quantities  of  the  component  elements  were  thor- 
oughly mixed  up  together,  and  then  crystallized  under  precisely  simi- 
lar conditions.  There  are,  however,  many  accidental,  or  "  occasional," 
minerals,  as  they  are  termed,  which  belong  to  granite.  Among  these, 
black  schorl  or  tourmaline,  actinolite,  zircon,  garnet,  and  fluor  spar 
are  not  uncommon  ;  but  they  are  too  sparingly  dispersed  to  modify 
the  general  aspect  of  the  rock.  They  show,  nevertheless,  that  the  in- 
gredients were  not  ever}7 where  exactly  the  same ;  and  a  still  greater 
variation  may  be  traced  in  the  ever-varying  proportions  of  the  felspar, 
quartz,  and  mica. 


708  PASSAGE  OF  GRANITE  INTO   TRAP.          [Cn.  XXXIIL 

Syenite. — When  hornblende  is  the  substitute  for  mica,  which  is 
very  commonly  the  case,  the  rock  becomes  Syenite ;  so  called  from 
the  celebrated  ancient  quarries  of  Syene  in  Egypt.  It  has  all  the 
appearance  of  ordinary  granite,  except  when  mineral ogically  examined 
in  hand  specimens,  and  is  fully  entitled  to  rank  as  a  geological  mem- 
ber of  the  same  plutonic  family  as  granite.  Syenite,  however,  after 
maintaining  the  granitic  character  throughout  extensive  regions,  is  not 
uncommonly  found  to  lose  its  quartz,  and  to  pass  insensibly  into 
syenitic  greenstone,  a  rock  of  the  trap  family.  Werner  considered 
syenite  as  a  binary  compound  of  felspar  and  hornblende,  and  regarded 
quartz  as  merely  one  of  its  occasional  minerals. 

Syenitic  Granite. — The  quadruple  compound  of  quartz,  felspar, 
mica,  and  hornblende,  may  be  so  termed.  This  rock  occurs  in  Scot- 
land and  in  Guernsey. 

Talcose  Granite,  or  Protogine  of  the  French,  is  a  mixture  of  felspar, 
quartz,  and  talc.  It  abounds  in  the  Alps,  and  in  some  parts  of  Corn- 
wall, producing  by  its  decomposition  the  China  clay,  more  than  12,000 
tons  of  which  are  annually  exported  from  that  country  for  the  pot- 
teries.* 

Schorl-JRock,  and  Schorly  Granite. — The  former  of  these  is  an 
aggregate  of  schorl,  or  tourmaline,  and  quartz.  When  felspar  and 
mica  are  also  present,  it  may  be  called  schorly  granite.  This  kind  of 
granite  is  comparatively  rare. 

Eurite. — A  rock  in  which  all  the  ingredients  of  granite  are  blended 
into  a  finely  granular  mass.  When  crystalline,  it  is  seen  to  contain 
crystals  of  quartz,  mica,  common  felspar,  and  soda  felspar.  When 
there  is  no  mica,  and  when  common  felspar  predominates,  so  as  to 
give  it  a  white  color,  it  becomes  a  felspathic  granite,  called  "  white- 
stone  "  (Weisstein)  by  Werner,  or  Leptynite  by  the  French,  in  which 
microscopic  crystals  of  garnet  are  often  present. 

All  these  and  other  varieties  of  granite  pass  into  certain  kinds  of 
trap — a  circumstance  which  affords  one  of  many  arguments  in  favor 
of  what  is  now  the  prevailing  opinion,  that  the  granites  are  also  of 
igneous  origin.  The  contrast  of  the  most  crystalline  form  of  granite 
to  that  of  the  most  common  and  earthy  trap  is  undoubtedly  great ; 
but  each  member  of  the  volcanic  class  is  capable  of  becoming  porphy- 
ritic,  and  the  base  of  the  porphyry  may  be  more  and  more  crystalline, 
until  the  mass  passes  to  the  kind  of  granite  most  nearly  allied  in  min- 
eral composition. 

The  minerals  which  constitute  alike  the  granitic  and  volcanic  rocks 
consist,  almost  exclusively,  of  seven  elements,  namely,  silica,  alumina, 
magnesia,  lime,  soda,  potash,  and  iron  (see  Table,  p.  608) ;  and  these 
may  sometimes  exist  in  about  the  same  proportions  in  a  porous  lava, 
a  compact  trap,  or  a  crystalline  granite.  It  may  perhaps  be  found, 
on  further  examination — for  on  this  subject  we  have  yet  much  to 

*  Boase  on  Primary  Geology,  p.  16. 


CH.  XXXIII.]       ROCKS  ALTERED  BY  GRANITE  VEINS.  Y09 

learn — that  the  presence  of  these  elements  in  certain  proportions  is 
more  favorable  than  in  others  to  their  assuming  a  crystalline  or  true 
granitic  structure ;  but  it  is  also  ascertained  by  experiment,  that  the 
same  materials  may,  under  different  circumstances,  form  very  different 
rocks.  The  same  lava,  for  example,  may  be  glassy,  or  scoriaceous,  or 
stony,  or  porphyritic,  according  to  the  more  or  less  rapid  rate  at 
which  it  cools;  and  some  trachytes  and  syenitic-greenstones  may 
doubtless  form  granite  and  syenite,  if  the  crystallization  take  place 
slowly. 

It  has  also  been  suggested  that  the  peculiar  nature  and  structure  of 
granite  may  be  due  to  its  retaining  in  it  that  water  which  is  seen  to 
escape  from  lavas  when  they  cool  slowly,  and  consolidate  in  the  atmos- 
phere. Boutigny's  experiments  have  shown  that  melted  matter,  at  a 
white  heat,  requires  to  have  its  temperature  lowered  before  it  can 
vaporize  water ;  and  such  discoveries,  if  they  fail  to  explain  the  manner 
in  which  granites  have  been  formed,  serve  at  least  to  remind  us  of  the 
entire  distinctness  of  the  conditions  under  which  plutonic  and  volcanic 
rocks  must  be  produced.* 

It  would  be  easy  to  multiply  examples  and  authorities  to  prove  the 
gradation  of  the  granitic  into  the  trap  rocks.  On  the  western  side  of 
the  fiord  of  Christiania,  in  Norway,  there  is  a  large  district  of  trap, 
chiefly  greenstone-porphyry  and  syenitic  greenstone,  resting  on  fossil- 
iferous  strata.  To  this,  on  its  southern  limit,  succeeds  a  region  equally 
extensive  of  syenite,  the  passage  from  the  volcanic  to  the  plutonic 
rock  being  so  gradual  that  it  is  impossible  to  draw  a  line  of  demar- 
cation between  them. 

"  The  ordinary  granite  of  Aberdeenshire,"  says  Dr.  MacCulloch,  "  is 
the  usual  ternary,  compound  of  quartz,  felspar,  and  mica ;  but  some- 
times hornblende  is  substituted  for  the  mica.  But  in  many  places  a 
variety  occurs  which  is  composed  simply  of  felspar  and  hornblende ; 
and  in  examining  more  minutely  this  duplicate  compound,  it  is  ob- 
served in  some  places  to  assume  a  fine  grain,  and  at  length  to  become 
undistinguishable  from  the  greenstones  of  the  trap  family.  It  also 
passes  in  the  same  uninterrupted  manner  into  a  basalt,  and  at  length 
into  a  soft  claystone,  with  "a  schistose  tendency  on  exposure,  in  no 
respect  differing  from  those  of  the  trap  islands  of  the  western  coast." 
The  same  author  mentions,  that  in  Shetland  a  granite  composed  of 
hornblende,  mica,  felspar,  and  quartz  graduates  in  an  equally  perfect 
manner  into  basalt,  f 

In  Hungary,  there  are  varieties  of  trachyte,  which,  geologically 
speaking,  are  of  modern  origin,  in  which  crystals,  not  only  of  mica, 
but  of  quartz,  are  common,  together  with  felspar  and  hornblende. 
It  is  easy  to  conceive  how  such  volcanic  masses  may,  at  a  certain 
depth  from  the  surface,  pass  downwards  into  granite. 

*  E.  de  Beaumont,  Bulletin,  vol.  iv.,  2e  ser.,  pp.  1318  and  1320. 
f  Syst.  of  Geol.,  vol.  i.  pp.  157  and  158. 


710 


ROCKS  ALTERED  BY  GRANITE  VEINS.       [Cn.  XXXIIL 


I  have  already  hinted  at  the  close  analogy  in  the  forms  of  certain 
granitic  and  trappean  veins ;  and  it  will  be  found  that  strata  pene- 
trated by  plutonic  rocks  have  suffered  changes  very  similar  to  those 
exhibited  near  the  contact  of  volcanic  dikes.  Thus,  in  Glen  Tilt,  in 
Scotland,  alternating  strata  of  limestone  and  argillaceous  schist  come 
in  contact  with  a  mass  of  granite.  The  contact  does  not  take  place 
as  might  have  been  looked  for,  if  the  granite  had  been  formed  there 
before  the  strata  were  deposited,  in  which  case  the  section  would  have 
appeared  as  in  fig.  738 ;  but  the  union  is  as  represented  in  fig.  739, 


Fig.  738. 


Fig.  739. 


-\*\S»\^\''  *M^ 


«**•  \  K  •«» 


Junction  of  granite  and  argillaceous  schist  in 
Glen  Tilt.    (MacCulloch.)* 

Fig.  740. 


Junction  of  granite  and  limestone  in  Glen  Tilt.    (MacCulloch.) 
a.  Granite.  &.  Limestone.  c.  Blue  argillaceous  schist. 


*  Geol.  Trans.,  First  Series,  vol.  iii.  pi.  21. 


CH.  xxxm.] 


STRUCTURE  OF  GRANITE  VEINS. 


the  undulating  outline  of  the  granite  intersecting  different  strata,  and 
occasionally  intruding  itself  in  tortuous  veins  into  the  beds  of  clay- 
slate  and  limestone,  from  which  it  differs  so  remarkably  in  compo- 
sition. The  limestone  is  sometimes  changed  in  character  by  the  prox- 
imity of  the  granitic  mass  or  its  veins,  and  acquires  a  more  compact 
texture,  like  that  of  horn  stone  or  chert,  with  a  splintery  fracture,  and 
effervescing  freely  with  acids. 

The  foregoing  diagram  (fig.  740)  represents  another  junction,  in  the 
same  district,  where  the  granite  sends  forth  so  many  veins  as  to  reticu- 
late the  limestone  and  schist,  the  veins  diminishing  towards  their 
termination  to  the  thickness  of  a  leaf  of  paper  or  a  thread.  In  some 
places  fragments  of  granite  appear  entangled,  as  it  were,  in  the  lime- 
stone, and  are  not  visibly  connected  with  any  larger  mass;  while 
sometimes,  on  the  other  hand,  a  lump  of  the  limestone  is  found  in  the 
midst  of  the  granite.  The  ordinary  color  of  the  limestone  of  Glen 
Tilt  is  lead  blue,  and  its  texture  large-grained  and  highly  crystalline ; 
but  where  it  approximates  to  the  granite,  particularly  where  it  is  pene- 
trated by  the  smaller  veins,  the  crystalline  texture  disappears,  and  it 
assumes  an  appearance  exactly  resembling  that  of  hornstone.  The 
associated  argillaceous  schist  often  passes  into  hornblende  slate,  where 
it  approaches  very  near  to  the  granite.* 

The  conversion  of  the  limestone  in  these  and  many  other  instances 
into  a  siliceous  rock,  effervescing  slowly  with  acids,  would  be  difficult 
of  explanation,  were  it  not  ascertained  that  such  limestones  are  always 
impure,  containing  grains  of  quartz,  mica,  or  felspar  disseminated 
through  them.  The  elements  of  these  minerals,  when  the  rock  has 
been  subjected  to  great  heat,  may  have  been  fused,  and  so  spread 
more  uniformly  through  the  whole  mass. 


Fig.  741. 


Fig.  742. 


Granite  veins  traversing  clay  elate, 
Table  Mountain,  Cape  of  Good  Hope.t 


Granite  veins  traversing  gneiss,  Cape  Wrath. 
(MacCnlloch.)t 


*  MacCulloch,  Geol.  Trans.,  vol.  iii.  p.  259. 

f  Capt.  B.  Hall,  Trans.  Roy.  Soc.  Edinburgh,  vol.  vii. 

\  Western  Islands,  pi.  31. 


712  MINERAL  STRUCTURE  OF        [Cn.  XXXHI. 

In  the  plutonic,  as  in  the  volcanic  rocks,  there  is  every  gradation 
from  a  tortuous  vein  to  the  most  regular  form  of  a  dike,  such  as  inter- 
sect the  tuffs  and  lavas  of  Vesuvius  and  Etna.  Dikes  of  granite  may 
be  seen,  among  other  places,  on  the  southern  flank  of  Mount  Battock, 
one  of  the  Grampians,  the  opposite  wall  sometimes  preserving  an  exact 
parallelism  for  a  considerable  distance. 

As  a  general  rule,  however,  granite  veins  in  all  quarters  of  the 
globe  are  more  sinuous  in  their  course  than  those  of  trap.  They  pre- 
sent similar  shapes  at  the  most  northern  point  of  Scotland,  and  the 
southernmost  extremity  of  Africa,  as  the  foregoing  drawings  (figs.  741 
and  742)  will  show. 

It  is  not  uncommon  for  one  set  of  granite  veins  to  intersect  another ; 
and  sometimes  there  are  three  sets,  as  in  the  environs  of  Heidelberg, 
where  the  granite  on  the  banks  of  the  river  JSTecker  is  seen  to  consist 
of  three  varieties,  differing  in  color,  grain,  and  various  peculiarities  of 
mineral  composition.  One  of  these,  which  is  evidently  the  second  in 
age,  is  seen  to  cut  through  an  older  granite  ;  and  another,  still  newer, 
traverses  both  the  second  and  the  first. 

In  Shetland  there  are  two  kinds  of  granite.  One  of  them,  com- 
posed of  hornblende,  mica,  felspar,  and  quartz,  is  of  a  dark  color,  and 
is  seen  underlying  gneiss.  The  other  is  a  red  granite,  which  pene- 
trates the  dark  variety  everywhere  in  veins.* 

The  accompanying  sketches  will  explain  the  manner  in  which  gran- 
ite veins  often  ramify  and  cut  each  other  (figs.  743  and  744).  They 

Fig.  743. 


Granite  veins  traversing  gneiss  at  Cape  Wrath,  in  Scotland.    (MacCulloch.) 

represent  the  manner  in  which  the  gneiss  at  Cape  Wrath,  in  Suther- 
landshire,  is  intersected  by  veins.  The  light  color  strongly  contrasted 
with  that  of  the  hornblende-schist,  here  associated  with  the  gneiss, 
renders  them  very  conspicuous. 

Granite  very  generally  assumes  a  finer  grain,  and  undergoes  a 
change  in  mineral  composition,  in  the  veins  which  it  sends  into  con- 
tiguous rocks.  Thus,  according  to  Professor  Sedgwick,  the  main 
body  of  the  Cornish  granite  is  an  aggregate  of  mica,  quartz,  and 

*  MacCulloch,  Syst.  of  Geol.,  vol.  i.  p.  58. 


CH.  XXXIII.] 


GRANITE  IN  VEINS. 


713 


felspar ;  but  the  veins  are  sometimes  without  mica,  being  a  granular 
aggregate  of  quartz  and  felspar.  In  other  varieties  quartz  prevails  to 
the  almost  entire  exclusion  both  of  felspar  and  mica ;  in  others,  the 
mica  and  quartz  both  disappear,  and  the  vein  is  simply  composed  of 
white  granular  felspar.* 

Fig.  744  is  a  sketch  of  a  group  of  granite  veins  in  Cornwall,  given 
by  Messrs.  Yon  Oeynhausen  and  Yon  Dechen.f  The  main  body  of 
the  granite  here  is  of  a  porphyritic  appearance,  with  large  crystals  of 
felspar ;  but  in  the  veins  it  «is  fine-grained,  and  without  these  large 
crystals.  The  general  height  of  the  veins  is  from  16  to  20  feet,  but 
some  are  much  higher. 

Fig.  744. 


Granite  veins  passing  through  hornblende  slate,  Carnsilver  Cove,  Cornwall. 

In  the  Yalorsine,  a  valley  not  far  from  Mont  Blanc  in  Savoy,  an 
ordinary  granite,  consisting  of  felspar,  quartz,  and  mica,  sends  forth 
veins  into  a  talcose  gneiss  (or  stratified  protogine),  and  in  some 

Fig.  745. 


Veins  of  granite  in  talcose  gneiss.    (L.  A.  Necker.) 

places  lateral  ramifications  are  thrown  off  from  the  principal  veins  at 
right  angles  (see  fig.  745),  the  veins,  especially  the  minute  ones,  being 
finer  grained  than  the  granite  in  mass. 

*  On  Geol.  of  Cornwall,  Camb.  Trans.,  vol.  i.  p.  124. 

f  Phil.  Mag.  and  Annals,  No.  27,  new  series,  March,  1829. 


714  GRANITE  IN  VEINS.  [On.  XXXIII. 

It  is  here  remarked,  that  the  schist  and  granite,  as  they  approach, 
seem  to  exercise  a  reciprocal  influence  on  each  other,  for  both  un- 
dergo a  modification  of  mineral  character.  The  granite,  still  remain- 
ing unstratified,  becomes  charged  with  green  particles;  and  the 
talcose  gneiss  assumes  a  granitiform  structure  without  losing  its  strati- 
fication.* 

Professor  Keilhau  drew  my  attention  to  several  localities  in  the 
country  near  Christiania,  where  the  mineral  character  of  gneiss  ap- 
pears to  have  been  affected  by  a  granite  of  much  newer  origin,  for 
some  distance  from  the  point  of  contact.  The  gneiss,  without  losing 
its  laminated,  structure,  seems  to  have  become  charged  with  a  larger 
quantity  of  felspar,  and  that  of  a  redder  color,  than  the  felspar  usu- 
ally belonging  to  the  gneiss  of  Norway. 

Granite,  syenite,  and  those  porphyries  which  have  a  granitiform 
structure,  in  short  all  plutonic  rocks,  are  frequently  observed  to  con- 
tain metals,  at  or  near  their  junction  with  stratified  formations.  On 
the  other  hand,  the  veins  which  traverse  stratified  rocks  are,  as  a 
general  law,  more  metalliferous  near  such  junctions  than  in  other 
positions.  Hence  it  has  been  inferred  that  these  metals  may  have 
been  spread  in  a  gaseous  form  through  the  fused  mass,  and  that  the 
contact  of  another  rock,  in  a  different  state  of  temperature,  or  some- 
times the  existence  of  rents  in  other  rocks  in  the  vicinity,  may  have 
caused  the  sublimation  of  the  metals.f 

There  are  many  instances,  as  at  Markerud,  near  Christiania,  in  Nor- 
way, where  the  strike  of  the  beds  has  not  been  deranged  throughout 
a  large  area  by  the  intrusion  of  granite,  both  in  large  masses  and  in 
veins.  This  fact  is  considered  by  some  geologists  to  militate  against 
the  theory  of  the  forcible  injection  of  granite  in  a  fluid  state.  But 
it  may  be  stated  in  reply,  that  ramifying  dikes  of  trap  also,  which 
almost  all  now  admit  to  have  been  once  fluid,  pass  through  the  same 
fossiliferous  strata,  near  Christiania,  without  deranging  their  strike  or 

Fig.  746. 


General  view  of  junction  of  granite  and  schist  of  the  Valorsine.    (L.  A.  Necker.) 

*  Necker,  Sur  la  Val  de  Valorsine,  Mem.  de  la  Soc.  de  Phys.  de  Geneve,  1828 
I  visited,  in  1832,  the  spot  referred  to  in  fig.  745. 
f  Necker,  Proceedings  of  Geol.  Soc.,  No.  26,  p.  392. 
\  See  Keilhau's  Gaea  Norvegica  ;  Christiania,  1838. 


CH.  XXXIIL] 


QUARTZ  VEINS. 


Y15 


Gneiss. 


The  real  or  apparent  isolation  of  large  or  small  masses  of  granite 
detached  from  the  main  body,  as  at  a,  6,  fig.  746,  and  above,  fig,  739, 
and  a,  fig.  745,  has  been  thought  by  some  writers  to  be  irreconcilable 
with  the  doctrine  usually  taught  respecting  veins  ;  but  many  of  them 
may,  in  fact,  be  sections  of  root-shaped  prolongations  of  granite ; 
while,  in  other  cases,  they  may  in  reality  be  detached  portions  of 
rock  having  the  plutonic  structure.  For  there  may  have  been  spots 
in  the  midst  of  the  invaded  strata,  in  which  there  was  an  assemblage 
of  materials  more  fusible  than  the  rest,  or  more  fitted  to  combine 
readily  into-  some  form  of  granite. 

Veins  of  pure  quartz  are  often  found  in  granite  as  in  many  strati- 
fied rocks,  but  they  are  not  traceable,  like  veins  of  granite  or  trap,  to 
large  bodies  of  rock  of  similar  composition.  They  appear  to  have 
been  cracks,  into  which  siliceous  matter  was  infiltered.  Such  segre- 
gation, as  it  is  called,  can  sometimes  be  shown  to  have  clearly  taken 
place  long  subsequently  to  the  original  consolidation  of  the  contain- 
ing rock.  Thus,  for  example,  I  observed  in  the  gneiss  of  Tronstad 
Strand,  near  Drammen,  in 
Norway,  the  annexed  sec- 
tion on  the  beach.  It  ap- 
pears that  the  alternating- 
strata  of  whitish  granitiform 
gneiss  and  black  hornblende- 
schist  were  first  cut  through 
by  a  greenstone  dike,  about 
2-J  feet  wide  ;  then  the  crack 
a  b  passed  through  all  these 
rocks,  and  was  filled  up  with 
quartz.  The  opposite  walls 
of  the  vein  are  in  some  parts 
incrusted  with  transparent 

crystals  of  quartz,  the  middle  of  the  vein  being  filled  up  with  com- 
mon opaque  white  quartz. 

We  have  seen  that  the  volcanic  formations  have  been  called  over- 
lying, because  they  not  only  penetrate  others,  but  spread  over  them. 
M.  Necker  has  proposed  to  call  the  granites  the  underlying  igneous 
rocks,  and  the  distinction  here  indicated  is  highly  characteristic.  It 
was  indeed  supposed  by  some  of  the  earlier  observers,  that  the  gran- 
ite of  Christiania,  in  Norway,  was  intercalated  in  mountain  masses 
between  the  primary  or  palaeozoic  strata  of  that  country,  so  as  to 
overlie  fossiliferous  shale  and  limestone.  But  although  the  granite 
sends  veins  into  these  fossiliferous  rocks,  and  is  decidedly  posterior  in 
origin,  its  actual  superposition  in  mass  has  been  disproved  by  Profes- 
sor Keilhau,  whose  observations  on  this  controverted  point  I  had 
opportunities  in  1837  of  verifying.  There  are,  however,  on  a  smaller 
scale,  certain  beds  of  euritic  porphyry,  some  a  few  feet,  others  many 
yards  in  thickness,  which  pass  into  granite,  and  deserve  perhaps  to  be 


a,  &.  Quartz  vein  passing  through  gneiss  and  green- 
stone, Tronstad  Strand,  near  Christiania. 


Y16 


CONFORMABLE  PORPHYRIES. 


[Cn.  XXXItt 


classed  as  plutonic  rather  tlian  trappean  rocks,  which,  may  truly  be 
described  as  interposed  conformably  between  fossiliferous  strata,  as 
the  porphyries  (a,  c,  fig.  748),  which  divide  the  bituminous  shales 


Euritic  porphyry  alternating  with  primary  fossiliferous  strata,  near  Christiania, 

and  argillaceous  limestones,  //.  But  some  of  these  same  porphyries 
are  partially  unconformable,  as  6,  and  may  lead  us  to  suspect  that  the 
others  also,  notwithstanding  their  appearance  of  interstratification, 
have  been  forcibly  injected.  Some  of  the  porphyritic  rocks  above 
mentioned  are  highly  quartzose,  others  very  felspathic.  In  propor- 
tion as  the  masses  are  more  voluminous,  they  become  more  granitic 
in  their  texture,  less  conformable,  and  even  begin  to  send  forth  veins 
into  contiguous  strata.  In  a  word,  we  have  here  a  beautiful  illustra- 
tion of  the  intermediate  gradations  between  volcanic  and  plutonic 
rocks,  not  only  in  their  mineralogical  composition  and  structure,  but 
also  in  their  relations  of  position  to  associated  formations.  If  the 
term  "  overlying  "  can  in  this  instance  be  applied  to  a  plutonic  rock, 
it  is  only  in  proportion  as  that  rock  begins  to  acquire  a  trappean 
aspect. 

It  has  been  already  hinted  that  the  heat,  which  in  every  active  vol- 
cano extends  downwards  to  indefinite  depths,  must  produce  simulta- 
neously very  different  effects  near  the  surface  and  far  below  it ;  and 
we  cannot  suppose  that  rocks  resulting  from  the  crystallizing  of  fused 
matter  under  a  pressure  of  several  thousand  feet,  much  less  miles,  of 
the  earth's  crust  can  resemble  those  formed  at  or  near  the  surface. 
Hence  the  production  at  great  depths  of  a  class  of  rocks  analogous 
to  the  volcanic,  and  yet  differing  in  many  particulars,  might  also  have 
been  predicted,  even  had  we  no  plutonic  formations  to  account  for. 
How  well  these  agree,  both  in  their  positive  and  negative  characters, 
with  the  theory  of  their  deep  subterranean  origin,  the  student  will  be 
able  to  judge  by  considering  the  descriptions  already  given. 

It  has,  however,  been  objected,  that  if  the  granitic  and  volcanic 
rocks  were  simply  different  parts  of  one  great  series,  we  ought  to  find 
in  mountain  chains  volcanic  dikes  passing  upwards  into  lava  and 
downwards  into  granite.  But  we  may  answer  that  our  vertical  sec- 
tions are  usually  of  small  extent ;  and  if  we  find  in  certain  places  a 
transition  from  trap  to  porous  lava,  and  in  others  a  passage  from 
granite  to  trap,  it  is  as  much  as  could  be  expected  of  this  evidence. 

The  prodigious  extent  of  denudation  which  has  been  already  de- 
monstrated to  have  occurred  at  former  periods,  will  reconcile  the 


CH.  XXXIV.]        TESTS  OF  AGE   OF  PLUTONIC  ROCKS.  717 

student  to  the  belief  that  crystalline  rocks  of  high  antiquity,  al- 
though deep  in  the  earth's  crust  when  originally  formed,  may  have 
become  uncovered  and  exposed,  at  the  surface.  Their  actual  ele- 
vation above  the  sea  may  be  referred  to  the  same  causes  to  which 
we  have  attributed  the  upheaval  of  marine  strata,  even  to  the  sum- 
mits of  some  mountain  chains.  But  to  these  and  other  topics  I 
shall  revert  when  speaking,  in  the  next  chapter,  of  the  relative  ages 
of  different  masses  of  granite. 


CHAPTER  XXXIY. 

ON    THE    DIFFERENT   AGES    OF   THE    PLUTONIC    BOCKS. 

Difficulty  in  ascertaining  the  precise  age  of  a  plutonic  rock — Test  of  age  by  relative 
position — Test  by  intrusion  and  alteration — Test  by  mineral  composition — Test 
by  included  fragments — Recent  and  Pliocene  plutonic  rocks,  why  invisible — Ter- 
tiary plutonic  rocks  in  the  Andes — Granite  altering  Cretaceous  rocks — Granite 
altering  Lias  in  the  Alps  and  in  Skye — Granite  of  Dartmoor  altering  Carbonifer- 
ous strata — Granite  of  the  Old  Red  Sandstone  period — Syenite  altering  Silurian 
strata  in  Norway — Blending  of  the  same  with  gneiss — Most  ancient  plutonic 
rocks — Granite  protruded  in  a  solid  form — On  the  probable  age  of  the  granites 
of  Arran,  in  Scotland. 

WHEN  we  adopt  the  igneous  theory  of  granite,  as  explained  in  the 
last  chapter,  and  believe  that  different  plutonic  rocks'  have  originated 
at  successive  periods  beneath  the  surface  of  the  planet,  we  must  be 
prepared  to  encounter  greater  difficulty  in  ascertaining  the  precise 
age  of  such  rocks,  than  in  the  case  of  volcanic  and  fossiliferous  for- 
mations. We  must  bear  in  mind,  that  the  evidence  of  the  age  of 
each  contemporaneous  volcanic  rock  was  derived,  either  from  lavas 
poured  out  upon  the  ancient  surface,  whether  in  the  sea  or  in  the 
atmosphere,  or  from  tuffs  and  conglomerates,  also  deposited  at  the 
surface,  and  either  containing  organic  remains  themselves,  or  inter- 
calated between  strata  containing  fossils.  But  all  these  tests  fail 
when  we  endeavor  to  fix  the  chronology  of  a  rock  which  has  crystal- 
lized from  a  state  of  fusion  in  the  bowels  of  the  earth.  In  that  case, 
we  are  reduced  to  the  following  tests :  1st,  relative  position ;  2dly, 
intrusion,  and  alteration  of  the  rocks  in  contact ;  3dly,  mineral  char- 
acters ;  4thly,  included  fragments. 

Test  of  Age  by  Relative  Position. — Unaltered  fossiliferous  strata  of 
every  age  are  met  with  reposing  immediately  on  plutonic  rocks ;  as 
at  Christiania,  in  Norway,  where  the  Post-pliocene  deposit  rests  on 
granite ;  in  Auvergne,  where  the  freshwater  Miocene  strata,  and  at 


718  RECENT  AND  PLIOCENE  [Cn.  XXXIV. 

* 

Heidelberg,  on  the  Rhine,  where  the  New  Red  Sandstone  occupy  a 
similar  place.  In  all  these,  and  similar  instances,  inferiority  in 
position  is  connected  with  the  superior  antiquity  of  granite.  The 
crystalline  rock  was  solid  before  the  sedimentary  beds  were  super- 
imposed, and  the  latter  usually  contain  in  them  rounded  pebbles  of 
the  subjacent  granite. 

Test  by  Intrusion  and  Alteration. — But  when  plutonic  rocks  send 
veins  into  strata,  and  alter  them  near  the  point  of  contact,  in  the 
manner  before  described  (p.  V09),  it  is  clear  that,  like  intrusive  traps, 
they  are  newer  than  the  strata  which  they  invade  and  alter.  Exam- 
ples of  the  application  of  this  test  will  be  given  in  the  sequel. 

Test  by  Mineral  Composition. — Notwithstanding  a  general  uniform- 
ity in  the  aspect  of  plutonic  rocks,  we  have  seen  in  the  last  chapter 
that  there  are  many  varieties,  such  as  Syenite,  Talcose  granite,  and 
others.  One  of  these  varieties  is  sometimes  found  exclusively  pre- 
vailing throughout  an  extensive  region,  where  it  preserves  a  homoge- 
neous character ;  so  that,  having  ascertained  its  relative  age  in  one 
place,  we  can  easily  recognize  its  identity  in  others,  and  thus  deter- 
mine from  a  single  section  the  chronological  relations  of  large  moun- 
tain masses.  Having  observed,  for  example,  that  the  syenitic  granite 
of  Norway,  in  which  the  mineral  called  zircon  abounds,  has  altered 
the  Silurian  strata  wherever  it  is  in  contact,  we  do  not  hesitate  to 
refer  other  masses  of  the  same  zircon-syenite  in  the  south  of  Norway 
to  the  same  era. 

Some  have  imagined  that  the  age  of  different  granites  might,  to  a 
great  extent,  be  determined  by  their  mineral  characters  alone  ;  syen- 
ite, for  instance,  or  granite  with  hornblende,  being  more  modern  than 
common  or  micaceous  granite.  But  modern  investigations  have 
proved  these  generalizations  to  have  been  premature.  The  syenitic 
granite  of  Norway  already  alluded  to  may  be  of  the  same  age  as  the 
Silurian  strata,  which  it  traverses  and  alters,  or  may  belong  to  the 
Old  Red  Sandstone  period;  whereas  the  granite  of  Dartmoor,  al- 
though consisting  of  mica,  quartz,  and  felspar,  is  newer  than  the  coal. 
(See  p.  725.) 

Test  by  Included  Fragments. — This  criterion  can  rarely  be  of  much 
importance,  because  the  fragments  involved  in  granite  are  usually  so 
much  altered,  that  they  cannot  be  referred  with  certainty  to  the  rocks 
whence  they  were  derived.  In  the  White  Mountains,  in  North  Amer- 
ica, according  to  Professor  Hubbard,  a  granite  vein,  traversing  gran- 
ite, contains  fragments  of  slate  and  trap  which  must  have  fallen  into 
the  fissure  when  the  fused  materials  of  the  vein  were  injected  from 
below,*  and  thus  the  granite  is  shown  to  be  newer  than  certain  super- 
ficial slaty  and  trappean  formations. 

Recent  and  Pliocene  Plutonic  Rocks,  why  Invisible. — The  explana- 
tions already  given  in  the  29th  and  in  the  last  chapter  of  the  probable 

*  Silliman's  Journ.,  No.  69,  p.  123. 


CH.  XXXIV.]  PLUTONIC  ROCKS.  719 

relation  of  the  plutonic  to  the  volcanic  formations,  will  naturally  lead 
the  reader  to  infer,  that  rocks  of  the  one  class  can  never  be  produced 
at  or  near  the  surface  without  some  members  of  the  other  being 
formed  below  simultaneously,  or  soon  afterwards.  It  is  not  uncom- 
mon for  lava-streams  to  require  more  than  ten  years  to  cool  in  the 
open  air  ;  and  when  they  are  of  great  depth,  a  much  longer  period. 
The  melted  matter  poured  from  Jorullo,  in  Mexico,  in  the  year  1759, 
which  accumulated  in  some  places  to  the  height  of  550  feet,  was 
found  to  retain  a  high  temperature  half  a  century  after  the  eruption.* 
We  may  conceive,  therefore,  that  great  masses  of  subterranean  lava 
may  remain  in  a  red-hot  or  incandescent  state  in  the  volcanic  foci 
for  immense  periods,  and  the  process  of  refrigeration  may  be  ex- 
tremely gradual.  Sometimes,  indeed,  this  process  may  be  retarded 
for  an  indefinite  period,  by  the  accession  of  fresh  supplies  of  heat  ; 
for  we  find  that  the  lava  in  the  crater  of  Stromboli,  one  of  the  Lipari 
Islands,  has  been  in  a  state  of  constant  ebullition  for  the  last  two 
thousand  years  ;  and  we  may  suppose  this  fluid  mass  to  communicate 
with  some  caldron  or  reservoir  of  fused  matter  below.  In  the  Isle 
of  Bourbon,  also,  where  there  has  been  an  emission  of  lava  once  in 
every  two  years  for  a  long  period,  the  lava  below  can  scarcely  fail  to 
have  been  permanently  in  a  state  of  liquefaction.  If  then  it  be  a 
reasonable  conjecture,  that  about  2000  volcanic  eruptions  occur  in  the 
course  of  every  century,  either  above  the  waters  of  the  sea  or  be- 
neath them,f  it  will  follow,  that  the  quantity  of  plutonic  rock  gen- 
erated, or  in  progress  during  the  Kecent  epoch,  must  already  have 
been  considerable. 

But  as  the  plutonic  rocks  originate  at  some  depth  in  the  earth's 
crust,  they  can  only  be  rendered  accessible  to  human  observation  by 
subsequent  upheaval  and  denudation.  Between  the  period  when  a 
plutonic  rock  crystallizes  in  the  subterranean  regions  and  the  era  of 
its  protrusion  at  any  single  point  of  the  surface,  one  or  two  geological 
periods  must  usually  intervene.  Hence,  we  must  not  expect  to  find 
the  Recent  or  even  the  Pliocene  granites  laid  open  to  view,  unless  we 
are  prepared  to  assume  that  sufficient  time  has  elapsed  since  the  com- 
mencement of  the  Pliocene  period  for  great  upheaval  and  denudation. 
A  plutonic  rock,  therefore,  must,  in  general,  be  of  considerable  an- 
tiquity relatively  to  the  fossiliferous  and  volcanic  formations,  before  it 
becomes  extensively  visible.  As  we  know  that  the  upheaval  of  land 
has  been  sometimes  accompanied  in  South  America  by  volcanic  erup- 
tions and  the  emission  of  lava,  we  may  conceive  the  more  ancient 
plutonic  rocks  to  be  forced  upwards  to  the  surface  by  the  newer  rocks 
of  the  same  class  formed  successively  below  —  subterposition  in  the 
plutonic,  like  superposition  in  the  sedimentary  rocks,  being  usually 
characteristic  of  a  newer  origin. 


*  See  "Principles,"  Index,  "Jorullo." 
f  Ibid.,  "  Volcanic  Eruptions." 


720 


PLUTONIC  ROCKS. 


[Cn.  XXXIV. 


I  J 


QQ  R 
«*  r4 


In  the  accompanying  diagram  (fig.  749)  an  attempt  is  made  to 
show  the  inverted  order  in  which  sedimentary  and  plutonic  forma- 
tions may  occur  in  the  earth's  crust. 

The  oldest  plutonic  rock,  No.  I.,  has  been  upheaved  at  successive 
periods  until  it  has  become  exposed  to  view  in  a  mountain-chain. 
This  protrusion  of  No.  I.  has  been  caused  by  the  igneous  agency 
which  produced  the  newer  plutonic  rocks  Nos.  II.,  III.,  and  IV. 
Part  of  the  primary  fossiliferous  strata,  No.  1,  have  also  been  raised 
to  the  surface  by  the  same  gradual  process.  It  will  be  observed  that 
the  Recent  strata  No.  4  and  the  Recent  granite  or  plutonic  rock  No. 


CH.  XXXIV.]  PLUTONIC  ROCKS  IN  THE  ANDES. 

IV.  are  the  most  remote  from  each  other  in  position,  although  of 
contemporaneous  date.  According  to  this  hypothesis,  the  convul- 
sions of  many  periods  will  be  required  before  Recent  or  Post-tertiary 
granite  will  be  upraised  so  as  to  form  the  highest  ridges  and  central 
axes  of  mountain-chains.  Daring  that  time  the  Recent  strata  No.  4 
might  be  covered  by  a  great  many  newer  sedimentary  formations. 

Eocene  Granite  and  Plutonic  Rocks. — In  a  former  part  of  this  vol- 
ume (p.  307),  the  great  nummulitic  formation  of  the  Alps  and  Pyre- 
nees was  referred  to  the  Eocene  period,  and  it  follows  that  those  vast 
movements  which  have  raised  fossiliferous  rocks  from  the  level  of  the 
sea  to  the  height  of  more  than  10,000  feet  above  its  level  have  taken 
place  since  the  commencement  of  the  tertiary  epoch.  Here,  therefore, 
if  anywhere,  we  might  expect  to  find  hypogene  formations  of  Eocene 
date  breaking  out  in  the  central  axis  or  most  disturbed  region  of  the 
loftiest  chain  in  Europe.  Accordingly,  in  the  Swiss  Alps,  even  the 
flysch,  or  upper  portion  of  the  nummulitic  series,  has  been  occasion- 
ally invaded  by  plutonic  rocks,  and  converted  into  crystalline  schists 
of  the  hypogene  class.  There  -can  be  little  doubt  that  even  the 
talcose  granite  or  gneiss  of  Mont  Blanc  itself  has  been  in  a  fused  or 
pasty  state  since  the  flysch  was  deposited  at  the  bottom  of  the  sea ; 
and  the  question  as  to  its  age  is  not  so  much  whether  it  be  a  second- 
ary or  tertiary  granite  or  gneiss,  as  whether  it  should  be  assigned  to 
the  Eocene  or  Miocene  epoch. 

Great  upheaving  movements  have  been  experienced  in  the  region 
of  the  Andes,  during  the  Post-tertiary  period.  In  some  part,  there- 
fore, of  this  chain,  we  may  expect  to  discover  tertiary  plutonic  rocks 
laid  open  to  view.  What  we  already  know  of  the  structure  of  the 
Chilian  Andes  seems  to  realize  this  expectation.  In  a  transverse  sec- 
tion, examined  by  Mr.  Darwin,  between  Valparaiso  and  Mendoza,  the 
Cordillera  was  found  to  consist  of  two  separate  and  parallel  chains, 
formed  of  sedimentary  rocks  of  different  ages,  the  strata  in  both  rest- 
ing ou  plutonic  rocks,  by  which  they  have  been  altered.  In  the  west- 
ern or  oldest  range,  called  the  Peuquenes,  are  black  calcareous  clay- 
slates,  rising  to  the  height  of  nearly  14,000  feet  above  the  sea,  in 
which  are  shells  of  the  genera  Gryphcea,  Turritella,  Terebratula,  and 
Ammonite.  These  rocks  are  supposed  to  be  of  the  age  of  the  central 
parts  of  the  secondary  series  of  Europe.  They  are  penetrated  and 
altered  by  dikes  and  mountain  masses  of  a  plutonic  rock,  which  has 
the  texture  of  ordinary  granite,  but  rarely  contains  quartz,  being  a 
compound  of  albite  and  hornblende. 

The  second  or  eastern  chain  consists  chiefly  of  sandstones  and  con- 
glomerates, of  vast  thickness,  the  materials  of  which  are  derived  from 
the  ruins  of  the  western  chain.  The  pebbles  of  the  conglomerates  are, 
for  the  most  part,  rounded  fragments  of  the  fossiliferous  slates  before 
mentioned.  The  resemblance  of  the  whole  series  to  certain  tertiary 
deposits  on  the  shores  of  the  Pacific,  not  only  in  mineral  character, 
but  in  the  imbedded  lignite  and  silicified  woods,  leads  to  the  conjec- 
46 


722  VOLUME  OF  HIDDEN  PLUTONIC  ROCKS.      [On.  XXXIV. 

ture  that  they  also  are  tertiary.  Yet  these  strata  are  not  only  associ- 
ated with  trap  rocks  and  volcanic  tuffs,  but  are  also  altered  by  a  gran- 
ite consisting  of  quartz,  felspar,  and  talc.  They  are  traversed,  more- 
over, by  dikes  of  the  same  granite,  and  by  numerous  veins  of  iron, 
copper,  arsenic,  silver,  and  gold ;  all  of  which  can  be  traced  to  the 
underlying  granite.*  We  have,  therefore,  strong  ground  to  presume 
that  the  plutonic  rock  here  exposed  on  a  large  scale  in  the  Chilian 
Andes  is  of  later  date  than  certain  tertiary  formations. 

But  the  theory  adopted  in  this  work  of  the  subterranean  origin  of 
the  hypogene  formations  would  be  untenable,  if  the  supposed  fact 
here  alluded  to,  of  the  appearance  of  tertiary  granite  at  the  surface, 
was  not  a  rare  exception  to  the  general  rule.  A  considerable  lapse 
of  time  must  intervene  between  the  formation  of  plutonic  and  meta- 
morphic  rocks  in  the  nether  regions,  and  their  emergence  at  the  sur- 
face. For  a  long  series  of  subterranean  movements  must  occur  before 
such  rock  can  be  uplifted  into  the  atmosphere  or  the  ocean;  and, 
before  they  can  be  rendered  visible  to  man,  some  strata  which  previ- 
ously covered  them  must  usually  have  been  stripped  off  by  denudation. 

We  know  that  in  the  Bay  of  Baiae  in  1538,  in  Cutch  in  1819,  and 
on  several  occasions  in  Peru  and  Chili,  since  the  commencement  of 
the  present  century,  the  permanent  upheaval  or  subsidence  of  land  has 
been  accompanied  by  the  simultaneous  emission  of  lava  at  one  or  more 
points  in  the  same  volcanic  region.  From  these  and  other  examples 
it  may  be  inferred  that  the  rising  or  sinking  of  the  earth's  crust, 
operations  by  which  sea  is  converted  into  land,  and  land  into  sea,  are 
a  j^art  only  of  the  consequences  of  subterranean  igneous  action.  It 
can  scarcely  be  doubted  that  this  action  consists,  in  a  great  degree,  of 
the  baking,  and  occasionally  the  liquefaction  of  rocks,  causing  them  to 
assume,  in  some  cases  a  larger,  in  others  a  smaller  volume  than  before 
the  application  of  heat.  It  consists  also  in  the  generation  of  gases, 
and  their  expansion  by  heat,  and  the  injection  of  liquid  matter  into 
rents  formed  in  superincumbent  rocks.  The  prodigious  scale  on 
which  these  subterranean  causes  have  operated  in  Sicily  since  the 
deposition  of  the  Newer  Pliocene  strata  will  be  appreciated,  when  we 
remember  that  throughout  half  the  surface  of  that  island  such  strata 
are  met  with,  raised  to  the  height  of  from  50  to  that  of  2000  and 
even  3000  feet  above  the  level  of  the  sea.  In  the  same  island  also  the 
older  rocks  which  are  contiguous  to  these  marine  tertiary  strata  must 
have  undergone,  within  the  same  period,  a  similar  amount  of  up- 
heaval. 

The  like  observations  may  be  extended  to  nearly  the  whole  of 
Europe,  for,  since  the  commencement  of  the  Eocene  period,  the  entire 
European  area,  including  some  of  the  central  and  very  lofty  portions 
of  the  Alps  themselves,  as  I  have  elsewhere  shown,f  has,  with  the  ex- 


*  Darwin,  pp.  390,  406;  second  edition,  p.  319. 

f  See  map  of  Euro-pe  and  explanation,  in  "  Principles,"  book  i. 


CH.  XXXIV.]     PLUTONIC   ROCKS  OF  OOLITE  AND  LIAS.  723 

ception  of  a  few  districts,  emerged  from  the  deep  to  its  present  alti- 
tude ;  and  even  those  tracts  which  were  already  dry  land  before  the 
Eocene  era,  have,  in  many  cases,  acquired  additional  height.  A  large 
amount  of  subsidence  has  also  occurred  during  the  same  period,  so 
that  the  extent  of  the  subterranean  spaces  which  have  either  become 
the  receptacles  of  sunken  fragments,  of  the  earth's  crust,  or  have  been 
rendered  capable  of  supporting  other  fragments  at  a  much  greater 
height  than  before,  must  be  so  great  that  they  probably  equal,,  if  not 
exceed  in  volume,  the  entire  continent  of  Europe.  We  are  entitled, 
therefore,  to  ask  what  amount  of  change  of  equivalent  importance  can 
be  proved  to  have  occurred  in  the  earth's  crust  within  an  equal  quan- 
tity of  time  anterior  to  the  Eocene  epoch.  They  who  contend  for 
the  more  intense  energy  of  subterranean  causes  in  the  remoter  eras 
of  the  earth's  history  may  find  it  more  difficult  to  give  an  answer  to 
this  question  than  they  anticipated. 

The  principal  effect  of  volcanic  action  in  the  nether  regions  during 
the  tertiary  period  seems  to  have  consisted  in  the  upheaval  to  the  sur- 
face of  hypogene  formations  of  an  age  anterior  to  the  carboniferous. 
The  repetition  of  another  series  of  movements,  of  equal  violence, 
might  upraise  the  plutonic  and  metamorphic  rocks  of  many  secondary 
periods ;  and,  if  the  same  force  should  still  continue  to  act,  the  next 
convulsions  might  bring  up  to  the  day  the  tertiary  and  recent  hypo- 
gene  rocks.  In  the  course  of  such  changes  many  of  the  existing  sedi- 
mentary strata  would  suffer  greatly  by  denudation,  others  might 
assume  a  metamorphic  structure,  or  become  melted  down  into  plutonic 
and  volcanic  rocks.  Meanwhile  the  deposition  of  a  vast  thickness  of 
new  strata  would  not  fail  to  take  place  during  the  upheaval  and  par- 
tial destruction  of  the  older  rocks.  But  I  must  refer  the  reader  to  the 
last  chapter  but  one  of  this  volume  for  a  fuller  explanation  of  these  views. 

Cretaceous  Period. — It  will  be  seen  in  the  next  chapter  that  chalk, 
as  well  as  lias,  has  been  altered  by  granite  in  the  eastern  Pyrenees. 
Whether  such  granite  be  cretaceous  or  tertiary  cannot  easily  be  de- 
cided.    Suppose  6,  c,  c?,  fig.  750,  to  be 
three  members  of  the  Cretaceous  series,  ^-  750. 

the  lowest  of  which,  ft,  has  been  altered 
by  the  granite  A,  the  modifying  influ- 
ence not  having  extended  so  far  as  c,  or 
having  but  slightly  affected  its  lowest 
beds.  Now  it  can  rarely  be  possible  for 
the  geologist  to  decide  whether  the  beds 

d  existed  at  the  time  of  the  intrusion  of  A,  and  alteration  of  b  and  c, 
or  whether  they  were  subsequently  thrown  down  upon  c. 

But  as  some  Cretaceous  and  even  tertiary  rocks  have  been  raised 
to  the  height  of  more  than  9000  feet  in  the  Pyrenees,  we  must  not 
assume  that  plutonic  formations  of  the  same  periods  may  not  have 
been  brought  up  and  exposed  by  denudation,  at  the  height  of  2000 
or  3000  feet  on  the  flanks  of  that  chain. 


724 


PLUTONIC  ROCKS  OF  THE 


[Cn.  XXXIV. 


Fig.  751. 


Period  of  Oolite  and  Lia$. — In  the  Department  of  the  Hautes 
Alpes,  in  France,  M.  Elie  de  Beaumont  traced  a  black  argillaceous 
limestone,  charged  with  belemnites,  to  within  a  few  yards  of  a  mass 
of  granite.  Here  the  limestone  begins  to  put  on  a  granular  texture, 
but  is  extremely  fine-grained.  "When  nearer  the  junction  it  becomes 
gray,  and  has  a  saccharoid  structure,  In  another  locality,  near  Cham- 
poleon,  a  granite  composed  of  quartz,  black  mica,  and  rose-colored 
felspar  is  observed  partly  to  overlie  the  secondary  rocks,  producing 

an  alteration  which  extends 
for  about  30  feet  down- 
wards, diminishing  in  the 
beds  which  lie  farthest  from 
the  granite.  (See  fig.  7 5 1 .) 
In  the  altered  mass  the 
argillaceous  beds  are  hard- 
ened, the  limestone  is  sac- 
charoid, the  grits  quartzose, 
and  in  the  midst  of  them 
is  a  thin  layer  of  an  im- 
perfect granite.  It  is  also 
an  important  circumstance, 
that  near  the  point  of  con- 
tact, both  the  granite  and 
the  secondary  rocks  be- 
come metalliferous,  and 
contain  nests  and  small 
veins  of  blende,  galena, 
iron,  and  copper  pyrites.  The  stratified  rocks  become  harder  and 
more  crystalline,  but  the  granite,  on  the  contrary,  softer  and  less  per- 
fectly crystallized  near  the  junction.* 

Although  the  granite  is  incumbent  in  the  above  section  (fig.  751), 
we  cannot  assume  that  it  overflowed  the  strata,  for  the  disturbances 
of  the  rocks  are  so  great  in  this  part  of  the  Alps  that  their  original 
position  is  often  inverted. 

'iisiderable  mass  of  syenite,  in  the  Isle  of  Skye,  is  described  by 
Dr.  MacCulloch  as  intersecting  limestone  and  shale,  which  are  of  the 
age  of  the  lias.f  The  limestone,  which  at  a  greater  distance  from  the 
granite  contains  shells,  exhibits  no  traces  of  them  near  its  junction,  where 
it  has  been  converted  into  a  pure  crystalline  marblc.J 

At  Predazzo,  in  the  Tyrol,  secondary  strata,  some  of  which  are 
limestones  of  the  Oolitic  period,  have  been  traversed  and  altered  by 
plutonic  rocks,  one  portion  of  which  is  an  augitic  porphyry,  which 


Junction  of  granite  with  Jurassic  or  Oolite  strata  in 
the  Alps,  near  Cbampoleon, 


*  EKe  de  Beaumont,  sur  les  Montagues  de  POfeans,  Ac.     M6m.  de  U  Soc,  d'ffist 
Nat  de  Paris,  torn.  v. 

f  Mupchiaoa,  Geol  Trans,,  Second  Scries,  vol.  ii.  part  iL  pp.  811-821. 
i  Western  Islands,  vol  i.  p,  SSO,  plate  18,  figs.  8,  4. 


CH.  XXXIV.]        CARBONIFEROUS  AND  SILURIAN  PERIODS.  725 

passes  insensibly  into  granite.  The  limestone  is  changed  into  granu- 
lar  marble,  with  a  band  of  serpentine  at  the  junction.* 

'  Carboniferous  Period. — The  granite  of  Dartmoor,  in  Devonshire, 
was  formerly  supposed  to  be  one  of  the  most  ancient  of  the  plutonic 
rocks,  but  is  now  ascertained  to  be  posterior  in  date  to  the  culm- 
measures  of  that  country,  which  from  their  position,  and  as  containing 
true  coal-plants,  are  regarded  by  Professor  Sedgwick  and  Sir  R.  Mar- 
ehison  as  members  of  the  true  carboniferous  series.  This  granite, 
like  the  syenitic  granite  of  Christiania,  has  broken  through  the  strati- 
fied formations  without  much  changing  their  strike.  Hence,  on  the 
northwest  side  of  Dartmoor,  the  successive  members  of  the  culm- 
measures  abut  against  the  granite,  and  become  metamorphic  as  they 
approach.  These  strata  are  also  penetrated  by  granite  veins,  and 
plutonic  dikes,  called  "  elvans."  f  The  granite  of  Cornwall  is  probably 
of  the  same  date,  and,  therefore,  as  modern  as  the  Carboniferous 
strata,  if  not  newer. 

Silurian  Period. — It  has  long  been  known  that  the  granite  near 
Christiania,  in  Norway,  is  of  newer  origin  than  the  Silurian  strata  of 
that  region.  Von  Buch  first  announced,  in  1813,  the  discovery  of  its 
posteriority  in  date  to  limestones  containing  orthocerata  and  trilobites. 
The  proofs  consist  in  the  penetration  of  granite  veins  into  the  shale 
and  limestone,  and  the  alteration  of  the  strata,  for  a  considerable  dis- 
tance from  the  point  of  contact  both  of  these  veins  and  the  central 
mass  from  which  they  emanate.  (See  p.  715.)  Von  Buch  supposed 
that  the  plutonic  rock  alternated  with  the  fossiliferous  strata,  and  that 
large  masses  of  granite  were  sometimes  incumbent  upon  the  strata; 
but  this  idea  was  erroneous,  and  arose  from  the  fact  that  the  beds  of 
shale  and  limestone  often  dip  towards  the  granite  up  to  the  point  of 
contact,  appearing  as  if  they  would  pass  under  it  in  mass,  as  at  a,  fig. 
752,  and  then  again  on  the  opposite  side  of  the  same  mountain,  as  at  6, 

Fig.  T53L 


Silurian.  Granite.  Silurian  strata. 

dip  away  from  the  same  granite.  When  the  junctions,  however,  are 
carefully  examined,  it  is  found  that  the  plutonic  rock  intrudes  itself 
in  veins,  and  nowhere  covers  the  fossiliferous  strata  in  large  over- 
lying masses,  as  is  so  commonly  the  case  with  trappean  formations.! 

Now  this  granite,  which  is  more  modern  than  the  Silurian  strata  of 
Norway,  also  sends  veins  in  the  same  country  into  an  ancient  fonna- 

*  Yon  Buch,  Annales  de  Chimie,  &c. 

f  Proceed.  Geol.  Soo,  voL  il  p.  562 ;  and  Trans.,  Second  Series,  voL  v.  p.  686. 
j  See  the  G«a  Norvegica  and  other  works  of  Keilhau,  with  whom  I  examined 
this  country. 


726  OLDEST  GRANITE  ROOKS.  [On.  XXXIV. 

tion  of  gneiss ;  and  the  relations  of  the  plutonic  rock  and  the  gneiss, 
at  their  junction,  are  full  of  interest  when  we  duly  consider  the  wide 
difference  of  epoch  which  must  have  separated  their  origin. 

The  length  of  this  interval  of  time  is  attested  by  the  following 
facts :  The  fossiliferous  or  Silurian  beds  rest  unconformably  upon  the 
truncated  edges  of  the  gneiss,  the  inclined  strata  of  which  had  been 
denuded  before  the  sedimentary  beds  were  superimposed  (see  fig.  753), 

Fig.  758. 

Silurian  strata. 


Gneiss.  Granite.  Gneiss. 

Granite  sending  veins  into  Silurian  strata  and  Gneiss.    Christiania,  Norway. 

The  signs  of  denudation  are  twofold ;  first,  the  surface  of  the  gneiss  is 
seen  occasionally,  on  the  removal  of  the  newer  beds,  containing  organic 
remains,  to  be  worn  and  smoothed;  secondly,  pebbles  of  gneiss 
have  been  found  in  some  of  these  Silurian  strata.  Between  the  origin, 
therefore,  of  the  gneiss  and  the  granite  there  intervened,  first,  the 
period  when  the  strata  of  gneiss  were  denuded ;  secondly,  the  period 
of  the  deposition  of  the  Silurian  deposits.  Yet  the  granite  produced 
after  this  long  interval  is  often  so  intimately  blended  with  the  ancient 
gneiss,  at  the  point  of  junction,  that  it  is  impossible  to  draw  any  other 
than  an  arbitrary  line  of  separation  between  them ;  and  where  this  is 
not  the  case,  tortuous  veins  of  granite  pass  freely  through  gneiss,  end- 
ing sometimes  in  threads,  as  if  the  older  rock  had  offered  no  resist- 
ance to  their  passage.  These  appearances  may  probably  be  due  to 
hydrothermal  action  (see  below,  p.  740).  I  shall  merely  observe  in 
this  place,  that  had  such  junctions  alone  been  visible,  and  had  we  not 
learned,  from  other  sections,  how  long  a  period  elapsed  between  the 
consolidation  of  the  gneiss  and  the  injection  of  this  granite,  we  might 
have  suspected  that  the  gneiss  was  scarcely  solidified,  or  had  not  yet 
assumed  its  complete  metamorphic  character  when  invaded  by  the 
plutonic  rock.  From  this  example  we  may  learn  how  impossible  it  is 
to  conjecture  whether  certain  granites  in  Scotland,  and  other  countries, 
which  send  veins  into  gneiss  and  other  metamorphic  rocks,  are  pri- 
mary, or  whether  they  may  not  belong  to  some  secondary  or  tertiary 
period. 

Oldest  Granites. — It  is  not  half  a  century  since  the  doctrine  was 
very  general  that  all  granitic  rocks  were  primitive,  that  is  to  say,  that 
they  originated  before  the  deposition  of  the  first  sedimentary  strata, 
and  before  the  creation  of  organic  beings  (see  above,  p.  9).  But  so 
greatly  are  our  views  now  changed,  that  we  find  it  no  easy  task  to 
point  out  a  single  mass  of  granite  demonstrably  more  ancient  than  all 
the  known  fossiliferous  deposits.  Could  we  discover  some  Lower 


CH.  XXXIV.]  PROTRUSION  OF  SOLID  GRANITE.  727 

Cambrian  strata  resting  immediately  on  granite,  there  being  no  alter- 
ations at  the  point  of  contact,  nor  any  intersecting  granitic  veins,  we 
might  then  affirm  the  plutonic  rock  to  have  originated  before  the 
oldest  known  fossiliferous  strata.  Still  it  would  be  presumptuous,  as 
we  have  already  pointed  out  (p.  587),  to  suppose  that  when  a  small 
part  only  of  the  globe  has  been  investigated,  we  are  acquainted  with 
the  oldest  fossiliferous  strata  in  the  crust  of  our  planet.  Even  when 
these  are  found,  we  cannot  assume  that  there  never  were  any  ante- 
cedent strata  containing  organic  remains,  which  may  have  become 
metamorphic.  If  we  find  pebbles  of  granite  in  a  conglomerate  of  the 
Lower  Cambrian  system,  we  may  then  feel  assured  that  the  parent 
granite  was  formed  before  the  Lower  Cambrian  formation.  But  if  the 
incumbent  strata  be  merely  Silurian  or  Upper  Cambrian,  the  funda- 
mental granite,  although  of  high  antiquity,  may  be  posterior  in  date 
to  known  fossiliferous  formations. 

Protrusion  of  Solid  Granite. — In  part  of  Sutherlandshire,  near 
Brora,  common  granite,  composed  of  felspar,  quartz,  and  mica,  is  in 
immediate  contact  with  Oolitic  strata,  and  has  clearly  been  elevated 
to  the  surface  at  a  period  subsequent  to  the  deposition  of  those  strata.* 
Professor  Sedgwick  and  Sir  R.  Murchison  conceive  that  this  granite 
has  been  upheaved  in  a  solid  form ;  and  that  in  breaking  through  the 
submarine  deposits,  with  which  it  was  not  perhaps  originally  in  con- 
tact, it  has  fractured  them  so  as  to  form  a  breccia  along  the  line  of 
junction.  This  breccia  consists  of  fragments  of  shale,  sandstone,  and 
limestone,  with  fossils  of  the  oolite,  all  united  together  by  a  calcareous 
cement.  The  secondary  strata,  at  some  distance  from  the  granite,  are 
but  slightly  disturbed,  but  in  proportion  to  their  proximity  the  amount 
of  dislocation  becomes  greater. 

If  we  admit  that  solid  hypogene  rocks,  whether  stratified  or  un- 
stratified,  have  in  such  cases  been  driven  upwards  so  as  to  pierce 
through  yielding  sedimentary  deposits,  we  shall  be  enabled  to  account 
for  many  geological  appearances  otherwise  inexplicable.  Thus,  for 
example,  at  Weinbohla  and  Hohnstein,  near  Meissen,  in  Saxony,  a 
mass  of  granite  has  been  observed  covering  strata  of  the  Cretaceous 
and  Oolitic  periods  for  the  space  of  between  300  and  400  yards 
square.  It  appears  clearly  from  a  memoir  of  Dr.  B.  Cotta  on  this  sub- 
ject, f  that  the  granite  was  thrust  into  its  actual  position  when  solid. 
There  are  no  intersecting  veins  at  the  junction — no  alteration  as  if  by 
heat,  but  evident  signs  of  rubbing,  and  a  breccia  in  some  places,  in 
which  pieces  of  granite  are  mingled  with  broken  fragments  of  the  sec- 
ondary rocks.  As  the  granite  overhangs  both  the  lias  and  chalk,  so 
the  lias  is  in  some  places  bent  over  strata  of  the  cretaceous  era. 

Relative  Age  of  the  Granites  of  Arran. — In  this  island,  the  largest 
in  the  Firth  of  Clyde,  being  twenty  miles  in  length  from  north  to 


*  Murchison,  Geol.  Trans.,  Second  Series,  vol.  ii.  p.  307. 
f  Geognostische  Wanderangen,  Leipzig,  1838. 


728  AGE  OF   THE   GRANITES  [Cn.  XXXIV. 

south,  the  four  great  classes  of  rocks,  the  fossiliferous,  volcanic,  plu- 
tonic,  and  metamorphic,  are  all  conspicuously  displayed  within  a 
very  small  area,  and  with  their  peculiar  characters  strongly  contrasted. 
In  the  north  of  the  island  the  granite  rises  to  the  height  of  nearly 
3000  feet  above  the  sea,  terminating  in  mountainous  peaks.  (See 
section,  fig.  754.)  On  the  flanks  of  the  same  mountains  are  chloritic- 
schists,  blue  roofing-slate,  and  other  rocks  of  the  metamorphic  order 
(No.  1),  into  which  the  granite  (No.  2)  sends  veins.  This  granite, 
therefore,  is  newer  than  the  hypogene  schists  (No.  1),  which  it  pene- 
trates. 

These  schists  are  highly  inclined.  Upon  them  rest  beds  of  con- 
glomerate and  sandstone  (No.  3),  which  are  referable  to  the  Old  Red 
formation,  to  which  succeed  various  shales  and  limestones  (No.  4) 
containing  the  fossils  of  the  Carboniferous  period,  upon  which  are 
other  strata  of  sandstone  and  conglomerate  (the  higher  beds  of  No. 
4),  in  which  no  fossils  have  been  met  with.  These  are  perhaps  car- 
boniferous, though  it  has  been  conjectured  that  they  may  belong  to 
the  New  Red  Sandstone,  or  at  least  to  some  part  of  the  Poikilitic 
period.  All  the  preceding  formations  are  cut  through  by  the  vol- 
canic rocks  (No.  6),  which  consist  of  greenstone,  basalt,  pitchstone, 
felstone,  and  other  varieties.  These  appear  either  in  the  form  of 
dikes,  or  in  dense  masses  from  50  to  700  feet  in  thickness,  overlying 
the  strata  (No.  4).  In  one  region,  at  Ploverfield,  in  Glen  Cloy,  a 
fine-grained  granite  (5  a)  is  seen  to  send  veins  through  the  sandstone 
or  the  upper  strata  of  No.  4.  This  interesting  discovery  of  granite 
in  the  southern  region  of  Arran,  at  a  point  where  it  is  separated  from 
the  northern  mass  of  the  same  rock  by  a  great  thickness  of  secondary 
strata,  was  made  by  M.  L.  A.  Necker  of  Geneva,  during  his  survey  of 
Arran  in  1839.  Dr.  MacCulloch  had  long  before  pointed  out  that  in 
the  granitic  nucleus  of  the  north  there  were  two  distinct  varieties  of 
granite  (see  diagram,  p.  730)  occupying  separate  tracts,  both  consist- 
ing of  quartz,  felspar,  and  mica,  but  the  crystalline  grains  in  the  fine 
variety  being  so  small  as  often  to  impart  to  it  an  arenaceous  aspect 
and  sandy  feel.  Prof.  Ramsay  afterwards  traced  out  the  geographi- 
cal limits  of  both  varieties,  and  these  have  since  been  more  precisely 
defined  and  laid  down  on  a  map  by  Dr.  Bryce,  author  of  a  valuable 
work  on  the  geology  of  Arran.  The  last-mentioned  observer  remarks 
that  the  fine-grained  kind  never  reaches  so  great  an  elevation  above 
the  level  of  the  sea  as  does  the  coarse-grained.  He  also  discovered, 
in  1864,  that  the  fine-grained  variety  is  not  entirely  isolated,  as  for- 
merly supposed,  within  a  boundary  of  the  coarse,  but  that,  on  the 
south  side  of  the  nucleus,  it  comes  into  contact  with  the  slates,  which 
it  penetrates  and  alters.  The  same  geologist  also  found  that,  besides 
the  outlier  of  fine-grained  granite  at  Ploverfield,  there  is  another 
smaller  outbreak  of  the  same  rock  to  the  westward,  a  quarter  of  a 
mile  long  and  from  250  to  300  yards  broad.  It  is  called  the  Craig- 
Dhu  granite,  and  seems  to  rise  at  the  junction  of  the  Old  Red  sand- 
stone with  the  Carboniferous  strata. 


CH.  XXXIV.}  OF  THE  ISLE  OF  ARRAN.  729 

At  and  near  the  point  of  contact  the  base  of  the  conglomerate  of 
the  Old  Red  consisting  of  sandstone  is  rendered  crystalline,  and  frag- 
ments of  granite  of  an  elliptical  form  and  of  the  same  mineral  struc- 
ture as  the  adjoining  mass  of  fine  granite  are  included  in  the  sandstone 
or  conglomerate.  It  has  been  already  stated  that  no  pieces  of  granite, 
rounded  or  angular,  occur  elsewhere  in  the  Old  Red,  and  as  they  are 
only  found  here  in  close  proximity  to  the  crystalline  and  intrusive 
rock,  Dr.  Bryce  supposes  that  they  were  injected  into  the  strata  in  a 
fluid  or  semi-fluid  state.  I  have  seen  a  similar  junction  in  Caithness, 
of  which  Sir  R.  Murchison  in  1827,  and  again  in  1828  jointly  with 
Professor  Sedgwick,  has  given  a  faithful  description.  Close  to  the 
point  of  contact  of  certain  oolitic  sandstones,  shales,  and  limestones  in 
the  Caithness  cliffs,  a  breccia  occurs  containing  granite  fragments 
mixed  with  those  of  the  invaded  rock.  The  granite,  they  say,  appears 
as  if  it  had  been  mechanically  driven  in  among  the  shattered  and 
altered  strata.*  In  the  coarse-grained  granite  of  the  northern  nucleus 
trap-dikes  of  pitchstone  and  basalt  are  numerous,  but  dikes  are  com- 
paratively rare  in  the  fine-grained  granite,  and  were  even  supposed  to 
be  entirely  wanting  until  three  or  four,  consisting  of  basalt  and  green- 
stone, were  discovered  by  Dr.  Bryce,  running  north  and  northwest. 
It  seems  therefore  fair  to  infer,  as  Prof.  Ramsay  has  done,  that  many 
of  the  dikes  penetrating  the  older  granite  are  cut  off  at  the  junction 
of  the  newer  or  fine-grained  variety  in  the  manner  expressed  at  6,  c,  d, 
fig.  754,  though  no  such  cutting  off  has  been  actually  observed.  We 
may  also  feel  assured  that  some  of  the  dikes  traversing  the  fine  must 
also  penetrate  the  coarse-grained  granite,  as  Dr.  Bryce  infers, 
although,  as  yet,  he  has  not  observed  the  actual  passage  of  any  one 
from  the  newer  to  the  older  rock.  There  can  be  scarcely  a  doubt 
that  the  fine-grained  variety  of  nucleus  and  the  similar  rocks  of 
Ploverfield  and  Craig-Dhu  are  of  contemporaneous  date,  and  they 
seem  to  be  more  modern  than  all  the  formations  of  Arran,  except  the 
overlying  trap  (No.  6)  and  its  associated  dikes.  But  the  coarser 
granite  (No.  2)  may  be  the  oldest  rock  in  Arran,  with  the  exception 
of  the  hypogene  slates  (No.  1),  into  which  it  sends  veins,  and  which 
it  alters  at  the  point  of  contact. 

An  objection  may  perhaps  at  first  be  started  to  this  conclusion, 
derived  from  the  curious  and  striking  fact,  the  importance  of  which 
was  first  emphatically  pointed  out  by  Dr.  MacCulloch,  that  no  pebbles 
of  granite  occur  in  the  conglomerates  of  the  red  sandstone  in  Arran, 
although  these  conglomerates  are  several  hundred  feet  in  thickness, 
and  lie  at  the  foot  of  lofty  granite  mountains,  which  tower  above 
them.  As  a  general  rule,  all  such  aggregates  of  pebbles  and  sand  are 
mainly  composed  of  the  wreck  of  preexisting  rocks  occurring  in  the 
immediate  vicinity.  The  total  absence  therefore  of  granitic  pebbles 
has  justly  been  a  theme  of  wonder  to  those  geologists  who  have 

*  Geol.  Trans.,  Second  Series,  vol.  ii.  p.  353,  and  vol.  iii.  p.  132. 


T30 


AGE  OF  THE  GRANITES 


[On.  XXXIV. 


r     I 


1! 


II 
Ji 


CH.  XXXIV.]  OF  THE  ISLE   OF  AKRAN. 

successively  visited  Arran,  and  they  have  carefully  searched  there,  as 
I  have  done  myself,  to  find  an  exception,  but  in  vain.  The  rounded 
masses  consist  exclusively  of  quartz,  chlorite-schist,  and  other  mem- 
bers of  the  metamorphic  series ;  nor  in  the  newer  conglomerates  of 
No.  3  have  any  granitic  fragments  been  discovered.  Are  we  then 
entitled  to  affirm  that  the  coarse-grained  granite  (No.  2),  like  the  fine- 
grained variety  (No.  5),  is  more  modern  than  all  the  other  rocks  of 
the  island  ?  This  we  cannot  assume,  but  we  may  confidently  infer 
that  when  the  various  beds  of  sandstone  and  conglomerate  were 
formed,  no  granite  had  reached  the  surface,  or  had  been  exposed  to 
denudation  in  Arran.  It  is  clear  that  the  crystalline  schists  were 
ground  into  sand  and  shingle  when  the  strata  No.  3  were  deposited, 
and  at  that  time  the  waves  had  never  acted  upon  the  granite,  which 
now  sends  its  veins  into  the  schist.  May  we  then  conclude,  that  the 
schists  suffered  denudation  before  they  were  invaded  by  granite? 
The  opinion,  although  not  inadmissible,  is  by  no  means  fully  borne 
out  by  the  evidence.  For  at  that  time  when  the  Old  Red  Sandstone 
originated,  the  metamorphic  strata  may  have  formed  islands  in  the 
sea,  as  in  fig.  755,  over  which  the  breakers  rolled,  or  from  which 

Fig.  755. 
Sea 


torrents  and  rivers  descended,  carrying  down  gravel  and  sand.  The 
plutonic  rock  or  granite  (B)  may  even  then  have  been  previously 
injected  at  a  certain  depth  below,  and  yet  may  never  have  been 
exposed  to  denudation. 

As  to  the  time  and  manner  of  the  subsequent  protrusion  of  the 
coarse-grained  granite  (No.  2),  this  rock  may  have  been  thrust  up 
bodily  in  a  solid  form,  during  that  long  series  of  igneous  operations 
which  produced  the  plutonic  formations  (No.  5),  and  some  of  the  trap 
dikes  of  the  same  age. 

"We  have  shown  that  these  eruptions,  whatever  their  date,  were 
posterior  to  the  deposition  of  all  the  fossiliferous  strata  of  Arran. 
We  can  also  prove  that  subsequently  both  the  granitic  and  trappean 
rocks  underwent  great  aqueous  denudation,  which  they  probably 
suffered  during  their  emergence  from  the  sea.  The  fact  is  demon- 
strated by  the  abrupt  truncation  of  numerous .  dikes,  such  as  those  at 
6,  c,  d,  which  are  cut  off  on  the  surface  of  the  granite  and  trap. 

The  theory  of  the  protrusion  in  a  solid  form  of  the  northern  nucleus 
of  granite  is  confirmed  by  the  manner  in  which  the  hypogene  slates 
(No.  1)  and  the  beds  of  conglomerate  (No.  3)  dip  away  from  it  on  all 
sides.  In  some  places  indeed  the  slates  are  inclined  towards  the 
granite,  but  this  exception  might  have  been  looked  for,  because  these 
hypogene  strata  have  undergone  disturbances  at  more  than  one  geo- 


732  METAMORPHIC  ROCKS.  [On.  XXXV. 

logical  epoch,  and  may  at  some  points,  perhaps,  have  their  original 
order  of  position  inverted.  The  high  inclination,  therefore,  and  the 
quaquaversal  dip  of  the  "beds  around  the  borders  of  the  granitic  boss, 
and  the  comparative  horizbntality  of  the  fossiliferous  strata  in  the 
southern  part  of  the  island,  are  facts  which  all  accord  with  the 
hypothesis  of  a  great  amount  of  movement  at  that  point  where  the 
granite  is  supposed  to  have  been  thrust  up  bodily,  and  where  we  may 
conceive  it  to  have  been  distended  laterally  by  the  repeated  injection 
of  fresh  supplies  of  melted  materials.* 


CHAPTER  XXXV. 

METAMORPHIC      BOCKS. 

General  character  of  metamorphic  rocks — Gneiss — Hornblende-schist — Mica-schist — 
Clay-slate — Quartzite — Chlorite-schist— Metamorphic  limestone — Alphabetical  list 
and  explanation  of  the  more  abundant  rocks  of  this  family — Origin  of  the  meta- 
morphic strata — Their  stratification — Fossiliferous  strata  near  intrusive  masses 
of  granite  converted  into  rocks  identical  with  different  members  of  the  metamor- 
phic series — Arguments  hence  derived  as  to  the  nature  of  plutonic  action — Time 
may  enable  this  action  to  pervade  denser  masses — From  what  kinds  of  sedi- 
mentary rock  each  variety  of  the  metamorphic  class  may  be  derived — Certain 
objections  to  the  metamorphic  theory  considered — Partial  conversion  of  Eocene 
slate  into  gneiss. 

WE  have  now  considered  three  distinct  classes  of  rocks :  first,  the 
aqueous  or  fossiliferous;  secondly,  the  volcanic;  and,  thirdly,  the 
plutonic,  or  granitic;  and  it  remains  for  us  to  examine  those  crys- 
talline (or  hypogene)  strata  to  which  the  name  of  metamorphic  has 
been  assigned.  The  last-mentioned  term  expresses,  as  before  ex- 
plained, a  theoretical  opinion  that  such  strata,  after  having  been 
deposited  from  water,  acquired,  by  the  influence  of  heat  and  other 
causes,  a  highly  crystalline  texture.  They  who  still  question  this 
opinion,  may  call  the  rocks  under  consideration  the  stratified  hypo- 
gene,  or  schistose  hypogene  formations. 

These  rocks,  when  iu  their  most  characteristic  or  normal  state,  are 
wholly  devoid  of  organic  remains,  and  contain  no  distinct  fragments 

*  For  the  geology  of  Arran,  which  I  examined  myself  in  1836,  consult  the 
works  of  Drs.  Button  and  MacCulloch,  the  Memoirs  of  Messrs.  Von  Dechen  and 
Oeynhausen,  that  of  Professor  Sedgwick  and  Sir  R.  Murchison  (Geol.  Trans.,  Sec- 
ond Series),  Mr.  L.  A.  Necker's  Memoir,  read  to  the  Royal  Soc.  of  Edin.,  20th 
April,  1840,  and  Prof.  Ramsay's  Geol.  of  Arran,  1841,  and  lastly,  Mr.  Bryce's  Geol. 
of  Arran  and  Clydesdale,  3d  ed.r  1864. 


CH.  XXXV.]  GNEISS.  ^33 

of  other  rocks,  whether  rounded  or  angular.  They  sometimes  break 
out  in  the  central  parts  of  narrow  mountain  chains,  but  in  other  cases 
extend  over  areas  of  vast  dimensions,  occupying,  for  example,  nearly 
the  whole  of  Norway  and  Sweden,  where,  as  in  Brazil,  they  appear 
alike  in  the  lower  and  higher  grounds.  In  Great  Britain,  those  mem- 
bers of  the  series  which  approach  most  nearly  to  granite  in  their  com- 
position, as  gneiss,  mica-schist,  and  hornblende-schist,  are  confined  to 
the  country  north  of  the  rivers  Forth  and  Clyde. 

However  crystalline  these  rocks  may  become  in  certain  regions, 
they  never,  like  granite  or  trap,  send  veins  into  contiguous  formations, 
whether  into  an  older  schist  or  granite  or  into  a  set  of  newer  fossil- 
iferous  strata. 

Many  attempts  have  been  made  to  trace  a  general  order  of  suc- 
cession or  superposition  in  the  members  of  this  family ;  clay-slate,  for 
example,  having  been  often  supposed  to  hold  invariably  a  higher  geo- 
logical position  than  mica-schist,  and  mica-schist  always  to  overlie 
gneiss.  But  although  such  an  order  may  prevail  throughout  limited 
districts,  it  is  by  no  means  universal.  To  this  subject,  however,  I 
shall  again  revert,  in  the  37th  chapter,  when  the  chronological  rela- 
tions of  the  metamorphic  rocks  are  pointed  out. 

The  following  may  be  enumerated  as  the  principal  members  of  the 
metamorphic  class:  gneiss,  mica-schist,  hornblende-schist,  clay-slate, 
chlorite-schist,  hypogene  or  metamorphic  limestone,  and  certain  kinds 
of  quartz-rock  or  quartzite. 

Gneiss.— The  first  of  these,  gneiss,  may  be  called  stratified,  or,  by 
those  who  object  to  that  term,  foliated  granite,  being  formed  of  the 
same  materials  as  granite,  namely,  felspar,  quartz,  and  mica.  In  the 
specimen  here  figured,  the  white  layers  consist  almost  exclusively  of 
granular  felspar,  with  here  and  there  a  speck  of  mica  and  grain  of 
quartz.  The  dark  layers  are  composed  of  gray  quartz  and  black  mica, 

Fig.  756. 


Fragment  of  gneiss,  natural  size ;  section  made  at  right  angles  to  the  planes  of  foliation. 

with  occasionally  a  grain  of  felspar  intermixed.  The  rock  splits  most 
easily  in  the  plane  of  these  darker  layers,  and  the  surface  thus  exposed 
is  almost  entirely  covered  with  shining  spangles  of  mica.  The  accom- 
panying quartz,  however,  greatly  predominates  in  quantity,  but  the 
most  ready  cleavage  is  determined  by  the  abundance  of  mica  in  cer- 
tain parts  of  the  dark  layer. 


734:  HORNBLENDE-SCHIST,  MICA-SCHIST,  ETC.        [Cn.  XXXV. 

Instead  of  consisting  of  these  thin  laminae,  gneiss  is  sometimes 
simply  divided  into  thick  beds,  in  which  the  mica  has  only  a  slight 
degree  of  parallelism  to  the  planes  of  stratification. 

The  term  "gneiss,"  however,  in  geology  is  commonly  used  in  a 
wider  sense,  to  designate  the  formation  in  which  the  above-mentioned 
rock  prevails,  but  with  which  any  one  of  the  other  metamorphic 
rocks,  and  more  especially  hornblende-schist,  may  alternate.  These 
other  members  of  the  metainorphic  series  are,  in  this  case,  considered 
as  subordinate  to  the  true  gneiss. 

The  different  varieties  of  rock  allied  to  gneiss,  into  which  felspar 
enters  as  an  essential  ingredient,  will  be  understood  by  referring  to 
what  was  said  of  granite.  Thus,  for  example,  hornblende  may  be 
superadded  to  mica,  quartz,  and  felspar,  forming  a  syenitic  gneiss;  or 
talc  may  be  substituted  for  mica,  constituting  talcose-gneiss,  a^  rock 
composed  of  felspar,  quartz,  and  talc,  in  distinct  crystals  or  grains 
(stratified  protogine  of  the  French). 

Hornblende-schist  is  usually  black,  and  composed  principally  of 
hornblende,  with  a  variable  quantity  of  felspar,  and  sometimes  grains 
of  quartz.  When  the  hornblende  and  felspar  are  nearly  in  equal 
quantities,  and  the  rock  is  not  slaty,  it  corresponds  in  character  with 
the  greenstones  of  the  trap  family,  and  has  been  called  "  primitive 
greenstone."  It  may  be  termed  hornblende  rock.  Some  of  these 
hornblendic  masses  may  really  have  been  volcanic  rocks,  which  have 
since  assumed  a  more  crystalline  or  metamorphic  texture. 

Mica-schist,  or  Micaceous  Schist,  is,  next  to  gneiss,  one  of  the  most 
abundant  rocks  of  the  metamorphic  series.-  It  is  slaty,  essentially 
composed  of  mica  and  quartz,  the  mica  sometimes  appearing  to  con- 
stitute the  whole  mass.  Beds  of  pure  quartz  also  occur  in  this  forma- 
tion. In  some  districts,  garnets  in  regular  twelve-sided  crystals  form 
an  integrant  part  of  mica-schist.  This  rock  passes  by  insensible  gra- 
dations into  clay-slate. 

Clay-slate,  or  Argillaceous  Schist. — This  rock  sometimes  resembles 
an  indurated  clay  or  shale.  It  is  for  the  most  part  extremely  fissile, 
often  affording  good  roofing-slate.  Occasionally  it  derives  a  shining 
and  silky  lustre  from  the  minute  particles  of  mica  or  talc  which  it  con- 
tains. It  varies  from  greenish  or  bluish-gray  to  a  lead  color ;  and  it 
may  be  said  of  this,  more  than  of  any  other  schist,  that  it  is  common 
to  the  metamorphic  and  fossiliferous  series,  for  some  clay-slates  taken 
from  each  division  would  not  be  distinguishable  by  mineral  characters 
alone. 

Quartzite,  or  Quartz  Rock,  is  an  aggregate  of  grains  of  quartz 
which  are  either  in  minute  crystals,  or  in  many  cases  slightly  rounded, 
occurring  in  regular  strata,  associated  with  gneiss  or  other  meta- 
morphic rocks.  Compact  quartz,  like  that  so  frequently  found  in 
veins,  is  also  found  together  with  granular  quartzite.  Both  of  these 
alternate  with  gneiss  or  mica-schist,  or  pass  into  those  rocks  by  the 
addition  of  mica,  or  of  felspar  and  mica. 


CH.  XXXV.]       CHLORITE-SCHIST,  ETC.— METAMORPHIC  ROCKS.          735 

Cklorite-schist  is  a  green  slaty  rock,  in  which  chlorite  is  abundant 
in  foliated  plates,  usually  blended  with  minute  grains  of  quartz,  or 
sometimes  with  felspar  or  mica  ;  often  associated  with,  and  graduating 
into,  gneiss  and  clay-slate. 

Crystalline  or  Metamorphic  Limestone. — This  hypogene  rock,  called 
by  the  earlier  geologists  primary  limestone,  is  sometimes  a  white  crys- 
talline granular  marble,  which  when  in  thick  beds  can  be  used  in 
sculpture  ;  but  more  frequently  it  occurs  in  thin  beds,  forming  a  foli- 
ated schist  much  resembling  in  color  and  appearance  certain  varieties 
of  gneiss  and  mica-schist.  When  it  alternates  with  these  rocks,  it 
often  contains  some  crystals  of  mica,  and  occasionally  quartz,  felspar, 
hornblende,  talc,  chlorite,  garnet,  and  other  minerals.  It  enters 
sparingly  into  the  structure  of  the  hypogene  districts  of  Norway, 
Sweden,  and  Scotland,  but  is  largely  developed  in  the  Alps. 

Before  offering  any  farther  observations  on  the  probable  origin  of 
the  metamorphic  rocks,  I  subjoin,  in  the  form  of  a  glossary,  a  brief 
explanation  of  some  of  the  principal  varieties  and  their  synonyms. 


Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of 
the  more  abundant  Metamorphic  RocJcs. 

ACTINOLITE-SCHIST.  A  slaty  foliated  rock,  composed  chiefly  of  actinolite  (an  em- 
erald-green mineral,  allied  to  hornblende),  with  some  admixture  of  garnet, 
mica,  and  quartz. 

AMPELITE.  Aluminous  slate  (Brongniart) ;  occurs  both  in  the  metamorphic  and 
fossiliferous  series. 

AMPHIBOLITE.     Hornblende  rock,  which  see. 

ARGILLACEOUS-SCHIST,  or  CLAY-SLATE.     See  p.  734. 

ARKOSE.  Name  given  by  Brongniart  to  a  compound  of  the  same  materials  as 
granite,  which  it  often  resembles  closely.  It  is  found  at  the  junction  of 
granite  with  formations  of  different  ages,  and  consists  of  crystals  of  felspar, 
quartz,  and  sometimes  mica,  which,  after  separation  from  their  original 
matrix  by  disintegration,  have  been  reunited  by  a  siliceous  or  quartzose 
cement.  It  is  often  penetrated  by  quartz  veins. 

CHIASTOLITE-SLATE  scarcely  differs  from  clay-slate,  but  includes  numerous  crystals 
of  Chiastolite:  in  considerable  thickness  in  Cumberland.  Chiastolite  oc- 
curs in  long  slender  rhomboidal  crystals.  For  composition,  see  Table,  p. 
608. 

CHLORITE-SCHIST.  A  green  slaty  rock,  in  which  chlorite,  a  green  scaly  mineral,  is 
abundant.  See  p.  735. 

CLAY-SLATE,  or  ARGILLACEOUS-SCHIST.    See  p.  734. 

EURITE  has  been  already  mentioned  as  a  plutonic  rock  (p.  708),  but  occurs  also 
with  precisely  the  same  composition  in  beds  subordinate  to  gneiss  or  mica- 
slate. 

GNEISS.  A  stratified  or  foliated  rock ;  has  the  same  composition  as  granite.  See 
p.  733. 

HORNBLENDE  ROCK,  or  AMPHIBOLITE.     See  above,  p.  605.    A  member  both  of  the 


736  METAMORPHIC  ROCKS.          [On.  XXXV. 

volcaric  and  metamorpMc  series.    Agrees  in  composition  with  hornblende- 

schist,  but  is  not  fissile. 

HORNBLENDE-SCHIST,  or  SLATE.     Composed  of  hornblende  and  felspar.     See  p.  734. 
HORNBLENDIC  or  SYENiTic  GNEISS.     Composed  of  felspar,  quartz,  and  hornblende. 
HYPOGENE  LIMESTONE.     See  p.  735. 

MARBLE.     See  pp.  12  and  735. 

MICA-SCHIST,  or  MICACEOUS-SCHIST.    A  slaty  rock,  composed  of  mica  and  quartz,  in 

variable  proportions.     See  p.  734. 
MICA-SLATE.     See  MICA-SCHIST,  p.  734. 


PHYLLADE.     D'Aubuisson's  term  for  clay-slate,  from  ^u/Uaf,  a  heap  of  leaves. 

PRIMARY  LIMESTONE.     See  HYPOGENE  LIMESTONE,  p.  735. 

PROTOGINE.     See  TALCOSE-GNEISS,  p.  734  ;  when  unstratified,  it  is  Talcose-granite. 

QUARTZ  ROCK,  or  QUARTZITE.    A  stratified  rock  ;  an  aggregate  of  grains  of  quartz. 
See  p.  734. 

SERPENTINE  has  already  been  described  (p.  606),  because  it  occurs  in  both  divisions 
of  the  hypogene  series,  as  a  stratified  or  unstratified  rock. 

TALCOSE-GNEISS.     Same  composition  as  talcose-granite  or  protogine,  but  stratified 

or  foliated.     See  p..  124:. 
TALCOSE-SCHIST  consists  chiefly  of  talc,  or  of  talc  and  quartz,  or  of  talc  and  felspar, 

and  has  a  texture  something  like  that  of  clay-slate. 


Origin  of  the  Metamorphic  Strata. 

Having  said  thus  much  of  the  mineral  composition  of  the  meta- 
morphic  rocks,  I  may  combine  what  remains  to  be  said  of  their 
structure  and  history  with  an  account  of  the  opinions  entertained  of 
their  probable  origin.  At  the  same  time,  it  may  be  well  to  forewarn 
the  reader  that  we  are  here  entering  upon  ground  of  controversy, 
and  soon  reach  the  limits  where  positive  induction  ends,  and  beyond 
which  we  can  only  indulge  in  speculations.  It  was  once  a  favorite 
doctrine,  and  is  still  maintained  by  many,  that  these  rocks  owe  their 
crystalline  texture,  their  want  of  all  signs  of  a  mechanical  origin,  or 
of  fossil  contents,  to  a  peculiar  and  nascent  condition  of  the  planet  at 
the  period  of  their  formation.  The  arguments  in  refutation  of  this 
hypothesis  will  be  more  fully  considered  when  I  show,  in  the  thirty- 
seventh  chapter,  to  how  many  different  ages  the  metamorphic  forma- 
tions are  referable,  and  how  gneiss,  mica-schist,  clay-slate,  and  hypo- 
gene  limestone  (that  of  Carrara  for  example)  have  been  formed,  not 
only  since  the  first  introduction  of  organic  beings  into  this  planet, 
but  even  long  after  many  distinct  races  of  plants  and  animals  had 
passed  away  in  succession. 

The  doctrine  respecting  the  crystalline  strata,  implied  in  the  name 
metamorphic,  may  properly  be  treated  of  in  this  place ;  and  we  must 
first  inquire  whether  these  rocks  are  really  entitled  to  be  called  strati- 
fied in  the  strict  sense  of  having  been  originally  deposited  as  sedi- 
ment from  water.  The  general  adoption  by  geologists  of  the  term 


CH.  XXXV.]          METAMORPHIC  ROCKS.  Y3Y 

stratified,  as  applied  to  these  rocks,  sufficiently  attests  their  division 
into  beds  very  analogous,  at  least  in  form,  to  ordinary  fossil iferous 
strata.  This  resemblance  is  by  no  means  confined  to  the  existence  in 
both  occasionally  of  a  laminated  structure,  but  extends  to  every  kind 
of  arrangement  which  is  compatible  with  the  absence  of  fossils,  and 
of  sand,  pebbles,  ripple-mark,  and  other  characters  which  the  meta- 
morphic  theory  supposes  to  have  been  obliterated  by  plutonic  action. 
Thus,  for  example,  we  behold  alike  in  the  crystalline  and  fossiliferous 
formations  an  alteration  of  beds  varying  greatly  in  composition,  color, 
and  thickness.  We  observe,  for  instance,  gneiss  alternating  with  lay- 
ers of  black  hornblende-schist,  or  of  green  chlorite-schist,  or  with 
granular  quartz,  or  limestone ;  and  the  interchange  of  these  different 
strata  may  be  repeated  for  an  indefinite  number  of  times.  In  the 
like  manner,  mica-schist  alternates  with  chlorite-schist,  and  with  beds 
of  pure  quartz  or  of  granular  limestone. 

We  have  already  seen  that,  near  the  immediate  contact  of  granitic 
veins  and  volcanic  dikes,  very  extraordinary  alterations  in  rocks  have 
taken  place,  more  especially  in  the  neighborhood  of  granite.  It  will 
be  useful  here  to  add  other  illustrations,  showing  that  a  texture  un- 
distinguishable  from  that  which  characterizes  the  more  crystalline 
metamorphic  formations  has  actually  been  superinduced  in  strata  once 
fossiliferous. 

In  the  southern  extremity  of  Norway  there  is  a  large  district,  on 
the  west  side  of  the  fiord  of  Christiania,  in  which  granite  or  syenite 
protrudes  in  mountain  masses  through  fossiliferous  strata,  and  usually 
sends  veins  into  them  at  the  point  of  contact.  The  stratified  rocks, 
replete  with  shells  and  zoophytes,  consist  chiefly  of  shale,  limestone, 
and  some  sandstone,  and  all  these  are  invariably  altered  near  the 
granite  for  a  distance  of  from  50  to  400  yards.  The  aluminous  shales 
are  hardened  and  have  become  flinty.  Sometimes  they  resemble  jas- 
per. Ribboned  jasper  is  produced  by  the  hardening  of  alternate 
layers  of  green  and  chocolate-colored  schist,  each  stripe  faithfully 
representing  the  original  lines  of  stratification.  Nearer  the  granite 
the  schist  often  contains  crystals  of  hornblende,  which  are  even  met 
with  in  some  places  for  a  distance  of  several  hundred  yards  from  the 
junction ;  and  this  black  hornblende  is  so  abundant  that  eminent 
geologists,  when  passing  through  the  country,  have  confounded  it 
with  the  ancient  hornblende-schist,  subordinate  to  the  great  gneiss 
formation  of  Norway.  Frequently,  between  the  granite  and  the 
hornblende  slate  above-mentioned,  grains  of  mica  and  crystalline  fel- 
spar appear  in  the  schist,  so  that  rocks  resembling  gneiss  and  mica- 
schist  are  produced.  Fossils  can  rarely  be  detected  in  these  schists, 
and  they  are  more  completely  effaced  in  proportion  to  the  more  crys- 
talline texture  of  the  beds,  and  their  vicinity  to  the  granite.  In  some 
places  the  siliceous  matter  of  the  schist  becomes  a  granular  quartz ; 
and  when  hornblende  and  mica  are  added,  the  altered  rock  loses  its 
stratification,  and  passes  into  a  kind  of  granite.  The  limestone, 
47 


738 


STRATA  IN  CONTACT  WITH   GRANITE.         [Cn.  XXXV. 


which  at  points  remote  from  the  granite  is  of  an  earthy  texture  and 
blue  color,  and  often  abounds  in  corals,  becomes  a  white  granular 
marble  near  the  granite,  sometimes  siliceous,  the  granular  structure 
extending  occasionally  upwards  of  400  yards  from  the  junction ;  the 
corals  being  for  the  most  part  obliterated,  though  sometimes  pre- 
served, even  in  the  white  marble.  Both  the  altered  limestone  and 

Fig.75T. 


Altered  zone  of  fossiliferous  slate  and  limestone  near  granite.    Christiania. 
The  arrows  indicate  the  dip,  and  the  straight  lines  the  strike,  of  the  beds. 

hardened  slate  contain  garnets  in  many  places,  also  ores  of  iron,  lead, 
and  copper,  with  some  silver.  These  alterations  occur  equally, 
whether  the  granite  invades  the  strata  in  a  line  parallel  to  the  general 
strike  of  the  fossiliferous  beds,  or  in  a  line  at  right  angles  to  their 
strike,  as  will  be  seen  by  the  accompanying  ground  plan.* 

The  indurated  and  ribboned  schists  above  mentioned  bear  a  strong 
resemblance  to  certain  shales  of  the  coal  found  at  Russell's  Hall,  near 
Dudley,  where  coal-mines  have  been  on  fire  for  ages.  Beds  of  shale 
of  considerable  thickness,  lying  over  the  burning  coal,  have  been 
baked  and  hardened  so  as  to  acquire  a  flinty  fracture,  the  layers  being 
alternately  green  and  brick-colored. 

The  granite  of  Cornwall,  in  like  manner,  sends  forth  veins  into  a 
coarse  argillaceous-schist,  provincially  termed  killas.  This  killas  is 
converted  into  hornblende-schist  near  the  contact  with  the  veins. 
These  appearances  are  well  seen  at  the  junction  of  the  granite  and 
killas,  in  St.  Michael's  Mount,  a  small  island  nearly  300  feet  high, 
situated  in  the  bay,  at  a  distance  of  about  three  miles  from  Penzance. 

The  granite  of  Dartmoor,  in  Devonshire,  says  Sir  H.  De  la  Beche, 
has  intruded  itself  into  the  slate  and  slaty  sandstone  called  graywacke, 
twisting  and  contorting  the  strata,  and  sending  veins  into  them. 
Hence  some  of  the  slate  rocks  have  become  "  micaceous ;  others  more 
indurated,  and  with  the  characters  of  mica-slate  and  gneiss ;  while 
others  again  appear  converted  into  a  hard-zoned  rock  strongly  im- 
pregnated with  felspar."  f 


*  Keilhau,  Gaea  Norvegica,  pp.  61-63. 


f  Geol.  Manual,  p.  479. 


CH.  XXXV.]  ALTERATIONS  OF  STRATA.  739 

We  learn  from  the  investigations  of  M.  Dufrenoy,  that  in  the  east- 
ern Pyrenees  there  are  mountain  masses  of  granite  posterior  in  date 
to  the  formations  called  lias  and  chalk  of  that  district,  and  that  these 
fossiliferous  rocks  are  greatly  altered  in  texture,  and  often  charged 
with  iron-ore,  in  the  neighborhood  of  the  granite.  Thus  in  the  envi- 
rons of  St.  Martin,  near  St.  Paul  de  Fenouillet,  the  chalky  limestone 
becomes  more  crystalline  and  saccharoid  as  it  approaches  the  granite, 
and  loses  all  trace  of  the  fossils  which  it  previously  contained  in 
abundance.  At  some  points,  also,  it  becomes  dolomitic,  and  filled 
with  small  veins  of  carbonate  of  iron,  and  spots  of  red  iron-ore.  At 
Eancie  the  lias  nearest  the  granite  is  not  only  filled  with  iron- ore,  but 
charged  with  pyrites,  tremolite,  garnet,  and  a  new  mineral  somewhat 
allied  to  felspar,  called,  from  the  place  in  the  Pyrenees  where  it 
occurs,  "  couzeranite." 

Now  the  alterations  above  described,  as  superinduced  in  rocks  by 
volcanic  dikes  and  granite  veins  prove  incontestably  that  powers 
exist  in  nature  capable  of  transforming  fossiliferous  into  crystalline 
strata — powers  capable  of  generating  in  them  a  new  mineral  charac- 
ter, similar  to,  nay,  often  absolutely  identical  with  that  of  gneiss, 
mica-schist,  and  other  stratified  members  of  the  hypogene  series.  The 
precise  nature  of  these  altering  causes,  which  may  provisionally  be 
termed  plutonic,  is  in  a  great  degree  obscure  and  doubtful ;  but  their 
reality  is  no  less  clear,  and  we  must  suppose  the  influence  of  heat  to 
be  in  some  way  connected  with  the  transmutation,  if,  for  reasons 
before  explained,  we  concede  the  igneous  origin  of  granite. 

The  experiments  of  Gregory  Watt,  in  fusing  rocks  in  the  laboratory, 
and  allowing  them  to  consolidate  by  slow  cooling,  prove  distinctly  that 
a  rock  need  not  be  perfectly  melted  in  order  that  a  rearrangement  of 
its  component  particles  should  take  place,  and  a  partial  crystallization 
ensue.*  We  may  easily  suppose,  therefore,  that  all  traces  of  shells  and 
other  organic  remains  may  be  destroyed ;  and  that  new  chemical  com- 
binations may  arise,  without  the  mass  being  so  fused  as  that  the  lines 
of  stratification  should  be  wholly  obliterated. 

We  must  not,  however,  imagine  that  heat  alone,  such  as  may  be 
applied  to  a  stone  in  the  open  air,  can  constitute  all  that  is  comprised 
in  plutonic  action.  We  know  that  volcanoes  in  eruption  not  only  emit 
fluid  lava,  bat  give  off  steam  and  other  heated  gases,  which  rush  out 
in  enormous  volume,  for  days,  weeks,  or  years  continuously,  and  are 
even  disengaged  from  lava  during  its  consolidation. 

We  also  know  that  long  after  volcanoes  have  spent  their  force,  hot 
springs  continue  for  ages  to  flow  out  at  various  points  in  the  same  area. 
In  regions  also  subject  to  violent  earthquakes  such  springs  are  fre- 
quently observed  issuing  from  rents,  usually  along  lines  of  fault  or 
displacement  of  the  rocks.  These  thermal  waters  are  most  commonly 
charged  with  a  variety  of  mineral  ingredients,  and  they  retain  a 

*  Phil.  Trans.,  1804. 


74:0  PLUTONIC  ACTION.  [Cn.  XXXY. 

remarkable  uniformity  of  temperature  from  century  to  century.  A 
like  uniformity  is  also  persistent  in  the  nature  of  the  earthy,  metallic, 
and  gaseous  substances  with  which  they  are  impregnated.  It  is  well 
ascertained  that  springs,  whether  hot  or  cold,  charged  with  carbonic 
acid,  and  especially  with  hydrofluoric  acid,  which  is  often  present  in 
small  quantities,  are  powerful  causes  of  decomposition  and  chemical 
reaction  in  rocks  through  which  they  percolate. 

The  changes  which  Daubre"e  has  shown  to  have  been  produced  by 
the  alkaline  waters  of  Plombieres  in  the  Vosges,  are  more  especially 
instructive.*  These  waters  have  a  heat  of  160°  F.,  or  an  excess  of 
109°  above  the  average  temperature  of  ordinary  springs  in  that  district. 
They  were  conveyed  by  the  Romans  to  baths  through  long  conduits 
or  aqueducts.  The  foundations  of  some  of  their  works  consisted  of  a 
bed  of  concrete  made  of  lime,  fragments  of  brick,  and  sandstone. 
Through  this  and  other  masonry  the  hot  waters  have  been  percolating 
for  centuries,  and  have  given  rise  to  various  zeolites — apophyllite  and 
chabazite  among  others ;  -also  to  calcareous  spar,  arragonite,  and  fluor 
spar,  together  with  siliceous  minerals,  such  as  opal — all  found  in  the 
interspaces  of  the  bricks  and  mortar,  or  constituting  part  of  their 
rearranged  materials.  The  quantity  of  heat  brought  into  action  in 
this  instance  in  the  course  of  2000  years  has,  no  doubt,  been  enormous, 
but  the  intensity  of  it  developed  at  any  one  moment  has  been  always 
inconsiderable. 

From  these  facts  and  from  the  experiments  and  observations  of 
Senarmont,  Daubree,  Delesse,  Scheerer,  Sorby,  Sterry,  Hunt,  and  others, 
we  are  led  to  infer  that  when  in  the  bowels  of  the  earth  there  are  large 
volumes  of  molten  matter,  containing  heated  water  and  various  acids 
under  enormous  pressure,  these  subterranean  fluid  masses  will  gradually 
part  with  their  heat  by  the  escape  of  steam  and  various  gases  through 
fissures,  producing  hot  springs ;  or  by  the  passage  of  the  same  through 
the  pores  of  the  overlying  and  injected  rocks.  Even  the  most  compact 
rocks  may  be  regarded,  before  they  have  been  exposed  to  the  air  and 
dried,  in  the  light  of  sponges  filled  with  water.  According  to  the 
experiments  of  Henry,  water,  under  an  hydrostatic  pressure  of  96  feet, 
will  absorb  three  times  as  much  carbonic  acid  gas  as  it  can  under  the 
ordinary  pressure  of  the  atmosphere.  There  are  other  gases,  as  well 
as  the  carbonic  acid,  which  water  absorbs,  and  more  rapidly  in  pro- 
portion to  the  amount  of  pressure.  Although  the  gaseous  matter  first 
absorbed  would  soon  be  condensed,  and  part  with  its  heat,  yet  the 
continual  arrival  of  fresh  supplies  from  below  might,  in  the  course  of 
ages,  cause  the  temperature  of  the  water,  and  with  it  that  of  the  con- 
taining rock,  to  be  materially  raised,  the  water  acts  not  only  as  a  vehicle 
of  heat,  but  also  by  its  affinity  for  various  silicates,  which,  when  some 
of  the  materials  of  the  invaded  rocks  are  decomposed,  form  quartz, 
felspar,  mica,  and  other  minerals.  As  for  quartz,  it  can  be  produced 

*  Daubree,  Sur  le  Metamorphisme  ;  Paris,  1860. 


CH.  XXXV.]          ROCKS  ALTERED  BY  SUBTERRANEAN  GASES.  741 

under  the  influence  of  heat  by  water  holding  alkaline  silicates  in  solution, 
as  in  the  case  of  the  Plombieres  springs,  without  any  chemical  reaction. 
The  quantity  of  water  required,  according  to  Daubree,  to  produce  great 
transformations  in  the  mineral  structure  of  rocks,  is  very  small.  As  to 
the  heat  required,  silicates  may  be  produced  in  the  moist  way  at  about 
incipient  red  heat,  whereas  to  form  the  same  in  the  dry  way  would 
require  a  much  higher  temperature. 

M.  Fournet,  in  his  description  of  the  metalliferous  gneiss  near  Cler- 
mont,  in  Auvergne,  states  that  all  the  minute  fissures  of  the  rock  are 
quite  saturated  with  free  carbonic  acid  gas ;  which  gas  rises  plentifully 
from  the  soil  there  and  in  many  parts  of  the  surrounding  country. 
The  various  elements  of  the  gneiss,  with  the  exception  of  the  quartz, 
are  all  softened ;  and  new  combinations  of  the  acid  with  lime,  iron, 
and  manganese  are  continually  in  progress.* 

Another  illustration  of  the  power  of  subterranean  gases  is  afforded 
by  the  Stufas  of  St.  Calogero,  situated  in  the  largest  of  the  Lipari 
Islands.  Here,  according  to  the  description  published  by  Hoffmann, 
horizontal  strata  of  tuff,  extending  for  four  miles  along  the  coast,  and 
forming  cliffs  more  than  200  feet  high,  have  been  discolored  in  various 
places,  and  strangely  altered  by  the  "  all-penetrating  vapors."  Dark 
clays  have  become  yellow,  or  often  snow-white ;  or  have  assumed  a 
chequered  or  brecciated  appearance,  being  crossed  with  ferruginous  red 
stripes.  In  some  places  the  fumeroles  have  been  found  by  analysis  to 
consist  partly  of  sublimations  of  oxide  of  iron ;  but  it  also  appears  that 
veins  of  chalcedony  and  opal,  and  others  of  fibrous  gypsum,  have 
resulted  from  these  volcanic  exhalations.f 

The  reader  may  also  refer  to  M.  Virlet's  account  of  the  corrosion 
of  hard,  flinty,  and  jaspideous  rocks  near  Corinth  by  the  prolonged 
agency  of  subterranean  gases ;  J  and  to  Dr.  Daubeny's  description  of 
the  decomposition  of  trachytic  rocks  in  the  Solfatara,  near  Naples,  by 
sulphuretted  hydrogen  and  muriatic  acid  gases. § 

Although  in  all  these  instances  we  can  only  study  the  phenomena 
as  exhibited  at  the  surface,  it  is  clear  that  the  gaseous  fluids  must  have 
made  their  way  through  the  whole  thickness  of  porous  or  fissured 
rock,  which  intervene  between  the  subterranean  reservoirs  of  gas  and 
the  external  air.  The  extent,  therefore,  of  the  earth's  crust  which  the 
vapors  have  permeated  and  are  now  permeating  may  be  thousands  of 
fathoms  in  thickness,  and  their  heating  and  modifying  influence  may 
be  spread  throughout  the  whole  of  this  solid  mass. 

We  learn  from  Professor  Bischoff  that  the  steam  of  a  hot  spring  at 
Aix-la-Chapelle,  although  its  temperature  is  only  from  133°  to  167°  F., 
has  converted  the  surface  of  some  blocks  of  black  marble  into  a 


*  See  "  Principles,"  Index,  "  Carbonated  Springs,"  &c. 

\  Hoffmann's  Liparischen  Inseln,  p.  38.     Leipzig,  1832. 

\  See  Princ.  of  Geol. ;  and  Bulletin  de  la  Soc.  Geol.  de  France,  torn.  ii.  p.  230. 

§  See  Princ.  of  Geol. ;  and  Daubeny's  Volcanoes,  p.  167. 


742  ROCKS  ALTERED  BY  SUBTERRANEAN  GASES.        [Cn.  XXXV. 

doughy  mass.  He  conceives,  therefore,  that  steam  in  the  bowels  of 
the  earth  having  a  temperature  equal  or  even  greater  than  the  melt- 
ing point  of  lava,  and  having  an  elasticity  of  which  even  Papin's 
digester  can  give  but  a  faint  idea,  may  convert  rocks  into  liquid 
matter.* 

The  above  observations  are  calculated  to  meet  some  of  the  objec- 
tions which  have  been  urged  against  the  metamorphic  theory  on  the 
ground  of  the  small  power  of  rocks  to  conduct  heat ;  for  it  is  well 
known  that  rocks,  when  dry  and  in  the  air,  differ  remarkably  from 
metals  in  this  respect.  It  has  been  asked  how  the  changes  which 
extend  merely  for  a  few  feet  from  the  contact  of  a  dike  could  have 
penetrated  through  mountain  masses  of  crystalline  strata  several  miles 
in  thickness.  Now  it  has  been  stated  that  the  plutonic  influence  of 
the  syenite  of  Norway  has  sometimes  altered  fossiliferous  strata  for  a 
distance  of  a  quarter  of  a  mile,  both  in  the  direction  of  their  dip  and 
of  their  strike.  (See  fig.  757,  p.  738.)  This  is  undoubtedly  an  ex- 
treme case ;  but  it  is  natural  to  suppose  that  analogous  causes  may, 
under  favorable  circumstances,  affect  masses  of  greater  volume.  The 
metamorphic  theory  does  not  require  us  to  affirm  that  some  contigu- 
ous mass  of  granite  has  been  the  altering  power ;  but  merely  that  an 
action,  existing  in  the  interior  of  the  earth  at  an  unknown  depth, 
whether  thermal,  hydrothermal,  or  other,  analogous  to  that  exerted 
near  intruding  masses  of  granite,  has,  in  the  course  of  vast  and  in- 
definite periods,  and  when  rising  perhaps  from  a  large  heated  surface, 
reduced  strata  thousands  of  yards  thick  to  a  state  of  semifusion,  so 
that  on  cooling  they  have  become  crystalline,  like  gneiss. 

The  prominent  part  which  water  has  played  in  distributing  the 
heat  of  the  interior  through  mountain  masses  of  incumbent  strata, 
and  in  conveying  various  mineral  elements  in  a  fluid  or  gaseous  state 
into  the  same  masses,  so  as  to  give  rise  in  the  course  of  long  geologi- 
cal periods  to  vast  chemical  changes,  enables  us  to  dispense  with  the 
intense  heat  formerly  thought  necessary  for  the  production  of  the 
metamorphic  rocks.  But,  on  the  other  hand,  the  length  of  time 
which  must  have  been  consumed  during  the  escape  of  so  much  heat 
from  molten  matter  underlying  the  solid  crust,  at  the  depth  of  many 
miles,  raises  our  conception  of  the  great  original  intensity  of  temper- 
ature required  to  bring  those  subterranean  sheets  of  lava  into  a  liquid 
state.  That  they  are  sometimes  of  vast  horizontal  extent,  even  hun- 
dreds of  miles  in  length,  seems  proved  by  facts  observed  during  erup- 
tions in  the  volcanic  region  of  the  Andes. 

The  scorching  heat  radiated  by  lava  in  a  volcanic  crater,  when  it 
is  white  and  glowing  like  the  sun,  prepares  us  to  believe  that  the 
temperature  of  the  same  fluid  thousands  of  fathoms  below,  must  far 
exceed  any  heat  which  can  ever  be  witnessed  at  the  surface.  The 
uniform  composition,  the  absence  of  stratification,  and  the  great  vol- 

*  Jam.  Ed.  New  Phil.  Journ.,  No.  51,  p.  43. 


CH.  XXXV.]        ORIGIN  OF  METAMORPHIC  STRUCTURE.  743 

ume  of  the  plutonic  rocks,  is  in  perfect  accordance  with  the  Huttonian 
hypothesis  of  the  intense  heat  to  which  this  class  of  rocks  has  owed 
its  origin. 

In  considering,  then,  the  various  data  already  enumerated,  the 
forms  of  stratification  and  lamination  in  metamorphic  rocks,  their 
passage  on  the  one  hand  into  the  fossiliferous,  and  on  the  other  into 
the  plutonic  formations,  and  the  conversions  which  can  be  ascer- 
tained to  have  occurred  in  the  vicinity  of  granite,  we  may  conclude 
that  gneiss  and  mica-schist  may  be  nothing  more  than  altered  mica- 
ceous and  argillaceous  sandstones,  that  granular  quartz  may  have  been 
derived  from  siliceous  sandstone,  and  compact  quartz  from  the  same 
materials.  Clay-slate  may  be  altered  shale,  and  granular  marble  may 
have  originated  in  the  form  of  ordinary  limestone,  replete  with  shells 
and  corals,  which  have  since  been  obliterated ;  and,  lastly,  calcareous 
sands  and  marls  may  have  been  changed  into  impure  crystalline  lime- 
stones. 

"Hornblende-schist,"  says  Dr.  MacCulloch,  "may  at  first  have 
been  mere  clay ;  for  clay  or  shale  is  found  altered  by  trap  into  Lydian 
stone,  a  substance  differing  from  hornblende-schist  almost  solely  in 
compactness  and  uniformity  of  texture."  *  "  In  Shetland,"  remarks 
the  same  author,  "  argillaceous-schist  (or  clay-slate),  when  in  contact 
with  granite,  is  sometimes  converted  into  hornblende-schist,  the  schist 
becoming  first  siliceous,  and  ultimately,  at  the  contact,  hornblende- 
schist."  f 

The  anthracite  and  plumbago  associated  with  hypogene  rocks  may 
have  been  coal ;  for  not  only  is  coal  converted  into  anthracite  in  the 
vicinity  of  some  trap  dikes,  but  we  have  seen  that  a  like  change  has 
taken  place  generally  even  far  from  the  contact  of  igneous  rocks,  in 
the  disturbed  region  of  the  Appalachians.];  At  Worcester,  in  the 
State  of  Massachusetts,  45  miles  due  west  of  Boston,  a  bed  of  plum- 
bago and  impure  anthracite  occurs,  interstratified  with  mica-schist. 
It  is  about  2  feet  in  thickness,  and  has  been  made  use  of  both  as  fuel 
and  in  the  manufacture  of  lead  pencils.  At  the  distance  of  30  mijes 
from  the  plumbago,  there  occurs,  on  the  borders  of  Rhode  Island,  an 
impure  anthracite  in  slates  containing  impressions  of  coal-plants  of 
the  genera  Pecopteris,  Neuropteris,  Calamites,  &c.  This  anthracite  is 
intermediate  in  character  between  that  of  Pennsylvania  and  the  plum- 
bago of  Worcester,  in  which  last  the  gaseous  or  volatile  matter 
(hydrogen,  oxygen,  and  nitrogen)  is  to  the  carbon  only  in  the  pro- 
portion of  3  per  cent.  After  traversing  the  country  in  various  direc- 
tions, I  came  to  the  conclusion  that  the  carboniferous  shales  or  slates 
with  anthracite  and  plants,  which  in  Rhode  Island  often  pass  into 
mica-schist,  have  at  Worcester  assumed  a  perfectly  crystalline  and 


*  Syst.  of  GeoL,  vol.  i.  p.  210. 

f  Ibid.,  p.  211. 

j  See  above,  pp.  497,  503. 


ORIGIN  OF  METAMORPHIC  STRUCTURE.        [Cii.  XXXV. 

metamorphic  texture ;  the  anthracite  having  been  nearly  transmuted 
into  that  state  of  pure  carbon  which  is  called  plumbago  or  graphite.* 

It  has  been  remarked  by  M.  Delesse  that  the  minerals  developed  in 
hypogene  limestone  vary  according  to  the  degree  of  metamorphism 
which  the  rock  has  undergone.  Thus,  for  example,  where  the  struc- 
ture is  but  slightly  crystalline,  talc,  chlorite,  serpentine,  andalusite,  and 
kyanite  are  commonly  present ;  where  it  is  more  highly  crystallized, 
garnet,  hornblende,  wallastonite,  dipyre,  couzeranite,  and  some  others 
appear ;  and,  lastly,  where  the  crystallization  is  complete,  there  are 
found,  in  addition  to  many  of  the  above  minerals,  felspar,  especially 
those  kinds  which  are  richest  in  alkali,  together  with  mica.  The 
same  author  observes  that,  as  calcareous  deposits  usually  contain  some 
aluminous  clay,  so  we  may  naturally  expect  to  meet  with  silicates  of 
alumina  in  crystalline  limestone ;  such  silicates,  accordingly,  are  fre- 
quent, and  occasionally  even  pure  alumina  crystallized  in  the  form  of 
corundum.f 

Mr.  Dana  has  suggested  that  the  phosphoric  acid  of  phosphate  of 
lime,  and  the  fluor  of  fluor-spar,  so  often  met  with  in  crystalline  lime- 
stones, may  have  been  derived  from  the  remains  of  mollusca,  and  other 
animals;  also  that  graphite  (which  is  pure  carbon  in  a  crystalline 
form,  with  or  without  admixture  of  alumina,  lime,  or  iron)  may 
have  been  derived  from  vegetable  remains  imbedded  in  the  original 
matrix. 

The  total  absence  of  any  trace  of  fossils  has  inclined  many  geologists 
to  attribute  the  origin  of  the  crystalline  strata  to  a  period  antecedent 
to  the  existence  of  organic  beings.  Admitting,  they  say,  the  oblitera- 
tion, in  some  cases,  of  fossils  by  plutonic  action,  we  might  still  expect 
that  traces  of  them  would  oftener  occur  in  certain  ancient  systems  of 
slate,  in  which,  as  in  Cumberland,  some  conglomerates  occur.  But  in 
urging  this  argument,  it  seems  to  have  been  forgotten  that  there  are 
stratified  formations  of  enormous  thickness,  and  of  various  ages,  and 
some  of  them  very  modern,  all  formed  after  the  earth  had  become  the 
abode  of  living  creatures,  which  are,  nevertheless,  in  certain  districts, 
entirely  destitute  of  all  vestiges  of  organic  bodies.  In  some,  the 
traces  of  fossils  may  have  been  effaced  by  water  and  acids,  at  many 
successive  periods ;  and  it  is  clear,  that  the  older  the  stratum,  the 
greater  is  the  chance  of  its  being  nonfossiliferous,  even  if  it  has  escaped 
all  metamorphic  action. 

It  has  been  also  objected  to  the  metamorphic  theory,  that  the 
chemical  composition  of  the  secondary  strata  differs  essentially  from 
that  of  the  crystalline  schists,  into  which  they  are  supposed  to  be  con- 
vertible.;); The  "  primary  "  schists,  it  is  said,  usually  contain  a  consider- 
able proportion  of  potash,  or  of  soda,  which  the  secondary  clays, 

*  See  Lyell,  Quart.  Geol.  Journ.,  vol.  i.  p.  199. 

|  Delesse,  Bulletin  Soc.  Geol.  France,  2e  serie,  torn.  ix.  p.  126,  1851. 

|  Dr.  Boase,  Primary  Geology,  p.  319. 


CH.  XXXV.]       OBJECTIONS  TO  METAMORPHIC  THEORY.  74.5 

shales,  and  slates  do  not,  these  last  being  the  result  of  the  decomposi- 
tion of  felspathic  rocks,  from  which  the'  alkaline  matter  has  been  ab- 
stracted during  the  process  of  decomposition.  But  this  reasoning 
proceeds  on  insufficient  and  apparently  mistaken  data;  for  a  large 
portion  of  what  is  usually  called  clay,  marl,  shale,  and  slate,  does  actu- 
ally contain  a  certain,  and  often  a  considerable  proportion  of  alkali ; 
so  that  it  is  difficult,  in  many  countries,  to  obtain  clay  or  shale  suf- 
ficiently free  from  alkaline  ingredients  to  allow  of  their  being  burnt 
into  bricks  or  used  for  pottery. 

Thus  the  argillaceous  shales  and  slates  of  the  Old  Red  sandstone, 
in  Forfarshire  and  other  parts  of  Scotland,  are  so  much  charged  with 
alkali,  derived  from  triturated  felspar,  that,  instead  of  hardening  when 
exposed  to  fire,  they  sometimes  melt  into  a  glass.  They  contain  no 
lime,  but  appear  to  consist  of  extremely  minute  grains  of  the  various 
ingredients  of  granite,  which  are  distinctly  visible  in  the  coarser- 
grained  varieties,  and  in  almost  all  the  interposed  sandstones.  These 
laminated  clays  and  shales  might  certainly,  if  crystallized,  resemble  in 
composition  many  of  the  primary  strata. 

There  is  also  potash  in  fossil  vegetable  remains,  and  soda  in  the 
salts  by  which  strata  are  sometimes  so  largely  impregnated,  as  in 
Patagonia.  But  recent  analysis  may  be  said  to  have  settled  the 
point  at  issue,  by  demonstrating  that  the  carboniferous  strata  in 
England,*  the  Upper  and  Lower  Silurian  in  East  Canada,f  and  the 
clay-slates  (of  Cambrian  or  Laurentian  date  ?)  in  Norway^  all  contain 
as  much  alkali  as  is  generally  present  in  metaniorphic  rocks. 

Another  objection  has  been  derived  from  the  alternation  of  highly 
crystalline  strata  with  others  having  a  less  crystalline  texture.  The 
heat,  it  is  said,  in  its  ascent  from  below  must  have  traversed  the  less 
altered  schists  before  it  reached  a  higher  and  more  crystalline  bed. 
In  answer  to  this,  it  may  be  observed,  that  if  a  number  of  strata 
differing  greatly  in  composition  from  each  other  be  subjected  to 
equal  quantities  of  heat,  or  hydrothermal  action,  there  is  every 
probability  that  some  will  be  much  more  fusible  or  soluble  than 
others.  Some,  for  example,  will  contain  soda,  potash,  lime,  or  some 
other  ingredient  capable  of  acting  as  a  flux  or  solvent ;  while  others 
may  be  destitute  of  the  same  elements,  and  so  refractory  as  to  be 
very  slightly  affected  by  the  same  causes.  Nor  should  it  be  forgot- 
ten that,  as  a  general  rule,  the  less  crystalline  rocks  do  really  occur  in 
the  upper,  and  the  more  crystalline  in  the  lower  part  of  each  meta- 
morphic  series. 

Moreover,  metamorphism  must  often  begin  to  exert  its  force  long 
after  the  strata  have  assumed  a  vertical  position,  and  it  may  then  act 
locally  or  within  limited  areas,  and  will  be  as  likely  to  affect  the 


*  H.  Taylor,  Edin.  New  Phil.  Journ.,  vol.  1.,  1851,  p.  140. 

f  Hunt,  Phil.  Mag.,  4th  ser.,  vol.  vii.  p.  237. 

|  Kyersly,  Norsk,  Mag.  for  Naturvidenp.,  vol.  viii.  p.  172. 


746  METAMORPHIC  ROCKS.  [Cn.  XXXVI. 

newer  as  the  older  beds.  As  an  illustration  of  such  partial  conver- 
sion into  gneiss  of  portions  of  a  highly  inclined  set  of  beds,  I  may 
cite  Sir  R.  Murchison's  memoir  on  the  structure  of  the  Alps.  Slates 
provincially  termed  "  flysch  "  (see  above,  p.  30Y),  overlying  the  num- 
mulitic  limestone  of  Eocene  date,  and  comprising  some  arenaceous 
and  some  calcareous  layers,  are  seen  to  alternate  several  times  with 
bands  of  granitoid  rock,  answering  in  character  to  gneiss.*  In  this 
case  heat,  vapor,  or  water  at  a  high  temperature  may  have  traversed 
the  more  permeable  beds,  and  altered  them  so  far  as  to  admit  of  an 
internal  movement  and  rearrangement  of  the  molecules,  while  the 
adjoining  strata  did  not  give  passage  to  the  same  heated  gases  or 
water,  or,  if  so,  remained  unchanged  because  they  were  composed  of 
less  fusible  or  decomposable  materials.  Whatever  hypothesis  we 
adopt,  the  phenomena  establish  beyond  a  doubt  the  possibility  of  the 
development  of  the  metamorphic  structure  in  a  tertiary  deposit  in 
planes  parallel  to  those  of  stratification. 

Whether  such  parallelism  be  the  rule  or  the  exception  in  gneiss, 
mica-schist,  and  other  formations  of  the  same  family,  is  a  question 
which  I  shall  discuss  at  length  in  the  next  chapter. 


CHAPTER  XXXVI. 

METAMORPHIC  ROCKS,  continued. 

Definition  of  joints,  slaty  cleavage,  and  foliation — Supposed  causes  of  these  struc- 
tures— Mechanical  theory  of  cleavage — Condensation  and  elongation  of  slate 
rocks  by  lateral  pressure — Supposed  combination  of  crystalline  and  mechanical 
forces — Lamination  of  some  volcanic  rocks  due  to  motion — Whether  the  folia- 
tion of  the  crystalline  schists  be  usually  parallel  with  the  original  planes  of  strati- 
fication— Examples  in  Norway  and  Scotland — Foliation  in  homogeneous  rocks 
may  coincide  with  planes  of  cleavage,  and  in  uncleaved  rocks  with  those  of 
stratification — Causes  of  irregularity  in  the  planes  of  foliation. 

WE  have  already  seen  that  chemical  forces  of  great  intensity  have 
frequently  acted  upon  sedimentary  and  fossiliferous  strata  long  subse- 
quently to  their  consolidation,  and  we  may  next  inquire  whether  the 
component  minerals  of  the  altered  rocks  usually  arrange  themselves  in 
planes  parallel  to  the  original  planes  of  stratification,  or  whether, 
after  crystallization,  they  more  commonly  take  up  a  different  position. 

In  order  to  estimate  fairly  the  merits  of  this  question,  we  must 
first  define  what  is  meant  by  the  terms  cleavage  and  foliation.  There 

*  Geol.  Quart.  Journ.,  vol.  v.  p.  211,  1848. 


CH.  XXXVI.]  METAMORPHIC  ROCKS.  747 

are  four  distinct  forms  of  structure  exhibited  in  rocks,  namely,  strati- 
fication, joints,  slaty  cleavage,  and  foliation  ;  and  all  these  must  have 
different  names,  even  though  there  be  cases  where  it  is  impossible, 
after  carefully  studying  the  appearances,  to  decide  upon  the  class  to 
which  they  belong. 

Professor  Sedgwick,  whose  essay  "  On  the  Structure  of  large  Min- 
eral Masses  "  first  cleared  the  way  towards  a  better  understanding  of 
this  difficult  subject,  observes,  that  joints  are  distinguishable  from 
lines  of  slaty  cleavage  in  this,  that  the  rock  intervening  between  two 
joints  has  no  tendency  to  cleave  in  a  direction  parallel  to  the  planes 
of  the  joints,  whereas  a  rock  is  capable  of  indefinite  subdivision  in 
the  direction  of  its  slaty  cleavage.  In  cases  where  the  strata  are 
curved,  the  planes  of  cleavage  are  still  perfectly  parallel.  This  has 
been  observed  in  the  slate  rocks  of  part  of  Wales  (see  fig.  758), 


Fig.  75a 


Parallel  planes  of  cleavage  intersecting  curved  strata.    (Sedgwick.) 

which  consist  of  a  hard  greenish  slate.  The  true  bedding  is  there 
indicated  by  a  number  of  parallel  stripes,  some  of  a  lighter  and  some 
of  a  darker  color  than  the  general  mass.  Such  stripes  are  found  to 
be  parallel  to  the  true  planes  of  stratification,  wherever  these  are 
manifested  by  ripple-mark,  or  by  beds  containing  peculiar  organic 
remains.  Some  of  the  contorted  strata  are  of  a  coarse  mechanical 
structure,  alternating  with  fine-grained  crystalline  chloritic  slates,  in 
which  case  the  same  slaty  cleavage  extends  through  the  coarser  and 
finer  beds,  though  it  is  brought  out  in  greater  perfection  in  propor- 
tion as  the  materials  of  the  rock  are  fine  and  homogeneous.  It  is 
only  when  these  are  very  coarse  that  the  cleavage  planes  entirely  van- 
ish. These  planes  are  usually  inclined  at  a  very  considerable  angle  to 
the  planes  of  the  strata.  In  the  Welsh  hills,  for  example,  the  average 
angle  is  as  much  as  from  30°  to  40°.  Sometimes  the  cleavage  planes 
dip  towards  the  same  point  of  the  compass  as  those  of  stratification, 
but  more  frequently  to  opposite  points.  It  may  be  stated  as  a  gen- 
eral rule,  that  when  beds  of  coarser  materials  alternate  with  those 
composed  of  finer  particles,  the  slaty  cleavage  is  either  entirely  con- 
fined to  the  fine-grained  rock,  or  is  very  imperfectly  exhibited  in  that 
of  coarser  texture.  This  rule  holds,  whether  the  cleavage  is  parallel 
to  the  planes  of  stratification  or  not.* 

In  regard  to  joints,  they  are  natural  fissures  which  often  traverse 
rocks   in   straight   and  well-determined  lines.     They  afford  to   the 

*  Geol.  Trans.,  Second  Series,  vol.  iii.  p.  461. 


748  JOINTED   STRUCTURE  AND   CLEAVAGE.       [Cn.  XXXVI. 

quarryman,  as  Sir  R.  Murchison  observes,  when  speaking  of  the  phe- 
nomena, as  exhibited  in  Shropshire  and  the  neighboring  counties, 
the  greatest  aid  in  the  extraction  of  blocks  of  stone ;  and,  if  a  sufficient 
number  cross  each  other,  the  whole  mass  of  rock  is  split  into  symmet- 
rical blocks.  The  faces  of  the  joints  are  for  the  most  part  smoother 
and  more  regular  than  the  surfaces  of  true  strata.  The  joints  are 
straight-cut  chinks,  often  slightly  open,  often  passing,  not  only  through 
layers  of  successive  deposition,  but  also  through  balls  of  limestone  or 
other  matter  which  have  been  formed  by  concretionary  action,  since 
the  original  accumulation  of  the  strata.  Such  joints,  therefore,  must 
often  have  resulted  from  one  of  the  last  changes  superinduced  upon 
sedimentary  deposits.* 

In  the  annexed  diagram  (fig.  759),  the  flat  surfaces  of  rock  A,  B,  c, 

Fig.  759. 


Stratification,  joints,  and  cleavage. 
(From  Murchison's  Silurian  System,  p.  245.) 

represent  exposed  faces  of  joints,  to  which  the  walls  of  other  joints, 
j  j,  are  parallel,  s  s  are  the  lines  of  stratification ;  D  D  are  lines  of 
slaty  cleavage,  which  intersect  the  rock  at  a  considerable  angle  to  the 
planes  of  stratification. 

In  the  Swiss  and  Savoy  Alps,  as  Mr.  Bakewell  has  remarked,  enor- 
mous masses  of  limestone  are  cut  through  so  regularly  by  nearly  ver- 
tical partings,  and  these  joints  are  often  so  much  more  conspicuous 
than  the  seams  of  stratification,  that  an  inexperienced  observer  will 
almost  inevitably  confound  them,  and  suppose  the  strata  to  be  perpen- 
dicular in  places  where  in  fact  they  are  almost  horizontal.f 

Now  such  joints  are  supposed  to  be  analogous  to  the  partings 
which  separate  volcanic  and  plutonic  rocks  into  cuboidal  and  pris- 
matic masses.  On  a  small  scale  we  see  clay  and  starch  when  dry 
split  into  similar  shapes ;  this  is  often  caused  by  simple  contraction, 
whether  the  shrinking  be  due  to  the  evaporation  of  water,  or  to  a 
change  of  temperature.  It  is  well  known  that  many  sandstones  and 
other  rocks  expand  by  the  application  of  moderate  degrees  of  heat, 
and  then  contract  again  on  cooling ;  and  there  can  be  no  doubt  that 

*  Silurian  System,  p.  246.  f  Introduction  to  Geology,  chap.  iv. 


CH.  XXXVL]  SLATY  CLEAVAGE.  Y49 

large  portions  of  the  earth's  crust  have,  in  the  course  of  past  ages,  been 
subjected  again  and  again  to  very  different  degrees  of  heat  and  cold. 
These  alternations  of  temperature  have  probably  contributed  largely 
to  the  production  of  joints  in  rocks. 

In  some  countries,  as  in  Saxony,  where  masses  of  basalt  rest  on 
sandstone,  the  aqueous  rock  has  for  the  distance  of  several  feet  from 
the  point  of  junction  assumed  a  columnar  structure  similar  to  that  of 
the  trap.  In  like  manner  some  hearthstones,  after  exposure  to  the 
heat  of  a  furnace  without  being  melted,  have  become  prismatic. 
Certain  crystals  also  acquire  by  the  application  of  heat  a  new  internal 
arrangement,  so  as  to  break  in  a  new  direction,  their  external  form 
remaining  unaltered. 

Professor  Sedgwick,  speaking  of  the  planes  of  slaty  cleavage,  where 
they  are  decidedly  distinct  from  those  of  sedimentary  deposition, 
declared,  in  the  essay  before  alluded  to,  his  opinion  that  no  retreat  of 
parts,  no  contraction  in  the  dimensions  of  rocks  in  passing  to  a  solid 
state,  can  account  for  the  phenomenon.  He  accordingly  referred  it 
to  crystalline  or  polar  forces  acting  simultaneously,  and  somewhat 
uniformly,  in  given  directions,  on  large  masses  having  a  homogeneous 
composition. 

Sir  John  Herschel,  in  allusion  to  slaty  cleavage,  has  suggested, 
"  that  if  rocks  have  been  so  heated  as  to  allow  a  commencement  of 
crystallization — that  is  to  say,  if  they  have  been  heated  to  a  point  at 
which  the  particles  can  begin  to  move  amongst  themselves,  or  at  least 
on  their  own  axes,  some  general  law  must  then  determine  the  position 
in  which  these  particles  will  rest  on  cooling.  Probably  that  position 
will  have  some  relation  to  the  direction  in  which  the  heat  escapes. 
Now,  when  all,  or  a  majority  of  particles  of  the  same  nature  have  a 
general  tendency  to  one  position,  that  must  of  course  determine  a 
cleavage-plane.  Thus  we  see  the  infinitesimal  crystals  of  fresh  pre- 
cipitated sulphate  of  barytes,  and  some  other  such  bodies,  arrange 
themselves  alike  in  the  fluid  in  which  they  float ;  so  as,  when  stirred, 
all  to  glance  with  one  light,  and  give  the  appearance  of  silky  filaments. 
Some  sorts  of  soap,  in  which  insoluble  margarates  *  exist,  exhibit  the 
same  phenomenon  when  mixed  with  water ;  and  what  occurs  in  our 
experiments  on  a  minute  scale  may  occur  in  nature  on  a  great  one."  f 

Professor  Phillips  has  remarked  that  in  some  slaty  rocks  the  form 
of  the  outline  of  fossil  shells  and  trilobites  has  been  much  changed  by 
distortion,  which  has  taken  place  in  a  longitudinal,  transverse,  or 
oblique  direction.  This  change,  he  adds,  seems  to  be  the  result  of 
a  "  creeping  movement "  of  the  particles  of  the  rock  along  the  planes 
of  cleavage,  its  direction  being  always  uniform  over  the  same  tract 
of  country,  and  its  amount  in  space  being  sometimes  measurable,  and 

*  Margaric  acid  is  an  oleaginous  acid,  formed  from  different  animal  and  vegeta- 
ble fatty  substances.  A  margarate  is  a  compound  of  this  acid  with  soda,  potash, 
or  some  other  base,  and  is  so  named  from  its  pearly  lustre. 

f  Letter  to  the  author,  dated  Cape  of  Good  Hope,  Feb.  20,  1836. 


750 


SLATE  ROCK  OF  NORTH  DEVON. 


[On.  XXXVI. 


Fig.  760. 


being  as  much  as  a  quarter  or  even  half  an  inch.  The  hard  shells  are 
not  affected,  but  only  those  which  are  thin.*  Mr.  D.  Sharpe,  follow- 
ing up  the  same  line  of  inquiry,  came  to  the  conclusion  that  the 
present  distorted  forms  of  the  shells  in  certain  British  slate  rocks  may 
be  accounted  for  by  supposing  that  the  rocks  in  which  they  are  im- 
bedded have  undergone  compression  in  a  direction  perpendicular  to 
the  planes  of  cleavage,  and  a  corresponding  expansion  in  the  direction 

of  the  dip  of  the  cleavage.f 

Subsequently  (1853)  Mr.  Sorby 
demonstrated  the  great  extent  to 
which  this  mechanical  theory  is 
applicable  to  the  slate  rocks  of 
North  Wales  and  Devonshire,^  dis- 
tricts where  the  amount  of  change 
in  dimensions  can  be  tested  and 
measured  by  comparing  the  differ- 
ent effects  exerted  by  lateral  pres- 
sure on  alternating  beds  of  finer  and 
coarser  materials.  Thus,  for  exam- 
ple, in  the  accompanying  figure  (fig. 
760)  it  will  be  seen  that  the  sandy 
bed  df,  which  has  offered  greater 
resistance,  has  been  sharply  con- 
torted, while  the  fine-grained  strata, 
a,  6,  c,  have  remained  comparatively 
unbent.  The  points  d  and  /  in  the 
stratum  df  must  have  been  origi- 
nally four  times  as  far  apart  as  they 
are  now.  They  have  been  forced 
so  much  nearer  to  each  other,  partly 
by  bending  and  partly  by  becoming 
elongated  in  the  direction  of  what 
may  be  called  the  longer  axes  of 
their  contortions,  and  lastly,  to  a 
certain  small  amount,  by  condensa- 
tion. The  chief  result  has  obviously 
been  due  to  the  bending;  but,  in 
proof  of  elongation,  it  will  be  ob- 
served that  the  thickness  of  the  bed 
df  is  now  about  four  times  greater 
in  those  parts  lying  in  the  main 
direction  of  the  flexures  than  in  a  plane  perpendicular  to  them  ;  and 
the  same  bed  exhibits  cleavage-planes  in  the  direction  of  the  greatest 

*  Report,  Brit.  Assoc.,  Cork,  1843,  Sect.  p.  60. 
f  Quart.  Geol.  Journ.,  vol.  iii.  p.  87,  1847. 

J  On  the  Origin  of  Slaty  Cleavage,  by  H.  C.  Sorby,  Edinb.  New  Phil.  Joura., 
1853,  vol.  Iv.  p.  137. 


(Drawn  by  II.  C.  Sorby.) 

Vertical  section  of  slate  rock  in  the  cliffs 

near  Ilfracombe,  North  Devon. 

Scale  one  inch  to  one  foot. 
a,  &,  c,  e.    Fine-grained  slates,  the  stratifi- 
cation being  shown  partly  by  lighter,  or 
darker  colors,  and  partly  by  different  de- 
grees of  fineness  in  the  grain. 
d,  f.  A  coarser-grained  light-colored  sandy 
slate  with  less  perfect  cleavage. 


CH.  XXXVL]  SLATE  ROCK  OF  NORTH  DEVON.  Y51 

movement,  although  they  are  much  fewer  than  in  the  slaty  strata 
above  and  below. 

Above  the  sandy  bed  d  /,  the  stratum  c  is  somewhat  disturbed,  while 
the  next  bed  b  is  much  less  so,  and  a  not  at  all ;  yet  all  these  beds  c,  6, 
and  a,  must  have  undergone  an  equal  amount  of  pressure  with  c£,  the 
points  a  and  g  having  approximated  as  much  towards  each  other  as  have 
d  and  /.  The  same  phenomena  are  also  Repeated  in  the  beds  below  c?, 
and  might  have  been  shown,  had  the  section  been  extended  downwards. 
Hence  it  appears  that  the  finer  beds  have  been  squeezed  into  a  fourth  of 
the  space  they  previously  occupied,  partly  by  condensation,  or  the  closer 
packing  of  their  ultimate  particles  (which  has  given  rise  to  the  great 
specific  gravity  of  such  slates),  and  partly  by  elongation  in  the  line  of 
the  dip  of  the  cleavage,  of  which  the  general  direction  is  perpendicular 
to  that  of  the  pressure.  "  These  and  numerous  other  cases  in  North 
Devon  are  analogous,"  says  Mr.  Sorby,  "to  what  would  occur  if  a 
strip  of  paper  were  included  in  a  mass  of  some  soft  plastic  material 
which  would  readily  change  its  dimensions.  If  the  whole  were  then 
compressed  in  the  direction  of  the  length  of  the  strip  of  paper,  it 
would  be  bent  and  puckered  up  into  contortions,  whilst  the  plastic 
material  would  readily  change  its  dimensions  without  undergoing  such 
contortions ;  and  the  difference  in  distance  of  the  ends  of  the  paper, 
as  measured  in  a  direct  line  or  along  it,  would  indicate  the  change  in 
the  dimensions  of  the  plastic  material." 

The  student  will  readily  conceive  that,  when  the  shape  of  a  fossil 
or  of  a  crystal  of  some  mineral,  or  of  a  spheroidal  concretion,  has 
been  altered  by  lateral  pressure,  the  new  forms  which  they  assume 
respectively  will  vary  according  to  whether  they  have  yielded  in  one 
or  more  directions.  They  may  have  been  drawn  out  solely  in  the 
direction  of  the  dip  of  the  cleavage,  or  they  may  have  yielded  in  a 
plane  perpendicular  to  that  dip,  or  they  may  have  undergone  both 
these  movements.  By  microscopic  examination  of  minute  crystals, 
and  by  other  observations  too  minute  to  be  detailed  here,  Mr.  Sorby 
comes  to  the  conclusion  that  the  absolute  condensation  of  the  slate 
rocks  amounts  upon  an  average  to  about  one-half  their  original  vol- 
ume. This  must  have  resulted  chiefly  from  the  forcing  of  the  particles 
more  closely  together,  so  as  to  fill  up  the  spaces  left  between  them, 
when  they  only  touched  each  other.  The  rest  of  the  change  has  been 
due  to  elongation  which  has  produced  slaty  cleavage. 

Most  of  the  scales  of  mica  occurring  in  certain  slates  examined  by 
Mr.  Sorby  lie  in  the  plane  of  cleavage  ;  whereas  in  a  similar  rock  not 
exhibiting  cleavage  they  lie  with  their  longer  axes  in  all  directions. 
May  not  their  position  in  the  slates  have  been  determined  by  the 
movement  of  elongation  before  alluded  to  ?  To  illustrate  this  theory 
some  scales  of  oxide  of  iron  were  mixed  with  soft  pipe-clay  in  such  a 
manner  that  they  inclined  in  all  directions.  The  dimensions  of  the 
mass  were  then  changed  artificially  to  a  similar  extent  to  what  has 
occurred  in  slate  rocks,  and  the  pipe-clay  was  then  dried  and  baked. 


752  CONDENSATION  OF  SLATE  ROCKS.  [On.  XXXVI. 

When  it  was  afterwards  rubbed  to  a  flat  surface  perpendicular  to  the 
pressure  and  in  the  line  of  elongation,  or  in  a  plane  corresponding 
to  that  of  the  dip  of  cleavage,  the  particles  were  found  to  have  be- 
come arranged  in  the  same  manner  as  in  natural  slates,  and  the 
mass  admitted  of  easy  fracture  into  thin  flat  pieces  in  the  plane 
alluded  to,  whereas  it  would  not  yield  in  that  perpendicular  to  the 
cleavage.* 

Dr.  Tyndall,  when  commenting  in  1856  on  Mr.  Sorby's  experi- 
ments, observed  that  pressure  alone  is  sufficient  to  produce  cleavage, 
and  that  the  intervention  of  plates  of  mica  or  scales  of  oxide  of  iron, 
or  any  other  substances  having  flat  surfaces,  is  quite  unnecessary.  In 
proof  of  this  he  showed  experimentally  that  a  mass  of  "  pure  white 
wax  after  having  been  submitted  to  great  pressure,  exhibited  a  cleav- 
age more  clean  than  that  of  any  slate-rock,  splitting  into  lamina  of 
surpassing  tenuity."  f  He  remarks  that  every  mass  of  clay  or  mud 
is  divided  and  subdivided  by  surfaces  among  which  the  cohesion  is 
comparatively  small.  On  being  subjected  to  pressure,  such  masses 
yield  and  spread  out  in  the  direction  of  least  resistance,  small  nodules 
become  converted  into  laminae  separated  from  each  other  by  surfaces 
of  weak  cohesion,  and  the  result  is  that  the  mass  cleaves  at  right 
angles  to  the  line  in  which  the  pressure  is  exerted.  The  experiments 
of  Mr.  Sorby  in  reference  to  the  manner  in  which  scales  of  mica  and 
oxide  of  iron  arrange  themselves  in  soft  pipe-clay  under  compression 
have  been  supposed  to  lend  countenance  to  the  opinion  that  the  lami- 
nation of  basalt  and  trachyte,  and  even  of  some  kinds  of  gneiss,  and 
the  grain  of  certain  granites,  may  all  have  been  determined  by  a 
mechanical  cause,  a  movement  having  taken  place  after  the  develop- 
ment of  crystals  in  the  pasty  mass. 

Mr.  Scrope,  in  his  description  of  the  Ponza  Islands,  ascribed  the 
zoned  structure  of  the  Hungarian  perlite  (a  semi-vitreous  trachyte)  to 
its  having  subsided,  in  obedience  to  the  impulse  of  its  own  gravity, 
down  a  slightly  inclined  plane,  while  possessed  of  an  imperfect  fluidity. 
In  the  Islands  of  Ponza  and  Palmarolo,  the  direction  of  the  zones  is 
more  frequently  vertical  than  horizontal,  because  the  mass  was  im- 
pelled from  below  upwards."  J  In  like  manner,  Mr.  Darwin  attributes 
the  lamination  and  fissile  structure  of  volcanic  rocks  of  the  trachytic 
series,  including  some  obsidians  in  Ascension,  Mexico,  and  elsewhere, 
to  their  having  moved  when  liquid  in  the  direction  of  the  laminae. 
The  zones  consist  sometimes  of  layers  of  air-cells  drawn  out  and 
lengthened  in  the  supposed  direction  of  the  moving  mass.  This 
division  into  parallel  zones,  thus  caused  by  the  stretching  of  a  pasty 
mass  as  it  flowed  slowly  onwards,  he  compares  to  the  zoned  or 
ribboned  structure  of  ice,  which  Professor  James  Forbes  has  endeav- 


*  Sorby,  as  cited  above,  p.  750,  note. 

f  Tyndall,  View  of  the  Cleavage  of  Crystals  and  Slate  Rocks. 

\  Geol.  Trans.,  Second  Series,  vol.  ii.  p.  227. 


CH.  XXX VL]         FOLIATION  OF  CRYSTALLINE  ROCKS.  753 

ored  to  explain  by  referring  to  the  fissuring  of  a  viscous  body  in 
motion.* 

Whatever  be  the  cause,  the  result,  observes  Darwin,  is  well  worthy 
the  attention  of  geologists ;  for,  in  a  volcanic  rock  of  the  trachytic 
series  in  Ascension,  layers  are  seen  often  of  extreme  tenuity,  even  as 
thin  as  hairs,  and  of  different  colors,  alternating  again  and  again,  some 
of  them  composed  of  crystals  of  quartz  and  diopside  (a  kind  of  augite), 
others  of  black  augitic  specks  with  granules  of  oxide  of  iron,  and 
lastly,  others  of  crystalline  felspar.  It  is  supposed  in  this  case  that 
the  crystallizing  force  acted  more  freely  in  the  direction  of  the  planes 
of  cleavage,  produced  when  the  pasty  mass  was  stretched,  whether 
because  confined  vapors  were  enabled  to  spread  themselves  through 
the  minute  fissures,  or  because  the  ultimate  molecules  had  more  free- 
dom of  motion  along  the  planes  of  less  tension,  or  for  some  other  rea- 
sons not  yet  understood. 

After  studying,  in  1835,  the  crystalline  rocks  of  South  America, 
Mr.  Darwin  proposed  the  term  foliation  for  the  laminae  or  plates  into 
which  gneiss,  mica-schist,  and  other  crystalline  rocks  are  divided. 
Cleavage,  he  observes,  may  be  applied  to  those  divisional  planes  which 
render  a  rock  fissile,  although  it  may  appear  to  the  eye  quite  or  nearly 
homogeneous.  Foliation  may  be  used  for  those  alternating  layers  or 
plates  of  different  mineralogical  nature  of  which  gneiss  and  other 
metamorphic  schists  are  composed.  The  cleavage  planes  of  the  clay- 
slate  in  Terra  del  Fuego  and  Chili  preserve  a  uniform  strike  for  hun- 
dreds  of  miles  in  regions  where  these  planes  are  quite  distinct  from 
stratification.  In  the  same  country  the  planes  of  foliation  of  the  mica- 
schist  and  gneiss  are  parallel  to  the  cleavage  of  the  clay-slate.  Hence 
we  are  tempted,  at  first  sight,  to  infer  that  some  common  cause  or  pro- 
cess, and  that  cause  not  connected  with  sedimentary  deposition,  has 
impressed  cleavage  on  the  one  set  of  rocks  and  foliation  on  the  other. 
But  such  an  inference  can  only  be  legitimately  drawn  in  those  rare 
cases  where  we  are  able,  by  a  continuous  section,  to  prove  that  not 
only  the  strike,  but  the  dip  of  the  slaty  cleavage  on  the  one  hand,  and 
of  the  foliation  on  the  other,  precisely  coincide ;  the  cleavage  at  the 
same  time  not  being  parallel  to  the  stratification  in  the  slate  rock.  In 
some  examples  cited  by  Mr.  Darwin,  in  Terra  del  Fuego,  the  Chonos 
Islands,  and  La  Plata,  this  uniformity  of  dip  seems  to  have  'been 
traced  in  a  manner  as  satisfactory  as  the  nature  of  such  evidence  will 
allow.  But  we  must  be  on  our  guard  against  a  source  of  deception 
which  may  mislead  us  in  this  chain  of  reasoning.  We  are  informed 
that  in  South  America,  as  in  other  countries,  the  strike  of  the  cleav- 
age in  clay-slate  conforms  to  the  axis  of  elevation  of  the  rocks  in  the 
same  districts.  Hence  it  must  follow  that  the  folia  of  gneiss,  mica- 
schist,  limestone,  and  other  crystalline  rocks,  even  if  they  strictly 
coincide  with  the  planes  of  original  stratification,  will  run  in  the  same 

*  Darwin,  Volcanic  Islands,  pp.  69,  70. 
48 


754  FOLIATION  OF  CRYSTALLINE  ROCKS.         [Cn.  XXXVI. 

direction  as  the  strike  of  the  slaty  cleavage ;  for  the  true  strata  always 
dip  at  right  angles  to  the  axis  of  elevation,  and  are  parallel  to  it  in 
their  strike.  No  argument,  therefore,  can  be  drawn  in  favor  of  a  com- 
mon origin  from  uniformity  of  strike  in  the  slaty  and  foliated  rocks ; 
for  we  require,  in  addition,  coincidence  of  dip;  and  such  is  the 
variability  of  the  dip  both  of  the  slates  and  folia  as  to  render  this  kind 
of  proof  very  difficult  to  obtain. 

That  the  planes  of  foliation  of  the  crystalline  schists  in  Norway 
accord  very  generally  with  those  of  original  stratification  is  a  con- 
clusion long  since  espoused  by  Keilhau.*  Numerous  observations 
made  by  Mr.  David  Forbes  in  the  same  country  (the  best  probably 
in  Europe  for  studying  such  phenomena  on  a  grand  scale)  confirm 
Keilhau's  opinion.  In  Scotland,  also,  Mr.  D.  Forbes  has  pointed  out 
a  striking  case  where  the  foliation  is  identical  with  the  lines  of  strati- 
fication in  rocks  well  seen  near  Crianlorich  on  the  road  to  Tyndrum, 
about  8  miles  from  Inverarnon  in  Perthshire.  There  is  in  that 
locality  a  blue  limestone  foliated  by  the  intercalation  of  small  plates 
of  white  mica,  so  that  the  rock  is  often  scarcely  distinguishable  in 
aspect  from  gneiss  or  mica-schist.  The  stratification  is  shown  by  the 
large  beds  and  colored  bands  of  limestone  all  dipping,  like  the  folia, 
at  an  angle  of  32  degrees  N.E.f 

In  stratified  formations  of  every  age  we  see  layers  of  siliceous  sand 
with  or  without  mica,  alternating  with  clay,  with  fragments  of  shells 
or  corals,  or  with  seams  of  vegetable  matter,  and  we  should  expect  the 
mutual  attraction  of  like  particles  to  favor  the  crystallization  of  the 
quartz,  or  mica,  or  felspar,  or  carbonate  of  lime  along  the  planes  of 
original  deposition,  rather  than  in  planes  placed  at  angles  of  20  or  40 
degrees  to  those  of  stratification. 

In  Patagonia,  a  series  of  thin  sedimentary  layers  of  tuff  were  ob- 
served by  Mr.  Darwin  to  have  become  porphyritic,  first  where  least 
altered,  by  a  process  of  aggregation,  small  patches  of  clay  appearing 
to  be  shortened  into  almond-shaped  concretions,  which  in  those  places 
where  they  were  more  changed  had  become  crystals  of  felspar,  having 
their  longer  axes  parallel  to  each  other.  In  other  associated  strata, 
grains  of  quartz  had  in  like  manner  aggregated  into  nodules  of  crys- 
talline quartz.J 

May  we  not,  then,  presume  that  in  rocks  where  no  cleavage  has 
intervened,  foliation  and  the  planes  of  stratification  will  usually  co- 
incide, as  in  all  cases  where  cleavage  happens  (as  in  the  writing-slates 
of  the  Niesen  on  the  Lake  of  Thun  in  Switzerland,  containing  fucoids) 
to  agree  with  the  original  planes  of  sedimentary  deposition?  Mr. 
Darwin  conceives  that  "  foliation  may  be  the  extreme  result  of  the 
process  of  which  cleavage  is  the  first  effect ; "  or,  at  any  rate,  that  the 


*  Norske  Mag.  Naturvidsk.,  vol.  i.  p.  71. 

f  Memoir  read  before  the  Geol.  Soc.  London,  Jan.  31,  1856. 

J  South  America,  p.  149. 


CH.  XXXVI.]         CLEAVAGE  OF  CRYSTALLINE  ROCKS.  755 

crystalline  force  may  have  been  most  energetic  in  the  direction  of 
cleavage.  As  bearing  on  this  view,  he  says,  "I  was  particularly 
struck  in  the  eastern  parts  of  Terra  del  Fuego  with  the  fact  that  the 
fine  laminae  of  clay-slate,  where  they  cut  straight  through  the  bands 
of  stratification,  and  therefore  indisputably  true  cleavage-planes,  differ 
slightly  from  one  another  in  their  grayish  and  greenish  tints  of  color, 
as  also  in  their  compactness,  and  in  some  laminae  having  a  more  jas- 
pery  appearance  than  others.  This  fact  shows  that  the  same  cause 
which  has  produced  the  highly  fissile  structure  has  altered  in  a  slight 
degree  the  mineralogical  character  of  the  rock  in  the  same  planes."  * 
As  one  step  farther  towards  tracing  a  passage  from  planes  of  cleavage 
to  those  of  foliation,  Professor  Sedgwick  observes  that  in  North 
Wales  the  surfaces  of  slates  are  sometimes  coated  over  with  chlorite, 
"  the  crystals  of  which  have  not  only  defined  the  cleavage  planes  but 
struck  through  the  whole  mass  of  the  rock."f  So  also,  says  Mr. 
Darwin,  in  some  places  in  South  America  crystals  of  epidote  and  of 
mica  coat  the  planes  of  cleavage. 

There  seems  to  be  no  difficulty  in  imagining  that  in  rocks  of 
homogeneous  composition  the  foliation  may  take  place  along  planes 
previously  caused  by  the  elongation  of  the  materials  along  the  dip  of 
the  cleavage  ;  for  experienced  geologists  have  been  at  a  loss  to  decide 
in  many  countries  which  of  two  sets  of  divisional  planes  were  referable 
to  cleavage,  and  which  to  stratification ;  and,  after  much  doubt,  have 
discovered  that  they  had  at  first  mistaken  the  lines  of  cleavage  for 
those  of  deposition,  because  the  former  were  by  far  the  most  marked 
of  the  two.  Now  if  such  slaty  masses  should  become  highly  crys- 
talline, and  be  converted  into  gneiss,  hornblende-schist,  or  any  other 
member  of  the  hypogene  class,  the  cleavage  planes  might  possibly  re- 
main more  visible  than  those  of  stratification.  Professor  Henslow 
had  noticed,  so  long  ago  as  the  year  1821,  that  the  lamination  of  the 
chloritic  and  other  crystalline  schists  in  Anglesea  was  approximately 
in  the  planes  of  bedding;  and  Professor  Ramsay,  in  1841,  observed 
the  same  in  regard  to  the  gneiss  and  mica-schist  of  Arran.  The  last- 
cited  geologist  says,  in  reference  to  Anglesea,  that  the  metamorphism 
probably  took  place  when  the  Lower  Silurian  volcanoes  were  in  activ- 
ity, and  therefore  long  before  the  cleavage  of  the  Welsh  rocks ;  for 
the  cleavage  of  the  latter  affects  in  common  the  Lower  Silurian  and 
the  Cambrian  strata.  In  the  same  memoir  he  adds,  when  referring  to 
Mr.  Darwin's  theory  of  foliation,  "that  if  the  rocks  be  uncleaved 
when  metamorphism  occurs,  the  foliation  planes  will  be  apt  to  coin- 
cide with  those  of  bedding ;  but  if  intense  cleavage  has  preceded,  then 
we  may  expect  that  the  planes  of  foliation  will  lie  in  the  planes  of 
cleavage."  J 


*  Geol.  Observ.  on  South  America,  p.  155. 

f  Sedgwick,  Geol.  Trans.,  Second  Series,  vol.  iii.  p.  471. 

i  Geol.  Quart.  Journ.,  1853,  vol.  ix.  p.  172. 


756 


IRREGULARITIES  IN  FOLIATION. 


[On.  XXXVI. 


From  what  I  have  myself  seen  in  the  Grampians,  both  in  Forfar- 
shire  and  Perthshire,  I  have  always  concluded  that  MacCulloch  was 
correct  in  the  opinion  that  gneiss  and  mica-schist  may  be  considered 
as  stratified  rocks,  and  that  certain  beds  of  pure  quartz,  one  or  two 
feet  thick,  which  run  for  miles  in  the  strike  of  their  foliation,  as  well 
as  the  intercalation  of  masses  of  limestone,  and  of  chloritic,  actinolitic, 
and  hornblende  schists,  all  indicate  the  planes  of  original  stratification. 
At  the  same  time,  I  fully  admit  that  the  alternate  layers  of  quartz,  or 
of  mica  and  quartz,  of  felspar,  or  of  mica  and  felspar,  or  of  carbonate 
of  lime,  are  more  distinct,  in  certain  metamorphic  rocks,  than  the 
ingredients  composing  alternate  layers  in  most  sedimentary  deposits, 
so  that  similar  particles  must  be  supposed  to  have  exerted  a  molecular 
attraction  for  each  other,  and  to  have  congregated  together  in  layers 
more  distinct  in  mineral  composition  than  before  they  were  crystal- 
lized. 

We  have  seen  how  much  the  original  planes  of  stratification  may 
be  interfered  with  or  even  obliterated  by  concretionary  action  in 
deposits  still  retaining  their  fossils,  as  in  the  case  of  the  magnesian 
limestone  (see  p.  37).  Hence  we  must  expect  to  be  frequently  baffled 
when  we  attempt  to  decide  whether  the  foliation  does  or  does  not 
accord  with  that  arrangement  which  gravitation,  combined  with  cur- 
rent-action, imparted  to  a  deposit  from  water.  Moreover,  when  we 
look  for  stratification  in  crystalline  rocks,  we  must  be  on  our  guard 
not  to  expect  too  much  regularity.  The  occurrence  of  wedge-shaped 
masses,  such  as  belong  to  coarse  sand  and  pebbles — diagonal  lami- 
nation (see  p.  16) — ripple-marked — unconformable  stratification  (p. 
16),  the  fantastic  folds  produced  by  lateral  pressure — faults  of  various 
width — intrusive  dikes  of  trap — organic  bodies  of  diversified  shapes 
— and  other  causes  of  unevenness  in  the  planes  of  deposition,  both  on 
the  small  and  on  the  large  scale,  will  interfere  with  parallelism.  If 
complex  and  enigmatical  appearances  did  not  present  themselves,  it 
would  be  a  serious  objection  to  the  metamorphic  theory. 

Mr.  Sorby  has  shown  that  the 
peculiar  structure  belonging  to 
ripple-marked  sands,  or  that  which 
is  generated  when  ripples  are 
formed  during  the  deposition  of 
the  materials,  is  distinctly  recog- 
nizable in  many  varieties  of  mica- 
schists  in  Scotland.* 

In  the  accompanying  diagram  I 
have  represented  carefully  the  lami- 
nation    of   a    coarse   argiUaceous 
schist  which  I  examined  in  1830 
in  the  Pyrenees.     In  part  it  approaches  in  character  to  a  green  and 


Fig.  761. 


H.  C.  Sorby,  Geol.  Quart.  Journ.,  vol.  xix.  p.  401. 


OH.  XXXVI.] 


LAMINATION  OF  CLAY-SLATE. 


Y5T 


blue  roofing-slate,  while  part  is  extremely  quartzose,  tlie  whole  mass 
passing  downwards  into  micaceous  schist.  The  vertical  section  here 
exhibited  is  about  three  feet  in  height,  and  the  layers  are  sometimes  so 
thin  that  fifty  may  be  counted  in  the  thickness  of  an  inch.  Some  of 
them  consist  of  pure  quartz. 

There  is  a  resemblance  in  such  cases  to  the  diagonal  lamination 
which  we  see  in  sedimentary  rocks,  even  though  the  layers  of  quartz 
and  of  mica,  or  of  felspar  and  other  minerals,  may  be  more  distinct  in 
alternating  folia  than  they  were  originally. 

M.  Elie  de  Beaumont,  while  he  regards  the  greater  part  of  the 
gneiss  and  mica-schist  of  the  Alps  as  sedimentary  strata  altered  by 
plutonic  action,  still  conceives  that  some  of  the  Alpine  gneiss  may 
have  been  erupted,  or,  in  other  words,  may  be  granite  drawn  out 
into  parallel  laminae  in  the  manner  of  trachyte,  as  above  alluded 
to.* 

If  the  mass  were  squeezed  and  elongated  in  a  certain  direction  after 
crystals  of  mica,  •  talc,  or  other  scaly  minerals  were  developed,  these 
may  perhaps  have  arranged  themselves  in  planes  parallel  to  those  of 
movement,  and  a  similar  process  may  account  for  what  the  quarrymen 
call  "  the  grain  "  in  some  granites,  or  a  tendency  to  split  in  one  direc- 
tion more  freely  than  in  another.  But,  as  a  general  rule,  the  fusion 
of  the  crystalline  schists  does  not  appear  to  have  gone  so  far  as  to 
allow  of  motion  analogous  to  that  of  lava  or  granite,  and  for  this  rea- 
son rocks  of  this  class  do  not  send  veins  into  surrounding  rocks.  In 
the  next  chapter  we  may  inquire  at  how  many  distinct  periods  the 
hypogene  or  metamorphic  schists  can  be  proved  to  have  originated, 
and  why  for  so  long  a  time  the  earlier  geologists  regarded  them  as 
entitled  to  the  name  of  "  primitive." 


*  Bulletin  Soc.  G6ol.  de  France,  2e  se"rie,  vol.  iv.  p.  1301. 


758  AGE  OF  METAMORPHIC  ROCKS.  [Cn.  XXXVII. 


CHAPTER  XXXVII. 

ON   THE    DIFFERENT    AGES    OF   THE    METAMORPHIC    ROCKS. 

Age  of  each  set  of  metamorphic  strata  twofold — Test  of  age  by  fossils  and  mineral 
character  not  available — Test  by  superposition  ambiguous — Conversion  of  dense 
masses  of  fossiliferous  strata  into  metamorphic  rocks — Limestone  and  shale  of 
Carrara — Metamorphic  strata  of  older  date  than  the  Cambrian  rocks — Others  of 
Lower  Silurian  origin — Others  of  the  Jurassic  and  Eocene  periods  in  the  Alps 
of  Switzerland  and  Savoy — Why  scarcely  any  of  the  visible  crystalline  strata 
are  very  modern — Order  of  succession  in  metamorphic  rocks — Uniformity  of 
mineral  character — Why  the  metamorphic  strata  are  less  calcareous  than  the 
fossiliferous. 

ACCORDING  to  the  theory  adopted  in  the  last  chapter,  the  age  of 
each  set  of  metamorphic  strata  is  twofold — they  have  been  deposited 
at  one  period,  they  have  become  crystalline  at  another.  We  can  rare- 
ly hope  to  define  with  exactness  the  date  of  both  these  periods,  the 
fossils  having  been  destroyed  by  plutonic  action,  and  the  mineral 
characters  being  the  same,  whatever  the  age.  Superposition  itself 
is  an  ambiguous  test,  especially  when  we  desire  to  determine  the 
period  of  crystallization.  Suppose,  for  example,  we  are  convinced 
that  certain  metamorphic  strata  in  the  Alps,  which  are  covered  by 
cretaceous  beds,  are  altered  lias ;  this  lias  may  have  assumed  its  crys- 
talline texture  in  the  cretaceous  or  in  some  tertiary  period,  the  Eocene 
for  example.  If  in  the  latter,  it  should  be  called  Eocene  when  regard- 
ed as  a  metamorphic  rock,  although  it  be  liassic  when  considered  in 
reference  to  the  era  of  its  deposition.  According  to  this  view,  the 
superposition  of  chalk  does  not  prevent  the  subjacent  metamorphic 
rock  from  being  Eocene. 

When  discussing  the  ages  of  the  plutonic  rocks,  we  have  seen  that 
examples  occur  of  various  primary,  secondary,  and  tertiary  deposits 
converted  into  metamorphic  strata,  near  their  contact  with  granite. 
There  can  be  no  doubt  in  these  cases  that  strata,  once  composed  of 
mud,  sand,  and  gravel,  or  of  clay,  marl,  and  shelly  limestone,  have  for 
the  distance  of  several  yards,  and  in  some  instances  several  hundred 
feet,  been  turned  into  gneiss,  mica-schist,  hornblende-schist,  chlorite- 
schist,  quartz  rock,  statuary  marble,  and  the  rest.  (See  the  two  pre- 
ceding chapters.) 

But  when  the  metamorphic  action  has  operated  on  a  grander  scale, 
it  tends  entirely  to  destroy  all  monuments  of  the  date  of  its  develop- 
ment. It  may  be  easy  to  prove  the  identity  of  two  different  parts  of 


CH.  XXXVIL]  NORTHERN  APENNINES.  759 

the  same  stratum ;  one,  where  the  rock  has  been  in  contact  with  a 
volcanic  or  plutonic  mass,  and  has  been  changed  into  marble  or  horn- 
blende-schist, and  another  not  far  distant,  where  the  same  bed  remains 
unaltered  and  fossiliferous ;  but  when  we  have  to  compare  two  por- 
tions of  a  mountain  chain — the  one  metamorphic,  and  the  other  un- 
altered— all  the  labor  and  skill  of  the  most  practised  observers  are 
required,  and  may  sometimes  be  at  fault.  I  shall  mention  one  or  two 
examples  of  alteration  on  a  grand  scale,  in  order  to  explain  to  the 
student  the  kind  of  reasoning  by  which  we  are  led  to  infer  that  dense 
masses  of  fossiliferous  strata  have  been  converted  into  crystalline 
rocks. 

Northern  Apennines — Carrara. — The  celebrated  marble  of  Carrara, 
used  in  sculpture,  was  once  regarded  as  a. type  of  primitive  limestone. 
It  abounds  in  the  mountains  of  Massa  Carrara,  or  the  "  Apuan  Alps," 
as  they  have  been  called,  the  highest  peaks  of  which  are  nearly  6000 
feet  high.  Its  great  antiquity  was  inferred  from  its  mineral  texture, 
from  the  absence  of  fossils,  and  its  passage  downwards  into  talc-schist 
and  garnetiferous  mica-schist;  these  rocks  again  graduating  down- 
wards into  gneiss,  which  is  penetrated,  at  Forno,  by  granite  veins. 
Now  the  researches  of  MM.  Savi,  Boue,  Pareto,  Guidoni,  De  la 
Beche,  Hoffmann,  and  Pilla  have  demonstrated  that  this  marble,  once 
supposed  to  be  formed  before  the  existence  of  organic  beings,  is,  in 
fact,  an  altered  limestone  of  the  oolitic  period,  and  the  underlying 
crystalline  schists  are  secondary  sandstones  and  shales,  modified  by 
plutonic  action.  In  order  to  establish  these  conclusions,  it  was  first 
pointed  out,  that  the  calcareous  rocks  bordering  the  Gulf  of  Spezia, 
and  abounding  in  oolitic  fossils,  assume  a  texture  like  that  of  Carrara 
marble,  in  proportion  as  they  are  more  and  more  invaded  by  certain 
trappean  and  plutonic  rocks,  such  as  diorite,  euphotide,  serpentine, 
and  granite,  occurring  in  the  same  country. 

It  was  then  observed  that,  in  places  where  the  secondary  forma- 
tions are  unaltered,  the  uppermost  consist  of  common  Apennine  lime- 
stone with  nodules  of  flint,  below  which  are  shales,  and  at  the  base  of 
all,  argillaceous  and  siliceous  sandstones.  In  the  limestone  fossils  are 
frequent,  but  very  rare  in  the  underlying  shale  and  sandstone.  Then 
a  gradation  was  traced  laterally  from  these  rocks  into  another  and 
corresponding  series,  which  is  completely  metamorphic ;  for  at  the  top 
of  this  we  find  a  white  granular  marble,  wholly  devoid  of  fossils,  and 
almost  without  stratification,  in  which  there  are  no  nodules  of  flint, 
but  in  its  place  siliceous  matter  disseminated  through  the  mass  in  the 
form  of  prisms  of  quartz.  Below  this,  and  in  place  of  the  shales,  are 
talc-schists,  jasper,  and  hornstone ;  and  at  the  bottom,  instead  of  the 
siliceous  and  argillaceous  sandstones,  are  quartzite  and  gneiss.*  Had 


*  See  notices  of  Savi,  Hoffinann,  and  others,  referred  to  by  Bou6,  Bull,  de  la 
Soc.  Geol.  de  France,  torn.  v.  p.  317  ;  and  torn.  iii.  p.  44  ;  also  Pilla,  cited  by  Mur- 
chison,  Quart.  Geol.  Journ.,  vol.  v.  p.  266. 


760  METAMORPHIC  ROCKS  OF  SWISS  ALPS.       [On.  XXXVII. 

these  secondary  strata  of  the  Apennines  undergone  universally  as 
great  an  amount  of  transmutation,  it  would  have  been  impossible  to 
form  a  conjecture  respecting  their  true  age ;  and  then,  according  to 
the  method  of  classification  adopted  by  the  earlier  geologists  they 
would  have  ranked  as  primary  rocks.  In  that  case  the  date  of  their 
origin  would  have  been  thrown  back  to  an  era  antecedent  to  the  de- 
position of  the  Lower  Silurian  or  Cambrian  strata,  although  in  reality 
they  were  formed  in  the  Oolitic  period,  and  altered  at  some  subse- 
quent and  perhaps  much  later  epoch. 

Alps  of  Switzerland.- — In  the  Alps,  analogous  conclusions  have 
been  drawn  respecting  the  alteration  of  strata  on  a  still  more  extended 
scale.  In  the  eastern  part  of  that  chain,  some  of  the  primary  fossil- 
iferous  strata,  as  well  as  the  older  secondary  formations,  together  with 
the  oolitic  and  cretaceous  rocks,  are  distinctly  recognizable.  Tertiary 
deposits  also  appear  in  a  less  elevated  position  on  the  flanks  of  the 
Eastern  Alps ;  but  in  the  Central  or  Swiss  Alps,  the  primary  fossilifer- 
ous  and  older  secondary  formations  disappear,  and  the  Cretaceous, 
Oolitic,  Liassic,  and  at  some  points  even  the  Eocene  strata,  graduate 
insensibly  into  metamofphic  rocks,  consisting  of  granular  limestone, 
talc-schist,  talcose-gneiss,  micaceous  schist,  and  other  varieties.  In 
regard  to  the  age  of  this  vast  assemblage  of  crystalline  strata,  we  can 
merely  affirm  that  some  of  the  upper  portions  are  altered  newer  sec- 
ondary, and  some  of  them  even  Eocene  deposits ;  but  we  cannot  avoid 
suspecting  that  the  disappearance  both  of  the  older  secondary  and 
primary  fossiliferous  rocks  may  be  owing  to  their  having  been  all  con- 
verted in  the  same  region  into  crystalline  schist. 

It  is  difficult  to  convey  to  those  who  have  never  visited  the  Alps 
a  just  idea  of  the  various  proofs  which  concur  to  produce  this  con- 
viction. In  the  first  place  there  are  certain  regions  where  Oolitic, 
Cretaceous,  and  Eocene  strata  have  been  turned  into  granular  marble, 
gneiss,  and  other  metamorphic  schists,  near  their  contact  with  granite. 
This  fact  shows  undeniably  that  plutonic  causes  continued  to  be  in 
operation  in  the  Alps  down  to  a  late  period,  even  after  the  deposition 
of  some  of  the  nummulitic  or  middle  Eocene  formations.  Having 
established  this  point,  we  are  the  more  willing  to  believe  that  many 
inferior  fossiliferous  rocks,  probably  exposed  for  longer  periods  to  a 
similar  action,  may  have  become  metamorphic  to  a  still  greater  ex- 
tent. 

We  also  discover  in  parts  of  the  Swiss  Alps  dense  masses  of  sec- 
ondary andr  even  tertiary  strata  which  have  assumed  that  semi-crys- 
talline texture  which  Werner  called  transition,  and  which  naturally  led 
his  followers,  who  attached  great  importance  to  mineral  characters 
taken  alone,  to  class  them  as  transition  formations,  or  as  groups  older 
than  the  lowest  secondary  rocks.  (See  p.  88.)  Now,  it  is  probable 
that  these  strata  have  been  affected,  although  in  a  less  intense  degree, 
by  that  same  plutonic  action  which  has  entirely  altered  and  rendered 
uietamorphic  so  many  of  the  subjacent  formations ;  for  in  the  Alps, 


CH.  XXXVIL]       CRYSTALLINE  ROCKS  OF  SWISS  ALPS.  761 

this  action  lias  by  no  means  been  confined  to  the  immediate  vicinity 
of  granite.  Granite,  indeed,  and  other  plutonic  rocks,  rarely  make 
their  appearance  at  the  surface,  notwithstanding  the  deep  ravines 
which  lay  open  to  view  the  internal  structure  of  these  mountains. 
That  they  exist  below  at  no  great  depth  we  cannot  doubt,  and  we  have 
already  seen  (p.  713)  that  at  some  points,  as  in  the  Yalorsine,  near 
Mont  Blanc,  granite  and  granitic  veins  are  observable,  piercing 
through  talcose  gneiss,  which  passes  insensibly  upwards  into  sec- 
ondary strata. 

It  is  certainly  in  the  Alps  of  Switzerland  and  Savoy,  more  than  in 
any  other  district  in  Europe,  that  the  geologist  is  prepared  to  meet 
with  the  signs  of  an  intense  development  of  plutonic  action ;  for  here 
we  find  the  most  stupendous  monuments  of  mechanical  violence,  by 
which  strata  thousands  of  feet  thick  have  been  bent,  folded,  and  over- 
turned. (See  p.  58.)  It  is  here  that  marine  secondary  formations  of 
a  comparatively  modern  date,  such  as  the  Oolitic  and  Cretaceous, 
have  been  upheaved  to  the  height  of  12,000,  and  some  Eocene  strata 
to  elevations  of  10,000  feet  above  the  level  of  the  sea;  and  even  de- 
posits of  the  Miocene  era  have  been  raised  4000  or  5000  feet,  so  as  to 
rival  in  height  the  loftiest  mountains  in  Great  Britain. 

If  the  reader  will  consult  the  works  of  many  eminent  geologists  who 
have  explored  the  Alps,  especially  those  of  MM.  de  Beaumont,  Studer, 
Necker,  Boue,  and  Murchison,  he  will  learn  that  they  all  share,  more 
or  less  fully,  in  the  opinions  above  expressed.  It  has,  indeed,  been 
stated  by  MM.  Studer  and  Hugi,  that  there  are  complete  alternations 
on  a  large  scale  of  secondary  strata,  containing  fossils,  with  gneiss  and 
other  rocks  of  a  perfectly  metamorphic  structure.  I  have  visited 
some  of  the  most  remarkable  localities  referred  to  by  these  authors ; 
but,  although  agreeing  with  them  that  there  are  passages  from  the 
fossiliferous  to  the  metamorphic  series  far  from  the  contact  of  granite 
or  other  plutonic  rocks,  I  was  unable  to  convince  myself  that  the  dis- 
tinct alternations  of  highly  crystalline,  with  unaltered  strata  above 
alluded  to,  might  not  admit  of  a  different  explanation.  In  one  of  the 
sections  described  by  M.  Studer  in  the  highest  of  the  Bernese  Alps, 
namely  in  the  Roththal,  a  valley  bordering  the  line  of  perpetual  snow 
on  the  northern  side  of  the  Jungfrau,  there  occurs  a  mass  of  gneiss 
1000  feet  thick  and  15,000  feet  long,  which  I  examined,  not  only 
resting  upon,  but  also  again  covered  by  strata  containing  oolitic 
fossils.  These 'anomalous  appearances  may  partly  be  explained  by 
supposing  great  solid  wedges  of  intrusive  gneiss  to  have  been  forced 
in  laterally  between  strata  to  which  I  found  them  to  be  in  many  sec- 
tions unconformable.  The  superposition,  also,  of  the  gneiss  to  the 
oolite  may,  in  some  cases,  be  due  to  a  reversal  of  the  original  position 
of  the  beds  in  a  region  where  the  convulsions  have  been  on  so  stu- 
pendous a  scale. 

On  the  Sattel  also,  at  the  base  of  the  Gestellihorn,  above  Enzen,  in 
the  valley  of  Urbach,  near  Meyringen,  some  of  the  intercalations  of 


HIGHLAND  METAMORPHIC  ROCKS.          [Cn.  XXXVII. 

gneiss  between  fossiliferous  strata  may,  I  conceive,  be  ascribed  to 
mechanical  derangement.  Almost  any  hypothesis  of  repeated  changes 
of  position  may  be  resorted  to  in  a  region  of  such  extraordinary  con- 
fusion. The  secondary  strata  having  first  become  vertical,  may  then 
in  certain  portions  have  become  metamorphic  (the  plutonic  influence 
ascending  from  below),  while  intervening  strata  remained  unchanged. 
The  whole  series  of  beds  may  then  again  have  been  thrown  into  a 
nearly  horizontal  position,  giving  rise  to  the  superposition  of  crystalline 
upon  fossiliferous  formations. 

It  was  remarked,  in  Chap.  XXXIV.,  that  as  the  hypogene  rocks, 
both  stratified  and  unstratified,  crystallize  originally  at  a  certain 
depth  beneath  the  surface,  they  must  always,  before  they  are  upraised 
and  exposed  at  the  surface,  be  of  considerable  antiquity,  relatively  to 
a  large  portion  of  the  fossiliferous  and  volcanic  rocks.  They  may  be 
forming  at  all  periods ;  but  before  any  of  them  can  become  visible, 
they  must  be  raised  above  the  level  of  the  sea,  and  some  of  the  rocks 
which  previously  concealed  them  must  have  been  removed  by  denuda- 
tion. 

In  Canada,  as  we  have  seen  (p.  583),  the  Lower  Laurentian  gneiss, 
quartzite,  and  limestone,  may  be  regarded  as  metamorphic,  because 
organic  remains  (Eozoon  Canadense)  have  been  detected  in  a  part  of 
one  of  the  calcareous  masses.  Nor  can  we  doubt  that  the  Upper 
Laurentian,  or  Labrador  series,  consisting  of  gneiss,  with  Labrador- 
felspar  and  felstones,  in  all  10,000  feet  thick,  have  assumed  their 
crystalline  structure  by  metamorphic  action,  since  they  lie  in  uncon- 
formable  stratification  on  the  Lower  Laurentian.  The  remote  date  of 
the  period  when  some  of  these  old  Laurentian  strata  of  Canada  were 
converted  into  gneiss,  may  be  inferred  from  the  fact  that  pebbles  of 
that  rock  are  found  in  the  overlying  Huronian  formation,  which  is  of 
Lower  Cambrian  age,  if  not  older  (p.  583).  The  oldest  stratified 
rock  of  Scotland  is  the  hornblendic  gneiss  of  Lewis,  in  the  Hebrides, 
and  that  of  the  northwest  coast  of  Rossshire,  represented  at  the  base 
of  the  section  given  at  p.  67,  fig.  90.  It  is  the  same  as  that  inter- 
sected by  numerous  granite  veins,  which  forms  the  cliffs  of  Cape 
Wrath,  in  Sutherlandshire  (see  fig.  743,  p.  712),  and  is  conjectured 
to  be  of  Laurentian  age.  Above  it,  as  shown  in  MacCulloch's  section 
(fig.  90,  p.  67),  lie  unconformable  beds  of  a  reddish  or  purplish  sand- 
stone and  conglomerate,  nearly  horizontal,  and  between  2000  and 
3000  feet  thick.  In  these  ancient  grits  no  fossils  have  been  found, 
but  they  are  supposed  to  be  of  Lower  Cambrian  date,  and  they  cer- 
tainly do  not  belong  to  the  Old  Red,  as  was  formerly  supposed,  for 
they  have  been  shown  by  Sir  Roderick  Murchison  to  pass  in  the 
North  Highlands  or  in  the  three  northern  counties  of  Scotland,  under 
quartz  rocks,  which,  with  a  subordinate  limestone,  rest  unconformably 
upon  them.  In  this  limestone,  in  1854,  Mr.  Charles  Peach  found 
some  obscure  organic  remains,  which  led  Sir  R.  Murchison  to  insti- 
tute a  searching  inquiry,  and  eventually  to  establish  beyond  all  doubt 


CH.  XXXVII.]        MINERAL  CHARACTER  OF  HYPOGENE  ROCKS.        763 

that  the  calcareous  formation  in  question  was  of  Lower  Silurian  age. 
This  was  one  of  the  most  important  steps  made  of  late  years  in  the 
progress  of  British  Geology,  for  it  led  to  a  very  unexpected  conclu- 
sion, namely,  that  all  the  Scotch  crystalline  strata  to  the  eastward, 
once  called  primitive,  which  overlie  the  limestone  and  quartzite  in 
question,  are  referable  to  some  part  of  the  Silurian  series.  The 
most  abundant  and  best  preserved  shells  of  the  limestone  are  those 
obtained  from  Durness  and  Assynt.  They  comprise,  among  others, 
three  or  four  species  of  Orthoceras,  also  the  genera  Cyrtoceras  and 
Lituites,  two  species  of  Murchisonia,  a  Pleurotomaria,  a  species 
of  Maclurea,  one  of  HJuomphalus,  and  an  Or  this.  Several  of  the 
species  are  believed  by  Mr.  Salter  to  be  identical  with  Lower  Silurian 
fossils  of  Canada  and  the  United  States.  The  mere  occurrence  of 
Cephalopoda  in  such  numbers  is  strongly  against  the  supposition  of 
their  being  Cambrian,  and  the  large  siphuncles  of  some  of  the  Ortho- 
cerata  point  distinctly  to  a  Lower  Silurian  date,  for  this  division 
of  the  genus,  both  in  Europe  and  North  America  (see  p.  565),  is 
eminently  characteristic  of  the  inferior  members  of  the  Silurian 
system  (see  above,  p.  565).  To  the  fossiliferous  rock  above  men- 
tioned, with  its  accompanying  quartzites,  succeed  in  conformable 
stratification  a  dense  series  of  gneiss,  mica-schists,  and  clay-slates, 
this  younger  gneiss  being  very  different  in  mineral  character  from  the 
fundamental  gneiss  before  mentioned.  There  can  be  no  question 
that  these  crystalline  formations,  which  are  similar  to  those  of  the 
Central  and  Southern  Highlands,  comprising  the  metamorphic  rocks 
of  Aberdeenshire,  Perthshire,  and  Forfarshire,  for  example,  are 
altered  Silurian  strata ;  *  the  inferences  of  Sir  R.  Murchison  on  this 
subject  having  been  confirmed  by  the  subsequent  observations  of 
three  able  geologists,  Messrs.  Ramsay,  Harkness,  and  Geikie.  The 
newest  of  the  series  is  a  clay-slate,  on  which,  along  the  southern 
borders  of  the  Grampians,  the  Lower  Old 'Red,  containing  Cepha- 
laspis  Lyelli,  Pterygotus  Anglicus,  and  Parka  decipiens,  rests  uncon- 
formably. 

In  Anglesea,  as  was  before  remarked,  the  metamorphism  of  the 
schists,  according  to  the  observations  of  Professor  Ramsay,  took 
place  during  the  Lower  Silurian  period.  Coupling  these  conclusions 
with  the  fact  that  a  hypogene  texture  has  been  superinduced  in  the 
Alps  on  Middle  Eocene  deposits  (see  p.  746),  we  cannot  doubt  that, 
hereafter,  geologists  will  succeed  in  detecting  crystalline  schists  of 
almost  every  age  in  the  chronological  series,  although  the  quantity  of 
metamorphic  rocks  visible  at  the  surface  must,  for  reasons  above  ex- 
plained, dimmish  rapidly  in  proportion  as  the  monuments  of  newer 
eras  are  investigated. 

Order  of  Succession  in  Metamorphic  Rocks. — There  is  no  universal 
and  invariable  order  of  superposition  in  metamorphic  rocks,  although 

*  Quart.  Geol.  Journ.,  vol.  xv.  p.  353,  1859.     Siluria,  3d  ed.,  Appendix,  p.  553. 


MINERAL  CHARACTER  OF  HYPOGENE  ROCKS.        [Cn.  XXXVII. 

a  particular  arrangement  may  prevail  throughout  countries  of  great 
extent,  for  the  same  reason  that  it  is  traceable  in  those  sedimentary 
formations  from  which  crystalline  strata  are  derived.  Thus,  for 
example,  we  have  seen  that  in  the  Apennines,  near  Carrara,  the  de- 
scending series,  where  it  is  metamorphic,  consists  of,  1st,  saccharine 
marble ;  2dly,  talcose-schist ;  and  3dly,  of  quartz-rock  and  gneiss : 
where  unaltered,  of  1st,  fossiliferous  limestone ;  2dly,  shale ;  and  3dly, 
sandstone. 

But  if  we  investigate  different  mountain  chains,  we  find  gneiss, 
mica-schist,  hornblende-schist,  chlorite-schist,  hypogene  limestone, 
and  other  rocks,  succeeding  each  other,  and  alternating  with  each 
other  in  every  possible  order.  It  is,  indeed,  more  common  to  meet 
with  some  variety  of  clay-slate  forming  the  uppermost  member  of  a 
metamorphic  series  than  any  other  rock ;  but  this  fact  by  no  means 
implies,  as  some  have  imagined,  that  all  clay-slates  were  formed  at 
the  close  of  an  imaginary  period,  when  the  deposition  of  the  crys- 
talline strata  gave  way  to  that  of  ordinary  sedimentary  deposits. 
Such  clay-slates,  in  fact,  are  variable  in  composition,  and  sometimes 
alternate  with  fossiliferous  strata,  so  that  they  may  be  said  to  belong 
almost  equally  to  the  sedimentary  and  metamorphic  order  of  rocks. 
It  is  probable  that  had  they  been  subjected  to  more  intense  plutonic 
action,  they  would  have  been  transformed  into  hornblende-schist, 
foliated  chlorite-schist,  scaly  talcose-schist,  mica-schist,  or  other 
more  perfectly  crystalline  rocks,  such  as  are  usually  associated  with 
gneiss. 

Uniformity  of  Mineral  Character  in  Hypogene  Hocks. — It  is  most 
true,'  as  Humboldt  has  happily  remarked,  that  when  we  pass  to 
another  hemisphere,  we  see  new  forms  of  animals  and  plants,  and 
even  new  constellations  in  the  heavens;  but  in  the  rocks  we  still 
recognize  our  old  acquaintances— the  same  granite,  the  same  gneiss, 
the  same  micaceous  schist,  quartz-rock,  and  the  rest.  There  is 
certainly  a  great  and  striking  general  resemblance  in  the  principal 
kinds  of  hypogene  rocks  in  all  countries,  however  different  their  ages ; 
but  each  of  them,  as  we  have  before  seen,  must  be  regarded  as  geo- 
logical families  of  rocks,  and  not  as  definite  mineral  compounds. 
They  are  more  uniform  in  aspect  than  sedimentary  strata,  because 
these  last  are  often  composed  of  fragments  varying  greatly  in  form, 
size,  and  color,  and  contain  fossils  of  different  shapes  and  mineral 
composition,  and  acquire  a  variety  of  tints  from  the  mixture  of  various 
kinds  of  sediment.  The  materials  of  such  strata,  if  melted  and  made 
to  crystallize,  would  be  subject  to  chemical  laws,  simple  and  uniform 
in  their  action,  the  same  in  every  climate,  and  wholly  undisturbed  by 
mechanical  and  organic  causes. 

It  would,  however,  be  a  great  error  to  assume,  as  some  have  done, 
that  the  hypogene  rocks,  considered  as  aggregates  of  simple  minerals, 
are  really  more  homogeneous  in  their  composition  than  the  several 
members  of  .the  sedimentary  series.  In  the  first  place,  different  as- 


CH.  XXXVIL]        SCARCITY  OF  LIME  IN  METAMORPHIC  ROCKS.        765 

semblages  of  hypogene  rocks  occur  in  different  countries ;  and,  sec- 
ondly, in  any  one  district,  the  rocks  which  pass  under  the  same  name 
are  often  extremely  variable  in  their  component  ingredients,  or  at 
least  in  the  proportions  in  which  each  of  these  are  present.  Thus,  for 
example,  gneiss  and  mica-schist,  so  abundant  in  the  Grampians,  are 
wanting  in  Cumberland,  Wales,  and  Cornwall ;  in  parts  of  the  Swiss 
and  Italian  Alps,  the  gneiss  and  granite  are  talcose,  and  not  mica- 
ceous, as  in  Scotland;  hornblende  prevails  in  the  granite  of  Scotland 
— schorl  in  that  of  Cornwall — albite  in  the  plutonic  rocks  of  the  Andes 
— common  felspar  in  those  of  Europe.  In  one  part  of  Scotland,  the 
mica-schist  is  full  of  garnets ;  in  another  it  is  wholly  devoid  of  them ; 
while  in  South  America,  according  to  Mr.  Darwin,  it  is  the  gneiss, 
and  not  the  mica-schist,  which  is  most  commonly  garnetiferous.  And 
not  only  do  the  proportional  quantities  of  felspar,  quartz,  mica,  horn- 
blende, and  other  minerals,  vary  in  hypogene  rocks  bearing  the  same 
name ;  but,  what  is  still  more  important,  the  ingredients,  as  we  have 
seen,  of  the  same  simple  mineral  are  not  always  constant  (see  p.  595, 
and  Table,  p.  102). 

The  Metamorphic  Strata,  why  less  Calcareous  than  the  Fossiliferous. 
— It  has  been  remarked,  that  the  quantity  of  calcareous  matter  in 
metamorphic  strata,  or,  indeed,  in  the  hypogene  formations  generally, 
is  far  less  than  in  fossiliferous  deposits.  Thus  the  crystalline  schists 
of  the  Eastern  and  Southern  Grampians  in  Scotland, ;  consisting  of 
gneiss,  mica-schist,  hornblende-schist,  and  other  rocks,  many  thou- 
sands of  yards  in  thickness,  contain  an  exceedingly  small  proportion 
of  interstratified  calcareous  beds,  although  these  have  been  the  objects 
of  careful  search  for  economical  purposes.  •  Yet  limestone  is  not  want- 
ing even  in  the  Southern  Grampians,  in  Perthshire  and  Forfarshire, 
for  example,  and  it  is  associated  sometimes  with  gneiss,  sometimes 
with  mica-schist,  and  in  other  places  with  other  members  of  the  meta- 
morphic series.  Where  limestone  occurs  abundantly,  as  at  Carrara, 
and  in  parts  of  the  Alps,  in  connection  with  hypogene  rocks,  it  usually 
forms  one  of  the  superior  members  of  the  crystalline  group.  The 
limestones  of  the  Lower  Laurentian  in  Canada,  consisting  of  several 
distinct  bands,  one  of  them  containing  Eozoon  Canadcnse,  and  of 
great  thickness  (from  700  to  1500  feet),  afford  a  remarkable  exception 
to  the  general  rule.  In  this  instance,  however,  augite,  serpentine,  and 
various  other  minerals  are  largely  intermixed  with  the  carbonate  of 
lime. 

.  The  general  scarcity  of  carbonate  of  lime  in  the  plutonic  and  meta- 
morphic rocks  seems  to  be  the  result  of  some  general  cause.  So  long 
as  the  hypogene  rocks  were  believed  to  have  originated  antecedently 
to  the  creation  of  organic  beings,  it  was  easy  to  impute  the  absence 
of  lime  to  the  non-existence  of  those  molluscaand  zoophytes  by  which 
shells  and  corals  are  secreted;  but  when  we  ascribe  the  crystalline 
formations  to  plutonic  action,  it  is  natural  to  inquire  whether  this 
action  itself  may  not  tend  to  expel  carbonic  acid  and  lime  from  the 


766  SCARCITY  OF  LIME  IN  METAMORPHIC  ROCKS.     [Cn.  XXXVII. 

materials  which  it  reduces  to  fusion  or  semi-fusion.  Although  we 
cannot  descend  into  the  subterranean  regions  where  volcanic  heat  is 
developed,  we  can  observe  in  regions  of  spent  volcanoes,  such  as  Au- 
vergne  and  Tuscany,  hundreds  of  springs,  both  cold  and  thermal, 
flowing  out  from  granite  and  other  rocks,  and  having  their  waters 
plentifully  charged  with  carbonate  of  lime.  The  quantity  of  calcare- 
ous matter  which  these  springs  transfer,  in  the  course  of  ages,  from  the 
lower  parts  of  the  earth's  crust  to  the  superior  or  newly  formed  parts 
of  the  same,  must  be  considerable.* 

If  the  quantity  of  siliceous  and  aluminous  ingredients  brought  up 
by  such  springs  were  great,  instead  of  being  utterly  insignificant,  it 
might  be  contended  that  the  mineral  matter  thus  expelled  implies 
simply  the  decomposition  of  ordinary  subterranean  rocks;  but  the 
prodigious  excess  of  carbonate  of  lime  over  every  other  substance 
must,  in  the  course  of  time,  cause  the  crust  of  the  earth  below  to  be 
almost  entirely  deprived  of  its  calcareous  constituents,  while  we  know 
that  the  same  action  imparts  to  newer  deposits,  ever  forming  in  seas 
and  lakes,  an  excess  of  carbonate  of  lime.  Calcareous  matter  is 
poured  into  these  lakes  and  the  ocean  by  a  thousand  springs  and 
rivers ;  so  that  part  of  almost  every  new  calcareous  rock  chemically 
precipitated,  and  of  many  reefs  of  shelly  and  coralline  stone,  must  be 
derived  from  mineral  matter  subtracted  by  plutonic  agency,  and  driven 
up  by  gas  and  steam  from  fused  and  heated  rocks  in  the  bowels  of  the 
earth. 

Not  only  carbonate  of  lime,  but  also  free  carbonic  acid  gas,  is  given 
off  plentifully  from  the  soil  and  crevices  of  rocks  in  regions  of  active 
and  spent  volcanoes,  as  near  Naples  and  in  Auvergne.  By  this  pro- 
cess, fossil  shells  or  corals  may  often  lose  their  carbonic  acid,  and  the 
residual  lime  may  enter  into  the  composition  of  augite,  hornblende, 
garnet,  and  other  hypogene  minerals.  That  the  removal  of  the  cal- 
careous matter  of  fossil  shells  is  of  frequent  occurrence,  is  proved  by 
the  fact  of  such  organic  remains  being  often  replaced  by  silex  or  other 
minerals,  and  sometimes  by  the  space  once  occupied  by  the  fossil 
being  left  empty,  or  only  marked  by  a  faint  impression.  We  ought 
not  indeed  to  marvel  at  the  general  absence  of  organic  remains  from 
the  crystalline  strata,  when  we  bear  in  mind  how  often  fossils  are  ob- 
literated, wholly  or  in  part,  even  in  tertiary  formations — how  often 
vast  masses  of  sandstone  and  shale,  of  different  ages,  and  thousands 
of  feet  thick,  are  devoid  of  fossils — how  certain  strata  may  first  have 
been  deprived  of  a  portion  of  their  fossils  when  they  became  semi- 
crystalline,  or  assumed  the  transition  state  of  Werner — and  how  the 
remaining  portion  may  have  been  effaced  when  they  were  rendered 
metamorphic.  Rocks  of  the  last-mentioned  class,  moreover,  have 
sometimes  been  exposed  again  and  again  to  renewed  plutonic  action. 

*  See  Principles  of  Geology,  by  the  Author,  Index,  "  Calcareous  Springs." 


CH.  XXXVIII.]  MINERAL  VEINS. 


•CHAPTER  XXXVIII. 

V  ;  MINERAL    VEINS. 

Werner's  doctrine  that  mineral  veins  were  fissures  filled  from  above — Veins  of 
segregation — Ordinary  metalliferous  veins  or  lodes — Their  frequent  coincidence 
with  faults — Proofs  that  they  originated  in  fissures  in  solid  rock — Veins  shifting 
other  veins — Polishing  of  their  walls  or  "  slicken-sides  " — Shells  and  pebbles  in 
lodes — Evidence  of  the  successive  enlargement  and  reopening  of  veins — Four- 
net's  observations  in  Auvergne — Dimensions  of  veins — Why  some  alternately 
swell  out  and  contract — Filling  of  lodes  by  sublimation  from  below — Chemical 
and  electrical  action — Relative  age  of  the  precious  metals — Copper  and  lead 
veins  in  Ireland  older  than  Cornish  tin — Lead  vein  in  lias,  Glamorganshire — 
Gold  in  Russia,  California,  and  Australia — Connection  of  hot  springs  and  min- 
eral veins — Concluding  remarks. 

THE  manner  in  which  metallic  substances  are  distributed  through 
the  earth's  crust,  and  more  especially  the  phenomena  of  those  nearly 
vertical  and  tabular  masses  of  ore  called  mineral  veins,  from  which 
the  larger  part  of  the  precious  metals  used  by  man  are  obtained — 
these  are  subjects  of  the  highest  practical  importance  to  the  miner, 
and  of  no  less  theoretical  interest  to  the  geologist. 

The  views  entertained  respecting  metalliferous  veins  have  been 
modified,  or,  rather,  have  undergone  an  almost  complete  revolution, 
since  the  middle  of  the  last  century,  when  Werner,  as  director  of  the 
School  of  Mines  at  Freiburg,  in  Saxony,  first  attempted  to  generalize 
the  facts  then  known.  He  taught  that  mineral  veins  had  originally 
been  open  fissures  which  were  gradually  filled  up  with  crystalline  and 
metallic  matter,  and  that  many  of  them,  after  being  once  filled,  had  been 
again  enlarged  or  reopened.  He  also  pointed  out  that  veins  thus  formed 
are  not  all  referable  to  one  era,  but  are  of  various  geological  dates. 

Such  opinions,  although  slightly  hinted  at  by  earlier  writers,  had 
never  before  been  generally  received,  and  their  announcement  by  one 
of  high  authority  and  great  experience  constituted  an  era  in  the  sci- 
ence. Nevertheless,  I  have  shown,  when  tracing,  in  another  work, 
the  history  and  progress  of  geology,  that  Werner  was  far  behind  some 
of  his  predecessors  in  his  theory  of  the  volcanic  rocks,  and  less  en- 
lightened than  his  contemporary,  Dr.  Hutton,  in  his  speculations  as  to 
the  origin  of  granite.*  According  to  him,  the  plutonic  formations, 
as  well  as  the  crystalline  schists,  were  substances  precipitated  from  a 

*  Principles  of  Geology,  chap.  iv. 


768  DIFFERENT  KINDS  OF  MINERAL  VEINS.     [On.  XXXVIII. 

chaotic  fluid  in  some  primeval  or  nascent  condition  of  the  planet ; 
and  the  metals,  therefore,  being  closely  connected  with  them,  had 
partaken,  according  to  him,  of  a  like  mysterious  origin.  He  also 
held  that  the  trap  rocks  were  aqueous  deposits,  and  that  dikes  of  por- 
phyry, greenstone,  and  basalt,  were  fissures  filled  with  their  several 
contents  from  above.  Hence  he  naturally  inferred  that  mineral  veins 
had  derived  their  component  materials  from  ^an  incumbent  ocean, 
rather  than  from  a  subterranean  source ;  that  these  materials  had 
been  first  dissolved  in  the  waters  above,  instead  of  having  risen  up 
by  sublimation  from  lakes  and  seas  of  igneous  matter  below. 

In  proportion  as  the  hypothesis  of  a  primeval  fluid,  or  "  chaotic 
menstruum,"  was  abandoned,  in  reference  to  the  plutonic  formations, 
and  when  all  geologists  had  come  to  be  of  one  mind  as  to  the  true 
relation  of  the  volcanic  and  trappean  rocks,  reasonable  hopes  began 
to  be  entertained  that  the  phenomena  of  mineral  veins  might  be  ex- 
plained by  known  causes,  or  by  chemical,  thermal,  and  electrical 
agency  still  at  work  in  the  interior  of  the  earth.  The  grounds  of 
this  conclusion  will  be  better  understood  when  the  geological  facts 
brought  to  light  by  mining  operations  have  been  described  and  ex- 
plained. 

On  Different  Kinds  of  Mineral  Veins. — Every  geologist  is  famil- 
iarly acquainted  with  those  veins  of  quartz  which  abound  in  hypogene 
strata,  forming  lenticular  masses  of  limited  extent.  They  are  some- 
times observed,  also,  in.  sandstones  and  shales.  Veins  of  carbonate 
of  lime  are  equally  common  in  fossiliferous  rocks,  especially  in  lime- 
stones. Such  veins  appear  to  have  once  been  chinks  or  small  cavities, 
caused,  like  cracks  in  clay,  by  the  shrinking  of  the  mass,  which  has 
consolidated  from  a  fluid  state,  or  has  simply  contracted  its  dimensions 
in  passing  from  a  higher  to  a  lower  temperature.  Siliceous,  calca- 
reous, and  occasionally  metallic  matters  have  sometimes  found  their 
way  simultaneously  into  such  empty  spaces,  by  infiltration  from  the 
surrounding  rocks,  or  by  segregation,  as  it  is  often  termed.  Mixed 
with  hot  water  and  steam,  metallic  ores  may  have  permeated  a  pasty 
matrix  until  they  reached  those  receptacles  formed  by  shrinkage,  and 
thus  gave  rise  to  that  irregular  assemblage  of  veins,  called  by  the 
Germans  a  "  stockwerk,"  in  allusion  to  the  different  floors  on  which 
the  mining  operations  are  in  such  cases  carried  on. 

The  more  ordinary  or  regular  veins  are  usually  worked  in  vertical 
shafts,  and  have  evidently  been  fissures  produced  by  mechanical  vio- 
lence. They  traverse 'all  kinds  of  rocks,  both  hypogene  and  fossilifer- 
ous, and  extend  downwards  to  indefinite  or  unknown  depths.  We 
may  assume  that  they  correspond  with  such  rents  as  we  see  caused 
(rom  time  to  time  by  the  shock  of  an  earthquake.  Metalliferous  veins, 
referable  to  such  agency,  are  occasionally  a  few  inches  wide,  but  more 
commonly  three  or  four  feet.  They  hold  their  course  continuously  in 
a  certain  prevailing  direction  for  miles  or  leagues,  passing  through 
rocks  varying  in  mineral  composition. 


CH.  XXXVIII.]       ORIGIN   OF  METALLIFEROUS  VEINS. 


769 


That  Metalliferous  Veins  were  Fissures.  —  As  some  intelligent  miners, 
after  an  attentive  study  of  metalliferous  veins,  have  been  unable  to 
reconcile  many  of  their  characteristics  with  the  hypothesis  of  fissures, 
I  shall  begin  by  stating  Fig.  762. 

the  evidence  in  its  favor. 
The  most  striking  fact, 
perhaps,  which  can  be  ad- 
duced in  its  support,  is 
the  coincidence  of  a  con- 
siderable proportion  of 
mineral  veins  with  faults, 
or  those  dislocations  of 
rocks  which  are  indispu- 
tably due  to  mechanical 
force,  as  above  explained 
(p.  61).  There  are  even 
proofs  in  almost  every 
mining  district  of  a  suc- 
cession of  faults,  by  which 
the  opposite  walls  of  rents, 
now  the  receptacles  of  me- 
tallic substances,  have  suf- 
fered displacement.  Thus, 
for  example,  suppose  a  a, 
fig.  762,  to  be  a  tin  lode 
in  Cornwall,  the  term  lode 
being  applied  to  veins  con- 
taining metallic  ores.  This 
lode,  running  east  and  west, 
is  a  yard  wide,  and  is  shift- 
ed by  a  copper  lode  (b  6), 
of  similar  width. 

The  first  fissure  (a  a) 
has  been  filled  with  vari- 
ous materials,  partly  of 
chemical  origin,  such  ^  as 
quartz,  fluor-spar,  peroxide 
of  tin,  sulphuret  of  copper,  arsenical  pyrites,  bismuth,  and  sulphuret 
of  nickel,  and  partly  of  mechanical  origin,  comprising  clay  and 
angular  fragments  or  detritus  of  the  intersected  rocks.  The  plates 
of  quartz  and  the  ores  are,  in  some  places,  parallel  to  the  vertical 
sides  or  walls  of  the  vein,  being  divided  from  each  other  by  alter- 
nating layers  of  clay,  or  other  earthy  matter.  Occasionally  the 
metallic  ores  are  disseminated  in  detached  masses  among  the  vein- 
stones. 

It  is  clear  that,  after  the  gradual  introduction  of  the  tin  and  other 
substances,  the  second  rent  (b  b)  was  produced  by  another  fracture 
49 


Vertical  Bections 


of  Huel  Peeverj  Redruthj 
Cornwall. 


770  ORIGIN  OF  METALLIFEROUS  VEINS.       [Cn.  XXXVHL 

accompanied  by  a  displacement  of  the  rocks  along  the  plane  of  b  b. 
This  new  opening  was  then  filled  with  minerals,  some  of  them  re- 
sembling those  in  a  a,  as  fluor-spar  (or  fluate  of  lime)  and  quartz ; 
others  different,  the  copper  being  plentiful  and  the  tin  wanting  or  very 
scarce. 

We  must  next  suppose  the  shock  of  a  third  earthquake  to  occur, 
breaking  asunder  all  the  rocks  along  the  line  c  c,  fig.  763  ;  the  fissure, 
in  this  instance,  being  only  6  inches  wide,  and  simply  filled  with  clay, 
derived,  probably,  from  the  friction  of  the  walls  of  the  rent,  or  partly, 
perhaps,  washed  in  from  above.  This  new  movement  has  heaved  the 
rock  in  such  a  manner  as  to  interrupt  the  continuity  of  the  copper 
vein  (b  b),  and,  at  the  same  time,  to  shift  or  heave  laterally  in  the 
same  direction  a  portion  of  the  tin  vein  which  had  not  previously  been 
broken. 

Again,  in  fig.  764,  we  see  evidence  of  a  fourth  fissure  (d  d),  also  filled 
with  clay,  which  has  cut  through  the  tin  vein  (a  a),  and  has  lifted  it 
slightly  upwards  towards  the  south.  The  various  changes  here  repre- 
sented are  not  ideal,  but  are  exhibited  in  a  section  obtained  in  work- 
ing an  old  Cornish  mine,  long  since  abandoned,  in  the  parish  of  Red- 
ruth,  called  Huel  Peever,  and  described  both  by  Mr.  Williams  and 
Mr.  Carne.*  The  principal  movement  here  referred  to,  or  that  of 
c  c,  fig.  764,  extends  through  a  space  of  no  less  than  84  feet ;  but  in 
this,  as  in  the  case  of  the  other  three,  it  will  be  seen  that  the  outline 
of  the  country  above,  rf,  c,  6,  a,  &c.,  or  the  geographical  features  of 
Cornwall,  are  not  affected  by  any  of  the  dislocations,  a  powerful  de- 
nuding force  having  clearly  been  exerted  subsequently  to  all  the  faults. 
(See  above,  p.  69.)  It  is  commonly  said  in  Cornwall,  that  there  are 
eight  distinct  systems  of  veins  which  can  in  like  manner  be  referred 
to  as  many  successive  movements  or  fractures ;  and  the  German  miners 
of  the  Hartz  Mountains  speak  also  of  eight  systems  of  veins,  referable 
to  as  many  periods. 

Besides  the  proofs  of  mechanical  action  already  explained,  the 
opposite  walls  of  veins  are  often  beautifully  polished,  as  if  glazed,  and 
are  not  unfrequently  striated  or  scored  with  parallel  furrows  and 
ridges,  such  as  would  be  produced  by  the  continued  rubbing  together 
of  surfaces  of  unequal  hardness.  These  smoothed  surfaces  resemble 
the  rocky  floor  over  Which  a  glacier  has  passed  (see  fig.,  p.  140). 
They  are  common  even  in  cases  where  there  has  been  no  shift,  and 
occur  equally  in  non-metalliferous  fissures.  They  are  called  by  miners 
"  slicken-sides,"  from  the  German  uchlichten,  to  plane,  and  seite,  side. 
It  is  supposed  that  the  lines  of  the  striae  indicate  the  direction  in 
which  the  rocks  were  moved.  During  one  of  the  minor  earthquakes 
in  Chili,  which  happened  about  the  year  1840,  and  was  described  to 
me  by  an  eye-witness,  the  brick  walls  of  a  building  were  rent  vertically 
in  several  places,  and  made  to  vibrate  for  several  minutes  during  each 

*  Geol.  Trans.,  vol.  iv.  p.  139 ;  Trans.  Roy.  Geol.  Soc.,  Cornwall,  vol.  ii.  p.  90. 


CH.  XXXVIII.]     SUCCESSIVE  ENLARGEMENTS  OF  VEINS. 

shock,  after  wliicli  they  remained  uninjured,  and  without  any  opening, 
although  the  line  of  each  crack  was  still  visible.  When  all  movement 
had  ceased,  there  were  seen  on  the  floor  of  the  house,  at  the  bottom 
of  each  rent,  small  heaps  of  fine  brickdust,  evidently  produced  by 
trituration. 

In  some  of  the  veins  in  the  mountain  limestone  of  Derbyshire,  con- 
taining lead,  the  vein-stuff,  which  is  nearly  compact,  is  occasionally 
traversed  by  what  may  be  called  a  vertical  crack  passing  down  the 
middle  of  the  vein.  The  two  faces  in  contact  are  slicken-sides,  well 
polished  and  fluted,  and  sometimes  covered  by  a  thin  coating  of  lead- 
ore.  When  one  side  of  the  vein-stuff  is  removed,  the  other  side 
cracks,  especially  if  small  holes  be  made  in  it,  and  fragments  fly  off 
with  loud  explosions,  and  continue  to  do  so  for  some  days.  The 
miner,  availing  himself  of  this  circumstance,  makes  with  his  pick  small 
holes  about  6  inches  apart  and  4  inches  deep,  and  on  his  return  in  a 
few  hours  finds  every  part  ready  broken  to  his  hand.*  These  phe- 
nomena and  their  causes  (probably  connected  with  electrical  action) 
seem  scarcely  to  have  attracted  the  notice  which  they  deserve. 

That  a  great  many  veins  communicated  originally  with  the  surface 
of  the  country  above,  or  with  the  bed  of  the  sea,  is  proved  by  the 
occurrence  in  them  of  well-rounded  pebbles,  agreeing  with  those  in 
superficial  alluviums,  as  in  Auvergne  and  Saxony.  In  Bohemia,  such 
pebbles  have  been  met  with  at  the  depth  of  180  fathoms.  In  -Corn- 
wall, Mr.  Carne  mentions  true  pebbles  of  quartz  and  slate  in  a  tin  lode 
of  the  Relistran  Mine,  at  the  depth  of  600  feet  below  the  surface. 
They  were  cemented  by  oxide  of  tin  and  bisulphuret  of  copper,  and 
were  traced  over  a  space  more  than  12  feet  long  and  as  many  wide.f 
Marine  fossil  shells,  also,  have  been  found  at  great  depths,  having 
probably  been  engulfed  during  submarine  earthquakes.  Thus,  a  gry- 
phaea  is  stated  by  M.  Virlet  to  have  been  met  with  in  a  lead-mine  near 
Semur,  in  France,  and  a  madrepore  in  a  compact  vein  of  cinnabar  in 
Hungary.); 

When  different  sets  or  systems  of  veins  occur  in  the  same  country, 
those  which  are  supposed  to  be  of  contemporaneous  origin,  and  which 
are  filled  with  the  same  kind  of  metals,  often  maintain  a  general 
parallelism  of  direction.  Thus,  for  example,  both  the  tin  and  copper 
veins  in  Cornwall  run  nearly  east  and  west,  while  the  lead-veins  run 
north  and  south ;  but  there  is  no  general  law  of  direction  common  to 
different  mining  districts.  The  parallelism  of  the  veins  is  another 
reason  for  regarding  them  as  ordinary  fissures,  for  we  observe  that 
contemporaneous  trap  dikes,  admitted  by  all  to  be  masses  of  melted 
matter  which  have  filled  rents,  are  often  parallel.  Assuming,  then, 
that  veins  are  simply  fissures  in  which  chemical  and  mechanical  de- 


*  Conyb.  and  Phil.  Geol.,  p.  401 ;  and  Farcy's  Derbysh.,  p.  243. 
f  Came,  Trans,  of  Geol.  Soc.  Cornwall,  vol.  iii.  p.  238. 
\  Four-net,  Etudes  sur  les  Depots  Metallif  eres. 


772 


SUCCESSIVE  FILLING  UP  OF  VEINS.        [Cn.  XXXVIII. 


posits  have  accumulated,  we  may  next  consider  the  proofs  of  their 
having  been  filled  gradually  and  often  during  successive  enlargements. 
I  have  already  spoken  of  parallel  layers  of  clay,  quartz,  and  ore. 
Werner  himself  observed,  in  a  vein  near  Gersdorff,  in  Saxony,  no  less 
than  thirteen  beds  of  different  minerals,  arranged  with  the  utmost 
regularity  on  each  side  of  the  central  layer.  This  layer  was  formed 
of  two  plates  of  calcareous  spar,  which  had  evidently  lined  the  oppo- 
site walls  of  a  vertical  cavity.  The  thirteen  beds  followed  each  other 
in  corresponding  order,  consisting  of  fluor-spar,  heavy  spar,  galena,  &c. 
In  these  cases  the  central  mass  has  been  last  formed,  and  the  two 
plates  which  coat  the  walls  of  the  rent  on  each  side  are  the  oldest  of 
all.  If  they  consist  of  crystalline  precipitates,  they  may  be  explained 
by  supposing  the  fissure  to  have  remained  unaltered  in  its 'dimen- 
sions, while  a  series  of  changes  occurred  in  the  nature  of  the  solu- 
tions which  rose  up  from  below ;  but  such  a  mode  of  deposition,  in 
the  case  of  many  successive  and  parallel  layers,  appears  to  be  excep- 
tional. 

If  a  veinstone  consist  of  crystalline  matter,  the  points  of  the  crystals 
are  always  turned  inwards,  or  towards  the  centre  of  the  vein ;  in  other 
words,  they  point  in  the  direction  where  there  was  space  for  the  de- 
velopment of  the  crystals.  Thus  each  new  layer  receives  the  impres- 
sion of  the  crystals  of  the  preceding  layer,  and  imprints  its  crystals  on 
the  one  which  follows,  until  at  length  the  whole  of  the  vein  is  filled ; 
the  two  layers  which  meet  dovetail  the  points  of  their  crystals  the  one 
into  the  other.  But  in  Cornwall,  some  lodes  occur  where  the  vertical 
plates,  or  combs,  as  they  are  there  called,  exhibit  crystals  so  dovetailed 
as  to  prove  that  the  same  fissure  has  been  often  enlarged.  Sir  H.  De 
la  Beche  gives  the  following  curious  and  instructive  example  (fig.  765) 

Fig.  765. 


Copper  lode,  near  Kedruth,  enlarged  at  six  successive  periods. 

from  a  copper-mine  in  granite,  near  Kedruth.*  Each  of  the  plates  or 
combs  (a,  b,  c,  d,  e,f)  is  double,  having  the  points  of  their  crystals 
turned  inwards  along  the  axis  of  the  comb.  The  sides  or  walls  (2,  3, 
4,  5,  and  6)  are  parted  by  a  thin  covering  of  ochreous  clay,  so  -that 
each  comb  is  readily  separable  from  another  by  a  moderate  blow  of 

*  Geol.  Rep.  on  Cornwall,  p.  340. 


CH.  XXXVIII.]  SWELLING  OUT  OF  VEINS.  773 

the  hammer.  The  breadth  of  each  represents  the  whole  width  of  the 
fissure  at  six  successive  periods,  and  the  outer  walls  of  the  vein,  where 
the  first  narrow  rent  was  formed,  consisted  of  the  granitic  surfaces 
1  and  7. 

A  somewhat  analogous  interpretation  is  applicable  to  many  other 
cases,  where  clay,  sand,  or  angular  detritus,  alternate  with  ores  and 
veinstones.  Thus,  we  may  imagine  the  sides  of  a  fissure  to  be  encrust- 
ed with  siliceous  matter,  as  Von  Buch  observed,  in  Lancerote,  the 
walls  of  a  volcanic  crater  formed  in  1731  to  be  traversed  by  an  open 
rent  in  which  hot  vapors  had  deposited  hydrate  of  silica,  the  incrusta- 
tion nearly  extending  to  the  middle.*  Such  a  vein  may  then  be  filled 
with  clay  or  sand,  and  afterwards  reopened,  the  new  rent  dividing  the 
argillaceous  deposit,  and  allowing  a  quantity  of  rubbish  to  fall  down. 
Various  metals  and  spars  may  then  be  precipitated  from  aqueous  solu- 
tions among  the  interstices  of  this  heterogeneous  mass. 

That  such  changes  have  repeatedly  occurred,  is  demonstrated  by 
occasional  cross-veins,  implying  the  oblique  fracture  of  previously 
formed  chemical  and  mechanical  deposits.  Thus,  for  example,  M. 
Fournet,  in  his  description  of  some  mines  in  Auvergne  worked  under 
his  superintendence,  observes  that  the  granite  of  that  country  was  first 
penetrated  by  veins  of  granite,  and  then  dislocated,  so  that  open  rents 
crossed  both  the  granite  and  the  granitic  veins.  Into  such  openings, 
quartz,  accompanied  by  sulphurets  of  iron  and  arsenical  pyrites,  was 
introduced.  Another  convulsion  then  burst  open  the  rocks  along  the 
old  line  of  fracture,  and  the  first  set  of  deposits  were  cracked  and  often 
shattered,  so  that  the  new  rent  was  filled,  not  only  with  angular  frag- 
ments of  the  adjoining  rocks,  but  with  pieces  of  the  older  veinstones. 
Polished  and  striated  surfaces  on  the  sides  or  in  the  contents  of  the 
vein  also  attest  the  reality  of  these  movements.  A  new  period  of 
repose  then  ensued,  during  which  various  sulphurets  were  introduced, 
together  with  hornstone  quartz,  by  which  angular  fragments  of  the 
older  quartz  before  mentioned  were  cemented  into  a  breccia.  This 
period  was  followed  by  other  dilatations  of  the  same  veins,  and  other 
sets  of  mineral  deposits,  until,  at  last,  pebbles  of  the  basaltic  lavas  of 
Auvergne,  derived  from  superficial  alluviums,  probably  of  Miocene  or 
older  Pliocene  date,  were  swept  into  the  veins.  I  have  not  space  to 
enumerate  all  the  changes  minutely  detailed  by  M.  Fournet,  but  they 
are  valuable,  both  to  the  miner  and  geologist,  as  showing  how  the 
supposed  signs  of  violent  catastrophes  may  be  the  monuments,  not  of 
one  paroxysmal  shock,  but  of  reiterated  movements. 

Such  repeated  enlargement  and  reopening  of  veins  might  have  been 
anticipated,  if  we  adopt  the  theory  of  fissures,  and  reflect  how  few  of 
them  have  ever  been  sealed  up  entirely,  and  that  a  country  with  fis- 
sures only  partially  filled  must  naturally  offer  much  feebler  resistance 
along  the  old  lines  of  fracture  than  anywhere  else.  It  is  quite  other- 

*  Principles,  chap,  xxvii.  8th  ed.  p.  422. 


774:  CONTRACTION  OF  VEINS.  [Cn.  XXXVIIL 

wise  in  tlie  case  of  dikes,  where  each  opening  has  been  the  receptacle 
of  one  continuous  and  homogeneous  mass  of  melted  matter,  the  con- 
solidation of  which  has  taken  place  under  considerable  pressure. 
Trappean  dikes  can  rarely  fail  to  strengthen  the  rocks  at  the  points 
where  before  they  were  weakest  ;  and  if  the  upheaving  force  is  again 
exerted  in  the  same  direction,  the  crust  of  the  earth  will  give  way 
anywhere  rather  than  at  the  precise  points  where  the  first  rents  were 
produced. 

A  large  proportion  of  metalliferous  veins  have  their  opposite  walls 
nearly  parallel,  and  sometimes  over  a  wide  extent  of  country.  There 
is  a  fine  example  of  this  in  the  celebrated  vein  of  Andreasburg  in  the 
Hartz,  which  has  been  worked  for  a  depth  of  500  yards  perpen- 
dicularly, and  200  horizontally,  retaining  almost  everywhere  a  width 
of  3  feet.  But  many  lodes  in  Cornwall  and  elsewhere  are  extremely 
variable  in  size,  being  1  or  2  inches  in  one  part,  and  then  8  or  10  feet 
in  another,  at  the  distance  of  a  few  fathoms,  and  then  again  narrowing 
as  before.  Such  alternate  swelling  and  contraction  is  so  often  charac- 
teristic as  to  require  explanation.  The  walls  of  fissures  in  general, 
observes  Sir  H.  De  la  Beche,  are  rarely  perfect  planes  throughout 
their  entire  course,  nor  could  we  well  expect  them  to  be  so,  since 
they  commonly  pass  through  rocks  of  unequal  hardness,  and  different 
mineral  composition.  If,  therefore,  the  opposite  sides  of  such  irregu- 
lar fissures  slide  upon  each  other,  that  is  to  say,  if  there  be  a  fault,  as 
in  the  case  of  so  many  mineral  veins,  the  parallelism  of  the  opposite 
walls  is  at  once  entirely  destroyed,  as  will  be  readily  seen  by  studying 
the  annexed  diagrams. 

Fig.  766. 


Fig.  76T. 


Fig.  768. 

•xmmzmmnxs^mmmm*^ I 


^7*  ~r 

Let  «  6,  fig.  766,  be  a  line  of  fracture  traversing  a  rock,  and  let  a  6, 
fig.  767,  represent  the  same  line.  Now,  if  we  cut  in  two  a  piece  of 
paper  representing  this  line,  and  then  move  the  lower  portion  of  this 
cut  paper  sideways  from  a  to  a',  taking  care  that  the  two  pieces  of 
paper  still  touch  each  other  at  the  points  1,  2,  3,  4,  5,  we  obtain  an 
irregular  aperture  at  c,  and  isolated  cavities  at  d  d  d ;  and  when  we 
compare  such  figures  with  nature  we  find  that,  with  certain  modifica- 
tions, they  represent  the  interior  of  faults  and  mineral  veins.  If, 
instead  of  sliding  the  cut  paper  to  the  right  hand,  we  move  the  lower 
part  towards  the  left,  about  the  same  distance  that  it  was  previously 


CH.  XXXVIII.]  CHEMICAL  DEPOSITS  IN  VEINS.  775 

slid  to  the  right,  we  obtain  considerable  variation  in  the  cavities  so 
produced,  two  long  irregular  open  spaces,  //,  fig.  768,  being  then 
formed.  This  will  serve  to  show  to  what  slight  circumstances  con- 
siderable variations  in  the  character  of  the  openings  between  unevenly 
fractured  surfaces  may  be  due,  such  surfaces  being  moved  upon  each 
other,  so  as  to  have  numerous  points  of  contact. 

Most  lodes  are  perpendicular  to  the  horizon,  or  nearly  so ;  but  some 
of  them  have  a  considerable  inclination  or  "  hade,"  as  it  is  termed, 
the  angles  of  dip  varying  from  15°  to  45°.     The  course  of  a  vein  is 
frequently  very  straight ;  but  if  tortuous,  it  is  found  to  be  choked  up 
with  clay,  stones,  and  pebbles,  at  points  where  it  departs  most  widely 
from  vertically.     Hence  at  places,  such  as  a,  fig.  769,  the  miner  com- 
plains that  the  ores  are  "  nipped,"  or  greatly  reduced 
in  quantity,  the  space  for  their  free  deposition  having        ¥ls  769. 
been  interfered  with  in  consequence  of  the  preoccu- 
pancy  of  the  lode  by  earthy  materials.     When  lodes 
are  many  fathoms  wide,  they  are  usually  filled  for  the 
most  part  with  earthy  matter,  and  fragments  of  rock, 
through  which  the  ores  are  much  disseminated.     The 
metallic  substances  frequently  coat  or  encircle  detached 
pieces  of  rock,  which  our  miners  call   "  horses "   or 
"riders."     That  we   should  find   some  mineral  veins 
which  split  into  branches  is  also  natural,  for  we  observe 
the  same  in  regard  to  open  fissures. 

Chemical  Deposits  in  Veins. — If  we  now  turn  from  the  mechanical 
to  the  chemical  agencies  which  have  been  instrumental  in  the  produc- 
tion of  mineral  veins,  it  may  be  remarked  that  those  parts  of  fissures 
which  were  not  choked  up  with  the  ruins  of  fractured  rocks  must 
always  have  been  filled  with  water ;  and  almost  every  vein  has  prob- 
ably been  the  channel  by  which  hot  springs,  so  common  in  countries 
of  volcanoes  and  earthquakes,  have  made  their  way  to  the  surface. 
For  we  know  that  the  rents  in  which  ores  abound  extend  downwards 
to  vast  depths,  where  the  temperature  of  the  interior  of  the  earth  is 
more  elevated.  We  also  know  that  mineral  veins  are  most  metallifer- 
ous near  the  contact  of  plutonic  and  stratified  formations,  especially 
where  the  former  send  veins  into  the  latter,  a  circumstance  which 
indicates  an  original  proximity  of  veins  at  their  inferior  extremity  to 
igneous  and  heated  rocks.  It  is  moreover  acknowledged  that  even 
those  mineral  and  thermal  springs  which,  in  the  present  state  of  the 
globe,  are  far  from  volcanoes,  are  nevertheless  observed  to  burst  out 
along  great  lines  of  upheaval  and  dislocation  of  rocks.*  It  is  also 
ascertained  that  all  the  substances  with  which  hot  springs  are  impreg- 
nated agree  with  those  discharged  in  a  gaseous  form  from  volcanoes. 
Many  of  these  bodies  occur  as  veinstones ;  such  as  silex,  carbonate  of 
lime,  sulphur,  fluor-spar,  sulphate  of  barytes,  magnesia,  oxide  of  iron, 

*  See  Dr.  Daubeny's  Volcanoes. 


776  CHEMICAL  DEPOSITS  IN  VEINS.  [Cn.  XXXVIII. 

and  others.  I  may  add  that,  if  veins  have  been  filled  with  gaseous 
emanations  from  masses  of  melted  matter,  slowly  cooling  in  the  sub- 
terranean regions,  the  contraction  of  such  masses  as  they  pass  from  a 
plastic  to  a  solid  state  would,  according  to  the  experiments  of  Deville 
on  granite  (a  rock  which  may  be  taken  as  a  standard),  produce  a  re- 
duction in  volume  amounting  to  10  per  cent.  The  slow  crystalliza- 
tion, therefore,  of  such  plutonic  rocks  supplies  us  with  a  force  not  only 
capable  of  rending  open  the  incumbent  rocks  by  causing  a  failure  of 
support,  but  also  of  giving  rise  to  faults  whenever  one  portion  of  the 
earth's  crust  subsides  slowly  while  another  contiguous  to  it  happens  to 
rest  on  a  different  foundation,  so  as  to  remain  unmoved. 

Although  we  are  led  to  infer,  from  the  foregoing  reasoning,  that 
there  has  oft£n  been  an  intimate  connection  between  metalliferous 
veins  and  hot  springs  holding  mineral  matter  in  solution,  yet  we  must 
not  on  that  account  expect  that  the  contents  of  hot  springs  and  min- 
eral veins  would  be  identical.  On  the  contrary,  M.  E.  de  Beaumont 
has  judiciously  observed  that  we  ought  to  find  in  veins  those  sub- 
stances which,  being  least  soluble,  are  not  discharged  by  hot  springs 
— or  that  class  of  simple  and  compound  bodies  which  the  thermal 
waters  ascending  from  below  would  first  precipitate  on  the  walls  of  a 
fissure,  as  soon  as  their  temperature  began  slightly  to  diminish.  The 
higher  they  mount  towards  the  surface,  the  more  will  they  cool,  till 
they  acquire  the  average  temperature  of  springs,  being  in  that  case 
chiefly  charged  with  the  most  soluble  substances,  such  as  the  alkalis, 
soda  and  potash.  These  are  not  met  with  in  veins,  although  they 
enter  so  largely  into  the  composition  of  granitic  rocks.* 

To  a  certain  extent,  therefore,  the  arrangement  and  distribution  of 
metallic  matter  in  veins  may  be  referred  to  ordinary  chemical  action, 
or  to  those  variations  in  temperature  which  waters  holding  the  ores 
in  solution  must  undergo,  as  they  rise  upwards  from  great  depths  in 
the  earth.  But  there  are  other  phenomena  which  do  not  admit  of 
the  same  simple  explanation.  Thus,  for  example,  in  Derbyshire, 
veins  containing  ores  of  lead,  zinc,  and  copper,  but  chiefly  lead, 
traverse  alternate  beds  of  limestone  and  greenstone.  The  ore  is 
plentiful  where  the  walls  of  the  rent  consist  of  limestone,  but  is  re- 
duced to  a  mere  string  when  they  are  formed  of  greenstone,  or  "  toad- 
stone,"  as  it  is  called  provincially.  Not  that  the  original  fissure  is 
narrower  where  the  greenstone  occurs,  but  because  more  of  the  space 
is  there  filled  with  veinstones,  and  the  waters  at  such  points  have  not 
parted  so  freely  with  their  metallic  contents. 

"  Lodes  in  Cornwall,"  says  Mr.  Robert  W.  Fox,  "  are  very  much 
influenced  in  their  metallic  riches  by  the  nature  of  the  rock  which 
they  traverse,  and  they  often  change  in  this  respect  very  suddenly, 
in  passing  from  one  rock  to  another.  Thus  many  lodes  which  yield 
abundance  of  ore  in  granite,  are  unproductive  in  clay-slate,  or  killas, 

*  Bulletin,  iv.  p.  1278. 


CH.  XXXYIH.]  RELATIVE  AGE  OF  METALS. 

and  vice  versd.  The  same  observation  applies  to  killas  and  the  gran- 
itic porphyry  called  elvan.  Sometimes,  in  the  same  continuous  vein, 
the  granite  will  contain  copper,  and  the  killas  tin,  or  vice  versd" * 
Mr.  Fox,  after  ascertaining  the  existence  at  present  of  electric  currents 
in  some  of  the  metalliferous  veins  in  Cornwall,  has  speculated  on  the 
probability  of  the  same  cause,  having  acted  originally  on  the  sulphurets 
and  muriates  of  copper,  tin,  iron,  and  zinc,  dissolved  in  the  hot  water 
of  fissures,  so  as  to  determine  the  peculiar  mode  of  their  distribution. 
After  instituting  experiments  on  this  subject,  he  even  endeavored  to 
account  for  the  prevalence  of  an  east  and  west  direction  in  the  prin- 
cipal Cornish  lodes  by  their  position  at  right  angles  to  the  earth's 
magnetism;  but  Mr.  Kenwood  and  other  experienced  miners  have 
pointed  out  objections  to  the  theory ;  and  it  must  be  owned  that  the 
direction  of  veins  in  different  mining  districts  varies  so  entirely  that  it 
seems  to  depend  on  lines  of  fracture,  rather  than  on  the  laws  of  vol- 
taic electricity.  Nevertheless,  as  different  kinds  of  rock  would  be 
often  in  different  electrical  conditions,  we  may  readily  believe  that 
electricity  must  often  govern  the  arrangement  of  metallic  precipitates 
in  a  rent. 

"  I  have  observed,"  says  Mr.  R.  Fox,  "  that  when  the  chloride  of 
tin  in  solution  is  placed  in  the  voltaic  circuit,  part  of  the  tin  is  de- 
posited in  a  metallic  state  at  the  negative  pole,  and  part  at  the  positive 
one  in  the  state  of  a  peroxide,  such  as  it  occurs  in  our  Cornish  mines. 
This  experiment  may  serve  to  explain  why  tin  is  found  contiguous  to, 
and  intermixed  with,  copper  ore,  and  likewise  separated  from  it,  in 
other  parts  of  the  same  lode."  f 

Relative  Age  of  the  Different  Metals. — After  duly  reflecting  on  the 
facts  above  described,  we  cannot  doubt  that  mineral  veins,  like  erup- 
tions of  granite  or  trap,  are  referable  to  many  distinct  periods  of  the 
earth's  history,  although  it  may  be  more  difficult  to  determine  the 
precise  age  of  veins;  because  they  have  often  remained  open  for 
ages,  and  because,  as  we  have  seen,  the  same  fissure,  after  having 
been  once  filled,  has  frequently  been  reopened  or  enlarged.  But 
besides  this  diversity  of  ao-e,  it  has  been  supposed  by  some  geologists 
that  certain  metals  have  been  produced  exclusively  in  earlier,  others 
in  more  modern  times — that  tin,  for  example,  is  of  higher  antiquity 
than  copper,  copper  than  lead  or  silver,  and  all  of  them  more  ancient 
than  gold.  I  shall  first  point  out  that  the  facts  once  relied  upon  in 
support  of  some  of  these  views  are  contradicted  by  later  experience, 
and  then  consider  how  far  any  chronological  order  of  arrangement 
can  be  recognized  in  the  position  of  the  precious  and  other  metals  in 
the  earth's  crust. 

In  the  first  place,  it  is  not  true  that  veins  in  which  tin  abounds  are 
the  oldest  lodes  worked  in  Great  Britain.  The  Government  survey  of 
Ireland  has  demonstrated,  that  in  Wexford  veins  of  copper  and  lead 

*  R.  W.  Fox  on  Mineral  Veins,  p.  10.  f  Ibid.,  p.  38. 


778  RELATIVE  AGE  OF  METALS.  [On.  XXXVIII. 

(the  latter  as  usual  being  argentiferous)  are  much  older  than  the  tin 
of  Cornwall.  In  each  of  the  two  countries  a  very  similar  series  of 
geological  changes  has  occurred  at  two  distinct  epochs — in  Wexford, 
before  the  Devonian  strata  were  deposited  ;  in  Cornwall,  after  the  car- 
boniferous epoch.  To  begin  with  the  Irish  mining  district :  We  have 
granite  in  Wexford,  traversed  by  granite  veins,  which  veins  also 
intrude  themselves  into  the  Silurian  strata,  the  same  Silurian  rocks  as 
well  as  the  veins  having  been  denuded  before  the  Devonian  beds  were 
superimposed.  Next  we  find,  in  the  same  county,  that  elvans,  or 
straight  dikes  of  porphyritic  granite,  have  cut  through  the  granite  and 
the  veins  before  mentioned,  but  have  not  penetrated  the  Devonian 
rocks.  Subsequently  to  these  elvans,  veins  of  copper  and  lead  were 
produced,  being  of  a  date  certainly  posterior  to  the  Silurian,  and 
anterior  to  the  Devonian ;  for  they  do  not  enter  the  latter,  and,  what 
is  still  more  decisive,  streaks  or  layers  of  derivative  copper  have  been 
found  near  Wexford  in  the  Devonian,  not  far  from  points  where  mines 
of  copper  are  worked  in  the  Silurian  strata.* 

Although  the  precise  age  of  such  copper  lodes  cannot  be  defined, 
we  may  safely  affirm  that  they  were  either  filled  at  the  close  of  the 
Silurian  or  commencement  of  the  Devonian  period.  Besides  copper, 
lead,  and  silver,  there  is  some  gold  in  these  ancient  or  primary  metal- 
liferous veins.  A  few  fragments  also  of  tin  found  in  Wicklow  in  the 
drift  are  supposed  to  have  been  derived  from  veins  of  the  same  age.f 

Next,  if  we  turn  to  Cornwall,  we  find  there  also  the  monuments  of 
a  very  analogous  sequence  of  events.  First  the  granite  was  formed ; 
then,  about  the  same  period,  veins  of  fine-grained  granite,  often  tor- 
tuous (see  fig.  744,  p.  713),  penetrating  both  the  outer  crust  of  gran- 
ite and  the  adjoining  fossiliferous  or  primary  rocks,  including  the  coal- 
measures  ;  thirdly,  elvans,  holding  their  course  straight  through  gran- 
ite, granitic  veins,  and  fossiliferous  slates ;  fourthly,  veins  of  tin  also 
containing  copper,  the  first  of  those  eight  systems  of  fissures  of  differ- 
ent ages  already  alluded  to,  p.  769.  Here,  then,  the  tin  lodes  are 
newer  than  the  elvans.  .  It  has  indeed  been  stated  by  some  Cornish 
miners  that  the  elvans  are  in  some  few  instances  posterior  to  the  old- 
est tin-bearing  lodes,  but  the  observation  of  Sir  H.  De  la  Beche  during 
the  survey  led  him  to  an  opposite  conclusion,  and  he  has  shown  how 
the  cases  referred  to  in  corroboration  can  be  otherwise  interpreted.! 
We  may,  therefore,  assert  that  the  most  ancient  Cornish  lodes  are 
younger  than  the  coal-measures  of  that  part  of  England,  and  it  follows 
that  they  are  of  a  much  later  date  than  the  Irish  copper  and  lead  of 
Wexford  and  some  adjoining  counties.  How  much  later  it  is  not  so 
easy  to  declare,  although  probably  they  are  not  newer  than  the  begin- 
ning of  the  Permian  period,  as  no  tin  lodes  have  been  discovered  in 

*  I  am  indebted  to  Sir  H.  De  la  Beche  for  this  information.  See  also  maps  and 
sections  of  Irish  Survey. 

f  Sir  H.  De  la  Beche,  MS.  notes  on  Irish  Survey. 
\  Report  on  Geology  of  Cornwall,  p.  310. 


CH.  XXXVIH.]  GOLD  OF  AUSTRALIA.  779 

any  red  sandstone  of  the  Poikilitic  group,  which  overlies  the  coal  in 
the  southwest  of  England. 

There  are  lead  veins  in  the  Mendip  hills  which  extend  through  the 
mountain  limestone  into  the  Permian  or  Dolomitic  conglomerate,  and 
others  in  Glamorganshire  which  enter  the  lias.  Those  worked  near 
Frome,  in  Somersetshire,  have  been  traced  into  the  Inferior  Oolite. 
In  Bohemia,  the  rich  veins  of  silver  of  Joachimsthal  cut  through  basalt 
containing  olivine,  which  overlies  tertiary  lignite,  in  which  are  leaves 
of  dicotyledonous  trees.  This  silver,  therefore,  is  decidedly  a  tertiary 
formation.  In  regard  to  the  age  of  the  gold  of  the  Ural  Mountains, 
in  Russia,  which,  like  that  of  California,  is  obtained  chiefly  from  aurifer- 
ous alluvium,  it  occurs  in  veins  of  quartz  in  the  schistose  and  granitic 
rocks  of  that  chain,  and  is  supposed  by  MM.  Murchison,  De  Verneuil, 
and  Keyserling  to  be  newer  than  the  syenitic  granite  of  the  Ural — 
perhaps  of  tertiary  date.  They  observe,  that  no  gold  has  yet  been 
found  in  the  Permian  conglomerates  which  lie  at  the  base  of  the  Ural 
Mountains,  although  large  quantities  of  iron  and  copper  detritus  are 
mixed  with  the  pebbles  of  those  Permian  strata.  Hence  it  seems  that 
the  Uralian  quartz  veins,  containing  gold  and  platinum,  were  not 
formed,  or  certainly  not  exposed  to  aqueous  denudation,  during  the 
Permian  era. 

In  the  auriferous  alluvium  of  Russia,  California,  and  Australia,  the 
bones  of  extinct  land-quadrupeds  have  been  met  with,  those  of  the 
mammoth  being  common  in  the  gravel  at  the  foot  of  the  Ural  Moun- 
tains, while  in  Australia  they  consist  of  huge  marsupials,  some  of  them 
of  the  size  of  the  rhinoceros  and  allied  to  the  living  wombat.  They 
belong  to  the  genera  Diprotodon  and  Nototherium  of  Professor  Owen. 
The  gold  of  Northern  Chili  is  associated  in  the  mines  of  Los  Hornos 
with  copper  pyrites,  in  veins  traversing  the  cretaceo-oolitic  formations, 
so  called  because  its  fossils  have  the  character  partly  of  the  cretaceous 
and  partly  of  the  oolitic  fauna  of  Europe.*  The  gold  found  in  the 
United  States,  in  the  mountainous  parts  of  Virginia,  North  and  South 
Carolina,  and  Georgia,  occurs  in  metamorphic  Silurian  strata,  as  well 
as  in  auriferous  gravel  derived  from  the  same. 

Gold  has  now  been  detected  in  almost  every  kind  of  rock,  in  slate, 
quartzite,  sandstone,  limestone,  granite,  and  serpentine,  both  in  veins 
and  in  the  rocks  themselves  at  short  distances  from  the  veins.  In 
Australia  it  has  been  worked  successfully  not  only  in  alluvium,  but  in 
veinstones  in  the  native  rock,  generally  consisting  of  Silurian  shales 
and  slates.  It  has  been  traced  on  that  continent  over  more  than  nine 
degrees  of  latitude  (between  the  parallels  of  30°  and  39°  S.),  and  over 
twelve  of  longitude,  and  yielded  in  1853  an  annual  supply  equal,  if 
not  superior,  to  that  of  California;  nor  is  there  any  apparent  prospect 
of  this  supply  diminishing,  still  less  of  the  exhaustion  of  the  gold-fields. 

It  has  been  remarked  by  M.  de  Beaumont,  that  lead  and  some 

*  Darwin's  S.  America,  p.  209,  &c. 


780  CONCLUDING  REMARKS.  [Cn.  XXXVIII. 

other  metals  are  found  in  dikes  of  basalt  and  greenstone,  as  well  as  in 
mineral  veins  connected  with  trap  rocks,  whereas  tin  is  met  with  in 
granite  and  in  veins  associated  with  the  granitic  series.  If  this  rule 
hold  true  generally,  the  geological  position  of  tin  in  localities  accessi- 
ble to  the  miners  will  belong,  for  the  most  part,  to  rocks  older  than 
those  bearing  lead.  The  tin  veins  will  be  of  higher  relative  antiquity 
for  the  same  reason  that  the  "underlying"  igneous  formations  or 
granites  which  are  visible  to  man  are  older,  on  the  whole,  than  the 
overlying  or  trappean  formations. 

If  different  sets  of  fissures,  originating  simultaneously  at  different 
levels  in  the  earth's  crust,  and  communicating,  some  of  them  with 
volcanic,  others  with  heated  plutonic  masses,  be  filled  with  different 
metals,  it  will  follow  that  those  formed  farthest  from  the  surface  will 
usually  require  the  longest  time  before  they  can  be  exposed  super- 
ficially. In  order  to  bring  them  into  view,  or  within  reach  of  the 
miner,  a  greater  amount  of  upheaval  and  denudation  must  take  place 
in  proportion  as  they  have  lain  deeper  when  first  moved.  A  con- 
siderable series  of  geological  revolutions  must  intervene  before  any 
part  of  the  fissure,  which  has  been  for  ages  in  the  proximity  of  the 
plutonic  rocks,  so  as  to  receive  the  gases  discharged  from  it  when  it 
was  cooling,  can  emerge  into  the  atmosphere.  But  I  need  not  enlarge 
on  this  subject,  as  the  reader  will  remember  what  was  said  in  the 
30th,  34th,  and  37th  chapters,  on  the  chronology  of  the  volcanic  and 
hypogene  formations. 

Concluding  Remarks. — The  theory  of  the  origin  of  the  hypogene 
rocks,  at  a  variety  of  successive  periods,  as  expounded  in  two  of  the 
chapters  just  cited,  and  still  more  the  doctrine  that  such  rocks  may 
be  now  in  the  daily  course  of  formation,  has  made  and  still  makes  its 
way,  but  slowly,  into  favor.  The  disinclination  to  embrace  it  has 
arisen  partly  from  an  inherent  obscurity  in  the  very  nature  of  the 
evidence  of  plutonic  action  when  developed  on  a  great  scale,  at  par- 
ticular periods.  It  has  also  sprung,  in  some  degree,  from  extrinsic 
considerations  ;  many  geologists  having  been  unwilling  to  believe  the 
doctrine  of  transformation  of  fossiliferous  into  crystalline  rocks,  be- 
cause they  were  desirous  of  finding  proofs  of  a  beginning,  and  of 
tracing  back  the  history  of  our  terraqueous  system  to  times  anterior 
to  the  creation  of  organic  beings.  But  if  these  expectations  have 
been  disappointed,  if  we  have  found  it  impossible  to  assign  a  limit  to 
that  time  throughout  which  it  has  pleased  an  Omnipotent  and  Eternal 
Being  to  manifest  his  creative  power,  we  have  at  least  succeeded  be- 
yond all  hope  in  carrying  back  our  researches  to  times  antecedent  to 
the  existence  of  man.  We  can  prove  that  man  had  a  beginning,  and 
that  all  the  species  now  contemporary  with  man,  and  many  others 
which  preceded,  had  also  a  beginning. 

It  can  be  shown  that  the  earth's  surface  has  been  remodelled  again 
and  again ;  mountain  chains  have  been  raised  or  sunk ;  valleys  formed, 
filled  up,  and  then  reexcavated ;  sea  and  land  have  changed  places ; 


CH.  XXXVIII.]  CONCLUDING  REMARKS.  Ygl 

yet  throughout  all  these  revolutions,  and  the  consequent  alternations 
of  local  and  general  climate,  animal  and  vegetable  life  has  been  sus- 
tained. This  has  been  accomplished  without  violation  of  the  laws 
now  governing  the  organic  creation,  whether  the  succession  of  living 
beings  has  been  brought  about  by  the  transmutation  of  species,  or,  as 
some  contend,  by  the  abrupt  introduction  into  the  earth  from  time  to 
time  of  new  plants  and  animals,  each  assemblage  of  new  species  must 
have  been  admirably  fitted  for  the  new  states  of"  the  globe  as  they 
arose,  or  they  would  not  have  increased  and  multiplied  and  endured 
for  indefinite  periods. 

Astronomy  has  been  unable  to  establish  the  plurality  of  habitable 
worlds  throughout  space,  however  favorite  a  subject  of  conjecture  and 
speculation ;  but  geology,  although  it  cannot  prove  that  other  planets 
are  peopled  with  appropriate  races  of  living  beings,  has  demonstrated 
the  truth  of  conclusions  scarcely  less  wonderful — the  existence  on  our 
own  planet  of  so  many  habitable  surfaces,  or  worlds  as  they  have  been 
called,  each  distinct  in  time,  and  peopled  with  its  peculiar  races  of 
aquatic  and  terrestrial  beings. 

The  proofs  now  accumulated  of  the  close  analogy  between  extinct 
and  recent  species  are  such  as  to  leave  no  doubt  on  the  mind  that  the 
same  harmony  of  parts  and  beauty  of  contrivance  which  we  admire  in 
the  living  creation  has  equally  characterized  the  organic  world  at 
remote  periods.  Thus  as  we  increase  our  knowledge  of  the  inex- 
haustible variety  displayed  in  living  nature,  and  admire  the  infinite 
wisdom  and  power  which  it  displays,  our  admiration  is  multiplied 
by  the  reflection,  that  it  is  only  the  last  of  a  great  series  of  preexist- 
ing creations,  of  which  we  cannot  estimate  the  number  or  limit  in 
times  past.* 

*  See  the  Author's  Anniv.  Address  to  the  Geol.  Soc.,  1837.  Proceedings  G.  S., 
vol.  ii.  p.  520. 


INDEX. 


[The  Fossils,  the  names  of  which  are  printed  in  Italics,  are  Jigured  in  the  Text.'] 


ABBEVILLE,  Post-pliocene,  flint  tools  of,  116. 
Aberdeenshire,  granite  of,  709. 
Abich,  M.,  on  trachytic  rocks,  599. 
Abridged  table  of  fossiliferous  strata,  101. 
Acer  rubrum,  (Eningen,  253. 

trilobatum,  GEmngeii,  252,  253. 

leaf  of,  (Eningen,  266. 

Acrodus  nobilis,  Lias,  421. 

Acrogens,  term  explained,  333. 

Acrolepis  Sedgwickii,  scale  of,  462. 

Actceon  acutm,  Great  Oolite,  405. 

Actinocyclas  in  Atlantic  mud,  320. 

Actinolite-scbist,  735. 

Adams,  Dr.,  on  Nile  river-terraces,  118. 

JEchmodud  Leachii,  Lias,  421. 

jEgean  Sea,  mud  of,  85. 

./Epiornis  of  Madagascar,  455. 

Africa,  South,  Devonian  strata  of,  546. 

Agassiz,  M.,  on  carboniferous  reptiles,  505. 

on  fish  of  Brown-coal,  679. 

on  fish  of  Lias,  420,  421. 

on  fish  of  Sheppey,  294. 

-  —  on  footprints,  455. 
.  —  on  glaciers,  141, 142. 

on  Monte  Bolca  fish,  694. 

on  Old  Red  fossil  fish,  532. 

on  Permian  fish,  461. 

on  Placodus,  440. 

on  Pterygotus,  526. 

Agglomerate,  603. 

Agnostus  integer,  A.  Rex,  580. 

Air-breathers  in  Coal,  510. 

rarity  of,  513. 

Aix-la-Chapelle,  cretaceous  flora  of,  333. 

hot  springs  at,  741. 

Alabama,  cretaceous  shingle  of,  839. 

river-section  near,  810. 

Alabaster  defined,  13. 

Albert!,  on  Keuper,  434 

Alkali  present  in  Silurian  and  Cambrian  strata, 

745. 
Alluvial  deposits,  Eccent  and  Post-pliocene, 

Alluvium,  term  explained,  79. 

•  formation  of,  81. 

in  Auvergne,  80. 

Alpine  erratics,  142. 

glaciers,  colossal  size  of  ancient,  142. 

blocks  on  the  Jura,  142. 

Alps,  age  of  metamorphic  rocks  in,  760. 

Austrian,  infra-liassic  strata  of,  435. 

curved  strata  of,  5S. 

elevated  fossiliferous  rocks  in,  4. 

nummulitic  limestone  of,  307. 

Swiss  and  Savoy,  cleavage  of,  748. 

Alteration  of  mstamorphic  rocks,  748. 

Alternations  of  different  rocks,  14. 

. of  marine  and  freshwater  formations,  32. 


Alum  Bay,  flora  of,  291. 

Alum  schists  of  Sweden  and  Norway,  681. 

Alumina  in  rocks,  11. 

Amblyrhynchus  cristatus,  living,  425. 

Armentacese  of  Swiss  Miocene  flora,  264. 

Amer,  volcanic  formations  near,  667. 

America,  North.  See  United  States,  Canada, 
and  Nova  Scotia. 

America,  South,  cleavage  of  clay-slate  in,  758. 

Cretaceous  strata  of,  340. 

—  gradual  rise  of  parts  of,  46. 

American  forms  in  Swiss  Miocene  flora,  268. 

Amiens,  Post-pliocene  flint  tools  of,  116. 

Ammonites  Bucklandi  (bisculatus),  419. 

bifrons  (  Walcotii),  Lias,  418. 

Braikenridgii,  Oolite,  413. 

Humphre&ianus,  Inferior  Oolite,  412. 

Jason  (A.  Elizabethce),  400. 

maerocephalits,  Oolite,  414. 

margaritatus  (Stokesii),  Middle  Lias,  419. 

NodoUanus  (striatulus),  Lias,  418. 

planorbis,  Lower  Lias,  419. 

Rhotomagensis,  331. 

atriatulus,  Upper  Lias,  419. 

Ampelite,  or  aluminous  slate,  735. 

Amphibole,  597. 

Amphibolite,  598,  604,  735. 

Amphistegina  Hauerina,  244 

Amphitherium  Broderipii,  407. 

Prevostii,  Stonesfleld  slate,  407. 

Ampullaria  glauca  (recent)^  80. 

Amsterdam,  or  St.  Paul  Island,  644 

Amygdaloid,  601,  604 

Analysis  of  volcanic  minerals,  608. 

Ananchytes  ovata,  White  chalk,  825. 

Ancilkiria  subulata^  Eocene,  81. 

Ancyloceras  gigns,  843. 

spinigerum,  832. 

Ancyl,u8  elegans,  Pleistocene,  29. 

Andelys,  chalk  cliffs  at,  854 

Andernach,  strata  near,  679. 

volcanic  sand  and  loess  at,  679. 

Andes,  plutonic  rocks  of,  721. 

volcanic  eruptions  of,  742. 

Andesite,  599. 

Andreasburg,  vein  of,  774. 

Angiosperms  in  the  coal,  479. 

term  explained,  333. 

Anodonta  Cordierii,  A.  latimarginaius  (re- 
cent), 28. 

Anopiotherium  commune,  Binstead,  288. 

gracile,  800. 

Antholithes,  Coal,  479. 

Anihophyllum  lineatum,  279 

Anthracite,  conversion  of  coal  Into,  748. 

in  Rhode  Island,  743. 

Anticlinal  line,  48,  57. 

Antiquity  of  living  epecies,  195. 


784: 


INDEX. 


Antiquity  of  man,  132. 

Antrim,  basalt,  age  of,  242. 

rocks  altered  by  dikes  in,  613. 

Ants,  winged,  of  (Eningen,  252. 

Antwerp  Crag,  fossils  of,  207. 

Apateon  pedestris,  a  carboniferous  reptile,  505. 

Apennines,  Northern,  metamorphic  rocks  of, 
759. 

Aphanite,  or  cornean,  604. 

Apiocrinites  rotundm,  Great  Oolite,  403. 

Appalachian  coal-tield,  497,  501. 

Appalachians,  conversion  of  coal  into  anthra- 
cite in,  743. 

Apteryx  of  New  Zealand,  129. 

Aptychus  latus,  395. 

Apuan  Alps,  marble  of,  759. 

Apus  (?)  dubius,  Coal,  493. 

Aquapendente,  Older  Pliocene  volcanic  rocks 
of,  673. 

Aqueous  deposits,  superposition  and  chronolo- 
gy of,  92. 

erosion  in  Palma,  637. 

rocks  defined,  2. 

rocks,  mineral  character  of,  94. 

Aquitanien,  term  explained,  258. 

Aralo-Caspian  formations,  211. 

Arans,  volcanic  formations,  700. 

Araucaria,  cone  of  fossil,  Inferior  Oolite,  410. 

Arbroath  paving-stone,  526. 

section  from,  to  the  Grampians,  48. 

ArcJicKopteryx  macrura,  Solenhofen,  397. 

Archegosaurus  minor.  Coal :  A.  medius,  skin 
of,  506. 

Archiac,  M.  d',  on  fossils  of  Chalk,  336. 

on  nummulites,  307. 

on  Merita  conoidea,  305. 

on  pisolitic  limestone,  313. 

on  Touraine  faluns,  218. 

Arctic  icebergs,  size  and  weight  of,  146. 

Ardeche,  lava  in,  617. 

Area  of  the  Wealden,  351. 

Arenaceous  rocks  described  in,  11. 

Arenig,  or  Lower  Llandeilo,  formation.  567. 

Arenigs,  volcanic  formations  of,  700. 

Argile  plastique,  305. 

Argillaceous  rocks,  11. 

— -  schist  734. 

Argyle,  Duke  of,  on  Isle  of  Mull  Leaf-beds,  242. 

Argyleshire,  trap  vein  in  cliff,  610. 

Arkose,  735. 

Arran,  age  of  granite  in,  727. 

amygdaloid  filled  with  brown  spar  near, 

622. 

greenstone  dike  in,  610. 

section  of,  722. 

Arthur's  seat,  altered  strata  of,  615. 

Arvicola,  teeth  of,  136. 

Asaphus  caudatus,  Silurian,  559. 

tyrannu^  Silurian,  566 ;  A.  £uchii,  566. 

Ascension,  lamination  of  volcanic  rocks  in,  752. 

Ashby-de-la-Zouch,  fault  in  coal-field  of,  69. 

Aspidura  loricala,  Muschelkalk,  439. 

Astarte  bipartita  (A.  Omalii),  204. 

borealis,  Clyde  drift,  153. 

compressa,  164. 

Asterolepis,  size  of,  533. 

Asterophyllites  foliosus,  Coal,  473. 

Asterias  limestone,  fossils  of,  232. 

Asti,  formations  at,  209. 

Astrangia  lineata,  Virginia,  279. 

Astrcea  basalliformis,  516. 

Astropecten  crispatm,  Sheppey,  294. 

Atherfield  beds,  Isle  of  Wight,  842. 

Athyris  namcula.  Ludlow,  553. 

Atlantic  mud  composed  of  organic  bodies,  820. 

Islands,  277. 

flora  of,  compared  to  American,  271. 

Atlantis.  Miocene,  theory  of,  267-275. 

Atmosphere  of  Coal  period,  490. 

Atrium  of  a  volcano,  636. 

Aturia  siczac  (Nautilus  zigsag\  Sheppey  and 
Porto  Santo,  293,  675. 

Atrypa  reticularis,  Aymestry,  554. 

Augite,  595,  598,  604. 

Augitic  porphyry,  604. 


Aulopora  serpens,  Devonian,  539. 
Aurillac,  freshwater  strata  of,  230. 
Austen,  Mr.,  on  Tipper  Greensand,  331. 
Australia,  auriferous  gravel  of,  7. 

cave-breccias  of,  126. 

gold  of,  779. 

mammalia  of,  127. 

Auvergne,  alluvium  in,  80. 

age  of  trachytic  rocks  in,  657. 

extinct  volcanoes  of,  684. 

granite  veins,  773. 

indusial  limestone  in,  226. 

lacustrine  strata  of,  222-228. 

Lower  Miocene,  freshwater  formations  of, 

227. 

mineral  veins  of,  773. 

springs  from  spent  volcanoes,  766. 

succession  of  changes  in,  220. 

Aoicula  cygnipes,  Lias,  416. 

contorta,  Trias,  441. 

incequivah/is,  Lias,  416. 

papyracea,  Coal,  495. 

socialis,  Muschelkalk,  439. 

Aviculopecten  mblobatus,  518. 
Aymestry  limestone,  fossils  of,  553. 
Azores,  Upper  Miocene,  shells  of,  676. 

Eacillaria  ance,ps,  White  Chalk,  326. 

Baculites  anceps,  Chloritic  Marl,  326. 

Faujasii,  White  Chalk,  826. 

Bulgaria  (?)  in  Tripoli,  25. 

Baffin's  Bay,  drift  of,  described,  144. 

Bagshot  beds,  fossils  of,  288. 

Baine,  Bay  of,  tufaceous  strata,  containing  Im- 
plements, 661. 

subterranean  igneous  action  in,  722. 

Bakewell,  Mr.,  on  cleavage  in  Swiss  Alps,  748. 

Bala  beds,  thickness  and  fossils  of,  564. 

Salcena  emarginata,  tympanic  bone  of,  202. 

Balgray,  near  Glasgow,  stumps  of  trees  in 
coal,  480. 

JBalistidce,  defensive  spine  of,  289. 

Bangor  group,  578. 

Barcelona,  marine  tertiary  strata  of,  673. 

Barmouth  sandstones,  578. 

Barranco,  section  through  the,  638. 

de  las  Angustias,  638. 

Barrande,  M.  Joachim,  on  primordial  zone, 
574-579. 

on  trilobites,  574,  580. 

Barrett,  M.  Louis,  on  bird  in  Blackdown  beds, 

Barton  clay,  shells  of,  287. 

Basalt,  598,  604. 

columnar,  in  the  Vicentin,  618. 

columnar,  of  Giant's  Causeway,  6. 

— —  columnar  in  the  Eifel,  618. 

specific  gravity  of  minerals  in,  657. 

Basanite,  604. 

Banilosaurus,  811. 

Basset,  term  explained,  56. 

Basterot,  M.  de,  on  Bordeaux  tertiary  strata, 
183. 

Bateman,  Mr.  J.  F.,  on  Blackpool  shells,  160. 

Batrachian  (?),  eggs  of,  in  Old  Ked,  Scotland, 
529. 

Bats,  molars  of  insectivorous,  Kyson,  294. 

Bay  of  Fundy,  impressions  in  red  mud  of,  453. 

denudation  of  coal-field  in,  488. 

Bayfield,  on  inland  cliffs  in  Gulf  of  St.  Law- 
rence, 78. 

Bean,  Mr.,  on  fossil  shells  from  Oolite,  411. 

Beaumont,  M.  E.  de,  on  line  between  Miocene 
and  Eocene,  218. 

on  pisolitic  limestone,  313. 

on  Chalk,  336. 

on  island  in  Eocene  sea,  367. 

on  Lias,  417. 

on  formation  of  granite,  705. 

on  chemical  deposits  in  veins,  775. 

on  Jurassic  plutonic  rocks,  724. 

on  plutonic  action  in  Alps,  757. 

Beauport,  near  Quebec,  glacial  drift  at,  168. 

Beche,  Sir  H.  de  la,  on  marine  lizards,  427. 

on  Oolite,  429. 


INDEX. 


785 


Beche,  Sir  H.  de  la,  on  teeth  of  saurians,  447. 

*v on  trap  of  Now  Bed,  696. 

on  Eedruth  copper  mine,  772. 

Beck,  Dr.,  on  graptolites,  565. 

on  Jutland  seaweed,  324. 

on  Phrysranea,  227. 

Beckles,  Mr.  S.  H.,  on  mammalia  of  Purbeck, 

881. 

on  upper  jaw  of  mammals,  385. 

on  footprints  in  Hastings  Sands,  388. 

Belemnites  Pusosianus,  Oxford  Clay,  401. 
mucronatus  (Belemnitella  mucronata). 

325. 

hafitatus,  Oxford  Clay,  400. 

Belgian  fossils,  233. 

•  Miocene  formations,  234. 

Belgium,  Limburg  beds  of,  237. 

Miocene  strata  of,  236. 

Bellerophon  costatus,  520. 

Belosepia  sepioidea,  Sheppey,  293. 

Bembridge  beds,  281. 

Bentham,  Mr.,  on  Miocene  Atlantis,  269. 

Berger,  Dr.,  on  rocks  altered  by  dikes,  614. 

Berlin,  Tertiary  strata  near,  237. 

Bermuda  Islands,  rocks  of,  78. 

Bernese  Alps,  gneiss  in,  761. 

Berthier.  M.,  on  augite  and  hornblende,  596. 

Bertrich-Baden,  basaltic  pillars  at,  619. 

Beudant,  Mr.,  on  volcanic  rocks  of  Hungary, 

683. 
Beyrich,  M.,  on  German  Miocene  strata,  236, 

246. 

Biaritz,  calcareous  cliffs  of,  72. 
Bilin  tripoli,  composed  of  Diatomacese,  25. 
Binney,  on  Stigmaria,  475. 
Bird,  in  Argile  plastique,  306. 

footprints  of,  454. 

Bischoff,  Prof.,  on  Nile  mud,  119. 

on  Aix-la-Chapelle  spring,  741. 

Black  crag,  recent  species  in,  208. 
Blackdown  beds,  332. 
Black  Eiver,  limestone  fossils  of,  572. 
Blackwood,  Capt.,  on  Island  of  St.  Paul,  642. 
Blainville,  M.  de,  on  quadrupeds  of  Gers,  233. 
Boblaye,  M.,  on  inland  cliffs,  73. 

cited,  696. 

Bog-iron-ore,  26. 

Bohemia,  Cambrian  rocks  of,  579. 

Bolderberg  in  Belgium,  Upper  Miocene  of,  235. 

Bone  of  reptile,  Great  Oolite,  "Woodstock,  406. 

Bone-bed  of  fish  remains,  Armagh,  521. 

of  Upper  Ludlow,  552. 

Bone-beds,  triassic,  in  Wiirtemberg,  433. 
Bonelli,  Prof.,  cited,  188. 

on  Italian  Tertiary  strata,  183. 

Boom  and  Eupelmonde,  237. 
Bordeaux,  Miocene  strata  of,  231. 
Borrowdale,  black  lead  of,  88. 
Bosquet,  M.,  on  chalk  fossils,  834. 

on  Maestricht  beds,  315. 

Boston,  U.  S.,  contorted  strata  near,  157. 
Boucher  de  Perthes,  M.,  on  Abbeville  alluvium, 

116. 
Bone,  M.  Ami,  on  human  skeleton  of  Ehine, 

117. 

on  Hungarian  shells,  684. 

on  arrangement  of  rocks,  91. 

Boulder  clay,  described,  137. 

formation  in  Canada,  163. 

formation  in  England,  158. 

fauna  of,  161. 

Bournemouth,  vegetation  of,  290. 
Boutigny,  on  evaporation  of  water  from  gran- 
ite, 709. 

Bovey  Tracey,  lignites  of,  240. 
Bowen,  Lieut.  A.,  K.N.,  drawings  of  rocks  in 

Gulf  of  St.  Lawrence,  78. 
Bowerbank,  Mr.,  on  plants  of  Sheppey,  292. 
Bowman,  Mr.,  on  coal-seams,  500. 
Brachiopoda,  Devonian,  542. 
Brachycepbalous  skull,  113. 
Brackish-water  and  marine  strata  in  coal,  492. 
Bracklesham  beds,  fossils  of,  288. 
Bradford  Encrinites,  402. 
Brash,  term  explained,  81. 

50 


Bravard,  M.,  on  fossils  of  Mount  Perrier,  687. 
Brazil,  ossiferous  caves  of,  128. 
Breccia  on  ancient  waste-lines,  73. 
Breccias  of  the  Caldera  of  Palma,  633. 
Brecciated  limestone,  459. 
Brick-earth,  or  fluviatile  loam,  117. 
Bridlington  beds,  fossils  of,  199. 
Brighton,  elephant -bed  of,  373. 
Bristol,  Dolomitic  conglomerate  of,  446. 

section  of  strata  near,  98. 

British  Miocene  formations,  233. 
Brixham  cave,  near  Torquay,  124. 
Brocchi,  on  Italian  Tertiary  strata,  183. 

on  Subapennine  strata,  209. 

Brockedon,  Mr.,  on  black-lead,  38. 

Brockenhurst,  shells  of,  286. 

Brodie,  Mr.,  on  Purbeck  mammalia,  381. 

Eev.  P.  B.,  on  Lias  insects,  427. 

Brongniart,  M.  Adolphe,  on  groups  of  fossil 

plants,  335. 

on  ferns,  468,  469. 

on  botanical  nomenclature,  333. 

on  erect  fossil  trees,  482. 

on  flora  of  Bunter,  440. 

on  age  of  acrogens,  479. 

on  Lias  plants,  428. 

on  Eocene  flora,  291. 

on  calamites,  472. 

Brongniart,  M.  Alex.,  on  Tertiary  series,  182. 

on  Eocene  strata  of  France,  298. 

on  shells  of  nummulitic  formation,  307. 

on  coal-mine  near  Lyons.  482. 

Bronn,  on  St.  Cassian  fossils,  437. 

Brontes  flabellifer,  540. 

Bronze  implements  found  at  Pompeii,  112. 

at  Herculaneum,  112. 

utensils  at  Nidau,  111. 

Brora,  Oolitic  coal  formation,  411. 
Brown,  Mr.  E.,  on  Stigmarise,  475. 

on  Cape  Breton  coal-field,  488. 

on  carboniferous  rain-prints,  489. 

Brown-coal  of  the  EifeL  679. 

Brownsville,  view  of  coal  at,  502. 

Bryce,  on  two  granites  of  Arran,  728. ' 

Bryozoum,  term  explained,  203. 

Buch,  Von.    See  Von  Buch. 

Buckley,  Dr.,  on  Eocene,  U.  S.,  810. 

Bucklaud,  Dr.,  on  violent  death  of  saurians, 

426. 

on  preservation  of  lower  jaws,  385. 

on  dirt-bed  at  Thame,  392. 

on  spines  of  fish,  422. 

on  Bristol  conglomerate,  447. 

on  chalk  flints,  322. 

Bridgewater  Treatise,  cited,  404,  406. 

on  footprints  of  Trias,  441 

on  term  Poikilitic,  432. 

on  Antrim  chalk,  323. 

on  Eocene  oysters,  295. 

on  coal-plants,  4SO. 

on  Kirkdale  cave,  125. 

Buddie,  Mr.,  on  ancient  river-channel  of  Coal 

period,  501 

—  on  creeps  in  coal-mines,  50. 
Bufadors  of  Olot,  672. 
Buist,  Dr.  G.,  on  saltness  of  Eed  Sea,  450. 
Bulimus  ellipticus.  Bembridge,  282. 

lubricus,^. 

Bunbury,  Sir  C.,  on  Virginian  fossil  plants,  452. 

on  Madeiran  fossil  plants,  649. 

Bunsen,  Prof.,  on  Palagonite,  603. 
Bunter  sandstein,  thickness  of,  440. 

Labyrinthodon  of,  440. 

Buprestis  ?  Elytron  of,  406. 
Burmeister,  on  trilobites,  568. 
Burnes,  Sir  A.,  on  Eunn  of  Cutch,  449. 

CAINOZOIO,  term  explained,  91. 
Cairo,  excavations  at,  3. 
Caithness,  fish-beds  of,  531. 
Calamary  in  Lias,  427. 
Cahimite,  structure  of,  472. 

-  root  of,  471. 
Calamites  eannceformis,  Coal,  471. 
Sucowii,  Coal,  471. 


T86 


INDEX. 


Calamodendron,  472. 

Calamophyllia  radtata,  402. 

Calcaire  grossier,  303. 

lower,  304. 

silicieux,  302. 

Calcareous  rocks,  11. 

formation,  Maastricht,  315. 

Oalcarina  rarispina,  Eocene,  303. 

Galceola  sandalina,  540. 

Calceola-schiefer,  term  explained,  540. 

Caldera,  the,  631. 

of  Palma,  section  through  the,  631. 

Calderas  of  Java,  626. 

of  the  Sandwich  Isles,  623. 

California,  auriferous  gravel  of,  779. 

Calymene  Blumenhachii,  559. 

Cambrian  group,  table  of,  575,  576. 

rocks  of  Bohemia,  579. 

strata  of  Norway  and  Sweden,  581. 

strata  of  U.  S.  and  Canada,  581. 

volcanic  rocks,  700. 

Campania,  volcanic  region  of,  661. 

Campophyllum  Jlexuosum,  Devonian,  515. 

CampopJiyllwm  flexuosuin,  515 ;  C.  turbina- 
lum,  557. 

Canada,  Cambrian  strata  of,  581. 

Devonian  strata  of,  546. 

lakes  of,  169. 

Labradonte  series  of,  584. 

Canadian  drift,  163. 

Canary,  Grand,  shelly  tuffs  of,  675. 

Islands,  volcanoes  of,  627. 

Cantal,  lacustrine  strata  of  the,  229. 

Plomb  do,  igneous  rocks  of,  691. 

Cape  Breton,  coal-measures  of,  488. 

Wrath,  granite  veins  at,  711,  762. 

Caradoc  and  Bala  beds,  nomenclature  of,  562. 

Carbonate  of  lime  in  rocks,  how  tested,  12. 

Carboniferous  flora,  467-479. 

formation,  divisions  of,  465. 

limestone,  514. 

limestone  of  North  America,  522. 

period,  plutonic  rocks  of,  725. 

reptiles,  505. 

volcanic  rocks,  697. 

Carcharodon  heterodon,  tooth  of,  290. 

Cardiocarpon  Ottonis,  Permian,  464. 

Oardita  planicosta  (Venericardia  plani- 
costa), 288. 

sulcata,  287. 

Cardium  dissimile,  Portland-stone,  395. 

porulosum,  305. 

rhceticum,  Trias,  441. 

Btriatulitm,  Kimmeridge  clay,  395. 

Came,  Mr.  N.,  on  Cornish  lodes,  769. 

on  pebbles  in  the  lode,  771. 

Carpenter,  Dr.,  on  OrMtoides,  309. 

Carrara,  hypogene  limestone  of,  736. 

marble  of,  759. 

Caryophyllia  ccespitosa,  193. 

Cashmere,  recent  formations  in,  108. 

Cassian,  St.,  beds,  position  and  fossils  of,  434, 
436. 

Cassiterides  (Cornwall),  tin  obtained  from,  112. 

Castell  Follit,  section  of  lava  at,  671. 

Castrogiovanni,  bent  strata  near,  58. 

Catalonia,  volcanic  rocks  of,  666. 

Catania,  tertiary  beds  of,  192. 

Catenipora  eseharoides,  Silurian,  557. 

Calillm  Lamarckii,  Chalk,  328. 

Cauldrons,  Giant,  of  Sweden,  141. 

Caulopteris  primceva,  carboniferous,  469. 

Cave  breccias  of  Australia,  126. 

Caverns  with  human  and  animal  deposits,  122. 

Caves  at  Engihoul  and  Brixham,  124. 

at  Kirkdale  and  Brixham,  125. 

in  Sicily,  195. 

of  Wellington  Valley,  126. 

Cellent  and  Olot,  section  of  volcanic  matter 
between,  669. 

Celts  described,  116. 

Ceplialaspis  Lyelli,  526. 

Ceratites  nodosus,  Muschelkalk,  438. 

Vtrithiwm  concavum,  Headon  series,  284. 

elegans.  Hempstead,  240. 


Ceridiium  melanoides,  296. 

plicatum,  Hempstead,  240. 

Cervus  alces,  molar  of,  135. 

Cestracion  Philippi,  recent,  830. 

Chalk,  differing  in  N.  and  S.  of  Europe,  336. 

escarpments,  360. 

of  Normandy,  856. 

pebbles  in,  323. 

white,  section  of,  317. 

white,  extent  and  origin  of,  318. 

white,  fossils  of,  26. 

white,  animal  origin  of,  318. 

needles  of,  in  Normandy,  356. 

of  Faxoe,  316. 

cliffs  on  Seine,  854. 

flints,  321. 

Chalk  pinnacle  at  Senneville,  355. 

Chalk-pit  with  potstones,  view  of,  322. 

Chaluzet,  lava  of,  690. 

Chama  squamosa,  287. 

Chcemerops  Helvetica,  Lower  Miocene,  259. 

Chambers,  Mr.  E.,  on  ice  in  Scotland,  151. 

Champoleon,  junction  of  granite  with  Jurassic 

strata,  724. 

Champradelle,  vertical  strata  of  marl  at,  225. 
Chara  elastica  (recent),  G.  medicaginida,  32. 

in  freshwater  strata,  31. 

in  flints  of  Cantal,  230. 

tuberculata,  Bembridge,  282. 

Charlesworth,  Mr.  E.,  on  Suffolk  strata,  196,  200. 

on  Stereognathus,  409. 

Charpentier,  M.,  on  Alpine  glaciers,  142. 
Chatham  coal-field,  457. 
Cheirptherium,  footsteps  of,  443.  507. 
Chemical  and  mechanical  deposits,  33. 

deposits  in  veins,  775. 

Chiapa,  fall  of  volcanic  dust  at,  657. 

Chiastolite  slate,  735. 

Chili,  gold  with  copper  pyrites  in,  779. 

earthquake  in,  770. 

Chillesford  beds,  fossils  of,  199. 
Chimcera  momtrosa,  Lias,  422. 
Chlorite-schist,  8,  735. 
Christiania,  metamorphic  rocks  of,  737. 

quartz  veins  in  gneiss  in,  715. 

granite  veins  in  Silurian  gneiss  of,  726. 

trap  and  syenite  of,  709. 

Chronology  of  deposits,  clue  to,  185. 

Test  of,  in  rocks,  97,  98. 

Oidaris  coronata,  Coral-rag,  399. 

Cinder-bed,  Purbeck,  380. 

Oinnamormt/m  polymorplmm,  CEningen,  254. 

- —  Rossm'dssleri,  264. 

Cladocora  stellaria,  194. 

Claiborne,  Eocene  strata  at,  311. 

Clarke  County,  Eocene  section  in,  310. 

Classification  of  Hastings  strata,  348. 

of  Silurian  rocks,  562,  568. 

of  Tertiary  formations,  178. 

of  Old  Bed  Sandstone  fish,  531. 

of  rocks  and  strata,  2, 10. 

of  Lower  Cretaceous  rocks,  341. 

of  Cretaceous  rocks,  314. 

remarks  on,  217. 

Clausen,  M.,  on  mammalia  of  Brazil,  128. 
ClavMlia  Mdens,  Khine  valley,  80. 
Clavulina  corrugata.  Eocene,  304. 
Clay,  defined,  11. 

slate,  8,  734,  735. 

Weald,  846. 

ironstone,  495. 


Clays,  plastic,  295. 
Claystone  and  Cl 


Clay  stone  Porphyry,  604. 
Cleavage  of  metamorphic  rocks,  747. 
Clermont,  metalliferous  gneiss  near,  741. 
Cliff-limestone,  corals  of,  545. 
Cliffs,  lines  of  inland,  355. 
Climate,  causes  of  change  in,  175. 

of  Coal  period,  504. 

effects  of  fluctuations  on  quadrupeds,  130, 

Clinkstone,  599,  604. 
Clinton  group,  U.  S.,  fossils  of,  571. 
Clyde,  northern  shells  in  drift  of,  153. 
Glymenia  linearis,  Devonian,  587. 
Clymenien-kalk,  term  explained,  537. 


INDEX. 


787 


Coal,  air-breathers  in,  510. 

causes  of  purity  of,  490. 

conversion  into  anthracite,  743. 

conversion  of  lignite  into,  51)3. 

.  continuity  of  seams  of,  503. 

zigzag  flexures  of,  near  Mons,  53. 

formation  at  Brora,  411. 

at  Brownsville,  Pennsylvania,  view  of,  502. 

how  formed,  4T9. 

period,  climate  of,  504. 

rain -prints  in,  489. 

seams,  union  of,  500. 

slow  accumulation  of,  492. 

Coal-bearing  strata,  thickness  of,  465. 
Coal-field  of  Ashby-de-la-Zouch,  69. 

of  Virginia,  451. 

Coal-fields  of  United  States,  496. 
Coal-measures,  466. 

thickness  of,  in  Wales,  466. 

Coal-mine  near  Lyons,  482. 

Coal-pipes,  danger  of,  481. 

Coalbrook  Dale,  coal-measures  of,  493. 

fossil  beetles  in,  494. 

faults  in,  62. 

Coan,  Mr.,  on  crater  of  Kilauea,  624. 
Cochliodus  contortua,  521. 
Cockfleld  rocks  altered  by  dikes,  614. 
Caelacanthuv  granulatus,  marl  slate,  462. 
Coleoptera  of  (Enmgen  beds,  257. 
CoUyrites  ringens,  Inferior  Oolite,  412. 
Columbia,  vinegar  river  of,  299. 
Columnar  basalt  in  the  Vicentin,  618. 

structure  of  volcanic  rocks,  616. 

Come,  ravine  in  lava  of,  689. 
Composition  of  volcanic  rocks,  594. 
Compact  felspar,  605. 
Concretionary  structure,  37. 
Condensation  of  rock-material,  38. 

of  slate-rock,  751. 

Cone  of  a  pine,  Purbeck,  394 

of  Tartaret,  68S. 

of  Catalonia,  663. 

Cones  and  craters,  593. 

absence  of,  in  England,  6. 

Conformable  stratification,  13. 
Conglom3rate,  or  pudding-stone,  11,  47. 

dolomltie  of  Bristol,  446. 

Conifene  of  Coal  period,  476. 
Connecticut,  New  Red  Sandstone  of,  453. 

beds,  antiquity  of,  456. 

Conocephalus  striatus,  580. 

Conoeoryphe  striata,  580. 

Consolidation  of  strata,  83. 

Contorted  strata  in  drift,  Forfarshire,  156. 

Conularia,  ornata,  540. 

Conui  deperditua,  290. 

Conybeara.  Mr.,  on  term  Poikilitic,  432. 

on  Plesiosaurus,  424. 

on  Bristol  conglomerate,  447. 

on  Oolite  and  Lias,  429. 

Coomb,  the,  »3ar  Lewes,  363. 

Coprolites  offish,  819. 

Coral  islands  and  reefs,  34,  46. 

Coral-rag,  fossils  of,  39d 

Coralline  crag,  white  or,  202. 

Corals  of  Devonian  strata  in  United  States,  545. 

of  mountain  limestone,  514. 

of  Sicily,  194. 

neozoic  type  of,  515. 


paljeo2oia  type  of,  515. 

Heinpstead 
alata,  850. 


Corbula  pi/wm,  Hempstead  beds,  239. 


Corinth,  corrosion  of  rocks  by  gases  near,  741. 

Cornbrash,  composition  of,  401. 

Cornean.  605. 

Cornwall,  granite  veins  of,  738. 

granite  veins  in  hornblende  slate  in,  713. 

Devonian  series  of,  535. 

— —  lodes  of,  772,  776. 

tin  obtained  by  ancients  from,  112. 

clay  in,  12. 

vertical  section  of  veins  in  mines,  769. 

Coryphodon  eoc*nus,  of  Sheppey,  292. 
Coseguina,  volcano  of,  656. 
Costa,  Pro/.,  cited,  188. 


Crag,  Norwich,  197. 

of  Antwerp,  207. 

coralline,  fossils  in,  203. 

of  Suffolk,  red  and  coralline,  200-202. 

tables  of  marine  testacea  in,  205. 

Crag  and  tail,  term  described,  152. 

Craig-Dhu,  granite,  728. 

Craigleith  quarry,  slanting  tree  in,  483. 

fossil  trees,  40. 

Crania  Parisiensis,  White  Chalk,  827. 

attached  to  JSoMnus,  28. 

Crassatella  sulcata,  287. 

Crater  of  the  Island  of  St.  Paul,  642. 

Craters  and  cones,  593. 

of  Lagoa,  Madeira,  650. 

of  the  Sandwich  Islands,  623. 

Credneria  in  quader-sandstein,  335. 
Creeps  in  coal-mines  described,  52. 
Cretaceous  fossils,  825. 

rocks,  classification  of,  814. 

volcanic  rocks,  696. 

plutonic  rocks,  723. 

formation  of  U.  S.,  338. 

flora.  332. 

derivation  of  term,  312. 

Crinoids,  Silurian,  558. 

Cristellaria  rotulata.  Chalk,  26. 

Croatia,  Lower  Miocene  of,  245. 

Croizet,  M.,  on  Auvergne  fossil  mammalia,  229. 

Cromer,  Norfolk  drift  at,  160. 

Crop  out,  term  explained,  55. 

Crossopterigidae,  or  fringe-finned  fish,  532. 

Crust  of  earth  defined,  2. 

Crustaceans  of  Old  Red  Sandstone,  526. 

Cryptodon  angulatum,  Hornsea,  294. 

Crystalline  rocks,  cleavage  of,  754. 

limestone,  459. 

rocks,  foliation  of,  753. 

- —  or  metamorphic  limestone,  735. 

erroneously  termed  primitive,  9. 

schists  defined,  7. 

Cumbrecito,  Pass  of,  640. 

Cuming,  Mr.,  collection  of,  190. 

Cunningham,  Mr.  J.,  on  rain-marks,  444 

Cup-and-star  corals,  515. 

Curral,  the,  in  Madeira,  651. 

Curved  strata,  48,  49. 

Cutch,  Runn  of,  449. 

Cuvier,  M.,  on  tertiary  series,  182. 

on  Amphitherium,  408. 

on  Eocene  formation,  293. 

on  fossils  of  Montmartro,  298. 

Cyathea  glauea,  Carboniferous,  469. 
Cyathina  Bowerbankii,  Gault,  515. 
Cyathoerinites  planus.  517. 
Gyathocrinus  car yocrino ides,  517. 
Cyathophyllum  ccespitoxum,  538. 
Cycadeoidea  (Mantellia)  megalophylla,  890. 
Cycadites  comptus,  Gristhorpe,  411. 
Cydas  obovata,  28. 
Cycloidal  scaled  fish,  533. 
Cyclopian  Islands,  beds  of  clay  and  tuff  at,  659. 
Cyclostomit  elegam,  Pleistocene,  80. 
Cyclopteris  Hibernica,  524 
Cylindrites  acutm,  Great  Oolite,  405. 
Cyprcea  europcea,  Red  Crag,  202. 
Cypress  swamps  of  Mississippi,  491. 
Cypria  fasciculata,  380. 

granulatit,  880. 

gibbosa,  Purbeck,  879. 

spiuigera,  Weald,  348. 

-  punctata,  Lower  Purbeck,  889. 

-  tifbercnlata,  Purbeck,  379. 

leguminella,  Purback,  379. 

Valdensis  (C.  faba),  343. 

-  (?)  iivftata,  Coal,  493. 

-  utriato-punctata,  330. 

Purbeekensis,  Lower  Purbeck,  389. 

Cyprides  in  Weald,  348. 
Cypridina  serrato-str-iata,  537. 
Cypridinien-schiefer,  term  explained,  537. 
Ci/rena  Jtumlnalis,  23. 

cortsobrina,  28. 

cuneiformis,  296. 

-  semistriata,  Hempstead  beds,  239. 


T88 


INDEX. 


Cystidefe  in  Silurian  rocks,  564. 
Cythere  (?)  inflata,  Coal,  493. 
Cytkerella,  Chalk,  26. 
Cytherina,  Chalk,  26. 

DACHSTEIN  beds,  composition  of,  435. 

Dadoxylon,  coal-plant,  476. 

Dana,  Mr.,  on  Sandwich  Islands  volcanoes,  623, 

625,  664. 

on  Kamschatka  soundings,  821. 

on  slope  of  lavas,  685. 

on  zoantharia  and  bryozoa,  214. 

on  minerals  of  metamorphic  rock,  744. 

on  coral-reef  of  Sandwich  Islands,  319. 

Dapedius  monilifer,  Lias,  421. 
Daphnogene  cinnamomifolia,  264. 
Darbishire,  Mr.  R.  D.,  on  Moel  Tryfaen  shells, 

159. 
Dartmoor,  intrusive  granite  of,  738. 

carboniferous  granite  of,  725. 

Darwin,  Mr.,  on  plutonic  rocks  of  Andes,  721. 

on  corals  of  Pacific,  319. 

on  mammalia  of  South  America,  129. 

on  Welsh  glacial  drift,  159. 

on  gravel-beds  of  South  America,  640. 

on  sinking  of  coral-reefs,  46. 

on  gradual  rise  of  part  of  S.  America,  46. 

on  pre-glacial  migration  of  plants,  273. 

on  transportation  of  pebbles,  323. 

on  dikes  of  St.  Helena,  664. 

on  marine  saurian,  426. 

on  South  American  ostrich,  456. 

on  foliation  and  cleavage,  753-755. 

Date  of  rocks  ascertained  by  organic  remains, 

180. 

Dates  of  discovery  of  fossil  vertebrata,  589. 
Daubeny,  Dr.,  on  basalt,  598. 

on  decomposition  of  trachytic  rocks,  741. 

on  age  of  Auvergne  volcanoes,  691. 

Daubr6e,  on  alkaline  waters  of  Plorabieres, 

740. 

Davidson,  Mr.,  on  fossils  of  Lias,  418. 
Dawes,  Mr.  J.  S.,  on  calamites,  472. 
Dawkins,  Mr.  W.  Boyd,  on  Trias  quadrupeds, 

ssa 

on  Triassic  mammifer,  442. 

Dawson,  Dr.,  on  Eozoon  Canadense,  584. 

on  Pupa  vetusta,  511. 

on  position  of  calamite,  472. 

on  Devonian  flora,  547. 

Dax,  inland  cliff  at,  72. 

Dean,  forest  of,  coal  in,  504. 

Deane,  Dr.,  on  footprints  in  Trias,  454. 

Debey,  Dr.,  on  flora  of  Aix-la-Chapelle,  333. 

Dechen,  M.  von,  on  Cornish  granite  veins,  713. 

on  reptiles  in  Saarbriick  coal-field,  506. 

on  remains  in  brown-coal,  678. 

Delesse,  M.,  on  minerals  of  hypogene  lime- 
stone, 744. 

on  augite  and  basalt,  598. 

on  globular  structure  of  volcanic  rock,  619. 

on  fel  spathic  rock  of  Madeira,  653. 

Deltas  of  Switzerland,  120. 

Deluge,  4. 

Dendrerpeton  found  in  Coal.  510. 

Dennis,  Rev.  J.  P.,  on  Stereognathus,  409. 

Denudation  explained,  66. 

terraces  of,  in  Sicily,  75. 

of  the  Weald  valley,  357-376. 

of  chalk,  364. 

of  Palma  fluviatile  or  marine  ?  639. 

Deposition,  proofs  of  gradual,  231. 
Derbyshire,  veins  in  mountain  limestone,  771. 
Deshayes,  M.,  on  recent  and  fossil  shells,  188. 

on  pisolitic  limestone,  313. 

on  shells  of  Etna,  190. 

on  Hungarian  shells,  6S3. 

on  Soissonnais  shells,  805. 

Desmarest,  on  trappean  rocks,  87. 
Desnoyers,  M.,  on  Eocene  fossil  footprints,  301. 

on  faluns  of  the  Loire,  183. 

Desor,  M.,  on  shells  of  the  Sahara,  176. 

on  Celtic  coins,  111. 

Devonian  period,  vegetation  of,  546. 
Brachiopoda,  542. 


Devonian  fossils  of  the  Eifel,  679. 

fossils  of,  537-543. 

series  of  North  Devon,  536. 

of  Russia,  542. 

of  United  States,  543. 

series,  table  of,  536. 

system,  term  explained,  535. 

Devonshire,  cleavage  of  slate  rocks  in,  750. 

Diablerets,  shells  from  the,  807. 

Diagonal,  or  cross-stratification,  16. 

Diagram  of  plutonic  and  sedimentary  forma- 
tions, 720. 

Diallage  rock,  605. 

Diastopora  diluviana,  403. 

Diatomacece  in  tripoli,  25. 

Diceras  arietina.  Coral-rag,  399. 

Lansdalii,  344. 

Limestone,  term  explained,  399. 

Dicotyledonous  leaves  in  chalk,  333. 

Didelphys  Azarce,  Oolite,  408. 

Didymograpsus  geminus,  Silurian,  567. 

Murchisonii,  Llandeilo,  565. 

Dicst  sands,  234. 

Dikelocephalous  skull,  113. 

Dikelocephalus  minnesotensis,  582. 

Dikes,  trap  and  volcanic,  609. 

in  Sicily,  665. 

of  coarse  and  fine-grained  granite,  730. 

of  Monte  Somma,  662. 

defined,  6. 

rocks  altered  by,  613. 

volcanic,  of  St.  Helena,  617. 

of  Vesuvius,  663. 

Diluvium,  origin  of  term,  187. 

Dinornis,  skeleton  of,  455. 

Dinotherium  giganteum,  213. 

Diorite,  599,  605. 

Dip,  term  explained,  53. 

ZHplograpaus  folium,  Silurian,  565. 

pristis,  Silurian,  565. 

Dirt-bed  of  Lower  Purbeck,  389. 

Distribution  of  fossil  quadrupeds,  128. 

Dolerite,  598,  605. 

Dolomite  defined,  13. 

of  cone  of  Monte  Somma,  661. 

Domite,  605. 

Downs,  South,  chalk  escarpment  of,  360,  361. 

Downton  Sandstone,  fossils  of,  551. 

Drew,  Mr.,  on  Hastings  sand,  348. 

Drift  of  Scandinavia,  North  Germany,  and  Rus- 
sia, 149. 

shells  in  Canada,  165. 

contorted,  156. 

in  Ireland,  160. 

northern,  of  Scotland,  151. 

North  Wales,  158. 

Norfolk,  160. 

transported  by  icebergs,  144. 

meteorites  in,  176. 

Dromatherium  sylvestre  of  N.  Carolina,  457. 

Dryandra  SehranMi,  Lower  Miocene,  262. 

Dryandroides  HakemfoUa.  near  Lausanne, 
262. 

Dudley  limestone.  557. 

burning  coal-mines  at,  738. 

Dufrenoy,  M.,  on  line  between  Miocene  and 
Eocene,  218. 

on  granite  of  Pyrenees,  739. 

Dumont,  Prof.,  on  Belgian  Lower  Eocene,  313. 

Duncan,  Dr.,  on  West  Indian  corals,  274. 

Dundry  Hill,  near  Bristol,  section  of,  98. 

Dunker,  Dr.,  on  Weald  of  Germany,  351. 

Dura  Den,  yellow  sandstone,  524. 

Durham,  intrusion  of  trap  between  beds  near, 
616. 

EARTHQUAKE  in  Olot,  672.. 
Echinoderms  in  coralline  crag,  205. 
Echinosphceriteft  balticux,  Silurian,  564. 
Echinus,  with  crania  attached,  23. 
Edeghem  beds,  fossils  of,  233. 
Edwards,  Mr.,  on  Brockenhurst  shells,  286. 
Egerton,  Mr.,  on  fossils  of  Southern  India,  340. 
Egerton,  Sir  P.,  on  fish  of  Penarth  beds,  442. 
on  Old  Red  fish,  532. 


INDEX. 


789 


Egerton,  Sir  P.,  on  fish  of  Permian,  462. 

-  on  fish  of  Hoadon  series,  285. 

-  on  Ichthyosaurus,  423. 

-  on  Ischypterus,  456. 

Egg-like  bodies  in  Old  Bed  Sandstone,  529. 
Ehrenberg,  Prof.,  on  bog-iron-ore,  26. 
--  on  infusoria,  25. 

-  on  term  Bryozoum,  203. 

-  on  Silurian  foraminifera,  5TO. 
Eifel,  age  of  trachytic  rocks  in,  65T. 

-  basaltic  pillars  of  the  Kasegrotte  in  the, 
619. 

-  lake-craters  of,  679. 

-  Lower  Miocene,  volcanic  rocks  of,  67T. 

-  Lower,  trass  of,  6S2. 
Elephant-bed,  Brighton,  378. 
Elephaa  meridionalis,  molar  of,  134. 

-  antiquus,  molar  of,  133. 

-  primigenius,  molar  of,  133. 
Elevation  craters,  634. 

Elmos  of  Ireland  and  Cornwall,  77a 

-  term  explained,  725. 

-  in  granite,  778. 
Elytron  of  Buprestis,  406. 
Emarginula  clathrata,  Great  Oolite,  405. 
Embotkrium,  or  Hakea  saligna,  O3ningen,  256. 
Emmons,  Prof.,  on  jaws  of  Triassic  quadru- 

ped, 389. 

-  on  DromatherJum,  457. 
Enorinite  with  serpulce  attached,  403. 
Encrinites  of  Bradford,  402. 
Encrinus  liliiformis  (moniliformis),  439. 
Endogens,  term  explained,  333. 
Enstfhoul  cave,  124. 

England,  Lower  Miocene  strata  of,  239. 

-  Newer  Pliocene  strata  of,  196. 

-  Upper  Eocene  formations  of,  281. 
Eocene  formations,  map  of,  280. 

-  foraminifera,  303,  304. 

-  formations  of  England,  281. 

-  strata  of  France,  table  of,  297. 

-  granite  and  plutonic  rocks,  721. 

-  and  Miocene,  line,  between,  217,  247. 

-  strata,  France,  fossil  footprints  in,  292. 

-  volcanic  rocks  of  Monte  Bolca,  694. 

-  strata  in  the  United  States,  309. 

-  term  explained,  188. 
Eosaurus  found  in  Coal,  511. 

Eozoon  Canadense,  in  Laurentian  rocks,  765. 

-  oldest  known  fossil,  584. 
Eppelsheim,  Dinotherium  of,  243. 
Equisetacea?  of  the  Coal,  471. 
Eiuisetites  columnaris,  434. 
Efuus  caballus,  molar  of,  134. 

Erman,  M.,  on  finding  of  meteoric  iron,  177. 
Erratic  blocks,  actions  of,  140. 

-  near  Chichester,  374 
Erratics  of  Canada,  163. 

-  of  Greenland,  144. 

-  of  Victoria  Land,  146. 

-  Alpine,  142. 

Erosion,  aqueous,  in  Palma,  637. 

Escarpments  of  the  Weald,  360. 

Exchara  distieha,  Chalk,  329. 

£ac.'tarina  oceani,  Chalk,  329. 

Escher  von  der  Linth,  on  submergence  of  Sa- 

hara, 176. 
Extheria  minuta,  Muschelkalk,  439. 


-  ovata,  Eichmond,  452. 

Etheridge,  Mr.,  tables  of  Oolitic  fossils,  413. 

-  on  fossils  of  Middle  Oolite,  401. 

-  on  cretaceous  fossils,  344. 

-  on  fossils  of  Upper  Oolite,  898. 
Etna,  Mt.,  652. 

-  lavas  of,  191. 

-  age  of  lavas  of,  658. 
Eanomia  radiata,  Great  Oolite,  402. 
Eunotia  bidens,  Atlantic  mud,  820. 
EuomphaluH  pentagulatus,  5l9. 
Euphotide,  605. 

Eurite,  708;  735. 

Euritic  porphyry  near  Christiania,  716. 

Europe,  divisions  of  Tertiary  strata  in, 

-  extinct  quadrupeds  of,  115,  116. 


187. 


Excavation  through  lava  by  rivers,  670. 
Exogens,  term  explained,  333. 
Exogyra  virgula,  Kimmeridge  clay,  395. 
Extracrinus  Briareus,  Lias,  420. 

FALCONER,  Mr.  A.  H.,  on  Dichodon,  285. 
Falconer,  Dr.,  on  Purbeck  mammalia,  882. 

on  flint  knives  of  Brixham  cave,  124. 

on  Mastodon  arvernenzis.  19a 

on  Siwalik  Hills,  276. 

on  cave  and  drift  fossils,  129. 

on  Plagiaulax,  384. 

Faluns  of  the  Loire,  183. 

of  Touraine,  213. 

Farnham,  phosphate  of  lime  near,  382. 
Fascicularia  aurantium,  Coralline  crag,  204. 
Fault,  term  explained,  62. 

in  Chalk  near  Lewes,  363. 

Faults,  origin  of,  64. 
Fauna  of  Nebraska,  278. 

of  Keuper,  432. 

of  Weald  clay,  346. 

and  flora  of  Upper  Val  d'Arno,  196. 

of  Montmartre,  298. 

of  Vienna  basin,  245. 

of  Headon  series,  285. 

of  Galapagos  Islands,  425. 

fluctuations  in,  186. 

Favorites  Gothlandica,  557. 

potymorpha,  538. 

Faxoe,  chalk  of,  316. 

Fells  tigris,  molar  of,  135. 

Felixstow,  remains  of  cetacea  near,  202. 

Felspar  porphyry,  605. 

Felspathic  lava,  specific  gravity  of  minerals  o^ 

658. 

Felstone,  605. 

Fenestella  retiformte,  460. 
Ferns  of  Carboniferous  period,  468. 
Ferruginous  sands,  sand-pipes  in,  235. 
Fife,  altered  rock  in,  615. 
Fife  shire,  carboniferous  trap  of,  697. 
Filling  up  of  veins,  772. 
Fish,  Eocene,  of  Monte  Bolca,  694. 

fossil,  of  mountain  limestone,  521. 

number  of  living,  534. 

of  the  Upper  Ludlow,  551. 

of  Lias,  420. 

fossil  of  Old  Eed  Sandstone,  525-534. 

of  Permian  marl-slate,  461. 

of  the  Brown  Coal,  678. 

oldest  known,  not  of  low  grade,  555. 

Fisher,  Mr.,  on  dirt-bed  at  Eidgway,  892. 
Fissures  filled  with  metallic  matter,  767. 

in  metalliferous  veins,  769. 

Fitton,  Dr.,  on  Lower  Cretaceous,  341. 

on  Hastings  sand,  346. 

on  dirt-bed  of  Boulonnais,  392. 

on  corals  of  Oolite,  399. 

Fleming,  Dr.,  on  Parka  decipiens,  528. 

on  carboniferous  trap,  696. 

on  scales  of  fish  in  Old  Bed,  525. 

Flint-breccias,  angular,  872. 

Flints  in  chalk,  321. 

Flora,  Miocene,  of  Switzerland,  richness  of; 

of  Carboniferous  period,  467,  478. 

of  Great  Oolite,  410. 

grade  of  Carboniferous,  478. 

Miocene,  of  Switzerland,  251-267. 

Upper  Cretaceous,  332. 

of  Subapennine  beds,  210. 

Eecent  and  Miocene  relations  of,  269. 

fluctuations  in,  186. 

of  the  Permian,  463. 

Miocene,  of  (Eningen,  251. 

of  Wealden,  352. 

Devonian,  compared  to  Carboniferous,  518. 

of  Vienna  basin,  245. 

Flotz,  term  explained,  87. 

Fluctuations  in  conformation  of  Weald,  369- 

371. 

Fluvia,  the,  cutting  through  lavas  of  Olot,  669. 
Flysch,  term  explained,  307. 
invaded  by  plutonic  rocks,  721. 


790 


INDEX. 


Foliated  gneiss,  733. 

Foliation,  irregularities  in,  756. 

of  crystalline  rocks,  753. 

Fontainebleau,  gres  de,  217. 

Footprints  of  reptiles,  507,  508. 

fossil,  in  New  Bed.  443. 

of  a  bird,  Connecticut,  454 

in  Connecticut  Valley,  453. 

fossil,  on  Potsdam  sandstone,  582. 

Foraminifera,  Chalk,  26. 

Cretaceous,  821. 

of  Mountain  Limestone,  522. 

Eocene,  803,  304. 

Forbes,  late  E.,  on  term  Pleistocene,  107. 

on  Post-glacial  fauna,  129. 

on  westward  extension  of  Europe,  269. 

on  depth  of  animal  life  in  ^Egean  Sea,  35. 

on  corals  of  Devonian  strata,  545. 

on  subdivisions  of  Bembridge  beds,  282. 

on  Older  Pliocene  shells,  205. 

on  Touraine  fossil  testacea,  213. 

Forbes,  Mr.  D.,  on  planes  of  foliation,  754. 

Forbes,  Prof.  J.  D.,  on  Alpine  glaciers,  142. 

Forest  marble,  401. 

Forests,  fossil,  in  Coal,  484-488. 

fossil,  of  Isle  of  Portland,  391. 

Forfarshire,  Cephalaspis  beds  of,  531. 

Formation  of  the  Weald,  845. 

of  the  Caldera  of  Palma,  634. 

term  defined,  3. 

Formations,  Belgian  and  British  Miocene,  233. 

intermediate  between  Eocene  and  Creta- 
ceous? 313. 

Formica  lignitum,  (Eningen,  251. 

Fossil  plants  of  Lias,  428. 

forest  near  Wolverhampton,  482. 

footprints,  Eocene,  801. 

trees  erect  in  Coal,  482,  483. 

plants  of  Lower  Miocene,  Switzerland, 

259. 

plants  of  Bovcy  Tracey,  240. 

term  defined.  4. 

wood,  perforated  by  Teredina,  24. 

petrifaction  of,  39. 

shells  in  Coal,  Nova  Scotia,  488. 

quadrupeds,  distribution  of,  128.   v 

shells,  Tertiary,  188. 

plants  of  Monte  Bolca,  695. 

Fossiliierous  strata,  general  table  of,  101. 

groups  of,  99,  100. 

table  of,  102. 

Fossils  of  Portland-stone  and  Kimmeridge 
clay,  394,  395. 

of  hippurite  limestone,  338. 

of  mountain  limestone,  516. 

common  to  Upper  and  Middle  Oolite,  398. 

common  to  Middle  and  Lower  Oolite,  401. 

of  the  Lias,  418. 

petrifaction  of,  39-43. 

test  of  the  age  of  formations,  98. 

arrangement" of,  in  strata,  21* 

freshwater  and  marine,  27. 

of  Liandovery  formation,  561. 

of  the  Muschelkalk.  438. 

of  Old  Ked  Sandstone,  524-534. 

proportions  of,  in  divisions  of  Oolite,  413. 

of  primordial  zone,  580. 

of  Lower  Greensand,  343. 

of  Coal,  498^95. 

of  Wealden  group,  348. 

of  Bolderberg  beds,  236. 

number  of,  in  Hallstadt  beds,  436. 

of  Permian  strata,  460. 

of  (Eningen  molasse,  249. 

of  nummulitic  formations,  307. 

of  the  Upper  Ludlow,  551. 

of  Ked  Crag,  201. 

of  Upper  Greensand,  831. 

of  the  Upper  Cretaceous  rocks,  825. 

of  Devonian,  537-548. 

Fournet,  on  Auvergne  metalliferous  gneiss, 
741. 

on  quartz,  705. 

on  veins  in  granite,  773. 

Fox,  Kev.  D.,  on  Isle  of  Wight  mammalia,  2S3. 


Fox,  Mr.,  on   cause  of  electric  currents   in 

veins,  776. 
Fracture,  lines  of,  in  the  Wealden,  366. 

lines  of,  in  rock,  774. 

Fragments,  included,  test  of  age  of  plutonio 

rocks,  717. 

test  of  age  of  volcanic  rocks,  658. 

France,  Lower  Miocene  strata  of,  217-222. 

map  of  Lower  Miocene  of,  221. 

Miocene  strata  of,  212. 

French  divisions  of  cretaceous  series,  814. 
Freshwater  formations  in  Auvergne,  227. 
how  distinguished  from  marine,  27,  28, 

80,  32. 

beds,  land-shells  numerous  in,  27. 

shells  in  brown-coal  near  Bonn,  679. 

Fulgur  canaliculatus,  Maryland,  278. 

Fuller's  earth,  shells  of,  412. 

Fundy,  Bay  of,  impressions  of  red  mud  in,  453. 

Fungi  on  fossil  leaves,  266. 

Fungia  patellaris  (recent),  515. 

Fusion  of  quartz,  705. 

Funulina  cylindrica,  522. 

Fusm  contrarius,  Eed  Crag,  202. 

quadricostatus,  Maryfand,  278. 

GABBEO,  or  Diallage  rock,  605. 

Gaillonella  distans,  G.  ferruginea,  25. 

Galapagos  Islands,  living  marine  saurian  in, 
425. 

Galeocerdo  latidens,  tooth  of.  290. 

Galerites  albogalerus,  White  Chalk,  325. 

Galestes  in  Middle  Purbeck,  385. 

Ganges,  buried  soil  in  delta  of,  492. 

Ganoids  of  Wealden,  349. 

preponderance  of,  in  Old  Eed  strata,  533. 

of  Trias,  452. 

Gap  in  time  between  Eocene  and  Cretaceous 
periods,  312. 

Gaps,  numerous,  in  the  transitions  of  strata, 
179. 

Gases,  subterranean,  rocks  altered  by,  740. 

Gaudin,  M.,  on  Subapennine  flora,  210. 

on  Swiss  Miocene,  248,  261. 

Gault  of  Upper  Cretaceous,  331. 

thickness  of,  332. 

Gavarnie,  flexures  of  strata  near,  59. 

Geikie,  Mr.,  on  ice-action  on  land,  158, 155. 

on  Pentland  Old  Ked  volcanic  rocks,  699. 

Gemunder  Maar,  view  of,  680. 

Genera  of  Hallstadt  and  St.  Cassian  mollusca, 
437. 

Geneva,  Lower  Molasse  of,  259,  260. 

Geographical  relationship  between  fossil  and 
living  vertebrata,  128, 129. 

Geography,  physical,  of  Cretaceous  and  Weal- 
den districts,  353. 

Geology  defined,  1. 

Gergovia,  associated  tuffs  and  lacustrine  strata 


Germany,  TrSassic  fauna  of,  432. 

Gers,  Upper  Miocene  strata  of,  232. 

Gervillia  anceps,  344. 

Giant  cauldrons  of  Sweden,  141. 

Giant's  Causeway,  columnar  basalt  of,  616. 

basalt,  age  of,  242. 

Gibbes,  R.  W.,  on  Eocene  cetacean,  U.  S.,  810. 

Girgenti.  limestone  of,  194. 

Glacial  formations  of  North  America,  162. 

erosion,  theory  of,  173. 

epoch,  136-177. 

Glaciation  of  Kussia,  149. 

of  Scotland,  151. 

of  Scandinavia,  149. 

Glaciers,  abrading  action  of,  138. 

Glasgow,  marine  strata  near,  109. 

Glass-cavities  in  quartz,  705. 

Glauconie  grossiere,  304. 

Glen  Tilt,  granite  and  argillaceous  schist  of 

710. 

Globigerina  bulloides,  Atlantic  mud,  320. 
Globular  structure  of  volcanic  rocks,  616. 
Glyphea  (?)  dubia.  Coal,  4<J3. 
Glyptoslrolnis  Europu-us.  (Eningen,  256. 
Gneiss,  foliated,  733-735. 


INDEX. 


791 


Gneiss,  fundamental,  of  Scotland,  585. 

granite  veins  traversing,  711. 

Gold,  age  of,  in  Ireland,  778. 

in  Ural  Mountains,  779. 

Gold  mines  of  Australia  and  Chili,  779. 
Goldenberg,  Mr.  Fr.,  on  Saarbruck  insects,  494. 
Goldfuss,  Prof.,  on  reptiles  in  Coal,  506. 
Goniatites  crenistria,  520. 

Listeri,  Coal,  495. 

evolutw.  520. 

Goppert,  M.,  on  petrifaction,  40. 

on  plants  of  coal-measures,  468. 

on  Swiss  Miocene,  248,  256. 

Gorgonia  infiindibuliformis,  460. 

Graham's  Island,  621. 

Grampians,  Old  Ked  conglomerates  in,  47. 

Old  Eed  of,  530. 

gneiss  and  crystalline  schists  of,  765. 

Grateloup,  M.  de,  on  Dax  fossils,  338. 

on  fossils  of  Chalk,  838. 

Grand  Canary,  shelly  tuffs  of,  675. 

Granite,  dikes  in  coarse  and  fine-grained,  729. 

described,  7. 

fine-grained,  of  Ploverfiold,  728,  729. 

schorly,  708. 

porphyritic,  707. 

veins,  structure  of,  712. 

formation  of,  702. 

protrusion  of  solid,  727,  731. 

veins  in  talcose  gneiss,  713. 

composition  of,  705. 

hydrotherraat  action  in  formation  of,  707. 

passage  of.  into  trap,  708. 

Granites,  Arran,  age  of,  727. 

oldest,  726. 

Graphic  granite,  704. 

Graphite,  powder  of,  consolidated  by  pressure, 

38. 

Graptolites,  565. 

Graptolites  Murchisonii,  Llandeilo,  565. 
Graptolithm  Ludensis,  Silurian,  559. 
Grasshopper,  wing  of,  in  coal-measures,  494. 
Grauwacke,  term  explained,  549. 
Gray,  Dr.  Asa,  on  Miocene  Atlantis,  269,  271. 
Grayrs  Thurrock,  Essex,  pachyderms  found  at, 

130. 

Graystone,  605. 
Graystone,  volcanic  rock,  605. 
Great  Oolite,  402. 

fossils  of,  402. 

Greece,  Upper  Miocene  of,  247. 
Greensburg,  Penn.,  reptile  footprints  of,  509. 
Greenland,  sinking  of  coast  of,  46. 

continual  ice  of,  144, 145. 

Greensand,  Lower,  341. 

Upper,  881. 

Greenstone,  599,  605. 

dike,  Christiania,  612. 

columns  of,  698. 

Grcs  de  Beauchamp,  302. 

Gres  de  Foutainebleau,  Miocene  or  Eocene? 

217. 

Grey  wackc,  Older  Rhenish,  equivalents  of,  541. 
Griffiths,  Sir  E.,  on  Coal  strata  of  Ireland,  466. 
Grignon,  fossil  shells  near,  303. 
Grit  defined,  11. 

Gryllacris  litkanthraca,  Coal,  494. 
GryphcKO,  coated  with  Serpulce,  22. 

arcuata,  G.  inourva,  29. 

incurva,  Lias,  41 7. 

virgula,  Kimmeridge  clay,  395. 

columba,  Chalk,  328. 

globosa,  Chalk,  328. 

Gryphite  limestone,  417. 

Guadaloupe,  glass-cavities  in  quartz  of,  706. 

Guidotti,  Prof.,  cited,  1S8. 

Guiscardi,  Signor,  on  shells  of  Vesuvius,  190. 

Gumbel,  M.,  on  Hallstadt  beds,  434. 

Gunn,  Mr.,  on  Norfolk  drift  fauna,  160. 

Mrs.,  on  Norwich  flints,  32i 

Gutbier.  Col.  von,  on  Permian  flora,  463. 
Guttenstein  beds,  thickness  of,  436. 
Gymnogens,  term  explained,  333. 
Gypseous  marls  of  Auvergne,  227. 
Gypsum  defined,  13. 


Gyrolepte  tenuistriatus,  442. 

HAIME,  M.,  on  Bryozoa,  214. 
Hakea  exulata,  Switzerland,  262. 

mlicina,  (Eningen,  255. 

saligna,  (Eningen,  255. 

Hall,  Capt,  on  Cyclopian  Isles,  659. 

Prof.,  on  exogen  in  Devonian  strata,  547. 

Sir  James,  on  curved  strata,  48. 

on  crag  and  tail,  152. 

on  cooling  of  metals,  663. 

Hallstadt  beds,  position  and  fossils  of,  434-436. 

Halysitea  catenularius,  Silurian,  557. 

Hamites  spiniger,  332 

Hamilton,  Sir  W.,  on  dikes  of  Vesuvius,  663. 

Hampshire,  Old  Harry  rocks  of,  372. 

Harlech  Grits,  fossils  of,  578. 

Harpaetor  maculipes,  (Eningen,  257. 

Harris,  Major,  on  salt  lakes,  450. 

Hartung,  M.,  on  aqueous  erosion  in  Palma,  642. 

on  Madeiran  fossil  plants,  649. 

on  Teneriffe,  645. 

on  lava  at  Port  Moniz,  654. 

on  shells  of  Azores,  676. 

on  geology  of  Madeira,  628. 

on  Madeira  and  Canary  Miocene  fossils, 

674. 
Hartz  Mountains,  mineral  veins  of,  770. 

bunter  sandstein  of,  440. 

Hastings,  Marchioness  of,  on  Headon  beds,  285. 

sands,  348. 

Hauer,  M.  von,  on  age  of  Werfen  sandstone, 

466. 

Hautes  Alpes,  rocks  of,  724. 
Hawkshaw,  on  fossil  trees  in  Coal,  480. 
Hayden,  Mr.,  on  Nebraska  plants,  340. 
Headon  series,  Isle  of  Wight,  284. 
Heat,  intense,  not  required  for  rnetamorphic 

rocks,  739. 
Hebert,  M.,  on  pisolitic  limestone,  313. 

on  Sables  de  Bracheux.  806. 

on  fossil  shells  of  Etampes,  218. 

on  French  Eocene  mammalia,  387. 

Hebrides,  dikes  in  trap  in,  611. 

Heer,  M.,  on  Superga  fossil  plants,  247. 

on  Lower  Miocene  plants,  243. 

on  North  American  Sequoia,  263. 

on  beds  of  Croatia,  246. 

on  Miocene  Atlantis,  269. 

on  Virginian  fossils,  451. 

on  fossil  plants  of  Switzerland,  248-267. 

on  Monte  Bolca  Eocene  plants,  695. 

•  on  Madeiran  fossil  plants,  650. 

on  Swiss  Miocene  insects,  267. 

Heidelberg,  varieties  of  granite  near,  712. 
Heliolites  porosa,  Devonian,  539. 
Helix  labyrinthica,  Headon  Hill,  284. 

occlusa,  Bembridge,  282. 

plebeia,  Khine,  119. 

Turonensis,  30. 

Hemicidaris  Purbeckensis,  380. 
Hemipneusten  radiatus.  Chalk,  316. 
Hemitelites  Brownii,  Lower  Oolite,  411 
Hempstead  beds,  subdivisions  of,  239. 
Henfrey,  Mr.  A.,  on  New  Jersey  Mastodon,  167. 
Uenslow,  Prof.,  on  altered   rock  near  Plas- 

Newydd,  613. 

on  trunks  in  dirt-bed,  891. 

Herculaneum,  bronze  instruments  found  at. 

112. 

Herodotus  on  lake-dwellings,  110. 
Herschel,  Sir  J.,  on  slaty  cleavage,  749. 
Hertfordshire  pudding-stone,  35. 
Heteroeercal  tail  of  fish,  461. 
tails   characteristic    of  fish  of  primary 

period,  534. 

Hibbert,  Dr.,  on  coal-field  at  Burdiehouse,  495. 
Hill  of  Gergovia,  strata  of,  693. 
Himalaya,  elevated  fossiliferous  rocks  in,  4. 

Tertiary  mammalia  of,  276. 

Hippurite  limestone,  836. 
Hippunte  organisans,  Chalk,  337. 
Hippopodium  ponderosum,  Lias,  418. 
Hippopotamus,  molar  of,  134. 
Hitter  coprolithorum,  CBuingen,  251. 


792 


INDEX. 


Hitchcock,  Prof.,  on  Trias  footprints,  453. 
Hoffmann,  on  stufas  of  St.  Calogero,  741. 
Holoptychius  nobilissimm,  tooth  of,  525. 

Hibberti,  tooth  of,  505. 

ffomalonolus  armatus,  541. 

delphinocephalus,  559. 

Homocercal  tail  of  fish,  461. 

tails  characterize  fish  of  secondary  period, 

Hooghly  Eiver,  analysis  of  water  of,  41. 
Hooker,  Dr.,  on  seaweed,  324. 

on  sporangia  of  Silurian  plant,  552. 

on  P.  Kichardi,  266. 

on  Sigillariie,  4T5 ;  on  Coniferse,  4TT. 

on  Carboniferous  flora,  478. 

on  Arctic  ice,  146. 

Hopkins,  Mr.,  on  fractures  of  Weald,  366. 
Horizontal  strata,  upheaval  of,  45. 
Horizontality  of  strata,  15. 
Hornblende  rock,  598,  605,  735. 

schist,  134,  736. 

composition  of,  595. 

Horner,  Mr.,  on  Holoptychius,  505. 

Homes,  Dr.,  on  inollusca  of  Vienna  basin,  244. 

Hornstone  porphyry,  605. 

Horstead,  potstones  at,  323. 

Howell,  Mr.,  on  Oolitic  strata,  415. 

Hubbard,  Prof.,  on  granite  veins  of  "White 

Mountains,  718. 

Hudson  Eiver  group,  fossils  of,  571. 
Hugi,  M.,  on  Swiss  Alps,  761. 
Human  remains  of  Eecent  period,  109-112. 

in  Post-pliocene  deposits,  117. 

deposits  in  caverns,  122, 124. 

Humboldt,  on  uniform  character  of  rocks,  764. 
Hungary,  trachyte  of,  709. 

volcanic  rocks  of,  633. 

Hunt,  Mr.,  experiments  on  clay -iron-stone,  495. 
Huronian  series,  583. 
Hutton,  opinions  of,  60. 
.Huttonian  theory,  87. 
Huxley,  Prof.,  on  fish  of  Old  Bed,  532. 

on  Atlantic  mud,  320. 

on  Pteraspis,  555. 

Hyaena  Speloea.  molar  and  lower  jaw  of,  135. 
Hybodus  plieatilis,  442. 
Hybodus  reticutatus,  Lias,  421. 
Hydrothermal  action,  739. 

in  formation  of  granite,  707. 

producing  granite  veins,  726. 

cause  of  inetamorphism,  739. 

Hylerpeton,  reptile  found  in  Coal,  511. 
Hylonomus,  reptile  found  in  Coal,  511. 
Hymenocaris  vermicauda,  577. 
Hypersthene  rock,  606. 
Hypogene  limestone,  736. 

rocks,  mineral  character  of,  764. 

term  defined,  9. 

Hyracotherium,  molar  of,  294. 

IBBETSON,  Mr.,  on  Stonesfield  slate,  410. 
Ice,  rocks  drifted  by,  138. 
Icebergs  of  Labrador,  148. 

mediums  of  transportation,  145. 

abrading  power  of,  148. 

Iceland,  flow  of  lava  in,  657. 

glass-cavities  in  quartz  of,  706. 

Ichthyodorulite  of  Lias,  421. 
Ichthyolites  of  Old  Eed  Sandstone,  534. 
Ichthyosaurus  communis,  Lias,  423. 

hind  fin  or  paddle  of,  423. 

Identification  of  fossil  plants,  266. 

Igneous  rocks,  6. 

— —  of  Siebengebirge  and  Westerwald,  679. 

of  Val  di  Noto,  621. 

Iguanodon  Mantelli,  Wealden,  347. 
Ilfracombe  group,  fossils  of,  538. 
India,  cretaceous  system  in,  840. 

Upper  Miocene  formations  of,  276. 

Indusial  limestone  in  Auvergne,  226. 
Inferior  Oolite,  fossils  of,  412. 
Infusoria  in  tripoli,  24 
inland  sea-clitts  in  South  of  England,  71. 
Inoceramus  Lamarckii,  Chalk,  328. 
Insect-bed  of  (Eningen,  251. 


Insect  limestone  of  Lias,  428. 
Insect,  wing  of  neuropterous,  428. 
Insects  of  Coal,  494. 

Miocene,  of  Croatia,  245. 

of  Swiss  Miocene  strata,  267. 

Intercalation  of  strata,  difficulties  of,  184. 
Intrusion,  test  of  age  of  plutonic  rocks,  718. 

test  of  age  of  volcanic  rocks,  655. 

Inundation  mud,  117. 
Ipswich,  section  near,  201. 
Ireland,  Old  Eed  Sandstone  of,  524. 

Devonian  plants  of,  524. 

drift  in,  160. 

an  archipelago,  160. 

Iron  weapons  at  Neufchatel,  111. 

sands  of  England,  234. 

Invertebrate  animals,  period  of,  582. 
Isastrcea  oblonga,  Portland  sand,  394. 
Ischia,  age  of  volcanoes  of,  658,  6bl. 

Newer  Pliocene  of,  189. 

Ischypterus  of  Trias,  456. 
Islands  in  Eocene  sea,  367. 
Isle  of  Mull,  Miocene  leaf-bed  of,  242. 

Wight  Hempstead  beds,  239. 

Isomorphism,  theory  of,  596. 

Issoire,  section  of  volcanic  formations  at,  686. 

Italian  Pliocene  fossils,  agreement  with  Brit' 

ish,  674 
Italy,  Miocene  strata  of,  247. 

Older  Pliocene  volcanic  rocks  of,  673. 

Older  Pliocene  formations  of,  208. 

JACKSON,  Dr.  C.  T.,  analysis  of  fossil  bones. 

167. 
Jamieson,  Mr.  T.  F.,  on  Scotch  glacial  drift, 

152. 

Japan,  flora  of,  compared  to  American,  271. 
Java,  volcanoes  of,  626. 

stream  of  sulphureoifs  water,  299. 

Jaws  of  mammalia  in  Purbeck,  381. 

Johnson,  Mr.  J.  Yate,  on  Madeira  Miocene 

shells,  675. 

Jointed  structure  of  metamorphic  rocks,  748. 
Jorullo,  lava  stream  of,  719. 
Jukes,  Mr.,  on  origin  of  lakes,  170. 
Jukes,  Prof.,  on  erosion  of  the  Weald,  374. 
Junghuhn  on  crater- walls,  639. 

on  Javanese  volcanoes,  626. 

Jura,  blocks  on,  142. 
structure  of,  55. 

KANGAKOO,  jaws  of,  127. 

Kaup,  Prof.,  on  Cheirotherium,  443. 

Kaye,  Mr.,  on  fossils  of  Southern  India,  340. 

Keeling  Island,  fragment  of  greenstone  in,  824. 

Keilhau,  Prof.,  on  granite  veins  in  gneiss,  714, 

715. 

— r-  on  planes  of  foliation,  754 
Keller,  Dr.  F.,  on  lake-dwellings,  110. 
Keiloway  rock,  34. 

fossils  of,  400. 

Kentish  chalk,  sandgalls  in,  82. 

rag,  341. 

Keuper,  or  Upper  Trias,  432. 

plants  of,  434 

marine  fauna  of,  434 

Keyserling,  Count,  on  Eussian  glacial  drift, 

150. 

Kiesel-gerolle  of  the  Eifel,  679. 
Kilauea,  volcanic  crater  of,  623. 
Kilkenny  yellow  sandstone,  fossil  plants  of, 

524 

Killas  in  granite  in  Cornwall,  738. 
Kimmeridge  clay,  composition  and  fossils  of, 

894    • 
King,  Mr.,  on  fauna  of  Norfolk  drift,  161. 

on  Permian  fossils,  458. 

on  footprints  of  reptile,  507. 

Kirkdale  cave,  hyrena's  den  of,  125. 
Kitchen-middens,  Danish,  109. 

of  Denmark,  109. 

Kleyn  Spawen,  Lower  Miocene  of,  238. 
Konen,  Baron  von,  on  Brockenhurst  shells, 

286. 
Koninck,  M.  de,  on  Kleyn  Spawen  beds,  243. 


INDEX. 


793 


Koninck,  M.  de,  on  mountain  limestone  fish, 
521. 

on  shells  of  Mayence  basin,  243. 

Koninckia  Leonhardi,  Hallstadt,  436. 
Kyson,  in  Suffolk,  strata  of,  294. 

LAACH,  lake-crater  of,  681. 
Labrador,  icebergs  of,  148. 

series,  584. 

Labradorite,  598. 

or  Labrador  felspar,  595. 

LabyrintJwdon,  tooth  of,  445. 

Jaegeri,  section  of  tooth,  445. 

Labyrinthodonts  of  Coal,  511. 
Lacustrine  strata  of  Auvergne,  222,  228. 
Lagoa,  view  of  crater  of,  650. 
Lagoons  at  mouth  of  rivers,  33. 

of  Bermuda  Islands,  319. 

Lake-crater  of  Laach,  681. 

craters  of  the  Eifel,  679. 

Lake-dwellings  of  Switzerland,  110. 
Lake-terraces,  Post-pliocene,  in  Switzerland, 

120. 
Lakes,  deposits  in,  3. 

how  formed,  171. 

Post-pliocene,  of  Switzerland,  173. 

how  far  connected  with   glacial  action, 

169-in. 

Lamarck,  on  bivalve  mollusca,  29. 
Lamination  of  clay-slate,  Pyrenees,  757. 
Lamnaj&legans,  tooth  of,  2i)0. 
Lancerote,  rent  in  volcanic  crater,  773. 
Land,  rising  and  sinking,  45. 
Landenian,  or  Lower  Eocene  beds,  313. 
Land-ice,  action  of,  152. 
Land's  End,  columnar  granite  of,  704. 

porphyritic  granite  of,  707. 

Lapidification  of  fossils,  43. 

La  Koche,  estuary  of.  14. 

Lartet,  M.,  on  French  Eocene  mammalia,  387. 

on  Gastornis  Parisiensis,  306. 

on  quadrumana  of  Gers,  233. 

on  reindeer  period,  125. 

on  Calcaire  de  la  Beauce,  219. 

Las  Nieves,  Santa  Cruz,  ravine  of,  641. 

Palmas,  raised  beach  north  ol^  676. 

Canadas,  645. 

Lastrcea  stiriaca,  Switzerland,  264. 

Laterite  of  Giant's  Causeway  and   Madeira, 


Laurent,  M.,  on  submergence  of  Sahara,  176. 
Lauren  tian  rocks,  upper  and  lower,  584. 

volcanic  rocks,  701. 

group,  table  of,  575,  576. 

Laurels  of  Miocene  flora,  264. 
Lava,  601. 

of  La  Coupe  d'Ayzac,  617. 

streams,  effects  of,  6. 

relation  to  trap,  640. 

stream  of  Jorullo,  719. 

of  Stromboli,  719. 

forming  beds  on  a  declivity,  637. 

of  Chaluzet,  690. 

Lava-currents  of  Auvergne,  688. 
Lavas  of  Catalonia,  668. 

of  Madeira,  648,  654. 

Lavini,  Signor  Spada,  on  Pliocene  strata,  Ischia, 

190. 

Lea,  Mr.,  reptile  footprints  found  by,  509. 
Lead  veins  in  Permian  rocks,  779. 
Leaf-bed  of  Madeira,  649. 

Miocene,  of  Isle  of  Mull,  242. 

Leda  trwncata,  Scotch  drift,  154. 

oblonga,  Clyde  drift,  153. 

Deshayexiana  (Syn.  Nucula  Deshayesi- 

ana),  237. 

amygdaloides.  Highgate,  294. 

Lee,  Mr.  J.  E.,  on  Pteraspis  of  L.  Ludlow,  555. 
Lehman,  on  classification  of  rocks,  86. 
Leibnitz,  theory  of,  89. 
Leidy,  Dr.,  on  Pliocene  mammalia,  272. 

on  Titanotherium,  279. 

on  Triassic  reptiles,  455. 

on  bone  in  chalk,  U.  S.,  839. 

Lepidodendron  iSternbergii,  Coal,  470. 


Lepidodendron,  stem  of,  524. 
Lepidostrobus  ornatus,  471. 
Lepidotus  gigas.  Lias,  420. 

Mantelli,  349. 

Leptcena  Moorei,  Upper  Lias,  418. 

depressa,  Silurian,  558. 

Leptynite,  or  white  stone,  708. 
Lesguereux,  on  Vancouver's  Island  fossils,  272. 
Lewes,  Coomb  near,  363. 
Lias,  volcanic  rocks  of,  696. 

fossils  of,  418,  419. 

plutonic  rocks  of,  723. 

reptiles  of,  422. 

formation  described,  415. 

fish  of,  420. 

origin  of,  429. 

fossil  plants  of,  428. 

Liebig,  Prof.,  on  stalactite,  123. 

on  conversion  of  lignite  into  coal,  503. 

Liege,  limestone  caverns  at,  123. 
Lightbody,  Mr.,  on  Aymestry  limestone,  555. 
Lignite,  conversion  of,  into  coal,  503. 

of  Madeira,  649. 

Lima  giganteum.  417. 

spinosa.  Chalk,  327. 

Jfoperi,  White  Chalk,  327. 

Limagne  d' Auvergne,  222. 
Limburg  beds,  table  of,  237. 

fossils,  238. 

Lime,  scarcity  of,  in  metamorphic  rocks,  765. 

in  solution,  source  of,  42. 

Limestone,  brecciated,  459. 

caverns  described,  122. 

compact,  461. 

crystalline,  459. 

fossiliferous,  460. 

hippurite,  336. 

— —  indusial,  Auvergne,  226. 

mountain  or  carboniferous,  514. 

magnesian,  458. 

primary  or  metamorphic,  735. 

of  Jura,  399. 

Devonian,  of  Germany,  537. 

striated,  139. 

Limulus  roturidatua,  493. 

Lindley,  Dr.,  on  botanical  nomenclature,  338. 

Lingma  Dumortieri,  Antwerp  crag,  207. 

Davisii,  Lingula  flags,  577. 

Lewisii,  Silurian,  554. 

Crednerii,  460. 

beds,  volcanic  tuffs  of,  700. 

flags,  fossils  of,  577. 

Link,  M.,  on  footprints  of  Trias,  444 
Linton  group,  equivalents  of,  541. 
Lipari  Isles,  stui'as  in,  741. 
Liquidamber  europceum,  (Eningen,  210. 
Liriodendron  Procaccinii,  258. 
Lithodomi  in  beaches  of  North  America,  7a 

in  inland  cliffs,  73. 

LUhostrotion    baaaltiforme    (striatum),    L. 

floriforme,  516. 
Lits  coquilliers,  804. 
Lituites  gigantem,  Silurian,  555. 
Llanberia  slates,  578. 
Llandeilo  flags,  composition  and  fossils  of,  565. 

Lower,  or  Arenig  formation,  567. 

Llandovery,  Upper,  formation,  560. 

Lower,  rocks,  thickness  of,  561. 

Loa,  Mount,  craters  of,  623. 
Loam  defined,  13, 117. 
Lodes.    See  Mineral  Veins. 

filled  with  earthy  matter,  775. 

Loess,  or  fluviatile  loam,  described,  117. 

fossil  shells  of,  119. 

Logan,  Sir  W.,  on  Stigmaria  in  underclays,  467. 

on  Eozoon  Canadense,  584. 

on  Potsdam  sandstone,  582. 

on  thickness  of  coal-beds,  485. 

Loire,  falnns  of  the,  183. 

London  clay,  relative  position  to  Eed  crag, 

201. 

clay  proper,  291. 

Longevity,  relative,  of  mammalia  and  testacea, 

132. 
Longmynd  group^  578. 


794 


INDEX. 


Lonsdale,  Mr.,  on  fossils  in  "White  Chalk,  26. 

on  corals,  279. 

on  Stonesfield  slate,  405. 

on  corals  of  Sicily,  194. 

Lonsdaleia  flori/ormis,  516. 

Lowe,  Rev.  K.  T.,  on  shells  of  Mogadore,  675. 

Lower  Oolite,  401-413. 

Miocene  of  Belgium,  238. 

Lucerne,  thickness  of  shingle  beds  near,  259. 

Lucina  serrato,  290. 

Ludlow  formation,  fossils  of,  551-556. 

Lower,  553-556. 

Lulworth  Cove,  dirt-bed  of,  391. 
Land,  M.,  on  mammalia  of  Brazils,  128. 
Lycett,  Mr.,  on  Great  Oolite  shells,  404. 
Lycopodium  densum,  470. 
Lyme  Eegis,  lias  at,  4*27. 
Lym-Fiord  invaded  by  the  sea,  33. 

kelp  in,  324. 

Lymnea  longiacata,  29,  2S2. 

caudata,  Headon  beds,  284. 

Lyons,  coal-mine  near,  4S2. 

M'ANDREW,  on  scarcity  of  fish  on  sea-bottoms, 

587. 
Maclaren,  Mr.,  on  Portland  Old  Eed  volcanic 

rocks,  699. 

Maclurc,  Dr.,  on  Olot  volcanic  rocks,  666. 
Maclurea  Logani,  Silurian,  572. 
M'Clintock,  Sir  Leopold,  on  Globigerina,  320. 

on  depth  of  North  Atlantic,  273. 

Macropus  atlas,  127. 

incisor  of,  127. 

major,  127. 

M'Culloch,  Dr.,  on  foliation  in  Scotland,  756. 

on  absence  of  pebbles  in  granite,  729. 

on  basaltic  columns  in  Skye,  616. 

on  denudation,  67. 

on  formation  of  hornblende  schist,  743. 

on  Glen  Tilt  granite,  710. 

on  Isle  of  Skye,  36. 

on  overlying  rocks,  7. 

on  relations  of  trap,  lava,  and  scoriae,  622. 

on  rocks  altered  by  trap,  615. 

on  two  granites  of  Arran,  728. 

on  trap-veins,  610. 

M'Culloch,  Mr.  J.,  on  Laurentian  fossil,  584. 
Madeira,  Upper  Miocene  shells  of,  674. 

dike  in  valley  in,  610. 

Island  of,  formation  and  length  of,  646. 

lavas,  absence  of  waterworn  pebbles  in, 

652. 

section  of,  648. 

Maastricht  beds,  315. 

Maffiote,  Don  Pedro,  on  shells  of  raised  beach, 

676. 

Hagas  pumila,  White  Chalk,  327. 
Magnesian  limestone,  concretionary  structure 

of,  37. 

limestone  denned,  13. 

limestone  group,  458. 

Maidstone,  fossils  in  White  Chalk  of,  330. 
Malaise,  Prof.,  on  Engihoul  cave,  124. 
Mammalia  anterior  to  Paris  gypsum,  Table  of, 

387. 

extinct,  coeval  with  man,  115. 

fossil,  of  Middle  Purbeck,  881. 

in  Auvergne  alluvium,  688. 

of  Bembridgo  beds,  2b3. 

of  Great  Oolite,  406. 

of  Siwalik  Hills,  276. 

Mammalian  fauna,  ancient,  of  North  America, 

Mammat,  Mr.,  cited,  69. 
Mammoth.    See  Elephas  primigenius,  133. 
Man  coeval  with  extinct  mammalia,  115. 
Mantel),  Dr.,  on  fossils  of  Weald,  849. 

on  belemnites  in  Oxford  clay,  400. 

on  Brighton  Elephant-bed,  873. 

on  freshwater  beds,  Isle  of  Wight,  283. 

on  Iguanodon,  347. 

on  Wealden  formation,  345. 

on  the  Coomb,  362. 

Mantellia  megalophylla,  390. 
Map  of  Palma,  628. 


Map  of  Caldera  of  Palma,  629. 

of  Eifel  volcanic  region,  678. 

of  Eocene  tertiary  basins,  280. 

to  illustrate  denudation  of  Weald,  857. 

-  of  Lower  Miocene  of  France.  221. 

showing  chalk  formation  in  France,  336. 

of  St.  Paul's  Island,  642. 

of  volcanic  district  of  Catalonia,  667. 

Marble  of  Carrara,  759. 

defined,  12. 

Marine  and  brackish- water  strata  in  Coal,  492. 
Marl,  red,  of  Auvergne,  224. 
—  defined,  13. 

in  Lake  Superior,  86. 

red,  white,  and  green,  in  England,  442. 

Marls,  green  and  white,  of  Auvergne,  223. 
Marl-slate  defined,  13. 
Marmpites  Milleri,  White  Chalk,  326. 
Martin,  Mr.,  on  chalk  fractures,  360. 

on  fractures  of  Weald,  366. 

Martins,  M.,  on  shells  of  Sahara,  176. 
Massachusetts,  plumbago  of,  743. 
Mastodon  arvernemis,  Norwich  crag,  198. 

giganteus,  United  States,  167. 

Mayence  basin,  tertiaries,  243. 
Mayencien,  term  explained,  258. 
May-Hill,  bone-beds  of,  552. 

sandstone,  thickness  and  fossils  of,  560. 

Silurian  strata  of,  550. 

Mediterranean,  deposits  forming  in,  96. 
Meek,  Mr.,  on  Nebraska  plants,  340. 
Meerfelder  Maar,  Lake  of,  6sl. 
Megalodon  cucullatus,  540. 
Megatherium,  molar  of,  136. 
Melawia  turritissima,  Bembridge,  282. 

Inquinata  (Oerithium  melanoides),  296. 

Melanopsis  buccinoidea  (recent),  29. 

Melaphyre,  606. 

Menai  Strait,  marine  shells  in  drift,  158. 

Mendip  Hills,  lead  veins  in,  779. 

Mendips,  denudation  in,  67. 

Mesozoic,  term  explained,  91. 

Metalliferous  veins.    See  Mineral  Veins. 

Metals,  relative  age  of,  777. 

Metamorphic  or  Crystalline  Limestone,  735, 

736. 

rocks,  defined,  8. 

rocks,  cleavage  of,  747. 

rocks,  order  of  succession,  764. 

rocks,  732. 

rocks,  age  of,  758. 

rocks,  scarcity  of  lime  in,  765. 

strata,  origin  of,  736. 

strata,  why  less  calcareous  than  fossilifer- 

ous  strata,  765. 

structure,  origin  of,  748. 

Metamorphism  not  requiring  intense  heat,  739. 

by  hydrothermal  action,  739. 

Metamorphosis  of  trilobites,  563.     See  Trilo- 

bites. 

Meteorites  in  drift,  176. 
Meyer,  M.  H.  von,  on  reptile  of  Coal,  506. 

on  specimens  of  Archegosaurus,  514. 

on  Weald  of  Germany,  351. 

Mexico,  melted  matter  from  Jorullo  in,  719. 

Micaceous  sandstone,  origin  ol,  14. 

Mica-schist,  734,  736. 

Micraster  cor-anguimim,  White  Chalk,  325. 

Microconchus  carbonarius,  498. 

Microlestes  antiquus,  molars  of,  483. 

Middendorf,  on  Siberian  ice-dril't,  157. 

Middle  crag,  recent  species  in,  208. 

Middle  Oolite,  398-401. 

Migration  of  Miocene  plants,  theory  of,  269. 

of  quadrupeds,  131. 

Miliolite  limestone,  304. 

Miller,  Hugh,  on  salt  lakes,  449. 

on  fossil  trees  in  coal  near  Edinburgh, 

484. 

on  Old  Eed  Sandstone,  530. 

Milne  Edwards,  M.,  on  bryozoa,  214. 
Miiichinhampton,  fossil  shells  at,  404. 
Mineral  composition,  test  ol'  age  of  plutonic 

rocks,  717. 
composition  considered  as  test  of  age,  96. 


INDEX. 


795 


Mineral  composition,  test  of  age  of  volcanic 

rocks,  657. 

composition  of  volcanic  rocks,  594. 

character  of  hypogene  rocks,  764 

character  of  aqueous  rocks,  10,  93.  . 

springs  connected   with   mineral  veins, 

768. 

veins  and  faults,  767-769. 

veins  of  ditferent  as;es,  767. 

veins,  pebbles  in,  771. 

veins  near  granite,  773. 

Mineralization  of  organic  remains,  88. 
Minerals,  table  of  analysis  of,  60S. 
Miocene,  Lower,  fossils  at  Mont  Perrier,  687. 

and  Eocene,  line  between,  217,  247. 

Atlantis,  theory  of,  268-275. 

Tipper,  of  the  Bolderberg,  235. 

Upper,  volcanic  rocks,  674. 

Upper,  Madeira  and  Porto  Santo  shelly 

tuffs,  674. 

Lower,  rocks  of  Eifel,  677. 

period,  212. 

plants  and  shells,  whether  distinct  genera 

or  varieties  of  living,  267. 

term  explained,  138. 

Mississippi,  accumulation  of  sediment  in,  491. 

fluviatile  strata  and  delta  of,  8. 

Mitchell,  Sir  T.,  on  Wellington  caves,  126. 
Mitra  scabra,  Barton  clay,  287. 
Mitscherlich,  on  Monte  Somma  cone,  661. 

on  augite  and  hornblende,  596. 

Modiola  acuminata,  Permian,  459. 
Modon,  lithodomi  in  cliff  at,  73. 
Moel  Tryfaen,  marine  shells  found  at,  158. 
Molasse,  Middle,  of  Switzerland,  258. 

freshwater,  of  Switzerland,  249. 

Lower,  of  Switzerland,  258. 

Mollusca  of  Hallstadt  beds,  437.      ' 

common  to  Upper  and  Middle  Oolite,  398. 

Mona  Loa,  652. 

Mons,  flexures  of  coal  at,  53. 

Mont  Blanc,  talcose  granite  of,  721. 

Dor,  volcano  of,  655. 

Perrier,  breccias  of,  with  bones,  685. 

Monte  Bolca,  Middle  Eocene,  fossil  fish  of,  694. 

Mario,  a?e  of  volcanic  deposits  of,  674. 

Montlosier,  M.,  on  cones  of  the  Vivarais,  639. 
Montmartre,  gypseous  series  of,  298. 
Montsacopa,  crater  of.  669. 
Monts  Dome,  Auvergne,  extinct  volcanoes  of, 

Moore,  Mr.  Charles,  on  San  Domingo  shells, 
274 

on  teeth  of  mammalia,  442. 

on  Upper  Trias  quadrupeds,  383. 

Moraine,  term  explained,  138. 

Moraines  of  glaciers,  149. 

terminal,  140. 

Morea,  inland  sea-cliffs  of,  43. 

Morlot,  M.,  on  lake-dwellings,  110. 

on  Swiss  deltas,  120. 

Morris,  Mr.,  on  Stonesfleld  slate,  410. 

Mortillet,  M.  de,  theory  of  lake- excavation, 
173. 

Mosasaurus  Camperi,  316. 

Mottled  clays  and  sand,  295. 

Mountain  limestone,  514 

strata  contemporaneous  with,  522. 

Mountains,  volcanic,  form,  structure,  and  ori- 
gin of,  625. 

Mull,  Isle  of,  leaf-bed,  242. 

Miinster,  Count,  on  fossils  of  Solenhofen,  396. 

on  Placodus,  440. 

Murat,  freshwater  limestone  near,  692. 

Murchison,  Sir  R.  I.,  on  granite  of  Caithness, 
729. 

on  flints  in  Dover  cliffs,  374. 

on  Silurian  strata,  551. 

on  Swiss  molassa,  250. 

on  carboniferous  plutonic  rocks,  725. 

on  Silurian  volcanic  rock,  699. 

on  cleavage,  747. 

on  conversion  into  gneiss,  746. 

on  Devonian  series,  536. 

on  fossil  fish  of  Monte  Bolca,  694 


Murchison,  Sir  R.  I.,  on  metamorphic  rocks  of 
North  Highlands,  762. 

on  name  Permian,  458. 

on  Permian  rocks,  462. 

on  Posidonia  minuta,  443. 

on  protrusion  of  solid  granite,  727. 

on  Russian  glacial  drift,  149. 

on  schists  of  Old  Red,  531. 

on  the  Cantal,  231. 

on  thickness  of  White  Chalk,  318. 

Murchisonia  gracilis,  Silurian,  572. 
Murex  vaginatus,  Ischia.  190. 
Muschelkalk,  fossils  of,  438. 
Myliobates  Edwardsi,  289. 
Myrmecobius  described,  409. 
Mytilus  septifer,  Permian,  459. 

NAPLES,  Post-pliocene  volcanic  formations  ot 

661. 

Nasaa  granulata,  Red  Crag,  202. 
Natica,  spawn  of,  528. 

claiisa,  Clyde  drift,  153. 

helicoides,  Norwich  crag,  197. 

Nautilus  tsiczac,  293. 

Danieus,  Faxoe,  816. 

centralis,  Highgate,  293. 

plicatus,  343. 

trun&ttus,  Lias,  418. 

Navarino,  lithodomi  found  in  cliff  at,  73. 

Nebraska,  Miocene  strata  of,  279. 

Necker,  M.  L.  A.,  on  dikes  of  Vesuvius,  668. 

on  Arran  granite,  728. 

terms  granite  "  underlying,"  7. 

Needles  of  chalk,  size  and  position  of,  855. 
•Nelson,  Capt.,  on  Bermuda  corals,  819. 

drawing  of  Bermuda,  79. 

Neocomian,  term  explained,  341. 
Neozoic  type  of  corals,  515. 
Neptunian  theory,  87. 
Nerincea  hieroglyphic.^  399. 

Goodhallii,  Coral-rag,  899. 

Nerinaean  limestone,  399. 

Nerita  conoidea  (Schmidelliand),  305. 

costulata,  Great  Oolite,  405. 

granulosa,  80. 

globulus,  30. 

Neritina,  concava,  Headon  series,  284 
Newberry,  Dr.,  on  Spenophyllum,  474 

on  New  Jersey  flora,  340. 

Newcastle  coal-field,  great  faults  in,  63. 

New  Red  Sandstone  of  Connecticut  valley,  453. 

Red  Sandstone  period,  trap  of,  696. 

Red  Sandstone  formation,  431. 

New  York,  Devonian  strata  of,  543. 

Cambrian  strata  of,  583. 

Laurentian  strata  of,  584 

Silurian  strata  of,  570. 

New  Jersey,  Mastodon  at,  167. 

New  Zealand,  sudden  rise  of  land  in,  172. 

Newer  Pliocene  volcanic  rocks,  658. 

Niagara  Limestone,  fossils  of,  571. 

Nile,  deposits  of,  118. 

——mud,  118. 

Nodosaria,  Chalk,  26. 
Noeggerathia  cuneifolia,  464 
Nomenclature  of  volcanic  minerals,  594 

changes  of,  89. 

of  Trias,  432. 

Norfolk,  buried  forest,  160. 

drift,  composition  of,  160. 

Normandy,  chalk  of,  354 

shells  in,  208. 

needles  and  chalk  cliffs  of,  356. 

North  America,  glacial  formations  of,  163. 

carboniferous  limestone  of,  522. 

North  Germany,  fossil  fauna  of,  236. 

North  Wales,  cleavage  of  slate  rocks  in,  750^ 

755. 

Northwich,  beds  of  salt  at,  448. 
Norway,  granite  veins  in  gneiss  of,  714. 

Cambrian  of,  5S1. 

Silurian  plutonic  rocks  of,  725. 

Norwich  crag,  shells  of,  197. 
sand-pipes  near,  82. 


INDEX. 


Nova  Scotia,  fossil  forests  of,  484. 

period  of  coal  accumulation  in,  491, 

Nucula  Cobboldia;,  Norwich'  crag,  197. 
Nummuliles  (Nummularia)l<xvigata,  289. 

exponens,  Europe  and  Asia,  808. 

Pmchi,  Pyrenees,  308. 

Nummulitic  formations,  308. 

Nyst,  Mr.,  on  testacea  in  Antwerp  crag,  207. 

on  Edeghem  shells,  234. 

OBOLTTS  grit  of  Russia,  569. 

Apollinis,  Silurian,  569. 

Obsidian,  606, 

Ocellaria  radiata,  329. 

CEningen,  Upper  Miocene  beds  of,  248. 

Oeynhausen,  M.  von,  on  Cornish  granite  veins, 
713. 

Ogygia  Suchii,  Silurian,  566. 

Ohio,  Falls  of,  Devonian  coral-reef  of,  544. 

Old  Ked,  supposed  reptilian  remains  of,  530. 

Old  Eed  Sandstone,  subdivisions  of,  524. 

• thickness  of,  524. 

trap  of,  698. 

Oldest  granites,  726. 

Olclhamia  radiata,  O.  antiqua,  579. 

Olenus  micrurm,  Lingula  flags,  577. 

Oligoclase,  composition  of,  595. 

Oliva  Dufremii,  Bolderberg,  Belgium,  236. 

Oliver,  Prof.,  on  Miocene  Atlantis,  270. 

Olivine,  598. 

Olot,  volcanic  rocks  of,  666. 

Omphyma  turbinatum,  Wenlock,  557. 

Onchus  tenuistriatus,  Silurian,  552. 

Oolite,  origin  of,  429. 

divisions  of,  compared,  414. 

Great,  fossils  of,  402. 

Great,  fossil  plants  of,  411. 

Inferior,  fossils  of,  412. 

plutonic  rocks  of,  723. 

physical  geography  of,  878. 

table  of  divisions  of,  377,  878. 

term  defined,  12. 

upper,  middle,  and  lower,  878. 

Oolitic  strata  of  England  and  France,  878. 

volcanic  rocks,  696. 

Ophioderma  Egertoni,  Middle  Lias,  420. 

Ophite,  Ophiolite.  606. 

Opossum,  molar  tooth  and  part  of  jaw  of,  294. 

Oppel,  M.,  on  zones  of  Lias,  416. 

Orbigny,  A.  d\  on  Orbitoides,  309,  811. 

on  cretaceous  series,  314. 

on  distinction  of  species,  215. 

on  Vienna  basin,  244. 

Orbigny,  M.  C.  d1,  on  pisolitic  limestone,  814. 
Oreodaphne  Heerii,  210. 
Organic  remains,  criterion  of  age  of  formation 
of,  93. 

tests  of  age  of  volcanic  rock,  656. 

Oriskany  sandstone,  classification  of,  544. 
Ormerod,  Mr.,  on  thickness  of  Trias,  44. 
Orthis  elegantula,  Upper  Ludlow,  553. 

tricenaria,   O.  vespertilio,   O.  grandis, 

Silurian,  563. 

Orthoceras  in  St.  Cassian  beds,  437. 
Orthoceras  ventricosum,  554. 

laterale,  520. 

duplex,  Silurian,  566. 

Ludense,  fragment  of,  555. 

Orthoclase,  composition  of,  595. 
Osborne,  or  St.  Helen's  series,  284. 
Osteolepi*,  Old  Ked  Sandstone,  533. 
Ostrea  gregarea,  Coral-rag.  899. 

aGuminata,  Fuller's  earth,  412. 

carinata,  Chalk,  323. 

columba,  Chalk,  328. 

deltoids,  Upper  Oolite,  395. 

distorta,  Purbeck,  380. 

expama,  Portland-stone,  395. 

venicularix,  Chalk,  328. 

Otodus  obliquu*,  tooth  of,  290. 

Overlying,  term  applied  to  volcanic  rocks,  7. 

Owen,  Prof.,  on  Eocene  mammalia,  387. 

on  carboniferous  limestone,  523. 

on  cave-breccia  fossils,  126. 

on  fauna  of  Sheppey,  292. 


Owen,  Prof.,  on  footsteps  on  Potsdam  sand- 
stone, 582. 

on  footprints  of  Trias,  445,  455. 

on  Gastornis  Parisiensis,  306. 

on  Ichthyosaurus,  424. 

on  Palreophis  typhoeus,  289. 

on  Plagiaulax,  384. 

on  Purbeck  mammalia,  882. 

on  reptile  of  Coal,  506. 

on  Triconodon,  885. 

on  Stonesfield  mammalia,  407-409. 

on  Zeuglodon,  310,  311. 

Ox,  common,  molar  of,  135. 
Oxford  clay,  fossils  of,  400. 

PACIFIC,  corals  and  chalk  of,  818. 
PaldBchinus  gigas,  Mountain  Limestone,  517. 
Palceonfecus  (Palceothrissum),  461. 

comptus,  P.  elegans,  P.  glaphyrus,  462. 

Palaeontology  of  cretaceous  recks,  344. 

term  explained,  100. 

Paloeophis  typhceus,  Bracklesham,  289. 
Palceosaurus  platyodon,  tooth  of,  447. 
Palceotherium  magnum,  283. 
Palaeozoic  type  of  corals,  515. 
Palagonite  tuff,  603,  606. 
Palermo,  caves  near,  74. 
Palma,  aqueous  erosion  in,  637. 

denudation  of  fluviatile  or  marine,  640. 

caldera  of,  629. 

structure  of,  628-631. 

Paludina,  fossil,  of  Auvergne,  226. 

lenta,  Hempstead,  29,  240. 

Mayence,  243. 

orbicularis,  Bembridge,  282. 

Paradoxides  Bohemicus,  580. 
Parasmilia  centralis,  Chalk,  515. 
Paris  basin,  tertiaries  of,  298. 
Parka  decipiens,  528. 
Parkinson,  Mr.,  on  Suffolk  crag,  183. 
Parrot,  Dr.  F.,  on  salt-lakes  of  Asia,  449. 
Patagonia,  sedimentary  layers  of,  754. 

ground-plan  of  dikes  near,  666. 

Patella  rugosa,  Great  Oolite,  405. 

Peach,  Mr.  C.,  Scotch  Devonian  fossils  found 

by,  531. 

Peak  of  Tenerife,  view  of,  644. 
Pearlstone,  606. 
Peat  of  Denmark,  109. 
Pebble-beds  of  Lower  Miocene,  Switzerland, 

Pebbles,  absence  of,  in  granite,  729. 

in  Chalk,  823. 

Pecopteris  lonchitica,  Carboniferous,  468. 
Pecten  islandicus,  Clyde  drift,  153. 

Beaveri,  White  Chalk,  327. 

papyracem,  Coal,  495. 

quinque  coatatw,  White  Chalk,  327. 

jacobceus,  Sicily,  194. 

Valoniensis,  Trias,  441. 

Pegmatite,  704. 

Penarth  beds,  442. 

Pengelly,  Dr.,  on  flint-knives  of  Brixham  cave, 

124. 

Pengelly,  Mr.,  on  Bovey  Tracey  lignite,  241. 
Pentacrinus  Uriareus,  Lias,  420. 
Pentainerus  beds,  560. 
Pentamerus  Kniyhtii,  Aymestry,  554. 

laivis,  561. 

oblongm,  561. 

Pentlaud  Hills,  volcanic  rocks  of,  699. 

Pentuan,  human  skulls  at,  109. 

Peperino,  606. 

Peperinos  of  Gergovia,  693. 

Pepys,  Mr.,  cited,  41. 

Period  of  Weald  denudation,  369. 

Permian  group,  458. 

flora,  463. 

Perna  Mulleti,  343. 
Petherwyn  group,  fossils  of.  537. 
Petrifaction  of  fossil  wood,  39. 

process  of,  43. 

Petrosilex,  606. 

Phacops  latifrons,  Devonian,  537. 

caudatus,  Silurian,  559. 


INDEX. 


797 


Phascolotherium  Bucklandi,  Stonesfield,  409. 
Phasianella  Heddingtonensis,  Coral -rag,  39. 
Philippi,  on  tertiary  shells  of  Sicily,  192. 
Phillips,  Prof.,  on  coal-bearing  strata,  465. 

on  Wenlock  shale,  559. 

on  slaty  cleavage,  749. 

Phillips,  Mr.  W.,  on  kaolin  of  China,  11. 

Phlebopteris  contigua,  Lower  Oolite,  411. 

Pholadomya  Jidicula,  Inferior  Oolite,  412. 

Phonolite,  599,  606. 

Phorus  extensus,  Highgate,  293. 

Phosphate  of  lime,  332. 

Phragmoceras  ventricosum,  554. 

Phryganea,  larva  of  recent,  226. 

Phyllade,  736. 

Physa  columnaris,  P.  hypnorum  (recent),  29. 

Bristovii,  Middle  Purbeck,  381. 

Pico  Torres,  &c.,  of  Madeira,  648. 

Pictou,  calamites  near,  491. 

Pile-dwellings  of  stone  and  bronze  age,  111. 

of  Switzerland,  110. 

Pilton  group,  fossils  of,  536. 
Pinnularia,  Atlantic  mud,  320. 
Pinus  sylvestris  in  peat,  109. 
Pisolitic  limestone,  France,  313. 
Pitchstone,  606. 
Placodus  gigas,  teeth  of;  439. 
Placoids  of  Wealden,  349. 

scarcity  of,  in  Old  Red  strata,  532. 

Plagiaulax  Becklevii.  jaw  of,  Middle  Pur- 
beck,  383. 

minor,  jaw  of,  Middle  Purbeck,  384. 

Plagiostoma  giganteum,  417. 

Hoperi,  White  Chalk,  327. 

Planera  Riehardi,  (Eningen,  266. 

Planitz,  tripoli  of,  26. 

Planorbis  discus,  Bembridge,  282. 

euomphalm,  29,  284. 

Plants  common  to  Eocene  and  Miocene,  295. 
-r —  fossil,  of  Madeira,  649. 

fossil,  of  Switzerland,  260. 

of  Purbeck  beds,  394. 

of  the  Keuper,  434. 

Plas  Newydd,  rock  altered  by  dike  near,  613. 
Plastic  clays  and  sand,  295. 
Platanus  aceroides,  (Eningen,  254. 
Platystoma  Suessii,  Hallstadt,  436. 
Playfair,  cited,  45,  88. 

on  faults,  61. 

on  Huttonian  theory  of  stratification,  60. 

Plectrodus  mirabilis,  Tipper  Ludlow,  552. 
Pleistocene,  term,  why  abandoned,  107. 
Plesiosaurus  dolichodeirus,  Lias,  423. 
Pleurodictyum  problematicum,  541. 
Pleurotoma,  attenuata,  290. 

rotata,  81. 

Pleurotomaria  carinata  (Jlammigera),  518. 

Anglica,  39. 

granwluta.  Inferior  Oolite,  412. 

ornata,  Inferior  Oolite,  412. 

xMieninger,  Prof.,  on  triasaic  mammifer,  432. 
Pliocene,  term  explained,  188. 

Older,  volcanic  rocks,  673. 

strata  in  Ischia,  189. 

period,  178. 

volcanic  rocks,  why  invisible,  718. 

Plomb  du  Cantal,  igneous  rocks  of.  691. 
Plombieres,  alkaline  waters  of,  740. 
Ploverfield,  fine-grained  granite  of,  728,  729. 
Plumbago  of  Massachusetts,  743. 
Plutonic  rocks,  7. 

action,  740. 

carboniferous,  725. 

cretaceous,  oolitic  and  liassic,  727. 

of  the  Andes,  721. 

rocks,  origin  of  name,  702. 

Silurian,  725. 

test  of  age  of,  717. 

Pluvial  action  on  chalk,  365. 
Podocarya,  portion  of  fruit,  410. 
Podogonium  Knorrii,  (Eningen,  251. 
Poikilitic,  term  explained,  432. 
Polyccelia  profunda,  Permian,  515. 
Polypterus,  living,  in  the  Nile,  532. 
Pomel,  M.,  on  fossil  of  Mont  Perrier,  687. 


Pompeii,  bronze  instruments  found  at  112. 

Ponza  Islands  in  Mediterranean,  619. 

zoned  structure  of  trachyte  in,  752. 

Ponza,  Isle  of,  globular  pitchstone  in,  619. 

Ponzi,  Prof.,  on  Subapennine  strata,  209. 

Porphyritic  granite,  707. 

Porphyry,  600. 

Portland,  Isle  of,  fossil  forests  in,  391. 

stone  and  sand,  394. 

Port  Moniz,  surface  of  lava  at,  654. 

Porto  da  Cruz,  trachytic  tuffs  of,  652. 

Porto  Santo,  Madeira,  Upper  Miocene  shells 
of,  674. 

Posidonia  minuta,  Muschelkalk,  439. 

Posidonomya  Becheri,  522. 

Post-pliocene  period,  human  remains  of,  113. 

mammalia,  teeth  of,  133. 

lakes  of  Switzerland,  173. 

valley  drifts  of,  114. 

volcanic  rocks,  661. 

strata,  107, 113. 

Potamides  cinctm,  30. 

Potsdam  sandstone,  581. 

Potstones  at  Horstead.  823. 

Pottery  in  upraised  strata,  121. 

Pottsville,  coal-seams  near,  499. 

footprints  of  reptiles  near,  509. 

Powrie,  Mr.,  on  Cephalaspis  beds,  531. 

Pozzolana,  36. 

Prasias,  Lake,  lake-dwellings  in,  110. 

Pratt,  Mr.,  on  fossils  of  Oxford  clay,  400. 

on  Isle  of  Wight  mammalia,  283. 

Precipitation  of  mineral  matter,  41. 

Predazzo,  altered  rocks  at,  724. 

Prestwich,  Mr.,  on  island  in  Eocene  sea,  867. 

on  Barton  clay  shells,  287. 

on  Blackheath  shingle,  296. 

- —  on  Eocene  strata,  369. 

on  shells  of  London  clay,  292. 

on  Weald  denudation,  367. 

on  iron-sands,  235. 

— —  on  Calais  flint-breccia,  374. 

on  cave  and  drift  fossils,  129. 

on  coal-measures  of  Coalbrook  Dale,  62. 

on  Sables  de  Bracheux.  387. 

Prevost,  M.  Constant,  on  fauna  of  Montmartre, 
299. 

Prevost,  M.,  on  Paris  basin,  299. 

Primary  Limestone,  736. 

"  Primary  "  schists,  composition  of,  744. 

Primordial  zone  of  Barrande,  573,  579. 

Productus  horridm,  460. 

semireticulatus  (antiquatus),  517. 

Progressive  development  and  oldest  fossil  fish, 
588. 

Proteaceae,  species  in  Lower  Molasse,  Switzer- 
land, 261. 

Protogine,  708,  736. 

Protrusion  of  solid  granite,  727,  731. 

Psammodm  porosus,  521. 

Psaronius  in  Permian  of  Saxony,  464. 

Pseudocrinites  bifaaciatus,  Wenlock,  558. 

Puilophyton  princeps,  Devonian,  548. 

Pteraspis  in  Lower  Ludlow  shale,  555. 

PtericMhys,  Old  Red  Sandstone,  534. 

Pterodactyl,  gigantic  size  of,  831. 

Pterodactyius  crassirostris,  Solenhofen,  896. 

Pterophyllum  comptum,  Gristhorpe,  411. 

Pterygoius  anglicun,  523. 

Ptychodus  decurrens,  Chalk,  380. 

Puggaard,  M.,  on  strata  of  Ischia,  190. 

Pulvermaar  of  Gillenfeld,  lake  of,  681. 

Pumice,  602,  606. 

Pupa  muscorum,  Ehine,  119. 

vetusta,  Coal,  512. 

tridens,  30. 

Purbeck,  Lower,  shells  of,  389. 

beds,  377,  879-394. 

fossil  mammalia  of,  381. 

marble,  880. 

Middle,  shells  of,  380. 

Upper,  shells  of,  379. 

Purity  of  coal,  causes  of,  490. 

Purpura  tetragona,  Red  crag,  202. 

Pur-puraidea  nodulata,  Great  Oolite,  405. 


798 


INDEX. 


Pay  de  Come,  volcano  of,  689. 

de  Pariou,  crater  of,  691. 

de  Tartaret,  eruptions  of,  688. 

Pyrenees,  curvatures  of  strata  in,  58. 

• altered  fossiliferous  rocks  of,  739. 

lamination  of  clay-slate  in,  756. 

Pyroxene,  597. 

Pyroxenic  porphyry,  606. 

Puzzuoli,  elevation  and  depression  of  land  at, 

661. 
Pyrula  reticulata,  Coralline  crag,  204. 

QUADEIIMANA  of  Upper  Miocene  strata,  Gers, 

233. 

Quadrupeds,  extinct,  in  alluvium,  11. 
Quartz,  fusion  of.  705. 

veins  in  gneiss  of  Norway,  715. 

Quartzite,  quartz  rock,  734,  736. 
Quebec  group,  fossils  of,  583. 
Quekett,  Prot,  on  Pupa  vetusta,  512. 
Quenstedt,  M.,  on  zones  of  Lias,  416. 

BADABOJ,  fossils  of,  245. 

Kadicofani,  Older  Pliocene  volcanic  rocks  of, 

673. 
Radiolites  foliaceus,  Chalk,  337. 

Mortoiii,  Chalk,  328. 

radiosa,  Chalk,  337. 

Eadnorshire.  stratified  trap  of,  700. 
Rain-prints  with  worm-tracks,  489. 

carboniferous,  489. 

Eaised  beach  of  San  Catalina,  676. 
Kamsay,  Prof.,  on  Welsh  glaciers,  159. 

on  causes  of  Weald  denudation,  374. 

on  cretaceous  fossils,  344. 

on  denudation,  67. 

— —  on  Devonian  Brachiopoda,  542. 

on  fossils  of  Mountain  Limestone,  517, 

518. 

on  relations  of  Oolitic  fossils,  413. 

on  St.  Cassian  fossils,  437. 

on  Tremadoe  slates,  &c.,  577. 

on  Trias  of  England,  440. 

on  two  granites  of  Arran,  728. 

on  volcanic  tufts  of  Snowdon,  700. 

on  zones  of  Lias,  416. 

Rastrites  peregrinus,  Silurian,  565. 
Kaulin,  M.  V.,  on  Diest  sands,  235. 
Kavine  of  Barranco  de  las  Angustias,  638. 
Recent  strata,  defined.  107. 

strata  near  Naples,  108. 

volcanic  rocks,  why  invisible,  718. 

Eecord,  imperfection  of,  in  the  earth's  history, 

180. 

Bed  crag  of  Suffolk,  200. 
Eed  Sandstone,  origin  of,  447. 
Bed  Sea,  saltness  of,  450. 

and  Mediterranean,  distinct  species  in,  96. 

Eeindeer  period  in  South  of  France,  125. 
Eelation  of  trap,  lava,  and  scoriae,  620. 
Eelistran  mine,  pebbles  in  tin,  771. 
Eeptile  of  the  Kupferschiefer,  463. 
Eeptiles  of  coal-measures,  511. 

carboniferous,  504. 

of  the  Lias,  422. 

s'upposed  remains  of,  in  Old  Eed,  529. 

Retepora  fluatracea,  460. 
Bhaetic  beds,  442. 
Ehine,  fossils  of,  120. 

valley,  human  skeleton  of,  117. 

Rhinocer'oH  leptorhinus,  molar  of,  134. 

tichorhinus,  molar  of,  134. 

Ehomboidal  scaled  fish,  533. 
Rfiynchonella  Wilxoni,  Aymestry,  554. 

navicula,  Ludlow,  553. 

octoplicata,  White  Chalk,  327. 

spinosa,  Inferior  Oolite,  412. 

Rhytisma  induratum,  CEningen,  267. 
Eichardson,  Sir  John,  on  fossil  Sequoia,  262. 
Eichmond,  Va.,  triassic  coal-field  of,  451. 
Rimula  elathrata,  Great  Oolite,  405. 
Eink,  Mr.,  on  ice  of  Greenland,  144. 
Eipple-murk,  formation  of,  19. 
Else  and  fall  of  land,  108,  114. 
in  Wealden  period,  352. 


Rissoa  Cliastelii,  Hempstead,  240. 
Bitter,  M.,  on  submergence  of  Sahara,  176. 
Eiver  terraces,  ancient,  of  Nile,  11& 

channels,  ancient,  504. 

Boche  de  Pignon,  Seine,  356. 
Boche  moutonnee  described,  141. 
Eoches  d'Orival,  Elbceuf,  355. 
Bock,  term  defined,  2. 

cretaceous,  340. 

and  Spindle,  St.  Andrew's,  697. 

salt,  origin  of,  447-450. 

Bocks,  four  classes  of,  contemporaneous,  8. 

altered  by  subterranean  gases,  741. 

classification  of,  86. 

composed  of  fossil  zoophytes  and  shells, 

glacial  scorings  on,  143. 

metamorphic,  732. 

metamorphic,  age  of,  758. 

trachytic,  of  Madeira,  653. 

trappean,  88. 

Silurian,  table  of,  550,  551. 

smoothed  and  striated,  139. 

volcanic  eocene,  694. 

Eocene,  granite,  and  plutonic,  721. 

altered  by  subterranean  gases,  615. 

tests  of  age  of,  655. 

volcanic,  structure  of,  616. 

Eoderberg,  volcano  of,  682. 

Eogers,  Prot,  on  Devonian  rocks,  U.  8.,  544. 

on  coal-field,  United  States,  498,  501. 

on  reptile  footprints,  509. 

on  Eichmond  coal-field,  451. 

Boman  relics  in  Swiss  strata,  121. 
Borne,  formations  at,  209,  673. 
Eomer,  F.,  on  chalk  of  Texas,  340. 

on  Aix-la-Chapelle  beds,  334. 

Bose,  Gustav,  on  fusion  of  quartz,  705. 

on  Fifeshire  dike,  698. 

on  hornblende,  596. 

Boss,  Capt,  on  greenstone  at  Keeling  Island, 

824. 

Boss-shire,  denudation  in,  67. 
Eosso  antico,  red  porphyry  of  Egypt,  601. 
Rostellaria  ampla,  293. 
Both,  M.,  on  Miocene  formations  of  Greece, 

247. 

Roxalina,  Chalk,  26. 
Bubble,  term  explained,  81. 
Eunn  of  Cutch,  salt  of,  449. 
Bupelian  of  Dumont,  237. 
Bupelmonde,  Upper  Eocene  beds,  238. 
Eussia,  glaciation  of,  149. 

Devonian  of,  542. 

fossil  meteoric  iron  in,  177. 

Biitimeyer,  M.,  on  Eocene  monkey,  294. 

SABLES  de  Bracheux,  806. 

moyens,  302. 

Saarbruck  coal-field.  506. 

Sabal  major,  Vevay,  259. 

Sahara,  submergence  of,  175. 

St.  Abb's  Head,  unconf'ormable  stratification  at, 

curved  strata  near.  49. 

St.  Andrew's,  Bock  and  Spindle  in,  697. 

St.  Helena,  volcanic  dike  of  horizontal  prisms, 

617. 
St.  Lawrence,  Gulf  of,    inland   beaches  and 

cliffs,  78. 

St.  Mary's,  shells  of,  676. 
St.  Mihiel,  France,  inland  cliffs  near,  77. 
St.  Paul's  or  Amsterdam  Island,  643. 
St.  Peter's  Mount,  near  Maestricht,  sandpipes 

in.  88. 

S.  Vicente,  tuffs  and  limestones  of,  646. 
Salisbury  Craig,  altered  strata  near,  615. 
Salt  rock,  origin  of,  448. 

lakes  of  Asia,  449. 

Salter,  Mr.,  on  fossils  of  Lower  Llandeilo,  567. 
San  Catalina,  raised  beach  of,  676. 
Sandberger,  Dr.  F.,  on  Mayence  Tertiary,  243. 
Sandpipes  of  North  Downs,  8(51. 

in  Norwich,  82. 

or  sandgalls,  term  explained,  82. 


INDEX. 


799 


,       . 

attel,  intercalations  of  gneiss  in  the,  761. 
aucats,  near  Bordeaux,  faluns  of,  232. 


Sands  of  Hastings,  349. 

-  of  Diest,  234. 

Sandstone,  Gray,  of  Upper  Ludlow,  552. 

-  and  conglomerate  of  Auvergnc,  223. 

-  New  Red,  of  Connecticut,  452. 

-  slab,  with  cracks,  350. 

Sandwich  Islands,  craters  and  calderas  of,  623. 

-  volcanoes  of,  623. 
Sao  hirsute,  530. 
Sattel 

Sa 

Saurians  of  Lias,  422-428. 

-  sudden  destruction  of,  426. 
Saurichthys  apicalis,  442. 
Saussure,  on  erratics,  142. 

-  on  vertical  conglomerates,  47. 
Saxieava  rugosa,  Clyde  drift,  153. 
Saxony,  protrusion  of  solid  granite  in,  727. 

-  beds  of  minerals.  772. 
Scandinavia,  glaciation  of,  149. 
Seaphites  cequalis,  Dorsetshire,  326. 
Scarborough,  oolitic  plants  of,  411. 
Schist,  micaceous,  734,  736. 

-  argillaceous,  734,  735. 
Schisodw  Sc/ilotheimi,  Permian,  459. 

-  truncatus,  Permian,  459. 
Schmerling,  Dr.,  on  Liege  caverns,  124,  125. 
Schorl  rock,  70& 

Schwab,  M.,  on  Celtic  coins,  111 
Scoliostonia,  St.  Caspian,  436. 
Scoresby,  on  Arctic  icebergs,  146. 
Scoriaceous  lava  in  part  amygdaloid,  600. 
Scoria),  602,  606. 

-  formation  of,  594. 

Scotland,  fundamental  gneiss  of,  585. 

-  Old  Red  Sandstone  of;  524. 

-  glaciation  of,  151. 

Scrope,    Mr.,   on   zoned    structure    of  Ponza 
Islands,  752. 

-  on  globular  structure  of  traps,  619. 

-  on  globiibrin  pitrhstone,  619. 

-  on  tuif  and  peperino,  602. 
Sea-beds,  scored  by  icebergs,  148. 

-  cliffs,  inland,  71. 

Section  through  part  of  Teneriffe,  645. 

-  at  Champradelle,  near  Clermont,  225. 

-  between  Atlantic  and  Mississippi,  497. 

-  between  rivers  Alabama  and  Tombeckbee, 
310. 

-  in  Isle  of  Portland,  391. 

-  of  Arran,  730. 

-  of  central  region  of  Madeira,  651. 

-  of  contorted  strata,  Forfarshire,  156. 

-  of  Dundry  Hill,  near  Bristol,  48,  98. 

-  of  escarpments  of  Weald  Valley,  358. 

-  of  Foriarsirire,  4a 

-  of  Isle  of  Arran,  730. 

-  of  lava  at  Casteil  Follit,  671. 

-  of  Madeira,  648. 

-  of  Falma,  631. 

--  of  South  Joggins  cliffs.  485. 

-  of  Chalk  and  Greensand,  317. 

-  of  Elephant-bed,  Brighton,  373. 

-  of  Lulworth  Cov«!  dirt-bed,  391. 

-  of  Old  and  New  Red  Sandstone,  431. 

-  of  the  Weald,  346,  358,  368. 

-  showing  chalk  in  Seine  Valley,  854. 

-  showing  erect  fossil  trees  in  Coal,  483. 

-  vertical,  of  slate-rock,  Devon.  750. 
Sedgwick.  Prof.,  on  concretionary  magnesian 

limestone,  37. 

-  on  brecciated  limestone,  459. 

-  on  Cambrian,  575. 

-  on  carboniferous  plutonic  rocks,  725. 

-  on  Coal  strata,  466. 

-  on  Cornish  granite,  712. 

-  on  Davoaian  series,  536. 

-  on  garnets  in  altered  rock,  613. 

-  on  granite  of  Caithness,  729. 

-  on  Silurian  strata,  560,  567. 

-  on  structure  of  mineral  masses,  746. 
Segregation  of  mineral  veins,  768. 
Semi-crystalline  strata  of  Alps,  760. 
Semi-opal,  Diatomace;e  in,  26. 
Senneville,  chalk  pinnacle  at,  355. 


Senonian,  term  explained,  315. 
Sequoia  Langsdorfii,  Switzerland,  263. 

Mackenzie  River,  263. 

Seraphs  convolutum,  287. 

Serapis  imbedded,  108. 

Serpentine,  606,  736. 

Serpulae  on  volcanic  rocks  in  Sicily,  192. 

attached  to  Encrinite,  403. 

attached  to  Gryphcea,  22. 

attached  to  Spatangus.  23. 

Shale,  Lower  Ludlow,  555. 

defined,  11. 

Sharks,  teeth  of,  290. 

Sharp  Tor,  Cornwall,  granite  of,  703. 

Sharpe,  Mr.  D.,  on  shells  in  slaty  cleavage, 

750. 

on  Silurian  fossils,  571. 

on  Upper  Canada,  331. 

Shell-mounds  of  Denmark,  109. 

Shells,  proportion  of  Northern  and  Southern, 

in  crag,  206. 

Arctic,  in  Scotch  drift,  154. 

fossil,  of  Virginia,  U.  S.,  278. 

fossil,  of  London  clay,  293. 

fossil,  of  mountain  limestone,  516-522. 

of  Barton  clay,  287. 

of  Edeghem,  234. 

of  faluns  compared  to  those  of  crag,  214. 

of  Faxoe,  316. 

of  Gergovia  formation,  693. 

of  Great  Oolite,  405. 

of  Mayence  basin,  243. 

of  Norwich  crag,  197. 

of  Sicily,  190,  194. 

of  Subapennine  beds,  208. 

of  Upper  and  Middle  Purbeck,  379,  880. 

preserving  their  color,  518. 

proportion  found  in  different  strata,  189. 

recent,  28,  2t>,  30. 

valuable  in  classification,  187. 

Sheppey,  fauna  and  flora  of,  292. 
Shetland,  granite  of,  709. 

J hornblende  schist  of,  743. 

Sicily,  volcanic  dikes  of,  192. 

corals  oi;  194. 

dikes  in,  665. 

inland  din's  in,  74. 

newer  Pliocene  beds  of,  192. 

terraces  of  denudation  in,  75. 

Sidlaw  Hills,  trap  of,  699. 
Siebengebirge,  igneous  rocks  of,  679. 
Sigillaria,  structure  and  size  of,  474,  481. 

lawigata,  Coal,  474. 

Siliceous  lime'stone  defined,  12. 

rocks  defined,  11. 

Silurian  plutonic  rocks,  725. 

derivation  of  name,  551. 

fossils,  552-570. 

lower  metamorphic,  in  Scotch  Highlands, 

762. 

rocks,  table  of,  550,  551. 

rocks,  Upper,  551;  Middle,  560;  Lower, 

rocks,  whether  of  deep-water  origin,  578. 

strata  of  Europe,  569. 

strata  of  United  States,  table  of,  570. 

volcanic  rocks,  699. 

Siphonia  pyriformis,  Blackdown  beds,  329. 
Siplionotreta  unguiculata,  Silurian,  569. 
Si  \valik  Hills,  freshwater  deposits  of,  276. 
Skaptar  Jokul,  flow  of  lava  from,  657. 
Skye,  plutonic  rocks  of  Lias  in,  724. 

decomposed  trap  of,  610. 

sandstone  in,  36. 

Skull  of  stone  age,  Denmark,  113. 

of  'iron  age,  Denmark,  113. 

Skulls,  brachycephalous,  113. 

dolichocephalous,  113. 

Slaty  cleavage,  749. 
Slicken-sides,  term  defined,  770. 
Smilex  obtiMf'olia,  (Euingen,  255. 

sagittifera,  (Eningen,  255. 

Smith,  Mr.,  of  Jordanhill,  on  Madeira  fossil 

plants,  64;). 
Snags,  fossil,  483. 


800 


INDEX. 


Snowdon,  volcanic  tuffs  of,  700. 

Soissonnais  sands,  304. 

Solenhofen,  fossils  in  lithographic   stone  of, 

395. 
Solfatara,    decomposition    of    rocks    in    the, 

Somma,  sahlband  at,  612. 

cone  and  dikes  of,  662. 

Sopwith,  Mr.  T.,  models  by,  57. 

Sorby,  Mr.,  on  ripple-marks  in  mica-schist, 
756. 

on  hydrothermal  action,  706. 

on  slate  cleavage,  751. 

South  Devon,  Old  Ked  of,  535. 

South  Downs,  transverse  valley,  362. 

view  of.  360. 

South  Joggins,  stigmaria  and  sigillaria  at, 
475. 

section  of  cliffs  at,  485. 

Spaccoforno  inland  cliffs,  76. 

Spain,  volcanoes  in,  6. 

Spalacotherium,  Purbeck,  406. 

Spanish  volcanoes,  age  of,  672. 

Spatangua  radiatus,  Chalk,  316. 

with  Serpula  attached,  23. 

Species,  antiquity  of  living,  195. 

of  Upper  and  Lower  Cretaceous,  344. 

of  plants  common  to  Older  Miocene  and 

flora  of  (Eningen,  260. 

variations  of,  215. 

Specific  gravity  of  basalt  and  trachyte,  599. 

Spezia,  Gulf  of,  calcareous  rocks,  759. 

Sphcerexochus  mirus^  Silurian,  559. 

Sphcerulites  agarici/ormis,  Chalk,  337. 

Sphenopteris  gracilis,  Wealden,  351. 

crenata,  Carboniferous,  468. 

Spicula  of  sponge,  Atlantic  mud,  320. 

Spirifer  trigonalis,  &  glaber,  Mountain  Lime- 
stone. 518. 

disjunctm,  Devonian,  537. 

mucronatus,  541. 

Walcotti,  Lower  Lias,  418. 

undulatus,  460. 

Spirolina  stenostoma.  Eocene,  303. 

SpirorMs  carbonarim,  493. 

Spondylm  spinosus,  Chalk,  327. 

Sponge  in  flint  (Chalk),  330. 

Spongitta,  spicula  of,  in  tripoli,  25. 

Springs,  mineral.    See  Mineral  Springs. 

Staffa,  columnar  basalt  of,  616. 

Stalactite,  origin  of,  123. 

Starfish  of  Lower  Ludlow,  555. 

Stauria,  astrcece/ormis,  Silurian,  515. 

Steno,  on  classification  of  rocks,  86. 

Stereognathus  described,  409. 

Sterabergia,  structure  of,  477. 

Stigmaria  in  coal-measures,  468. 

ficoides,  Coal,  476. 

and  Sigillaria,  475. 

Stirling  Castle,  rock  of,  altered  by  dike,  615. 

Stiper-stones  group,  567. 

Stockwerk,  assemblage  of  veins,  768. 

Stokes,  Mr.,  on  petrifaction,  43. 

Stone  weapons  at  Geneva,  111. 

Stonesfield  slate,  composition  and  fossils,  405. 

Strata  of  Kyson,  294. 

arrangement  of,  determined  by  fossils,  21, 

consolidation  of,  34. 

contortions  of,  in  Cyclopian  Isles,  659. 

contorted,  in  drift.  156. 

curved  and  vertical,  47,  58. 

elevation  of,  above  the  sea,  44. 

fossiliferous,  tabular  view  of,  102. 

horizontally  of,  15,  45. 

infraliassic,  of  Austrian  Alps,  435. 

Lacustrine,  of  the  Cantal,  i>29. 

Lower  Miocene,  of  England,  239. 

Lower  Miocene,  of  France,  217. 

metamorphic,  origin  of,  786. 

mineral  composition  of,  10. 

Miocene,  of  Italy,  247. 

Miocene,  of  Belgium,  236. 

Miocene,  of  Bordeaux,  231. 

Miocene,  of  France,  212. 


Strata,  Miocene,  of  Switzerland,  248. 

Newer  Pliocene,  of  England,  196. 

Older  Pliocene,  of  England,  200. 

outcrop  of,  56. 

Post-pliocene,  107. 

prominence  of  harder,  364. 

Recent,  107. 

Silurian,  of  Europe,  569. 

Subapennine,  208. 

table  of  New  York  Devonian,  543. 

term  defined,  2. 

Upper  Miocene,  of  Gers,  232. 

Stratification,  unconi'ormable,  60. 

forms  of,  13, 16,  47. 

unconformable,  59. 

Striae,  production  of,  139. 

Striation  of  rocks,  139. 

Strickland,  Mr.,  on  Posidonia  minuta,  443. 

Strike,  term  explained,  53. 

Stringocephalus  £urtini,  539. 

Stromboli,  lava  of,  719. 

Strophomena  grandis,  Silurian,  563. 

depressa,  Silurian,  558. 

Strozzi,    Marquis,  on    Upper   Miocene   flora 

210. 
Structure,  columnar  and  globular,  of  volcanic 

rocks,  6i6. 

jointed,  of  metamorphic  rocks,  747. 

metamorphic,  origin  of,  743. 

Studer,  M.,  on  gneiss  of  Jungfrau,  761. 

on  boulders  of  Jura,  143. 

Subapennine  strata,  208. 
Subdivisions  of  Bembridge  beds,  282. 
Submergence  of  North  America,  165. 

and  reelevation  of  land  in  Scotland,  152. 

Succession,   order  of,  in  metamorphic  rocks. 

764. 
Succinea  amphibia^  29. 

elongata,  Rhine,  119. 

Suess,  M.,  on  Hallstadt  fossils,  436. 

on  Koessen  beds,  435. 

on  Vienna  basin,  244. 

Suffolk,  crag  of,  196,  200. 

Superga,    near   Turin,    tertiaries    of    hill   of, 

209. 

Superior,  Lake,  marl  in,  36. 
Superposition  of  aqueous  deposits,  96. 

of  Catalonian  rocks,  673. 

test  of  age  of  volcanic  rocks,  655. 

Supracretaceous,  term  defined,  99. 

Sus  scrofa,  molar  of,  134. 

Sussex  marble,  348. 

Swanage,  fossil  mammalia  found  at,  381. 

Swansea,  coal-measures  at,  467. 

Sweden,  Cambrian  of,  581. 

Swiss  pile-dwellings,  110,  111. 

Jura,  structure  of,  55. 

Switzerland,  age  of  metamorphic   rocks   in. 

760. 

lake-terraces  of,  120. 

lake-dwellings,  110. 

Miocene  strata  of,  248,  266. 

fossil  plants  of  Lower  Miocene  of,  260. 

Sydney  coal-field,  Cape  Breton,  489. 
Syenite,  formation  of,  7JJ8, 
Syenitic  granite,  708. 

gneiss,  786. 

Symonds,  Rev.  W.  8..  on  Moel  Tryfaen  shells. 

158. 
Synclinal  line,  term  defined,  48. 

TABLE  MOUNTAIN,  strata  horizontal  in,  45. 

granite  veins  in,  711. 

Table  of  fossil  vertebrata,  588. 

from  Portland-stone  to  Lower  Greensand, 

892. 

of  Devonian  series,  536. 

of  French  Eocene  strata,  297,  298. 

of  Limburg  beds,  237,  233. 

of  New  York  Devonian  strata,  543. 

of  Silurian  rocks,  550,  551. 

of  minerals  analyzed,  608. 

of  Cambrian  and  Laurentian  strata,  575, 

576. 
of  Eocene  formations,  England,  281. 


INDEX. 


801 


Table  of  fossil  mammalia  older  than  Paris  gyp- 
sum, 387. 

of  fossiliferous  strata,  101. 

of  Permian  strata,  458. 

Tabular  view  of  fossiliferous  strata,  102. 

Tails  of  hoinocercal  and  heterocercal  fish, 
461. 

Talcose  granite,  708. 

gneiss,  736. 

gneiss  granite  veins,  713. 

schist,  736. 

Tarannon  shale,  thickness  of,  560. 

Tartaret,  cone  and  lava-current  of,  688. 

Teeth  of  extinct  mammalia,  133-135. 

Teleostei,  term  explained,  534. 

Tellina  dbliqua,  Norwich  crag,  197. 

proximo,  Scotch  drift,  154. 

Temnechinus  excavatits,  Coralline  crag,  204. 

Temnopleurus  excavatus,  204. 

Teneriffe,  view  of  Peak  of,  644. 

Tentaculites  annulatus,  Silurian,  561. 

Tephrine,  607. 

Terebellum  sopita  (SerapTts  convolutum). 
287. 

fusiforme,  Barton,  287. 

Terebratula  porrecta,  539. 

diffona,  Bradford  clay,  405. 

sella,  344. 

carnea,  White  Chalk,  827. 

Jvmbria,  Inferior  Oolite,  412. 

fiastata,  518. 

Witeoni,  Aymestry,  554. 

Terebratula  biplicata,  Cretaceous,  827. 
Terebratulina  striata,  White  Chalk,  327. 
Terebrirostra  lyra,  331. 

Teredina  personata,  fossil  wood  bored  by, 

Teredo  navalis  boring  wood,  24. 

Tertiary  formations,  classification  of,  178. 

term  defined,  182. 

of  Paris.  297. 

volcanic' rocks  of  Auvergne,  687. 

Termites  of  (Eningen,  257. 

Terra  del  Fuego,  clay  slates  of,  755. 

Testacea  of  plastic  clays,  295,  296. 

Tete  d'Homme,  Andelys,  854,  355. 

Texas,  chalk  in,  840. 

Thallogens,  term  explained,  333. 

Thamnastr&a,  Coral-rag,  398. 

Thanet  sands,  297. 

Thecodontosaurus,  tooth  of,  447. 

Thecosmilia  annularis,  Coral-rag,  898. 

Thelodw,    shagreen    scales   of  placoid   fish, 

o52. 

Thickness  of  Laurentian  rocks,  583. 
Thirria,  M.,  on  Oolitic  group,  429. 
Thompson,    Dr.,  on   nummulites  of  Thibet, 

308. 
Thurmann,  M.,  on  anticlinal  ridges  of  Jura, 

366. 

cited,  55. 

on  Bernese  Jura  Oolite,  404 

Thylacotheriwm  Prevostii,  Valenc.,  407. 

Tilestones  of  Silurian  strata,  551. 

Tilgate  Forest,  remains  in,  849. 

Till,  described,  137^ 

Tin,  whence  obtained  by  ancients,  112. 

veins,  age  of,  780. 

Toadstone,  607. 

Tongrian  of  Dumont,  237,  238. 

Torell,  Dr.  Otto,  on  icebergs,  144. 

Touraine,  faluns  of,  213. 

Tournouer,  M.,  on  Lower  Miocene  shells,  232. 

Trachyte,  599,  607. 

porphyry,  599. 

Trachytic  lava,  age  of,  657. 

tuffs  of  Madeira,  653. 

Transition,  term  explained,  88. 
Transverse  valleys,  362. 
Trap,  term  explained,  592. 

between  limestone  and  shale,  Durham, 

616. 

dike,  intercepting   strata  covered  with 

alluvium,  621. 

51 


Trap  dikes,  609. 

intrusion  of,  between  strata,  616. 

of  New  Eed  Sandstone  period,  696. 

passage  of  granite  into,  708. 

relation  of,  to  active  volcanic  products, 

620. 

rocks,  name  and  origin  of,  592. 

spheroidal,  of  Madeira,  653. 

tuff,  602,  607. 

veins  in  Airdnamurchan,  610. 

Trappean  rocks,  88. 

relation  to  lava,  620. 

Trass  of  Lower  Eifel,  682. 

term  explained,  607. 

Travertin,  how  deposited,  34. 

inferieur,  302. 

Tree-fern  from  Brazil.  469. 

from  Isle  of  Bourbon,  469. 

Tree,  fossil,  obUque  in  Coal,  483, 486. 
Trees,  erect,  in  Coal,  479,  482. 
Tremadoc  slates,  fossils  of,  776. 
Trenton  limestone,  fossils  of,  571. 
Trezza,  beds  of  clay  and  lava  at,  658. 
Trias  of  United  States,  451. 

nomenclature  of,  432. 

in  Cheshire  and  Lancashire,  443. 

subdivisions  of,  432. 

Triassic  group  in  England.  440. 
Triconodon  in  Middle  Purbeck,  385. 
TrigoneUites  latus,  Kimmeridge  clay,  895. 
Trigonia  cavdata,  344. 

gibl>osa,  Portland-stone,  394. 

Trigonoearpum  ovatum,  477;  T.  olivceforme, 

Trigonotreta  undulala,  460. 
Trilobites  of  primordial  zone,  580. 

in  Devonian  strata,  537. 

in  Cambrian,  574. 

metamorphosis  of,  580. 

Triloculina  inftata,  Eocene,  804. 

Trimmer,    Mr.,    on  shells  of  Moel   Tryfaen, 

158. 

on  contorted  strata,  157. 

on  sand-galls,  82. 

Trinucleus  concentricus  (T.  ornatus),  Tri- 

nucleua  Caroctaci,  563. 
Trionyx,  carapace  of,  Bembridge,  282. 
Tripoli  composed  of  Diatomacese,  24. 
Tristram,    M.,    on    submergence    of    Sahara, 

176. 

Trochoceras  giganteus,  Silurian,  555. 
Trophon  clathratum.  Clyde  drift,  158. 
Tuffs  of  Ischia,  189. 

volcanic  and  trap,  6,  602. 

of  Lower  Llandeilo,  567. 

described,  607. 

Tuomey,  Mr.,  on  burr-stone  strata,  812. 

Tupaia  Tana,  Oolite,  408. 

Turner,  Dr.,  on  chemical  decomposition,  41, 

42. 

Turrilites  costatus,  Chalk,  826. 
Turritella  multisulcata,  290. 
Tuscany,  springs  from  spent  volcanoes,  766. 

Older  Pliocene  volcanic  rocks  of,  678. 

Tyndall,  Dr.,  on  slate  cleavage,  752. 

Tynedale  fault.  64. 

Tynemouth  cliff,  limestone  at,  459. 

Tyrol,  junction  of  plutonic  rocks  with  Oolitic 

strata,  724. 
Typhis  pungens,  Barton  clay,  287. 

UNCONFOBMABLE  stratification,  60,  61. 
Underlying,  term  applied  to  granite,  7. 
Unger,  Prof.,  on  Planera  Kichardi,  266. 

on  Miocene  Atlantis,  269. 

on  Miocene  plants  of  Croatia,  245. 

on  Swiss  Miocene,  248,  256. 

Ungulite  or  Obolus  grit  of  Kussia,  569. 
Unio  UUoralis  (recent),  2a 

Valdensis,  850. 

United  States,  Eocene  strata  in,  809. 

Cambrian  strata  of,  581. 

cretaceous  rocks  of,  888. 

coal-fields  of,  496. 


802 


INDEX. 


United  States,  Devonian  strata  of,  543. 

Lower  Miocene  of,  2T9. 

Older  Pliocene  and  Miocene  formations 

in,  277. 

section  of  geological  structure  of,  497. 

Silurian  strata  of,  570. 

Trias  of,  451. 

TJnstratification  of  Nile  deposits,  118. 
Upheaval,  theory  of  violent,  considered,  723. 

of  calderas,  theory  of,  635. 

of  the  Weald,  366. 

Upper  Greensand,  331. 

Miocene  sea  in  area  of  Downs,  371. 

Val  d'Arno,  newer  Pliocene    strata   of, 

196. 

Upraised  marine  strata  in  Sardinia,  121. 
Upsala,  erratics  on  modern  marine  drift  near, 

150. 
Ural  Mountains,  quartz  veins  of,  779. 

gold  of,  779. 

Uraus  spelceus,  molar  of,  135. 

Urville,  Capt.  d',  on  size  of  icebergs,  146. 

VAL  DI  NOTO,  inland  cliffs  in,  76. 

volcanic  formations  of,  665. 

igneous  rock  of,  621. 

Valleys,  origin  of,  70. 

transverse,  of  "Weald,  362. 

Valorsine  granite,  713. 
Valvata,  Pleistocene,  29. 
Vanessa  Pluto,  Croatia,  245. 
Vegetation  of  Middle  Eocene  period,  290. 

of  Devonian  period,  546. 

Veins,  granite,  rocks  altered  by,  709. 

mineral.    See  Mineral  Veins. 

chemical  deposits  in,  775. 

Veinstones  in  parallel  layers,  772. 
Velay,  volcanic  formations  of,  692. 
Venericardia  planicosta  (cardita  plani- 

costa),  288. 

Venetz,  M.,  on  Alpine  glaciers,  142. 
Ventriculites  radiatm,  Chalk,  329. 
Verneuil,  M.  de,  on  Permian  flora,  462. 

on  glacial  drift  of  Kussia,  149. 

on  Lower  Silurian,  United  States,  571. 

Vertebrata,  absence  of,  in  oldest  fossiliferous 

rocks,  585. 

absence  of,  in  lower  rocks,  585. 

fossil,  progress  of  discovery  of,  588. 

Vesuvius,  Newer  Pliocene  beds  of,  189. 

age  of  lavas  of,  658. 

dikes  of,  663. 

depth  of  crater  of,  645. 

Vicentin,  columnar  basalt  in,  618. 
Vicenza,  basaltic  column  near,  618. 
Victoria  Land,  erratics  of,  146. 
Vienna  basin,  Upper  Miocene  of,  244. 
View  of  volcanoes  of  Olot,  668. 

of  lava-current  of  Chaluzet,  690. 

of  Isle  of  Cyclops,  659. 

of  Gemunder  Maar,  680. 

Virginia,  coal-field  of,  451. 

-  Miocene  strata  of,  278. 

Virlet,  M.,  on  corrosion  of  rocks  near  Corinth, 

741. 

on  cretaceous  traps  of  Greece,  696. 

on  inland  cliffs,  73. 

volcanic  dikes,  6. 

mountains,  form  of,  5. 

Viterbo,  Older   Pliocene   volcanic   rocks   of, 

673. 

Vitreous  lava,  607. 
Volcanic  rocks  of  Olot,  666. 

breccia,  602,  603. 

carboniferous  rocks,  698. 

dike  at  St.  Helena,  617. 

dikes  of  Sicily,  192. 

Eocene  rock,  694. 

formation  of  Val  di  Noto,  665. 

mountains,  form,  structure,  and  origin  of, 


of, 


mountains,  form  of,  623. 
rocks,  sj 


Volcanic  rocks,  592. 

rocks  of  Auvergne,  684. 

rocks,  Cambrian,  700. 

rocks,  Cretaceous,  Oolitic,  and  Lias,  696. 

columnar  and  globular  structure  of,  616. 

rocks,  Laurentian,  701. 

rocks,  structure  of,  616-619. 

rocks,  Silurian,  700. 

tuff,  6,  602,  607. 

Volcano  of  Puy  de  Come,  689. 

of  Verigojo,  height  of,  642. 

Volcanoes,  extinct,  6. 

of  Auvergne,  684. 

of  Canaries,  627. 

of  Java,  626. 

of  Sandwich  Isles,  623. 

Voltzla  heterophylla  (brevifolia\  439. 
Volume  of  hidden  plutonic  rocks,  722. 
Valuta  Lamberti,  Touraine  Faluns,  215. 

ambigua,  Barton  clay,  287. 

athleta,  Barton,  287. 

Lamberti,  Coralline  and  Bed  Crag,  204. 

nodosa,  Highgate,  293. 

Selseiensis,  290. 

Von  Buch,  on  Caldera  of  Palma,  634. 

on  land  rising,  45. 

on  Silurian  plutonic  rocks,  725. 

WACKE.  607. 

Wael,  M.  de,  on  testacea  in  Antwerp  crag, 

207. 

Wagner,  M.,  on  Miocene  of  Greece,  247. 
WalcMa  piniformis,  Permian,  463. 
Wales,  glaciation  of,  158. 
Walker,  Dr.,  on  Sequoia,  262. 
Waller,  quoted,  88. 
Wallich,  Dr.,  on  Atlantic  mud,  320. 
Water,  action  of,  in  distributing  heat,  742. 
Waterhouse,  Mr.,  on  Tupaia  Tana,  408. 
Watt,   Mr.    Gregory,   on   cooling  of  metals, 

663. 

on  fusion,  739. 

Waves,  action  of,  on  limestone,  78. 

Weald,  map  to  illustrate  denudation  of,  357. 

valley,  denudation  of,  357,  367. 

Wealden  formations,  345. 

term  explained,  365. 

area  of  the,  351. 

plants  and  animals  of,  333,  849. 

theory  of  fracture  and  upheaval  of,  366, 

Webster,  Mr.  T.,  on  tertiary  strata,  182. 
— -  on  Headon  series,  284. 
Weisstein,  term  explained,  708. 
Wellington  Valley  caves,  126. 
Wenlock  formation,  fossils  of,  557-560. 

limestone,  557. 

shale,  fossils  of,  559. 

Werfen  beds,  composition  of,  435. 
Werner,  on  classification  of  rocks,  87. 

on  plutonic  formations,  767. 

Westerwald,  igneous  rocks  of,  679. 

Westwood,  Mr.,  on  Lias  beetles,  428. 

Wexford,  veins  of  copper  at,  777. 

Whinstone,  607. 

White  Chalk,  12. 

Mountains,  centres  of  erratic  dispersion, 

166. 

sand  of  Alum  Bay,  12. 

sands  and  Barton  clay,  287. 

Wigham,  Mr.,  on  jaw  of  Mastodon,  198. 

Williamson,  Prof.,  on  calamites,  472. 

Wood,  fossil  and  recent,  perforated  by  mollus- 

ca,  24. 

fragment  of,  in  Lias,  428. 

Wood,  Mr.  Scarles,  on  fish  of  Headon  series, 

285. 

on  Voluta  Lamberti,  215. 

Woodstock,  bone  of  reptile  found  at,  406. 
Woodward,  Dr.  8.  P.,  tables  on  marine  testa- 
cea, 205,  206. 

on  Bridlington  fossils,  199. 

on  Hallstadt  fossils,  436. 

— —  on   Madeira   and   Canarian   shells,  675, 

676. 


Woodwardia  Rossneriana,  Lower  Miocene, 

258. 

"Woolhope  limestone  and  grit,  560. 
Wrekin,  trap  of,  70. 
Wright,  Dr.,  on  zones  of  Lias,  416. 
on  Headon  series,  285. 

XIPHODON  GEACILE  (Anoploffierium,  gracile), 

300. 
Xylobiua  Sigillwia,  Coal,  512. 

YELLOW  CBAG,  recent  species  in,  208. 


INDEX. 

Yorkshire  Oolite,  plants  of,  411. 


803 


ZAMIA  SPIRALIB,  Australia,  390. 

Zechstein,  458. 

Zeuglodon  cetoides,  Owen,  811. 

Ziegler,  M.,  on  Mastodon  angustidens,  256. 

Zoantharia  aporosa,  515. 

rugosa,  515. 

Zones,  successive,  of  Lias,  416. 

Zoophytes,  fossil,  22,  192,  279,  399,  515,  538V 


Zurich,  lake-dwellings  in  Lake  of,  110. 


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